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Cognitive impairment and dementia in Parkinson disease

Cognitive impairment and dementia in Parkinson disease
Author:
Robert L Rodnitzky, MD
Section Editor:
Steven T DeKosky, MD, FAAN, FACP, FANA
Deputy Editor:
Janet L Wilterdink, MD
Literature review current through: Dec 2022. | This topic last updated: Nov 02, 2022.

INTRODUCTION — Cognitive dysfunction is common in Parkinson disease (PD) and exists on a continuum of severity; prevalence increases with the duration of the movement disorder. When severe, dementia often surpasses the motor features of PD as a major cause of disability and mortality.

While PD can coexist with other common causes of dementia, such as Alzheimer disease (AD) and vascular dementia, mild cognitive impairment (MCI) and dementia are increasingly recognized as common features of PD itself. The clinical characteristics and course of cognitive impairment, its pathologic features, and the most appropriate treatment are areas of current investigation. Clinical features can generally distinguish between PD and other movement disorders associated with dementia, such as dementia with Lewy bodies (DLB) or progressive supranuclear palsy (PSP). However, whether PD dementia (PDD) and DLB are distinct disorders, or whether they represent different presentations of the same disease, is an area of debate and investigation [1,2].

This topic will discuss cognitive impairment and dementia associated with PD. Other aspects of PD and DLB are discussed separately. (See "Clinical manifestations of Parkinson disease" and "Management of nonmotor symptoms in Parkinson disease" and "Initial pharmacologic treatment of Parkinson disease" and "Epidemiology, pathology, and pathogenesis of dementia with Lewy bodies" and "Clinical features and diagnosis of dementia with Lewy bodies" and "Prognosis and treatment of dementia with Lewy bodies".)

EPIDEMIOLOGY

Incidence and prevalence — In one study, PD dementia (PDD) was estimated to account for 3.6 percent of all cases of dementia in the population [3].

Dementia is a common feature of PD [4]. Cross-sectional studies suggest that the mean prevalence of dementia is 30 to 40 percent . In prospective cohort studies, the incidence rate of dementia in patients with PD is consistently estimated at approximately 100 per 1000 patient-years, a rate almost five- to sixfold higher than controls without PD [3,5-7]. These studies suggest that dementia is nearly inevitable in patients with PD; cumulative incidence rates of over 80 percent have been reported in patients followed for more than 20 years after onset of PD [8-10].

Milder degrees of cognitive impairment are also common in patients with PD, particularly early in the disease course [11-14]. In studies of patients with a new diagnosis of PD, the prevalence of mild cognitive impairment (MCI) ranges from approximately 10 to 35 percent [10,12,13,15].

Risk factors — The incidence of dementia in PD appears to be increased if one or more of the following risk factors are present [6-8,16-19]:

●Older age – In a community-based study, the prevalence of PDD in the general population was 787 per 100,000 for those ≥80 years, while the prevalence for those <50 years was zero [16].

●Longer disease duration – In a prospective, follow-up study evaluating the effect of disease duration, a 26 percent prevalence of dementia was noted at baseline in 224 patients with a mean disease duration of 11.5 years [8]. The prevalence of dementia was 52 percent four years later, and 78 percent eight years later. The mean PD duration at the onset of dementia in this study was 14 years.

●Older age at disease onset – In a population-based study, 37 percent of patients whose PD began after the age 70 years had dementia, compared with 9 percent of patients whose symptoms had begun before 70 years [19]. After five years of follow-up, the prevalences had risen to 62 and 17 percent, respectively.

●Severity of parkinsonism – In a population-based study, the relative risk (RR) for dementia was 9.7 in older (≥72 years), high-severity (Unified Parkinson Disease Rating Scale [UPDRS] >24) PD patients, compared with young, low-severity patients [20]. Young, high-severity patients and older, low-severity patients were not at higher risk of dementia compared with the reference population, suggesting that age and PD severity interact to increase the risk of dementia.

Additional risk factors for the development of more severe or early cognitive impairment in patients with PD include the presence of rapid eye movement sleep behavior disorder (RBD), autonomic dysfunction (especially hypotension), hyposmia, abnormal visual color discrimination, slow resting electroencephalography (EEG) frequencies, and gait dysfunction [21-24].

Poor cognitive functioning at baseline has also been associated with an increased risk of parkinsonism [25].

Only limited data have examined the impact of sex on the risk of cognitive decline in PD. In a longitudinal study of 392 patients with PD who were cognitively intact at baseline, a higher percentage of males than females ultimately fulfilled criteria for MCI or PDD [26].

Genetic factors — Although the majority of cases of PD appear to be sporadic, monogenetic forms of PD are increasingly recognized, some of which often involve early or severe cognitive changes. Examples include PD associated with mutations in the glucocerebrosidase (GBA) gene [27-30] and some forms of alpha-synuclein (SNCA) associated PD [31-33]. By contrast, dementia is an uncommon feature of PD associated with parkin (PARK2) mutations [34]. (See "Epidemiology, pathogenesis, and genetics of Parkinson disease", section on 'Genetics'.)

There may also be genetic risk factors for the development of dementia in patients with sporadic PD [4].

●Both the epsilon 2 (ε2) and epsilon 4 (ε4) alleles of the apolipoprotein E (APOE) gene have been implicated as possible risk factors for PDD [35-38]. As an example, in a prospective cohort study of 212 patients with PD, the presence of the ε4 allele was associated with more rapid cognitive decline [39]. However, other studies and meta-analyses have found no or only modest associations between PDD and alleles of the APOE gene [40,41]. In AD, APOE ε4 is well established as a risk factor, whereas APOE ε2 has a protective effect. APOE ε4 was found to be associated with the development of PDD in one study; the authors posited that the gene may have a greater effect on the severity of dementia than on its onset [42]. Another study found that this gene was associated with a steeper decline in several measures of cognition in PD [43]. (See "Genetics of Alzheimer disease", section on 'Apolipoprotein E'.)

●Allelic variation in the gene encoding microtubule-associated protein tau (MAPT) appears to affect susceptibility as well. The genotype H1/H2 has been implicated in the development of PDD [44,45]. In one cohort of 126 patients with PD, the MAPT H1/H1 genotype was strongly associated with incident dementia (OR = 12.1) [44]. In a subsequent study, this haplotype was noted to have a specific association with declining memory, but not the overall rate of cognitive decline [39]. Similarly, a high catechol-O-methyl transferase (COMT) activity haplotype has been found to be associated with a higher risk of developing cognitive decline in PD [46].

●A phosphatidylinositol binding clathrin assembly protein (PICALM) polymorphism that is a known susceptibility gene for AD has also been found to be associated with cognitive impairment in PD [47].

PATHOPHYSIOLOGY

Neuropathology — The anatomic and pathologic basis of PD dementia (PDD) is not fully understood and is likely heterogeneous. Historically, the dementia in PD was often attributed to coexisting Alzheimer or vascular pathology. However, neuropathologic studies have found that the degree of Lewy body pathology (Lewy bodies and Lewy neurites) in the cortex and other areas correlates better with cognitive decline and dementia than does the degree of Alzheimer pathology, which may be relatively modest in these patients [48-54].

Lewy bodies constitute the pathologic hallmark of PD, and to some extent there is a relatively predictable neuroanatomic spread of Lewy body pathology in PD that correlates with clinical dementia. Lewy body pathology is initially most prominent in the olfactory system and lower brainstem, then progresses to involve the midbrain structures. In later stages, other brain structures are involved, including the cortex (figure 1). The neuropathologic stage of PD correlates with the severity of both motor parkinsonism and dementia [55]. However, not all patients with PD and dementia have cortical Lewy body pathology [56]. (See "Epidemiology, pathogenesis, and genetics of Parkinson disease", section on 'Pathology'.)

The density of cortical Lewy body pathology has also been implicated in the degree of cognitive impairment [48-54]. In one study, Lewy body density in the entorhinal cortex and anterior cingulate accounted for up to one-third of the variability in clinical dementia severity [50]. In another study, the severity of Lewy body pathology in the basal forebrain and hippocampus distinguished PD patients with and without dementia [57].

Important exceptions are noted; some individuals have significant cognitive decline in the absence of cortical Lewy pathology, while others have normal cognitive function in the presence of widespread cortical pathology [55,58]. A few studies have found that reduced amyloid beta (1 to 42) in the cerebrospinal fluid is associated with cognitive decline in patients with PD, as it is in other patient groups [59-61]. Given the substantial prevalence of both Alzheimer disease (AD) and PD, some patients with PD have cognitive decline that is attributable to or exacerbated by pathologic features of AD such as neurofibrillary tangles and beta-amyloid neuritic plaques [54]. (See "Mild cognitive impairment: Prognosis and treatment", section on 'CSF biomarkers' and "Clinical features and diagnosis of Alzheimer disease", section on 'Other laboratory testing'.)

Magnetic resonance imaging (MRI) and neuropathologic studies demonstrate more prominent global brain atrophy in PD patients with dementia than those without [62-65]. By contrast, patients with PD without dementia have rates of brain atrophy similar to controls. MRI studies have found that atrophy in patients with PDD is most prominent in limbic and paralimbic structures, including the hippocampus and the anterior cingulate gyrus [63,66]. Another neuroimaging study found that patients with PDD have more white matter hyperintensities in the cholinergic pathways compared with cognitively intact patients with PD [67].

Whether the neuropathology of PDD differs from that seen in dementia with Lewy bodies (DLB), or whether both conditions exist on a continuum is not clear; there are few comparative neuropathologic studies [68,69]. Cortical Lewy bodies and Lewy neurites appear to substantially contribute to the pathologic substrate for dementia in both conditions [68,70,71]. One small study did find that neuronal loss in the substantia nigra was more significant in PDD than in DLB; other features including cortical Lewy pathology and Alzheimer pathology did not differ in PDD and DLB [72]. By contrast, an evaluation of brain pathology in 57 patients with DLB or PDD found that a longer duration of parkinsonism prior to dementia was associated with more pronounced cortical cholinergic deficits and less severe cortical Lewy body pathology [73].

Biochemical correlates — There is mounting evidence that cholinergic deficit is a consistent biochemical correlate of cognitive dysfunction in PD:

●Loss of cholinergic neurons in the nucleus basalis of Meynert and decreased cholinergic activity in the cortex appear to be at least as significant in PDD as in AD, if not more so [74-78].

●Anticholinergic drugs often exacerbate cognitive deficits in PD patients [79]. In addition, in one observational study, prolonged use of these agents in early-stage PD increased the risk of subsequent dementia [80].

●Cholinesterase inhibitors improve cognitive function modestly in PDD. (See 'Cholinesterase inhibitors' below.)

By contrast, dopaminergic loss, while central to the pathogenesis of motor symptoms, is not consistently linked with the degree of cognitive dysfunction in patients with PD [81]. While some neuroimaging studies have implicated frontostriatal dopaminergic pathways [82], dopaminergic medication has mild, variable effects on cognitive performance; it may improve short-term memory early in the disease but not in more advanced patients [83,84]. While primary dopaminergic influence on cognition may be minimal, one study has shown that dopaminergic and cholinergic degenerations exhibit both independent and, possibly more importantly, interactive contributions to cognitive impairment in PD [85]. (See 'Treatment' below.)

Other neurotransmitter systems may be involved in producing visual hallucinations. A positron emission tomography study found increased serotoninergic type 2A receptor binding in PD patients with visual hallucinations compared with those without hallucinations [86]. A subsequent study found an increase in the number of serotonergic type 2A receptors in the inferolateral temporal cortex of PD patients with hallucinations [87].

CLINICAL FEATURES

Cognitive impairment — Cognitive impairment in PD has a heterogeneous cognitive profile that is different from that of Alzheimer disease (AD) [4,88,89]. The general pattern is one of executive dysfunction and impaired visuospatial function, with less prominent memory deficits and relatively preserved language function (table 1) [12,88,90,91].

Executive dysfunction is often present early in the disease course and is manifested by deficiencies in set shifting, attention, and planning [92]. Tests of face recognition, one measure of visuospatial function, are impaired early in the course of PD [88]. Other measures of visuospatial function become impaired in more severe PD and are more impaired in those with, rather than without, dementia. All of these deficits may impair higher-level functioning well before patients meet criteria for dementia [93,94].

Memory deficits, while less prominent than in AD, do occur in PD dementia (PDD) but appear to be related to retrieval of learned information, which is improved by cuing. Conspicuously absent in PDD are aphasia, apraxia, and severe memory loss, features that are more common in AD [6,7,95-99]. (See "Clinical features and diagnosis of Alzheimer disease", section on 'Cardinal symptoms'.)

Comparison of neuropsychological test profiles among patients with dementia with Lewy bodies (DLB), AD, and PDD reveals no differences between DLB and PDD [100,101]. AD patients are more likely to have significant impairment on memory testing, while patients with PDD and DLB are more likely to have visuoperceptive, visuoconstructive, and attentional deficits [100,102].

Neuropsychiatric symptoms — A variety of neuropsychiatric and behavioral symptoms may occur in patients with PD; while many such symptoms can occur in PD patients without dementia, they are increasingly common in patients with more severe cognitive impairment.

Visual hallucinations are common in PD with and without dementia and can be identified in as many as 50 percent of all PD patients [103,104]. Complex visual hallucinations (eg, animals, people) are the most common type, but other visual disturbances can occur, including sensations of presence, sensations of movement in the periphery, and illusionary experiences [105]. Auditory, tactile, and olfactory hallucinations can also occur but are less common.

The presence of visual hallucinations, even mild illusory phenomena, is associated strongly with cognitive dysfunction and to a lesser extent with rigidity and autonomic dysfunction [106,107]. A variety of antiparkinson drugs, most notably anticholinergic agents, dopaminergic agents, and amantadine, can exacerbate visual hallucinations. In PD patients with normal cognition, those with hallucinations are more likely to develop dementia than are patients without this symptom [6,8,17,108].

Other manifestations of psychosis in PD include delusions, often paranoid and related to spousal infidelity and persecution. These also may be exacerbated by antiparkinson drugs. The neuropsychiatric features of PD are discussed in more detail separately. (See "Management of nonmotor symptoms in Parkinson disease", section on 'Psychosis'.)

PD patients with and without dementia are also subject to depression, anxiety, and sleep disorders [104,105]. Depression occurs in 30 to 40 percent and correlates poorly with degree of motor impairment, but may be predictive of cognitive decline [69,109]. (See "Clinical manifestations of Parkinson disease", section on 'Mood disorders'.)

Sleep disorders include sleep fragmentation, nightmares, and rapid eye movement (REM) sleep behavior disorder (RBD). The last is a parasomnia characterized by vivid dreams in REM sleep without the usual accompanying muscle atonia. This causes individuals to "act out" their dreams, especially when they are vivid or frightening. RBD is generally accepted to be a predictor for development of an alpha-synucleinopathy such as PD or DLB, often appearing years before the onset of overt neurologic or cognitive symptoms [110]. Rates of mild cognitive impairment (MCI) are three to six times higher in PD patients with RBD compared with those without RBD, and RBD is a marker for earlier onset of dementia [105,111-113]. (See "Rapid eye movement sleep behavior disorder".)

Excessive daytime sleepiness (EDS) is also common in patients with PD, both with and without dementia, although the latter has been identified as a risk factor. Some patients have sudden sleep attacks. Both symptoms pose risks for patients who drive. (See "Clinical manifestations of Parkinson disease", section on 'Excessive daytime sleepiness' and "Evaluation and treatment of insomnia, daytime sleepiness, and other sleep disorders in Parkinson disease", section on 'Excessive daytime sleepiness'.)

Cardinal motor features — Patients with PDD have core motor features of PD that include (table 2):

●Bradykinesia and akinesia

●Rigidity

●Resting tremor

●Postural instability

Resting tremor is more specific to PD than are other parkinsonian features; however, PD patients with tremor as their predominant motor symptom are less likely to develop cognitive impairment than are those with more prominent postural instability and gait impairment [114-116]. (See "Clinical manifestations of Parkinson disease", section on 'Cardinal features'.)

Other features — Other signs of neurologic impairment in patients with and without cognitive impairment include autonomic dysfunction, olfactory dysfunction, pain and sensory disturbances, and mood disorders. These are summarized in the tables (table 2 and table 3) and discussed in more detail elsewhere. (See "Clinical manifestations of Parkinson disease".)

Clinical course — The severity of cognitive impairment tends to progress in most patients over the course of the disease, although reported rates of conversion from MCI to dementia are quite variable [95,96].

While most studies suggest that early evidence of cognitive impairment in PD identifies a higher risk of future dementia [6,7,97,117], the prognosis is somewhat uncertain. In a study of PD patients diagnosed within the past 3.5 years, 41 percent had MCI based on Montreal Cognitive Assessment (MoCA) testing, and an additional 21 percent converted from normal cognition to MCI after an additional 18 months of follow-up; 5 percent of patients progressed from MCI to dementia over the same time period [99]. In another study of patients with a longer disease history (mean disease duration five years) and normal baseline cognition, all patients who developed incident MCI over the course of the study period converted to dementia within the next five years [118]. However, in a more recent five-year study, only 29 percent of initially cognitively normal patients developing MCI went on to dementia; 28 percent of patients with baseline MCI and 24 percent of those with incident MCI reverted to normal cognition at study end [119].

Frank dementia typically occurs late in the clinical course of PD, whereas it is often one of the presenting features of DLB. Similarly, hallucinations are a late-appearing consequence of PD or PDD but are seen early in the course of DLB and may be among the presenting features of the illness. (See 'Dementia with Lewy bodies' below.)

DIFFERENTIAL DIAGNOSIS — PD dementia (PDD) is one of a number of conditions that include dementia and parkinsonism as prominent features.

Dementia with Lewy bodies — The differentiation of PDD and dementia with Lewy bodies (DLB) is somewhat arbitrary. In PDD, dementia occurs in the setting of well-established parkinsonism, while in DLB, dementia usually occurs before, at the same time as, or very shortly after the development of parkinsonian signs. If parkinsonism is present for more than one year before the onset of dementia, it is officially classified as PDD. This "one-year rule" is somewhat arbitrary; the length of time that parkinsonism precedes other symptoms in otherwise similar patients does not correlate with pathologic differences [120,121].

Other features that may help distinguish between PDD and DLB are a faster clinical decline, earlier onset of hallucinations and delusions, and decreased levodopa responsivity for DLB compared with PDD [122]. Parkinsonian features are more likely to be bilaterally asymmetric and more severe in PDD according to most, although not all, studies [123]. Tremor is more common in PDD than DLB [124]. Significant fluctuations in cognition are common in DLB, but rarely occur in PDD.

In one study, volumetric analysis of MRI scans found that patients with DLB had more pronounced cortical atrophy than did patients with PDD despite having similar dementia severity [125]. Another study also found that patients with PDD and DLB with similar dementia severity could be distinguished by patterns of fractional anisotropy on diffuse tensor imaging MRI [126]. However, it seems unlikely that these observations are sufficiently sensitive and specific to aid in diagnosis of DLB versus PDD in individual patients [127].

Despite these observed clinical trends, no individual symptom characteristic or test finding reliably distinguishes the motor parkinsonism of PD versus DLB. It remains uncertain even whether these are distinct disorders (versus the onset of clinical symptoms of the same underlying pathology at different times). Both disorders are characterized pathologically as an alpha-synucleinopathy. (See "Clinical features and diagnosis of dementia with Lewy bodies".)

Progressive supranuclear palsy — Progressive supranuclear palsy (PSP) is a rare syndrome that can mimic PDD early on. Distinctive early features of this disorder include vertical supranuclear gaze palsy and prominent postural instability with falls [128,129]. The response to levodopa is typically poor, but approximately 20 percent of patients may have some improvement with L-dopa in early stages of the disease [128]. Bradykinesia and rigidity are typically symmetric in onset [130]. Behavioral changes including apathy, disinhibition, dysphoria, and anxiety are common [131]. (See "Diagnosis and differential diagnosis of Parkinson disease", section on 'Progressive supranuclear palsy'.)

Multiple system atrophy — An umbrella term for olivopontocerebellar atrophy, striatonigral degeneration, and Shy-Drager syndrome, multiple system atrophy (MSA) commonly presents with parkinsonism. Other features can include dysautonomia, cerebellar ataxia, and corticospinal tract deficits.

The prominence of these manifestations and the symmetry of onset, absence of tremor, and poor response to levodopa suggest this diagnosis rather than PDD [132]. Traditionally, the dementia of MSA has been thought to be milder than that seen in PSP or corticobasal degeneration (CBD) [133]; however, a large prospective cohort of patients with PSP and MSA found that dementia, while slightly less common in MSA, was no less severe [134]. (See "Multiple system atrophy: Clinical features and diagnosis".)

Corticobasal degeneration — Patients with this condition (CBD; also referred to as corticobasal syndrome [CBS] when neuropathologic confirmation is lacking) can manifest asymmetric parkinsonism, including bradykinesia, rigidity, and postural instability. More distinctive features can include ideomotor apraxia, alien limb phenomenon, aphasia, and loss of cortical sensory function [135]. Absence of tremor and lack of levodopa response are typical for CBD and help to distinguish it from PDD. (See "Corticobasal degeneration".)

Alzheimer disease — Although subtle extrapyramidal signs may be present in early stages of Alzheimer disease (AD), clinically evident parkinsonism does not develop until late stage AD [136]. In most cases, the relative timing of the appearance of dementia and parkinsonism is obvious, such that this feature, in itself, does not confuse AD and PDD.

Alternatively, AD may develop in a patient with PD, as the two disorders are not rare. This might be hard to distinguish from PDD early on, but the ultimate appearance of cortical dysfunction, such as aphasia or apraxia, or a more profound amnesic syndrome usually suggests the presence of the second dementing condition. Prominent neuropsychiatric symptoms, however, suggest that the dementia is due to PDD rather than AD [108].

Cerebrovascular disease — Infarctions in multiple vascular territories affecting periventricular and subcortical white matter, basal ganglia, and brainstem can produce dementia and a vascular parkinsonism. An abrupt onset of symptoms, predominant involvement of the lower extremities, a stepwise course, vascular risk factors, focal neurologic signs, pseudobulbar palsy, and evidence of vascular disease on neuroimaging suggest this diagnosis. (See "Etiology, clinical manifestations, and diagnosis of vascular dementia".)

Other considerations — When cognitive impairment occurs in the setting of PD, clinicians should consider possibilities other than dementia. Depression and other neuropsychiatric symptoms are common in PD and may contribute to cognitive impairment. Motor impairments of PD, particularly physical inactivity and bradyphrenia, may lead to the appearance of dementia. Similarly, patients with PD should be screened for causes of delirium that can lead to superimposed cognitive impairment, usually presenting more acutely and with altered sensorium and disrupted attention.

Patients with AD or other dementias may be treated with neuroleptic drugs associated with extrapyramidal side effects. Valproate also has been associated with a syndrome of reversible parkinsonism and cognitive decline (see "Antiseizure medications: Mechanism of action, pharmacology, and adverse effects", section on 'Valproate'). Because medication effects can be prolonged, even for a year or more, after medication discontinuation, a complete history of medication use should be elicited [132].

EVALUATION — The evaluation of a patient with suspected cognitive impairment first establishes the spectrum of cognitive and behavioral changes and provides a measure of its severity. The cornerstone of the evaluation is the clinical interview, which ideally should be supplemented by interview of an informant. The latter can be particularly helpful in determining premorbid level of functioning and pattern of decline, which the patient may not be able to describe accurately.

There are several basic tests of global cognitive function that can be performed easily at the bedside to screen for cognitive dysfunction and follow changes over time. Of the available tools, we prefer the Montreal Cognitive Assessment (MoCA), which has been found to be an accurate brief bedside test for cognitive impairment in patients with PD [137]. The MoCA is accessible online and in several languages. The Mini-Mental State Examination (MMSE) cannot be solely relied upon to detect disabling cognitive impairment in PD dementia (PDD) because it is not very sensitive to executive dysfunction, a key feature of PDD. (See 'Cognitive impairment' above.)

Neuropsychological testing is more sensitive for defining cognitive impairments than global cognitive scales and provides a more detailed assessment of the pattern of cognitive dysfunction [138]. While not required in all patients for diagnostic purposes, formal neuropsychological testing can be particularly useful when there is diagnostic uncertainty after clinical assessment, when it is important to assess for risk of future cognitive decline, or to help identify patients with patterns of cognitive dysfunction that pose risk for future loss of functional independence. (See "Mild cognitive impairment: Epidemiology, pathology, and clinical assessment", section on 'Neuropsychological testing'.)

Treatable causes of cognitive impairment and dementia should be excluded (see 'Other considerations' above). All medications should be reviewed, particularly those that have been introduced recently. Anticholinergics, tricyclic antidepressants, benzodiazepines, and dopamine agonists are among the more common medications to cause or aggravate cognitive dysfunction in patients with PD. The evaluation also generally includes a neuroimaging study (usually MRI) and basic laboratory evaluations (eg, vitamin B12 level and thyroid function tests). This topic is discussed in more detail elsewhere. (See "Evaluation of cognitive impairment and dementia".)

Because of the frequent comorbidity of depression in PD, screening for depression as an alternative cause or a contributor to cognitive impairment is recommended. The Beck Depression Inventory is available only by license, requiring a fee. The Hamilton Depression Rating Scale and the Montgomery-Asberg Depression Rating Scale have demonstrated utility in this setting [139-142] and are available in the public domain. The Patient Health Questionnaire (PHQ-9) is another questionnaire for depression screening that has been validated in the general population and is also available in the public domain (table 4). (See "Screening for depression in adults".)

DIAGNOSIS — Cognitive impairment in PD exists on a continuum of severity. Based on the extent to which it interferes with daily activities, it is generally divided into two major categories: mild cognitive impairment (MCI) and PD dementia (PDD). MCI and dementia in patients with PD are clinical diagnoses that should be suspected in patients with a decline in cognitive abilities that is interfering with daily function (for PDD).

Both diagnoses are contingent upon established parkinsonism (of at least one year) and the exclusion of other diagnoses. (See 'Differential diagnosis' above.)

There are no specific findings on neuroimaging, neuropsychological testing, or laboratory results that are useful in the positive diagnosis of PDD.

Mild cognitive impairment — MCI appears to be prevalent in patients with PD. In one meta-analysis of 41 studies (7053 patients with PD), the prevalence of MCI was estimated to be 40 percent [143].

Clinical criteria for the diagnosis MCI in patients with PD were first proposed by an international consensus panel in 2012 [98] and have since been validated. A diagnosis of PD-MCI requires all of the following [98]:

●A firmly established diagnosis of PD (see "Diagnosis and differential diagnosis of Parkinson disease", section on 'Diagnosis')

●Gradual decline, in the context of established PD, in cognitive ability reported by either the patient or informant, or observed by the clinician

●Cognitive deficits on either formal neuropsychological testing or a scale of global cognitive abilities

●Cognitive deficits are not sufficient to interfere with functional independence, although subtle difficulties on complex functional tasks may be present

●Other primary explanations for cognitive impairment (eg, delirium, stroke, major depression, metabolic abnormalities, adverse effects of medication, or head trauma) have been excluded

●Other PD-associated comorbid conditions (eg, motor impairment or severe anxiety, depression, excessive daytime sleepiness [EDS], or psychosis) have not significantly influenced cognitive testing, in the opinion of the clinician

Parkinson disease dementia — The core features of PDD include the following [91]:

●A firmly established diagnosis of PD (see "Diagnosis and differential diagnosis of Parkinson disease", section on 'Diagnosis')

●A dementia syndrome with insidious onset and slow progression, developing in the context of established PD and diagnosed by history, clinical, and mental examination, defined as:

•Impairment in more than one cognitive domain (attention, executive function, visuospatial function, memory) (see 'Cognitive impairment' above)

•Decline from a premorbid level

•Deficits severe enough to impair daily life (social, occupational, or personal care), independent of the impairment ascribable to motor or autonomic symptoms

Behavioral features such as apathy, changes in personality or mood, hallucinations, delusions, and EDS are supportive of the diagnosis but not required [91].

TREATMENT — The treatment of PD dementia (PDD) is symptomatic. No therapies have been shown to modify the course of the disease or influence prognosis.

Cognitive impairment — We initiate treatment trials of cholinesterase inhibitors and/or memantine in a stepwise fashion in patients with PDD, monitoring for side effects and tapering if no improvement or side effects develop.

Cholinesterase inhibitors — We suggest the use of cholinesterase inhibitors in patients with PDD. Most, but not all, studies of cholinesterase inhibitors in PDD have noted a mild to moderate benefit but an increased risk of side effects, including worsened tremor and nausea [144-154]:

●Rivastigmine was evaluated in a 24-week, double-blind, placebo-controlled study of 501 patients with mild to moderate PDD and was found to result in moderate improvement in dementia, mean improvement of 2.1 points on the Alzheimer Disease Assessment Scale-Cognitive Subscale (ADAS-cog) score compared with 0.7-point decline in the placebo-treated group [145]. Clinically meaningful improvements were seen in 20 and 14.5 percent in the treatment and placebo groups, respectively, while clinically meaningful worsening was observed in 13 and 23 percent. This suggests that overall, 15 percent of patients benefited from treatment [146].

●Donepezil therapy was evaluated in a randomized study of 550 patients with PDD [152]. After 24 weeks, active therapy was associated with significant benefit on the ADAS-cog score but not when the analysis was performed using the predefined statistical model that included a treatment-by-country interaction term. Donepezil also appeared to be associated with benefit by other, although not all, primary and secondary outcome measures, including measures of executive function and attention.

Another potential benefit of cholinesterase inhibitors in PDD is improvement in neuropsychiatric symptoms, such as hallucinations. While this benefit has been inconsistently observed in studies, increased dropouts due to worsened tremor, nausea, and vomiting were also reported [145,150,151]. (See "Management of neuropsychiatric symptoms of dementia", section on 'Antidementia drugs'.)

Based on the available data showing a benefit for cholinesterase inhibitors, albeit modest, we suggest their use in PDD if the patient does not experience intolerable side effects. We generally administer these drugs for a trial period of two to three months and then review the patient's response with family or caregivers. Treatment is continued if improvement is noted either on bedside testing or by the family or caregiver. We taper patients off treatment if there has been no improvement or if there are intolerable side effects. When cholinesterase inhibitors are discontinued, they should not be abruptly terminated, if at all possible, but rather tapered to avoid sudden cognitive and behavioral worsening [155]. A more detailed discussion reviewing the different formulations, the administration, and the side effects of cholinesterase inhibitors in dementia is found separately. (See "Cholinesterase inhibitors in the treatment of dementia".)

Memantine — Memantine has reported efficacy in moderate to severe Alzheimer disease (AD) and in vascular dementia. One 24-week randomized controlled study of 72 patients with either dementia with Lewy bodies (DLB) or PDD found that patients treated with memantine performed better on the primary outcome assessment measure, the clinical global impression of change, but not on other secondary outcome measures [156]. In a more recent, 24-week randomized controlled study, DLB patients, but not PDD patients, were improved on the same outcome measure [157]. Memantine was well tolerated in these trials and in another shorter study of patients with PDD [158]. However, hallucinations and worsened neuropsychiatric symptoms have occasionally been reported with the use of memantine, suggesting some caution with its use in PDD [159-161].

Psychosis — Visual hallucinations and delusions are a frequent manifestation of PD, particularly in advanced stages of the disease, and patients with PDD may be more sensitive to the neuropsychiatric side effects of antiparkinsonian medications. (See "Management of nonmotor symptoms in Parkinson disease", section on 'Psychosis'.)

The management of psychosis in patients with PD may involve adjusting antiparkinsonian drugs. Some patients with more severe symptoms may require antipsychotic medications, which require extra caution in patients with PD. The treatment of psychosis and hallucinations in patients with PD is discussed separately. (See "Management of nonmotor symptoms in Parkinson disease", section on 'Psychosis'.)

Motor parkinsonism — With some exceptions, the treatment of motor parkinsonian symptoms is similar in PD with and without dementia. (See "Initial pharmacologic treatment of Parkinson disease".)

One caveat is that patients with PDD may be particularly susceptible to the neuropsychiatric side effects of dopaminergic medications; these may be dose limiting and/or require concomitant use of antipsychotic agents. Observational studies suggest that L-dopa does not adversely affect cognition overall [162]; however, in other studies, dopaminergic therapy has been shown to have beneficial effects on some specific cognitive measures and detrimental effects on others [163,164]. Individual baseline cognition and learning style may modulate the effect of dopamine as well [165].

Anticholinergic agents frequently exacerbate cognitive impairment and are generally avoided in patients with PDD. (See "Initial pharmacologic treatment of Parkinson disease", section on 'Anticholinergics'.)

In a study of 29 PD patients without dementia, a program of anabolic and aerobic exercise resulted in an improvement in executive function [166]. The efficacy of exercise in improving cognition in PD is yet to be proven.

Patients with PDD are generally excluded from consideration for deep brain stimulation (DBS) therapy because of poor outcomes. As an example, in a study of 41 patients evaluated after suboptimal response to DBS, 20 percent of these patients had preoperative dementia [167]. On the other hand, in PD patients with mild or no dementia, accumulated evidence suggests that bilateral subthalamic DBS can result in small declines in measures of executive function and a moderate decline in verbal fluency [168]. A review of nine studies presenting head-to-head comparisons of subthalamic DBS with globus pallidus DBS noted that in two of the nine reports, patients undergoing subthalamic DBS fared slightly better than those receiving pallidal surgery on measures of attention and memory, yet quality of life was similar in the two groups [169].

PROGNOSIS AND COUNSELING — Dementia in PD is associated with reduced patient and caregiver quality of life, reduced survival, increased risks of nursing home admission, and other neuropsychiatric symptoms [6,19,35,139,170-173]. The burden of comorbidities is greater in these patients, contributing to a higher frequency of emergency department visits and hospitalizations for diagnoses unrelated to PD [174]. Among a cohort of 180 patients with PD who did not have dementia at baseline, incident dementia was associated with a twofold increase in mortality over a mean four-year follow-up, even after controlling for severity of motor symptoms [171].

Cognitive impairment in patients with PD can affect decision-making capacity. While brief tests of cognitive function such as the Montreal Cognitive Assessment (MoCA) can be useful in predicting the likelihood of impaired capacity, they do not substitute for a formal assessment of capacity, particularly when high-risk decisions are being contemplated. (See "Assessment of decision-making capacity in adults".)

As dementia progresses, patients require greater oversight. A variety of safety concerns arise in a relatively predictable manner, and addressing these issues proactively with patients and caregivers can prevent serious incidents. Driving safety is often one of the earlier issues to be confronted. In contrast to what many patients and caregivers may believe, driving impairment in patients with mild to moderate PD is correlated mostly with cognitive and visual deficits, rather than motor impairment [175]. These and other management issues are discussed in detail separately. (See "Management of the patient with dementia" and "Care of patients with advanced dementia", section on 'Decision-making support'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Parkinson disease".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

●Basics topics (see "Patient education: Parkinson disease (The Basics)")

●Beyond the Basics topics (see "Patient education: Dementia (including Alzheimer disease) (Beyond the Basics)" and "Patient education: Parkinson disease symptoms and diagnosis (Beyond the Basics)")

PATIENT PERSPECTIVE TOPIC — Patient perspectives are provided for selected disorders to help clinicians better understand the patient experience and patient concerns. These narratives may offer insights into patient values and preferences not included in other UpToDate topics. (See "Patient perspective: Parkinson disease".)

SUMMARY AND RECOMMENDATIONS

●Epidemiology – Cognitive dysfunction and dementia are common in Parkinson disease (PD). The risk of dementia in patients with PD increases with age of onset, age of the patient, duration, and severity of the illness. Additional risk factors include the presence of rapid eye movement (REM) sleep behavior disorder (RBD), autonomic dysfunction, and abnormal visual color discrimination. (See 'Epidemiology' above.)

●Neuropathology – Neuropathologic studies suggest that Lewy body pathology rather than coincident Alzheimer or cerebrovascular disease is responsible for dementia in most patients with PD. (See 'Pathophysiology' above.)

●Clinical features – The cognitive dysfunction of PD dementia (PDD) is distinct from Alzheimer disease (AD). With PDD, memory impairment is less prominent early on, while executive dysfunction and visual spatial impairments are features that may be apparent and functionally limiting before the patient meets criteria for dementia. (See 'Cognitive impairment' above.)

●Differential diagnosis – Other disorders that produce dementia and parkinsonism include dementia with Lewy bodies (DLB), progressive supranuclear palsy (PSP), multiple system atrophy (MSA), and corticobasal degeneration (CBD). PDD is distinguished from DLB by the onset of dementia in the setting of well-established parkinsonism of at least one year's duration. (See 'Differential diagnosis' above.)

●Evaluation – The evaluation of a patient with suspected cognitive impairment first establishes the spectrum of cognitive and behavioral changes and provides a measure of its severity. The cornerstone of the evaluation is the clinical interview, which ideally should be supplemented by interview of an informant. Neuropsychological testing may aid in the diagnosis of dementia; laboratory studies and neuroimaging are performed to exclude other conditions. The Mini-Mental State Examination (MMSE) cannot be solely relied upon to detect disabling cognitive impairment in PDD because it is not very sensitive to executive dysfunction. (See 'Evaluation' above.)

●Diagnosis – The diagnosis of PD is discussed separately. (See "Diagnosis and differential diagnosis of Parkinson disease".)

Cognitive impairment in PD exists on a continuum of severity. Based on the extent to which it interferes with daily activities, it is generally divided into two major categories: mild cognitive impairment (MCI) and PDD. Both MCI and dementia are clinical diagnoses in patients with firmly established PD of at least one year's duration that should be suspected in patients with a decline in cognitive abilities that is interfering with daily function (for PDD). (See 'Diagnosis' above.)

●Treatment

•Cognitive impairment – We suggest the use of cholinesterase inhibitors in patients with PDD (Grade 2C). These appear to confer a modest benefit for cognition in patients with PDD; evidence for improved neuropsychiatric symptoms is less convincing. Treatment response should be monitored regularly, and therapy should be tapered off if there are no observed benefits or if side effects are intolerable. (See 'Cholinesterase inhibitors' above.)

•Psychosis – Visual hallucinations and delusions are a frequent manifestation of PD, particularly in advanced stages of the disease, and patients with PDD may be more sensitive to the neuropsychiatric side effects of antiparkinsonian medications. The management of psychosis in patients with PD is discussed separately. (See "Management of nonmotor symptoms in Parkinson disease", section on 'Psychosis'.)

•Motor parkinsonism – The treatment of motor parkinsonism is similar to that for the patient with PD without dementia. An exception is that dementia is a relative contraindication for deep brain stimulation (DBS) therapy. (See 'Treatment' above.)

  1. Friedman JH. Dementia with Lewy Bodies and Parkinson Disease Dementia: It is the Same Disease! Parkinsonism Relat Disord 2018; 46 Suppl 1:S6.
  2. Jellinger KA, Korczyn AD. Are dementia with Lewy bodies and Parkinson's disease dementia the same disease? BMC Med 2018; 16:34.
  3. Aarsland D, Zaccai J, Brayne C. A systematic review of prevalence studies of dementia in Parkinson's disease. Mov Disord 2005; 20:1255.
  4. Svenningsson P, Westman E, Ballard C, Aarsland D. Cognitive impairment in patients with Parkinson's disease: diagnosis, biomarkers, and treatment. Lancet Neurol 2012; 11:697.
  5. Cummings JL. Intellectual impairment in Parkinson's disease: clinical, pathologic, and biochemical correlates. J Geriatr Psychiatry Neurol 1988; 1:24.
  6. Hobson P, Meara J. Risk and incidence of dementia in a cohort of older subjects with Parkinson's disease in the United Kingdom. Mov Disord 2004; 19:1043.
  7. Aarsland D, Andersen K, Larsen JP, et al. Risk of dementia in Parkinson's disease: a community-based, prospective study. Neurology 2001; 56:730.
  8. Aarsland D, Andersen K, Larsen JP, et al. Prevalence and characteristics of dementia in Parkinson disease: an 8-year prospective study. Arch Neurol 2003; 60:387.
  9. Buter TC, van den Hout A, Matthews FE, et al. Dementia and survival in Parkinson disease: a 12-year population study. Neurology 2008; 70:1017.
  10. Hely MA, Reid WG, Adena MA, et al. The Sydney multicenter study of Parkinson's disease: the inevitability of dementia at 20 years. Mov Disord 2008; 23:837.
  11. Louis ED, Schupf N, Manly J, et al. Association between mild parkinsonian signs and mild cognitive impairment in a community. Neurology 2005; 64:1157.
  12. Muslimovic D, Post B, Speelman JD, Schmand B. Cognitive profile of patients with newly diagnosed Parkinson disease. Neurology 2005; 65:1239.
  13. Foltynie T, Brayne CE, Robbins TW, Barker RA. The cognitive ability of an incident cohort of Parkinson's patients in the UK. The CamPaIGN study. Brain 2004; 127:550.
  14. Poletti M, Frosini D, Pagni C, et al. Mild cognitive impairment and cognitive-motor relationships in newly diagnosed drug-naive patients with Parkinson's disease. J Neurol Neurosurg Psychiatry 2012; 83:601.
  15. Weintraub D, Simuni T, Caspell-Garcia C, et al. Cognitive performance and neuropsychiatric symptoms in early, untreated Parkinson's disease. Mov Disord 2015; 30:919.
  16. Mayeux R, Denaro J, Hemenegildo N, et al. A population-based investigation of Parkinson's disease with and without dementia. Relationship to age and gender. Arch Neurol 1992; 49:492.
  17. Stern Y, Marder K, Tang MX, Mayeux R. Antecedent clinical features associated with dementia in Parkinson's disease. Neurology 1993; 43:1690.
  18. Hughes TA, Ross HF, Musa S, et al. A 10-year study of the incidence of and factors predicting dementia in Parkinson's disease. Neurology 2000; 54:1596.
  19. Reid WG, Hely MA, Morris JG, et al. A longitudinal of Parkinson's disease: clinical and neuropsychological correlates of dementia. J Clin Neurosci 1996; 3:327.
  20. Levy G, Schupf N, Tang MX, et al. Combined effect of age and severity on the risk of dementia in Parkinson's disease. Ann Neurol 2002; 51:722.
  21. Schrag A, Siddiqui UF, Anastasiou Z, et al. Clinical variables and biomarkers in prediction of cognitive impairment in patients with newly diagnosed Parkinson's disease: a cohort study. Lancet Neurol 2017; 16:66.
  22. Hussain MW, Camicioli R. Nonmotor Symptoms of Parkinson's Disease as Predictors of Dementia. Can J Neurol Sci 2018; 45:97.
  23. Lin YQ, Chen SD. RBD: a red flag for cognitive impairment in Parkinson's disease? Sleep Med 2018; 44:38.
  24. Anang JB, Gagnon JF, Bertrand JA, et al. Predictors of dementia in Parkinson disease: a prospective cohort study. Neurology 2014; 83:1253.
  25. Darweesh SKL, Wolters FJ, Postuma RB, et al. Association Between Poor Cognitive Functioning and Risk of Incident Parkinsonism: The Rotterdam Study. JAMA Neurol 2017; 74:1431.
  26. Bakeberg MC, Gorecki AM, Kenna JE, et al. Differential effects of sex on longitudinal patterns of cognitive decline in Parkinson's disease. J Neurol 2021; 268:1903.
  27. Alcalay RN, Caccappolo E, Mejia-Santana H, et al. Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study. Neurology 2012; 78:1434.
  28. Chahine LM, Qiang J, Ashbridge E, et al. Clinical and biochemical differences in patients having Parkinson disease with vs without GBA mutations. JAMA Neurol 2013; 70:852.
  29. Inzelberg R, Hassin-Baer S, Jankovic J. Genetic movement disorders in patients of Jewish ancestry. JAMA Neurol 2014; 71:1567.
  30. Liu G, Boot B, Locascio JJ, et al. Specifically neuropathic Gaucher's mutations accelerate cognitive decline in Parkinson's. Ann Neurol 2016; 80:674.
  31. Obi T, Nishioka K, Ross OA, et al. Clinicopathologic study of a SNCA gene duplication patient with Parkinson disease and dementia. Neurology 2008; 70:238.
  32. Bostantjopoulou S, Katsarou Z, Papadimitriou A, et al. Clinical features of parkinsonian patients with the alpha-synuclein (G209A) mutation. Mov Disord 2001; 16:1007.
  33. Fuchs J, Nilsson C, Kachergus J, et al. Phenotypic variation in a large Swedish pedigree due to SNCA duplication and triplication. Neurology 2007; 68:916.
  34. Grünewald A, Kasten M, Ziegler A, Klein C. Next-generation phenotyping using the parkin example: time to catch up with genetics. JAMA Neurol 2013; 70:1186.
  35. de Lau LM, Schipper CM, Hofman A, et al. Prognosis of Parkinson disease: risk of dementia and mortality: the Rotterdam Study. Arch Neurol 2005; 62:1265.
  36. Pankratz N, Byder L, Halter C, et al. Presence of an APOE4 allele results in significantly earlier onset of Parkinson's disease and a higher risk with dementia. Mov Disord 2006; 21:45.
  37. Harhangi BS, de Rijk MC, van Duijn CM, et al. APOE and the risk of PD with or without dementia in a population-based study. Neurology 2000; 54:1272.
  38. Huang X, Chen P, Kaufer DI, et al. Apolipoprotein E and dementia in Parkinson disease: a meta-analysis. Arch Neurol 2006; 63:189.
  39. Morley JF, Xie SX, Hurtig HI, et al. Genetic influences on cognitive decline in Parkinson's disease. Mov Disord 2012; 27:512.
  40. Jasinska-Myga B, Opala G, Goetz CG, et al. Apolipoprotein E gene polymorphism, total plasma cholesterol level, and Parkinson disease dementia. Arch Neurol 2007; 64:261.
  41. Williams-Gray CH, Goris A, Saiki M, et al. Apolipoprotein E genotype as a risk factor for susceptibility to and dementia in Parkinson's disease. J Neurol 2009; 256:493.
  42. Fang L, Tang BS, Fan K, et al. Alzheimer's disease susceptibility genes modify the risk of Parkinson disease and Parkinson's disease-associated cognitive impairment. Neurosci Lett 2018; 677:55.
  43. Kim R, Park S, Yoo D, et al. Impact of the apolipoprotein E ε4 allele on early Parkinson's disease progression. Parkinsonism Relat Disord 2021; 83:66.
  44. Williams-Gray CH, Evans JR, Goris A, et al. The distinct cognitive syndromes of Parkinson's disease: 5 year follow-up of the CamPaIGN cohort. Brain 2009; 132:2958.
  45. Goris A, Williams-Gray CH, Clark GR, et al. Tau and alpha-synuclein in susceptibility to, and dementia in, Parkinson's disease. Ann Neurol 2007; 62:145.
  46. Lin CH, Fan JY, Lin HI, et al. Catechol-O-methyltransferase (COMT) genetic variants are associated with cognitive decline in patients with Parkinson's disease. Parkinsonism Relat Disord 2018; 50:48.
  47. Periñán MT, Macías-García D, Labrador-Espinosa MÁ, et al. Association of PICALM with Cognitive Impairment in Parkinson's Disease. Mov Disord 2021; 36:118.
  48. Aarsland D, Perry R, Brown A, et al. Neuropathology of dementia in Parkinson's disease: a prospective, community-based study. Ann Neurol 2005; 58:773.
  49. Apaydin H, Ahlskog JE, Parisi JE, et al. Parkinson disease neuropathology: later-developing dementia and loss of the levodopa response. Arch Neurol 2002; 59:102.
  50. Kövari E, Gold G, Herrmann FR, et al. Lewy body densities in the entorhinal and anterior cingulate cortex predict cognitive deficits in Parkinson's disease. Acta Neuropathol 2003; 106:83.
  51. Edison P, Rowe CC, Rinne JO, et al. Amyloid load in Parkinson's disease dementia and Lewy body dementia measured with [11C]PIB positron emission tomography. J Neurol Neurosurg Psychiatry 2008; 79:1331.
  52. Petrou M, Bohnen NI, Müller ML, et al. Aβ-amyloid deposition in patients with Parkinson disease at risk for development of dementia. Neurology 2012; 79:1161.
  53. Kotzbauer PT, Cairns NJ, Campbell MC, et al. Pathologic accumulation of α-synuclein and Aβ in Parkinson disease patients with dementia. Arch Neurol 2012; 69:1326.
  54. Irwin DJ, White MT, Toledo JB, et al. Neuropathologic substrates of Parkinson disease dementia. Ann Neurol 2012; 72:587.
  55. Braak H, Rüb U, Jansen Steur EN, et al. Cognitive status correlates with neuropathologic stage in Parkinson disease. Neurology 2005; 64:1404.
  56. Parkkinen L, Pirttilä T, Alafuzoff I. Applicability of current staging/categorization of alpha-synuclein pathology and their clinical relevance. Acta Neuropathol 2008; 115:399.
  57. Hall H, Reyes S, Landeck N, et al. Hippocampal Lewy pathology and cholinergic dysfunction are associated with dementia in Parkinson's disease. Brain 2014; 137:2493.
  58. Colosimo C, Hughes AJ, Kilford L, Lees AJ. Lewy body cortical involvement may not always predict dementia in Parkinson's disease. J Neurol Neurosurg Psychiatry 2003; 74:852.
  59. Siderowf A, Xie SX, Hurtig H, et al. CSF amyloid {beta} 1-42 predicts cognitive decline in Parkinson disease. Neurology 2010; 75:1055.
  60. Alves G, Brønnick K, Aarsland D, et al. CSF amyloid-beta and tau proteins, and cognitive performance, in early and untreated Parkinson's disease: the Norwegian ParkWest study. J Neurol Neurosurg Psychiatry 2010; 81:1080.
  61. Alves G, Lange J, Blennow K, et al. CSF Aβ42 predicts early-onset dementia in Parkinson disease. Neurology 2014; 82:1784.
  62. Burton EJ, McKeith IG, Burn DJ, O'Brien JT. Brain atrophy rates in Parkinson's disease with and without dementia using serial magnetic resonance imaging. Mov Disord 2005; 20:1571.
  63. Nagano-Saito A, Washimi Y, Arahata Y, et al. Cerebral atrophy and its relation to cognitive impairment in Parkinson disease. Neurology 2005; 64:224.
  64. Beyer MK, Janvin CC, Larsen JP, Aarsland D. A magnetic resonance imaging study of patients with Parkinson's disease with mild cognitive impairment and dementia using voxel-based morphometry. J Neurol Neurosurg Psychiatry 2007; 78:254.
  65. Melzer TR, Watts R, MacAskill MR, et al. Grey matter atrophy in cognitively impaired Parkinson's disease. J Neurol Neurosurg Psychiatry 2012; 83:188.
  66. Carlesimo GA, Piras F, Assogna F, et al. Hippocampal abnormalities and memory deficits in Parkinson disease: a multimodal imaging study. Neurology 2012; 78:1939.
  67. Shin J, Choi S, Lee JE, et al. Subcortical white matter hyperintensities within the cholinergic pathways of Parkinson's disease patients according to cognitive status. J Neurol Neurosurg Psychiatry 2012; 83:315.
  68. Rahkonen T, Eloniemi-Sulkava U, Rissanen S, et al. Dementia with Lewy bodies according to the consensus criteria in a general population aged 75 years or older. J Neurol Neurosurg Psychiatry 2003; 74:720.
  69. McKeith IG, Galasko D, Kosaka K, et al. Consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB): report of the consortium on DLB international workshop. Neurology 1996; 47:1113.
  70. Stevens T, Livingston G, Kitchen G, et al. Islington study of dementia subtypes in the community. Br J Psychiatry 2002; 180:270.
  71. Mori H. Pathological substrate of dementia in Parkinson's disease--its relation to DLB and DLBD. Parkinsonism Relat Disord 2005; 11 Suppl 1:S41.
  72. Tsuboi Y, Dickson DW. Dementia with Lewy bodies and Parkinson's disease with dementia: are they different? Parkinsonism Relat Disord 2005; 11 Suppl 1:S47.
  73. Ballard C, Ziabreva I, Perry R, et al. Differences in neuropathologic characteristics across the Lewy body dementia spectrum. Neurology 2006; 67:1931.
  74. Perry EK, Curtis M, Dick DJ, et al. Cholinergic correlates of cognitive impairment in Parkinson's disease: comparisons with Alzheimer's disease. J Neurol Neurosurg Psychiatry 1985; 48:413.
  75. Mattila PM, Röyttä M, Lönnberg P, et al. Choline acetytransferase activity and striatal dopamine receptors in Parkinson's disease in relation to cognitive impairment. Acta Neuropathol 2001; 102:160.
  76. Bohnen NI, Kaufer DI, Ivanco LS, et al. Cortical cholinergic function is more severely affected in parkinsonian dementia than in Alzheimer disease: an in vivo positron emission tomographic study. Arch Neurol 2003; 60:1745.
  77. Bohnen NI, Kaufer DI, Hendrickson R, et al. Cognitive correlates of cortical cholinergic denervation in Parkinson's disease and parkinsonian dementia. J Neurol 2006; 253:242.
  78. Shimada H, Hirano S, Shinotoh H, et al. Mapping of brain acetylcholinesterase alterations in Lewy body disease by PET. Neurology 2009; 73:273.
  79. Ehrt U, Broich K, Larsen JP, et al. Use of drugs with anticholinergic effect and impact on cognition in Parkinson's disease: a cohort study. J Neurol Neurosurg Psychiatry 2010; 81:160.
  80. Hong CT, Chan L, Wu D, et al. Antiparkinsonism anticholinergics increase dementia risk in patients with Parkinson's disease. Parkinsonism Relat Disord 2019; 65:224.
  81. Press DZ, Mechanic DJ, Tarsy D, Manoach DS. Cognitive slowing in Parkinson's disease resolves after practice. J Neurol Neurosurg Psychiatry 2002; 73:524.
  82. Ekman U, Eriksson J, Forsgren L, et al. Functional brain activity and presynaptic dopamine uptake in patients with Parkinson's disease and mild cognitive impairment: a cross-sectional study. Lancet Neurol 2012; 11:679.
  83. Marini P, Ramat S, Ginestroni A, Paganini M. Deficit of short-term memory in newly diagnosed untreated parkinsonian patients: reversal after L-dopa therapy. Neurol Sci 2003; 24:184.
  84. Morrison CE, Borod JC, Brin MF, et al. Effects of levodopa on cognitive functioning in moderate-to-severe Parkinson's disease (MSPD). J Neural Transm (Vienna) 2004; 111:1333.
  85. Bohnen NI, Albin RL, Müller ML, et al. Frequency of cholinergic and caudate nucleus dopaminergic deficits across the predemented cognitive spectrum of Parkinson disease and evidence of interaction effects. JAMA Neurol 2015; 72:194.
  86. Ballanger B, Strafella AP, van Eimeren T, et al. Serotonin 2A receptors and visual hallucinations in Parkinson disease. Arch Neurol 2010; 67:416.
  87. Huot P, Johnston TH, Darr T, et al. Increased 5-HT2A receptors in the temporal cortex of parkinsonian patients with visual hallucinations. Mov Disord 2010; 25:1399.
  88. Levin BE, Llabre MM, Reisman S, et al. Visuospatial impairment in Parkinson's disease. Neurology 1991; 41:365.
  89. Stern Y, Richards M, Sano M, Mayeux R. Comparison of cognitive changes in patients with Alzheimer's and Parkinson's disease. Arch Neurol 1993; 50:1040.
  90. Aarsland D, Brønnick K, Larsen JP, et al. Cognitive impairment in incident, untreated Parkinson disease: the Norwegian ParkWest study. Neurology 2009; 72:1121.
  91. Emre M, Aarsland D, Brown R, et al. Clinical diagnostic criteria for dementia associated with Parkinson's disease. Mov Disord 2007; 22:1689.
  92. Raskin SA, Borod JC, Tweedy J. Neuropsychological aspects of Parkinson's disease. Neuropsychol Rev 1990; 1:185.
  93. Uc EY, Rizzo M, Anderson SW, et al. Visual dysfunction in Parkinson disease without dementia. Neurology 2005; 65:1907.
  94. Bronnick K, Ehrt U, Emre M, et al. Attentional deficits affect activities of daily living in dementia-associated with Parkinson's disease. J Neurol Neurosurg Psychiatry 2006; 77:1136.
  95. Aarsland D, Bronnick K, Williams-Gray C, et al. Mild cognitive impairment in Parkinson disease: a multicenter pooled analysis. Neurology 2010; 75:1062.
  96. Emre M. Dementia in Parkinson's disease: cause and treatment. Curr Opin Neurol 2004; 17:399.
  97. Taylor JP, Rowan EN, Lett D, et al. Poor attentional function predicts cognitive decline in patients with non-demented Parkinson's disease independent of motor phenotype. J Neurol Neurosurg Psychiatry 2008; 79:1318.
  98. Litvan I, Goldman JG, Tröster AI, et al. Diagnostic criteria for mild cognitive impairment in Parkinson's disease: Movement Disorder Society Task Force guidelines. Mov Disord 2012; 27:349.
  99. Hu MT, Szewczyk-Królikowski K, Tomlinson P, et al. Predictors of cognitive impairment in an early stage Parkinson's disease cohort. Mov Disord 2014; 29:351.
  100. Noe E, Marder K, Bell KL, et al. Comparison of dementia with Lewy bodies to Alzheimer's disease and Parkinson's disease with dementia. Mov Disord 2004; 19:60.
  101. Ballard CG, Aarsland D, McKeith I, et al. Fluctuations in attention: PD dementia vs DLB with parkinsonism. Neurology 2002; 59:1714.
  102. Bronnick K, Emre M, Lane R, et al. Profile of cognitive impairment in dementia associated with Parkinson's disease compared with Alzheimer's disease. J Neurol Neurosurg Psychiatry 2007; 78:1064.
  103. Williams DR, Lees AJ. Visual hallucinations in the diagnosis of idiopathic Parkinson's disease: a retrospective autopsy study. Lancet Neurol 2005; 4:605.
  104. Aarsland D, Brønnick K, Ehrt U, et al. Neuropsychiatric symptoms in patients with Parkinson's disease and dementia: frequency, profile and associated care giver stress. J Neurol Neurosurg Psychiatry 2007; 78:36.
  105. Aarsland D, Taylor JP, Weintraub D. Psychiatric issues in cognitive impairment. Mov Disord 2014; 29:651.
  106. Fénelon G, Mahieux F, Huon R, Ziégler M. Hallucinations in Parkinson's disease: prevalence, phenomenology and risk factors. Brain 2000; 123 ( Pt 4):733.
  107. Bejr-Kasem H, Sampedro F, Marín-Lahoz J, et al. Minor hallucinations reflect early gray matter loss and predict subjective cognitive decline in Parkinson's disease. Eur J Neurol 2021; 28:438.
  108. Galvin JE, Pollack J, Morris JC. Clinical phenotype of Parkinson disease dementia. Neurology 2006; 67:1605.
  109. Kandiah N, Narasimhalu K, Lau PN, et al. Cognitive decline in early Parkinson's disease. Mov Disord 2009; 24:605.
  110. Boeve BF, Silber MH, Ferman TJ, et al. Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder. Sleep Med 2013; 14:754.
  111. Vendette M, Gagnon JF, Décary A, et al. REM sleep behavior disorder predicts cognitive impairment in Parkinson disease without dementia. Neurology 2007; 69:1843.
  112. Gagnon JF, Vendette M, Postuma RB, et al. Mild cognitive impairment in rapid eye movement sleep behavior disorder and Parkinson's disease. Ann Neurol 2009; 66:39.
  113. Jozwiak N, Postuma RB, Montplaisir J, et al. REM Sleep Behavior Disorder and Cognitive Impairment in Parkinson's Disease. Sleep 2017; 40.
  114. Burn DJ, Rowan EN, Allan LM, et al. Motor subtype and cognitive decline in Parkinson's disease, Parkinson's disease with dementia, and dementia with Lewy bodies. J Neurol Neurosurg Psychiatry 2006; 77:585.
  115. Burn DJ, Rowan EN, Minett T, et al. Extrapyramidal features in Parkinson's disease with and without dementia and dementia with Lewy bodies: A cross-sectional comparative study. Mov Disord 2003; 18:884.
  116. Verbaan D, Marinus J, Visser M, et al. Cognitive impairment in Parkinson's disease. J Neurol Neurosurg Psychiatry 2007; 78:1182.
  117. Janvin CC, Larsen JP, Aarsland D, Hugdahl K. Subtypes of mild cognitive impairment in Parkinson's disease: progression to dementia. Mov Disord 2006; 21:1343.
  118. Pigott K, Rick J, Xie SX, et al. Longitudinal study of normal cognition in Parkinson disease. Neurology 2015; 85:1276.
  119. Pedersen KF, Larsen JP, Tysnes OB, Alves G. Natural course of mild cognitive impairment in Parkinson disease: A 5-year population-based study. Neurology 2017; 88:767.
  120. McKeith I, Mintzer J, Aarsland D, et al. Dementia with Lewy bodies. Lancet Neurol 2004; 3:19.
  121. McKeith IG, Dickson DW, Lowe J, et al. Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium. Neurology 2005; 65:1863.
  122. Molloy S, McKeith IG, O'Brien JT, Burn DJ. The role of levodopa in the management of dementia with Lewy bodies. J Neurol Neurosurg Psychiatry 2005; 76:1200.
  123. Mega MS, Masterman DL, Benson DF, et al. Dementia with Lewy bodies: reliability and validity of clinical and pathologic criteria. Neurology 1996; 47:1403.
  124. Galasko D, Katzman R, Salmon DP, Hansen L. Clinical and neuropathological findings in Lewy body dementias. Brain Cogn 1996; 31:166.
  125. Beyer MK, Larsen JP, Aarsland D. Gray matter atrophy in Parkinson disease with dementia and dementia with Lewy bodies. Neurology 2007; 69:747.
  126. Lee JE, Park HJ, Park B, et al. A comparative analysis of cognitive profiles and white-matter alterations using voxel-based diffusion tensor imaging between patients with Parkinson's disease dementia and dementia with Lewy bodies. J Neurol Neurosurg Psychiatry 2010; 81:320.
  127. Seppi K, Rascol O. Dementia with Lewy bodies and Parkinson disease with dementia: can MRI make the difference? Neurology 2007; 69:717.
  128. Litvan I, Campbell G, Mangone CA, et al. Which clinical features differentiate progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome) from related disorders? A clinicopathological study. Brain 1997; 120 ( Pt 1):65.
  129. Litvan I, Agid Y, Jankovic J, et al. Accuracy of clinical criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome). Neurology 1996; 46:922.
  130. Quinn N. Parkinsonism--recognition and differential diagnosis. BMJ 1995; 310:447.
  131. Litvan I, Mega MS, Cummings JL, Fairbanks L. Neuropsychiatric aspects of progressive supranuclear palsy. Neurology 1996; 47:1184.
  132. Christine CW, Aminoff MJ. Clinical differentiation of parkinsonian syndromes: prognostic and therapeutic relevance. Am J Med 2004; 117:412.
  133. Bak TH, Crawford LM, Hearn VC, et al. Subcortical dementia revisited: similarities and differences in cognitive function between progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and multiple system atrophy (MSA). Neurocase 2005; 11:268.
  134. Brown RG, Lacomblez L, Landwehrmeyer BG, et al. Cognitive impairment in patients with multiple system atrophy and progressive supranuclear palsy. Brain 2010; 133:2382.
  135. Armstrong MJ, Litvan I, Lang AE, et al. Criteria for the diagnosis of corticobasal degeneration. Neurology 2013; 80:496.
  136. Portet F, Scarmeas N, Cosentino S, et al. Extrapyramidal signs before and after diagnosis of incident Alzheimer disease in a prospective population study. Arch Neurol 2009; 66:1120.
  137. Dalrymple-Alford JC, MacAskill MR, Nakas CT, et al. The MoCA: well-suited screen for cognitive impairment in Parkinson disease. Neurology 2010; 75:1717.
  138. Goldman JG, Holden S, Ouyang B, et al. Diagnosing PD-MCI by MDS Task Force criteria: how many and which neuropsychological tests? Mov Disord 2015; 30:402.
  139. Miyasaki JM, Shannon K, Voon V, et al. Practice Parameter: evaluation and treatment of depression, psychosis, and dementia in Parkinson disease (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology 2006; 66:996.
  140. Leentjens AF, Verhey FR, Luijckx GJ, Troost J. The validity of the Beck Depression Inventory as a screening and diagnostic instrument for depression in patients with Parkinson's disease. Mov Disord 2000; 15:1221.
  141. Leentjens AF, Verhey FR, Lousberg R, et al. The validity of the Hamilton and Montgomery-Asberg depression rating scales as screening and diagnostic tools for depression in Parkinson's disease. Int J Geriatr Psychiatry 2000; 15:644.
  142. Naarding P, Leentjens AF, van Kooten F, Verhey FR. Disease-specific properties of the Rating Scale for Depression in patients with stroke, Alzheimer's dementia, and Parkinson's disease. J Neuropsychiatry Clin Neurosci 2002; 14:329.
  143. Baiano C, Barone P, Trojano L, Santangelo G. Prevalence and clinical aspects of mild cognitive impairment in Parkinson's disease: A meta-analysis. Mov Disord 2020; 35:45.
  144. Rolinski M, Fox C, Maidment I, McShane R. Cholinesterase inhibitors for dementia with Lewy bodies, Parkinson's disease dementia and cognitive impairment in Parkinson's disease. Cochrane Database Syst Rev 2012; :CD006504.
  145. Emre M, Aarsland D, Albanese A, et al. Rivastigmine for dementia associated with Parkinson's disease. N Engl J Med 2004; 351:2509.
  146. Maidment I, Fox C, Boustani M. Cholinesterase inhibitors for Parkinson's disease dementia. Cochrane Database Syst Rev 2006; :CD004747.
  147. Ravina B, Putt M, Siderowf A, et al. Donepezil for dementia in Parkinson's disease: a randomised, double blind, placebo controlled, crossover study. J Neurol Neurosurg Psychiatry 2005; 76:934.
  148. Aarsland D, Laake K, Larsen JP, Janvin C. Donepezil for cognitive impairment in Parkinson's disease: a randomised controlled study. J Neurol Neurosurg Psychiatry 2002; 72:708.
  149. Linazasoro G, Lasa A, Van Blercom N. Efficacy and safety of donepezil in the treatment of executive dysfunction in Parkinson disease: a pilot study. Clin Neuropharmacol 2005; 28:176.
  150. Aarsland D, Hutchinson M, Larsen JP. Cognitive, psychiatric and motor response to galantamine in Parkinson's disease with dementia. Int J Geriatr Psychiatry 2003; 18:937.
  151. Grace J, Amick MM, Friedman JH. A double-blind comparison of galantamine hydrobromide ER and placebo in Parkinson disease. J Neurol Neurosurg Psychiatry 2009; 80:18.
  152. Dubois B, Tolosa E, Katzenschlager R, et al. Donepezil in Parkinson's disease dementia: a randomized, double-blind efficacy and safety study. Mov Disord 2012; 27:1230.
  153. Wang HF, Yu JT, Tang SW, et al. Efficacy and safety of cholinesterase inhibitors and memantine in cognitive impairment in Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies: systematic review with meta-analysis and trial sequential analysis. J Neurol Neurosurg Psychiatry 2015; 86:135.
  154. Pagano G, Rengo G, Pasqualetti G, et al. Cholinesterase inhibitors for Parkinson's disease: a systematic review and meta-analysis. J Neurol Neurosurg Psychiatry 2015; 86:767.
  155. Minett TS, Thomas A, Wilkinson LM, et al. What happens when donepezil is suddenly withdrawn? An open label trial in dementia with Lewy bodies and Parkinson's disease with dementia. Int J Geriatr Psychiatry 2003; 18:988.
  156. Aarsland D, Ballard C, Walker Z, et al. Memantine in patients with Parkinson's disease dementia or dementia with Lewy bodies: a double-blind, placebo-controlled, multicentre trial. Lancet Neurol 2009; 8:613.
  157. Emre M, Tsolaki M, Bonuccelli U, et al. Memantine for patients with Parkinson's disease dementia or dementia with Lewy bodies: a randomised, double-blind, placebo-controlled trial. Lancet Neurol 2010; 9:969.
  158. Leroi I, Overshott R, Byrne EJ, et al. Randomized controlled trial of memantine in dementia associated with Parkinson's disease. Mov Disord 2009; 24:1217.
  159. Ridha BH, Josephs KA, Rossor MN. Delusions and hallucinations in dementia with Lewy bodies: worsening with memantine. Neurology 2005; 65:481.
  160. Menendez-Gonzalez M, Calatayud MT, Blazquez-Menes B. Exacerbation of Lewy bodies dementia due to memantine. J Alzheimers Dis 2005; 8:289.
  161. Monastero R, Camarda C, Pipia C, Camarda R. Visual hallucinations and agitation in Alzheimer's disease due to memantine: report of three cases. J Neurol Neurosurg Psychiatry 2007; 78:546.
  162. Molloy SA, Rowan EN, O'Brien JT, et al. Effect of levodopa on cognitive function in Parkinson's disease with and without dementia and dementia with Lewy bodies. J Neurol Neurosurg Psychiatry 2006; 77:1323.
  163. Cools R, Barker RA, Sahakian BJ, Robbins TW. Enhanced or impaired cognitive function in Parkinson's disease as a function of dopaminergic medication and task demands. Cereb Cortex 2001; 11:1136.
  164. Cools R. Dopaminergic modulation of cognitive function-implications for L-DOPA treatment in Parkinson's disease. Neurosci Biobehav Rev 2006; 30:1.
  165. Mattis PJ, Tang CC, Ma Y, et al. Network correlates of the cognitive response to levodopa in Parkinson disease. Neurology 2011; 77:858.
  166. Cruise KE, Bucks RS, Loftus AM, et al. Exercise and Parkinson's: benefits for cognition and quality of life. Acta Neurol Scand 2011; 123:13.
  167. Okun MS, Tagliati M, Pourfar M, et al. Management of referred deep brain stimulation failures: a retrospective analysis from 2 movement disorders centers. Arch Neurol 2005; 62:1250.
  168. Parsons TD, Rogers SA, Braaten AJ, et al. Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis. Lancet Neurol 2006; 5:578.
  169. Mehanna R, Bajwa JA, Fernandez H, Wagle Shukla AA. Cognitive Impact of Deep Brain Stimulation on Parkinson's Disease Patients. Parkinsons Dis 2017; 2017:3085140.
  170. Aarsland D, Larsen JP, Karlsen K, et al. Mental symptoms in Parkinson's disease are important contributors to caregiver distress. Int J Geriatr Psychiatry 1999; 14:866.
  171. Levy G, Tang MX, Louis ED, et al. The association of incident dementia with mortality in PD. Neurology 2002; 59:1708.
  172. Weintraub D, Moberg PJ, Duda JE, et al. Effect of psychiatric and other nonmotor symptoms on disability in Parkinson's disease. J Am Geriatr Soc 2004; 52:784.
  173. Aarsland D, Larsen JP, Tandberg E, Laake K. Predictors of nursing home placement in Parkinson's disease: a population-based, prospective study. J Am Geriatr Soc 2000; 48:938.
  174. Chandler JM, Nair R, Biglan K, et al. Characteristics of Parkinson's Disease in Patients with and without Cognitive Impairment. J Parkinsons Dis 2021; 11:1381.
  175. Uc EY, Rizzo M, Anderson SW, et al. Impaired navigation in drivers with Parkinson's disease. Brain 2007; 130:2433.
Topic 5089 Version 33.0

References

1 : Dementia with Lewy Bodies and Parkinson Disease Dementia: It is the Same Disease!

2 : Are dementia with Lewy bodies and Parkinson's disease dementia the same disease?

3 : A systematic review of prevalence studies of dementia in Parkinson's disease.

4 : Cognitive impairment in patients with Parkinson's disease: diagnosis, biomarkers, and treatment.

5 : Intellectual impairment in Parkinson's disease: clinical, pathologic, and biochemical correlates.

6 : Risk and incidence of dementia in a cohort of older subjects with Parkinson's disease in the United Kingdom.

7 : Risk of dementia in Parkinson's disease: a community-based, prospective study.

8 : Prevalence and characteristics of dementia in Parkinson disease: an 8-year prospective study.

9 : Dementia and survival in Parkinson disease: a 12-year population study.

10 : The Sydney multicenter study of Parkinson's disease: the inevitability of dementia at 20 years.

11 : Association between mild parkinsonian signs and mild cognitive impairment in a community.

12 : Cognitive profile of patients with newly diagnosed Parkinson disease.

13 : The cognitive ability of an incident cohort of Parkinson's patients in the UK. The CamPaIGN study.

14 : Mild cognitive impairment and cognitive-motor relationships in newly diagnosed drug-naive patients with Parkinson's disease.

15 : Cognitive performance and neuropsychiatric symptoms in early, untreated Parkinson's disease.

16 : A population-based investigation of Parkinson's disease with and without dementia. Relationship to age and gender.

17 : Antecedent clinical features associated with dementia in Parkinson's disease.

18 : A 10-year study of the incidence of and factors predicting dementia in Parkinson's disease.

19 : A longitudinal of Parkinson's disease: clinical and neuropsychological correlates of dementia.

20 : Combined effect of age and severity on the risk of dementia in Parkinson's disease.

21 : Clinical variables and biomarkers in prediction of cognitive impairment in patients with newly diagnosed Parkinson's disease: a cohort study.

22 : Nonmotor Symptoms of Parkinson's Disease as Predictors of Dementia.

23 : RBD: a red flag for cognitive impairment in Parkinson's disease?

24 : Predictors of dementia in Parkinson disease: a prospective cohort study.

25 : Association Between Poor Cognitive Functioning and Risk of Incident Parkinsonism: The Rotterdam Study.

26 : Differential effects of sex on longitudinal patterns of cognitive decline in Parkinson's disease.

27 : Cognitive performance of GBA mutation carriers with early-onset PD: the CORE-PD study.

28 : Clinical and biochemical differences in patients having Parkinson disease with vs without GBA mutations.

29 : Genetic movement disorders in patients of jewish ancestry.

30 : Specifically neuropathic Gaucher's mutations accelerate cognitive decline in Parkinson's.

31 : Clinicopathologic study of a SNCA gene duplication patient with Parkinson disease and dementia.

32 : Clinical features of parkinsonian patients with the alpha-synuclein (G209A) mutation.

33 : Phenotypic variation in a large Swedish pedigree due to SNCA duplication and triplication.

34 : Next-generation phenotyping using the parkin example: time to catch up with genetics.

35 : Prognosis of Parkinson disease: risk of dementia and mortality: the Rotterdam Study.

36 : Presence of an APOE4 allele results in significantly earlier onset of Parkinson's disease and a higher risk with dementia.

37 : APOE and the risk of PD with or without dementia in a population-based study.

38 : Apolipoprotein E and dementia in Parkinson disease: a meta-analysis.

39 : Genetic influences on cognitive decline in Parkinson's disease.

40 : Apolipoprotein E gene polymorphism, total plasma cholesterol level, and Parkinson disease dementia.

41 : Apolipoprotein E genotype as a risk factor for susceptibility to and dementia in Parkinson's disease.

42 : Alzheimer's disease susceptibility genes modify the risk of Parkinson disease and Parkinson's disease-associated cognitive impairment.

43 : Impact of the apolipoprotein Eε4 allele on early Parkinson's disease progression.

44 : The distinct cognitive syndromes of Parkinson's disease: 5 year follow-up of the CamPaIGN cohort.

45 : Tau and alpha-synuclein in susceptibility to, and dementia in, Parkinson's disease.

46 : Catechol-O-methyltransferase (COMT) genetic variants are associated with cognitive decline in patients with Parkinson's disease.

47 : Association of PICALM with Cognitive Impairment in Parkinson's Disease.

48 : Neuropathology of dementia in Parkinson's disease: a prospective, community-based study.

49 : Parkinson disease neuropathology: later-developing dementia and loss of the levodopa response.

50 : Lewy body densities in the entorhinal and anterior cingulate cortex predict cognitive deficits in Parkinson's disease.

51 : Amyloid load in Parkinson's disease dementia and Lewy body dementia measured with [11C]PIB positron emission tomography.

52 : Aβ-amyloid deposition in patients with Parkinson disease at risk for development of dementia.

53 : Pathologic accumulation ofα-synuclein and Aβin Parkinson disease patients with dementia.

54 : Neuropathologic substrates of Parkinson disease dementia.

55 : Cognitive status correlates with neuropathologic stage in Parkinson disease.

56 : Applicability of current staging/categorization of alpha-synuclein pathology and their clinical relevance.

57 : Hippocampal Lewy pathology and cholinergic dysfunction are associated with dementia in Parkinson's disease.

58 : Lewy body cortical involvement may not always predict dementia in Parkinson's disease.

59 : CSF amyloid {beta} 1-42 predicts cognitive decline in Parkinson disease.

60 : CSF amyloid-beta and tau proteins, and cognitive performance, in early and untreated Parkinson's disease: the Norwegian ParkWest study.

61 : CSF Aβ42 predicts early-onset dementia in Parkinson disease.

62 : Brain atrophy rates in Parkinson's disease with and without dementia using serial magnetic resonance imaging.

63 : Cerebral atrophy and its relation to cognitive impairment in Parkinson disease.

64 : A magnetic resonance imaging study of patients with Parkinson's disease with mild cognitive impairment and dementia using voxel-based morphometry.

65 : Grey matter atrophy in cognitively impaired Parkinson's disease.

66 : Hippocampal abnormalities and memory deficits in Parkinson disease: a multimodal imaging study.

67 : Subcortical white matter hyperintensities within the cholinergic pathways of Parkinson's disease patients according to cognitive status.

68 : Dementia with Lewy bodies according to the consensus criteria in a general population aged 75 years or older.

69 : Consensus guidelines for the clinical and pathologic diagnosis of dementia with Lewy bodies (DLB): report of the consortium on DLB international workshop.

70 : Islington study of dementia subtypes in the community.

71 : Pathological substrate of dementia in Parkinson's disease--its relation to DLB and DLBD.

72 : Dementia with Lewy bodies and Parkinson's disease with dementia: are they different?

73 : Differences in neuropathologic characteristics across the Lewy body dementia spectrum.

74 : Cholinergic correlates of cognitive impairment in Parkinson's disease: comparisons with Alzheimer's disease.

75 : Choline acetytransferase activity and striatal dopamine receptors in Parkinson's disease in relation to cognitive impairment.

76 : Cortical cholinergic function is more severely affected in parkinsonian dementia than in Alzheimer disease: an in vivo positron emission tomographic study.

77 : Cognitive correlates of cortical cholinergic denervation in Parkinson's disease and parkinsonian dementia.

78 : Mapping of brain acetylcholinesterase alterations in Lewy body disease by PET.

79 : Use of drugs with anticholinergic effect and impact on cognition in Parkinson's disease: a cohort study.

80 : Antiparkinsonism anticholinergics increase dementia risk in patients with Parkinson's disease.

81 : Cognitive slowing in Parkinson's disease resolves after practice.

82 : Functional brain activity and presynaptic dopamine uptake in patients with Parkinson's disease and mild cognitive impairment: a cross-sectional study.

83 : Deficit of short-term memory in newly diagnosed untreated parkinsonian patients: reversal after L-dopa therapy.

84 : Effects of levodopa on cognitive functioning in moderate-to-severe Parkinson's disease (MSPD).

85 : Frequency of cholinergic and caudate nucleus dopaminergic deficits across the predemented cognitive spectrum of Parkinson disease and evidence of interaction effects.

86 : Serotonin 2A receptors and visual hallucinations in Parkinson disease.

87 : Increased 5-HT2A receptors in the temporal cortex of parkinsonian patients with visual hallucinations.

88 : Visuospatial impairment in Parkinson's disease.

89 : Comparison of cognitive changes in patients with Alzheimer's and Parkinson's disease.

90 : Cognitive impairment in incident, untreated Parkinson disease: the Norwegian ParkWest study.

91 : Clinical diagnostic criteria for dementia associated with Parkinson's disease.

92 : Neuropsychological aspects of Parkinson's disease.

93 : Visual dysfunction in Parkinson disease without dementia.

94 : Attentional deficits affect activities of daily living in dementia-associated with Parkinson's disease.

95 : Mild cognitive impairment in Parkinson disease: a multicenter pooled analysis.

96 : Dementia in Parkinson's disease: cause and treatment.

97 : Poor attentional function predicts cognitive decline in patients with non-demented Parkinson's disease independent of motor phenotype.

98 : Diagnostic criteria for mild cognitive impairment in Parkinson's disease: Movement Disorder Society Task Force guidelines.

99 : Predictors of cognitive impairment in an early stage Parkinson's disease cohort.

100 : Comparison of dementia with Lewy bodies to Alzheimer's disease and Parkinson's disease with dementia.

101 : Fluctuations in attention: PD dementia vs DLB with parkinsonism.

102 : Profile of cognitive impairment in dementia associated with Parkinson's disease compared with Alzheimer's disease.

103 : Visual hallucinations in the diagnosis of idiopathic Parkinson's disease: a retrospective autopsy study.

104 : Neuropsychiatric symptoms in patients with Parkinson's disease and dementia: frequency, profile and associated care giver stress.

105 : Psychiatric issues in cognitive impairment.

106 : Hallucinations in Parkinson's disease: prevalence, phenomenology and risk factors.

107 : Minor hallucinations reflect early gray matter loss and predict subjective cognitive decline in Parkinson's disease.

108 : Clinical phenotype of Parkinson disease dementia.

109 : Cognitive decline in early Parkinson's disease.

110 : Clinicopathologic correlations in 172 cases of rapid eye movement sleep behavior disorder with or without a coexisting neurologic disorder.

111 : REM sleep behavior disorder predicts cognitive impairment in Parkinson disease without dementia.

112 : Mild cognitive impairment in rapid eye movement sleep behavior disorder and Parkinson's disease.

113 : REM Sleep Behavior Disorder and Cognitive Impairment in Parkinson's Disease.

114 : Motor subtype and cognitive decline in Parkinson's disease, Parkinson's disease with dementia, and dementia with Lewy bodies.

115 : Extrapyramidal features in Parkinson's disease with and without dementia and dementia with Lewy bodies: A cross-sectional comparative study.

116 : Cognitive impairment in Parkinson's disease.

117 : Subtypes of mild cognitive impairment in Parkinson's disease: progression to dementia.

118 : Longitudinal study of normal cognition in Parkinson disease.

119 : Natural course of mild cognitive impairment in Parkinson disease: A 5-year population-based study.

120 : Dementia with Lewy bodies.

121 : Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium.

122 : The role of levodopa in the management of dementia with Lewy bodies.

123 : Dementia with Lewy bodies: reliability and validity of clinical and pathologic criteria.

124 : Clinical and neuropathological findings in Lewy body dementias.

125 : Gray matter atrophy in Parkinson disease with dementia and dementia with Lewy bodies.

126 : A comparative analysis of cognitive profiles and white-matter alterations using voxel-based diffusion tensor imaging between patients with Parkinson's disease dementia and dementia with Lewy bodies.

127 : Dementia with Lewy bodies and Parkinson disease with dementia: can MRI make the difference?

128 : Which clinical features differentiate progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome) from related disorders? A clinicopathological study.

129 : Accuracy of clinical criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome).

130 : Parkinsonism--recognition and differential diagnosis.

131 : Neuropsychiatric aspects of progressive supranuclear palsy.

132 : Clinical differentiation of parkinsonian syndromes: prognostic and therapeutic relevance.

133 : Subcortical dementia revisited: similarities and differences in cognitive function between progressive supranuclear palsy (PSP), corticobasal degeneration (CBD) and multiple system atrophy (MSA).

134 : Cognitive impairment in patients with multiple system atrophy and progressive supranuclear palsy.

135 : Criteria for the diagnosis of corticobasal degeneration.

136 : Extrapyramidal signs before and after diagnosis of incident Alzheimer disease in a prospective population study.

137 : The MoCA: well-suited screen for cognitive impairment in Parkinson disease.

138 : Diagnosing PD-MCI by MDS Task Force criteria: how many and which neuropsychological tests?

139 : Practice Parameter: evaluation and treatment of depression, psychosis, and dementia in Parkinson disease (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology.

140 : The validity of the Beck Depression Inventory as a screening and diagnostic instrument for depression in patients with Parkinson's disease.

141 : The validity of the Hamilton and Montgomery-Asberg depression rating scales as screening and diagnostic tools for depression in Parkinson's disease.

142 : Disease-specific properties of the Rating Scale for Depression in patients with stroke, Alzheimer's dementia, and Parkinson's disease.

143 : Prevalence and clinical aspects of mild cognitive impairment in Parkinson's disease: A meta-analysis.

144 : Cholinesterase inhibitors for dementia with Lewy bodies, Parkinson's disease dementia and cognitive impairment in Parkinson's disease.

145 : Rivastigmine for dementia associated with Parkinson's disease.

146 : Cholinesterase inhibitors for Parkinson's disease dementia.

147 : Donepezil for dementia in Parkinson's disease: a randomised, double blind, placebo controlled, crossover study.

148 : Donepezil for cognitive impairment in Parkinson's disease: a randomised controlled study.

149 : Efficacy and safety of donepezil in the treatment of executive dysfunction in Parkinson disease: a pilot study.

150 : Cognitive, psychiatric and motor response to galantamine in Parkinson's disease with dementia.

151 : A double-blind comparison of galantamine hydrobromide ER and placebo in Parkinson disease.

152 : Donepezil in Parkinson's disease dementia: a randomized, double-blind efficacy and safety study.

153 : Efficacy and safety of cholinesterase inhibitors and memantine in cognitive impairment in Parkinson's disease, Parkinson's disease dementia, and dementia with Lewy bodies: systematic review with meta-analysis and trial sequential analysis.

154 : Cholinesterase inhibitors for Parkinson's disease: a systematic review and meta-analysis.

155 : What happens when donepezil is suddenly withdrawn? An open label trial in dementia with Lewy bodies and Parkinson's disease with dementia.

156 : Memantine in patients with Parkinson's disease dementia or dementia with Lewy bodies: a double-blind, placebo-controlled, multicentre trial.

157 : Memantine for patients with Parkinson's disease dementia or dementia with Lewy bodies: a randomised, double-blind, placebo-controlled trial.

158 : Randomized controlled trial of memantine in dementia associated with Parkinson's disease.

159 : Delusions and hallucinations in dementia with Lewy bodies: worsening with memantine.

160 : Exacerbation of Lewy bodies dementia due to memantine.

161 : Visual hallucinations and agitation in Alzheimer's disease due to memantine: report of three cases.

162 : Effect of levodopa on cognitive function in Parkinson's disease with and without dementia and dementia with Lewy bodies.

163 : Enhanced or impaired cognitive function in Parkinson's disease as a function of dopaminergic medication and task demands.

164 : Dopaminergic modulation of cognitive function-implications for L-DOPA treatment in Parkinson's disease.

165 : Network correlates of the cognitive response to levodopa in Parkinson disease.

166 : Exercise and Parkinson's: benefits for cognition and quality of life.

167 : Management of referred deep brain stimulation failures: a retrospective analysis from 2 movement disorders centers.

168 : Cognitive sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a meta-analysis.

169 : Cognitive Impact of Deep Brain Stimulation on Parkinson's Disease Patients.

170 : Mental symptoms in Parkinson's disease are important contributors to caregiver distress.

171 : The association of incident dementia with mortality in PD.

172 : Effect of psychiatric and other nonmotor symptoms on disability in Parkinson's disease.

173 : Predictors of nursing home placement in Parkinson's disease: a population-based, prospective study.

174 : Characteristics of Parkinson's Disease in Patients with and without Cognitive Impairment.

175 : Impaired navigation in drivers with Parkinson's disease.