INTRODUCTION — Deep brain stimulation (DBS) is used to treat a variety of neurologic and psychiatric diseases, including movement disorders (eg, Parkinson disease, essential tremor, and dystonia), epilepsy, obsessive compulsive disorder, and refractory major depression [1-5]. Advantages to DBS rather than surgical treatments, such as thalamotomy and pallidotomy, are that DBS is nondestructive, reversible, and adjustable [3].
This topic will discuss anesthetic management and potential perioperative complications in patients undergoing DBS implantation. The anesthetic implications of a pre-existing implanted DBS system are also discussed, since these patients may undergo subsequent surgical procedures. Indications for deep brain stimulation are discussed in other topics.
●(See "Deep brain stimulation for treatment of obsessive-compulsive disorder".)
●(See "Surgical treatment of essential tremor", section on 'Deep brain stimulation'.)
●(See "Treatment of dystonia in children and adults", section on 'Deep brain stimulation'.)
SURGICAL PROCEDURE — Deep brain stimulators (DBSs) are usually placed bilaterally. However, in patients with essential tremor, a unilateral lead is usually placed. The DBS hardware has three main components:
●Multicontact intracranial quadripolar electrodes
●A programmable single- or dual-channel internal pulse generator (IPG) with battery unit
●An extension cable connecting the DBS electrodes to the IPG
The overall surgical procedure involves two stages. In the first stage, electrode(s) are placed in the target area of the brain usually using an "awake (conscious) brain surgery" technique. In the second stage, the electrodes and the extension cable are tunneled subcutaneously from the cranial area to the infraclavicular area, often on the right side, where they are connected to the programmable IPG. This stage is either performed immediately following the procedure or as a separate procedure at a later date.
Most centers do not initiate stimulation until two to four weeks following lead implantation; edema around freshly implanted electrodes (the so-called "microlesion effect") may interfere with immediate postoperative assessment of clinical symptoms [6].
Placement of stimulating electrodes — The therapeutic effectiveness of DBS depends on the placement of the stimulating electrodes in close proximity to the target nuclei. The therapeutic target sites selected for stimulation (eg, the subthalamic nuclei, globus pallidus interna nuclei, or the ventralis intermedius nucleus of the thalamus) depend upon the patient's disease and symptoms [7]. Since the target nuclei are often deep-seated and small, a combination of methods is most commonly used to accurately place the electrodes, starting with stereotactic frame-based imaging. Additional methods of localization (microelectrode recording [MER], macrostimulation) may be used during the procedure, since the brain can shift during intracranial placement of electrodes due to changes in patient positioning and/or loss of cerebrospinal fluid through the burr hole wound. Frameless imaging using intraoperative or diagnostic magnetic resonance imaging (MRI), without the need for MER or macrostimulation, is emerging as an alternative to frame-based imaging for DBS placement.
Frame-based imaging to identify the target nuclei — A stereotactic head frame is usually applied using local anesthesia with the patient awake (picture 1). Patients with developmental delay, uncooperative patients, and those with severe dystonia may require intravenous sedation or general anesthesia (GA) for this portion of the procedure. With the stereotactic frame in place, MRI is performed to identify target nuclei, allowing the surgeon to establish external coordinates for electrode insertion. Computed tomography (CT) scanning can be used if MRI is contraindicated or not possible in an individual patient.
●Target localization with the use of MER – Many centers utilize an electrophysiologic technique known as MER to further fine-tune localization of the target sites. The neurophysiology team obtains MERs to detect and amplify the activity of individual neurons.
This process may be time-consuming. A microelectrode is inserted to a point 10 to 15 mm above the target, then slowly advanced in 0.5 to 1.0 mm increments while its tip records and amplifies neuronal discharges along its path. Specific brain structures can be identified based on their unique firing patterns. Using these variations in spontaneous firing rates between specific nuclei, as well as changes in the firing rates related to specific patient active and passive movements, the neurophysiology team is able to localize the specific brain target. This allows feedback along the entire trajectory and fine adjustments of position before inserting the final electrode.
●Macrostimulation testing – Ideally, the patient is awake during surgery, allowing the team to briefly activate the implanted deep brain electrode in order to confirm clinical improvement (efficacy) and detect any adverse side effects during neurostimulation. The electrode is secured when the team is satisfied with its location, then the burr hole wound is closed. A second electrode may be inserted in the contralateral brain hemisphere if bilateral DBS is planned.
Interventional MRI-guided technique — Interventional or intraoperative MRI (iMRI) scanners may be used for some indications (eg, Parkinson disease) to allow DBS insertion without the use of a stereotactic head frame, MER, or macrostimulation. DBS insertion using iMRI is usually performed under GA. (See 'General anesthesia' below.)
Accuracy of frameless stereotaxis has improved significantly with advances in imaging technology, and reported outcomes are similar to or better than those with frame-based techniques [8-12].
iMRI-guided lead implantation allows DBS placement for patients who cannot tolerate or refuse an awake procedure, and does not require discontinuation of preoperative medication for intraoperative testing. Other advantages of iMRI guidance include real time imaging, shorter duration of the procedure, reduced number of electrode penetrations, and early detection of complications (eg, intracerebral hemorrhage) [10,13,14]. The electrode trajectory is planned from magnetic resonance (MR) images obtained after the burr hole is created, and after brain shift with loss of cerebrospinal fluid.
The safety considerations associated with procedures performed in the MRI environment are discussed separately. (See "Anesthesia for magnetic resonance imaging and computed tomography procedures".)
PREOPERATIVE EVALUATION AND PREPARATION — These patients should generally have preanesthesia evaluation prior to the day of surgery for electrode insertion. For standard stereotactic frame-based procedures, patients should be assessed for their willingness and ability to tolerate a potentially lengthy procedure awake, and should fully understand what will happen on the day of the procedure. Many patients undergoing DBS implantation are older and have associated comorbidities. In addition to a complete anesthesia-directed history and physical examination, we focus preanesthesia evaluation for these procedures on the following:
●Airway assessment – The patient should be assessed for potential difficulty with airway management and the possibility of airway obstruction with sedation. The stereotactic frame is normally placed on the scalp with local anesthesia, with or without sedation, and is ultimately clamped to the operating table. Laryngoscopy with the patient's head immobilized in a stereotactic frame may be difficult or impossible, especially if the need arises emergently. Thus, regardless of the original anesthetic plan, a plan for urgent airway management should be formulated, and the equipment necessary to remove the frame should be immediately available throughout the procedure. (See 'Perioperative complications of DBS implantation' below and "Airway management for induction of general anesthesia", section on 'Airway assessment'.)
●Preoperative medication management – The plan for perioperative medication management should be coordinated with the neurosurgical team.
•Discontinuation of antiplatelet and anticoagulant medications prior to DBS electrode insertion to minimize the risk of intracranial hemorrhage may require coordination with the patient's primary care clinician or cardiologist.
•Depending on institutional preferences, drugs prescribed for the patient's neurologic or psychiatric disease may be withheld on the morning of the surgery to facilitate testing. However, this practice may lead to flares of symptoms (eg, bulbar and motor symptoms in patients with Parkinson disease) that complicate anesthetic management. If symptoms are severe, a reduced dose of the patient's regular medication may be administered after consultation with the neurosurgical team. (See "Perioperative care of the surgical patient with neurologic disease", section on 'Parkinson disease' and "Perioperative care of the surgical patient with neurologic disease", section on 'Perioperative medication management'.)
•For most patients, we continue antihypertensive medications (including angiotensin-converting enzyme [ACE] inhibitors and angiotensin receptor blockers [ARBs]) up to and including the day of surgery for DBS electrode insertion. In a retrospective review of 136 patients who underwent awake DBS electrode placement in one center, withholding ACE inhibitors or ARBs was an independent risk factor for the need for aggressive intraoperative antihypertensive therapy [15]. (See "Perioperative medication management", section on 'ACE inhibitors and angiotensin II receptor blockers' and 'Hemodynamic management' below.)
●Disease-specific considerations – The disease processes for which the DBS is indicated may affect anesthetic management [16-18].
•Patients with long-standing Parkinson disease may have autonomic dysfunction, impaired respiratory reserve, poor cough reflex, sleep apnea, and increased risk for aspiration. In addition, these patients are often taking multiple prescription medications, which may increase the risk of perioperative drug interactions. (See "Clinical manifestations of Parkinson disease" and "Perioperative care of the surgical patient with neurologic disease", section on 'Other medication interactions, concerns'.)
•Patients with debilitating dystonia are often malnourished and hypovolemic; thus, they are at risk for hemodynamic instability. Contractures in these patients can cause skeletal deformity, which may cause challenging venous access and difficulty with positioning during surgery.
•Developmental delay, dementia, behavioral problems, and communication difficulties are common in patients having DBS implantation. Such patients may be unable to tolerate and cooperate with awake surgical procedures and may have difficulty assessing symptoms for postoperative stimulus titration, and therefore often require general anesthesia (GA) for the entire procedure.
•Patients with chronic pain require special consideration for management of pain medications perioperatively. (See "Perioperative medication management", section on 'Chronic opioid therapy'.)
ANESTHESIA FOR PLACEMENT OF STIMULATING ELECTRODES — The goals of anesthetic care during placement of the stimulating electrodes include providing optimal surgical conditions, hemodynamic stability, and patient comfort, while facilitating intraoperative monitoring and target localization.
Monitoring — Standard physiologic monitors should be applied, as for any anesthetic (table 1). Invasive arterial blood pressure monitoring is not usually required, but may be considered for patients with cardiovascular or pulmonary comorbidities, or to guide administration of vasoactive drug infusions in patients with labile blood pressure.
Positioning — Proper patient positioning is important to ensure maximal comfort and optimal surgical conditions. Patients are usually placed in the semi-sitting or semi-Fowler's position, with the head elevated approximately 30 degrees (picture 2). We usually confirm the ease of swallowing before finalizing the neck position. Wrapping the neck with blankets can relieve the sensation of a floating head. Draping should allow access to the patient's face, arms, and legs (picture 3), while maintaining a sterile surgical site. Attention to thermal control also enhances patient comfort.
Foley catheter — Insertion of a urinary catheter may be avoided because the patient is awake. However, vigilant monitoring of fluid administration is necessary in order to minimize bladder distention due to excessive fluid administration while avoiding hypovolemia due to inadequate fluid administration.
Hemodynamic management — Hypertension is a common perioperative problem during awake DBS electrode insertion; blood pressure should be controlled to minimize the risk of intracerebral hemorrhage during electrode insertion. Parameters for optimal intraoperative blood pressure are not well defined; we suggest maintaining the systolic blood pressure below 140 mmHg, or within 20 percent of the patient's usual systolic blood pressure [19-24].
Hypotension is more common during general anesthesia (GA), and may occur due to autonomic dysfunction in patients with Parkinson disease and/or the vasodilating effects of anti-Parkinson medications and anesthetics. For most patients, we aim for a mean blood pressure within 20 percent of the patient's baseline, and administer fluids and vasoactive medications as necessary. (See "Anesthesia for patients with hypertension", section on 'Determination of target blood pressure values' and "Anesthesia for patients with hypertension", section on 'Prevention and treatment of intraoperative hypertension'.)
For procedures performed in the semi-sitting position, cerebral perfusion pressure at the level of the brain is lower than the pressure measured with a blood pressure cuff at the level of the arm. Therefore, noninvasive blood pressure measurements should be corrected for the hydrostatic difference between the measurement site and the brain, and transducers used for invasive blood pressure monitoring should be leveled at the external auditory meatus. These issues are discussed separately. (See "Patient positioning for surgery and anesthesia in adults", section on 'Physiologic effects of sitting position'.)
Choice of anesthetic technique — The choice of anesthetic technique for DBS electrode placement is debated among anesthesiologists and neurosurgeons. We prefer the use of monitored anesthesia care (MAC) with local anesthesia and sedation rather than GA whenever possible for stereotactic frame-based stimulating electrode placement, to allow optimal microelectrode recording (MER) localization and macrostimulation testing [21]. The decision for MAC with sedation (versus GA) is best made before surgery after careful preoperative assessment, including airway assessment. (See 'Preoperative evaluation and preparation' above.)
●MAC – Advantages to MAC for DBS electrode insertion include the following:
•An appropriate level of sedation allows assessment of clinical efficacy and side effects during macrostimulation testing of implanted electrodes.
•MAC with sedation may also avoid emergence excitation after GA, with associated hemodynamic fluctuations.
•Depending on the medications administered, sedation may be associated with a lower incidence of postoperative nausea and vomiting than GA, and may therefore allow earlier resumption of oral medications. (See "Postoperative nausea and vomiting".)
●GA – GA is used for patients who cannot tolerate awake electrode placement, including those who have a fear of undergoing surgery while awake, as well as those with chronic pain syndromes, severe "off-medication" movements, or severe dystonia or choreoathetosis. GA can be used for most patients who undergo electrode insertion guided by real time magnetic resonance imaging (MRI) scanning (intraoperative MRI [iMRI]-guided technique). GA is commonly used for pediatric patients undergoing DBS implantation, although conscious sedation has been used successfully in some children [25].
GA may interfere with MER, depending on the target nucleus, and prevents macrostimulation testing for efficacy and assessment of side effects. In some patients with Parkinson disease requiring only subthalamic nuclei stimulation, placement of stimulating electrodes may be performed with GA with or without MER [13,26]. (See 'Effect of anesthetic agents on target localization with MER' below.)
Outcomes with MAC versus GA — There are very few studies on the effects of the choice of GA versus MAC for DBS placement on outcomes. Existing reports of outcomes include small numbers of patients, involve a variety of anesthetic agents, and have measured heterogeneous outcomes. A 2019 meta-analysis of 16 cohort studies involving 1523 patients found similar clinical outcomes in terms of improvement of symptoms and the incidence of adverse events with GA and MAC [27]. In a 2021 single-center randomized trial of 110 patients with Parkinson’s disease who underwent frame-based microelectrode-guided DBS, improvement in motor function and the incidence of adverse cognitive, mood, and behavioral effects were similar in patients who had GA versus MAC [28]. Hence, GA may be an alternative option for patients who may not tolerate MAC.
Monitored anesthesia care
Local anesthesia — The scalp must be anesthetized at sites of incision and skull pin placement, or with a scalp block [29] (see "Scalp block and cervical plexus block techniques", section on 'Scalp block'). Scalp block may provide more stable hemodynamics during the procedure. In a retrospective single center study of 47 patients who underwent DBS placement with local anesthetic infiltration or with scalp block, scalp block was associated with lower mean systolic blood pressure and heart rate, and less use of antihypertensive medication during the procedure [30].
Sedation during MAC — Frequent communication with the patient should be maintained throughout the procedure, with emphasis on reassurance and motivation. A goal for sedation for DBS electrode placement is to have a patient who can communicate, report symptoms, and cooperate with testing. The ideal sedative agent should have no effect, or at least a readily reversible effect, on subcortical activity in order to allow MER and clinical testing. Conscious sedation is often employed during incisions and bony opening, reduced or discontinued for electrode insertion and electrophysiologic testing, and restarted for closure after macrostimulation testing. Residual sedative effects during the macrostimulation testing phase may be minimized if short-acting agents are used and they are stopped well before this phase [19-21,31].
We suggest use of a dexmedetomidine infusion with opioids and avoidance of benzodiazepines and propofol. Cerebral subcortical areas are extremely sensitive to gamma-aminobutyric acid (GABA) receptor-mediated medications such as propofol and midazolam, and the use of these medications, even in small doses, has been shown to affect the quality of MER [32,33].
Agents commonly used for sedation in this setting include the following:
●Dexmedetomidine – In many institutions, including the author's, dexmedetomidine is the sedative agent of choice. Dexmedetomidine has no effect on GABA receptors, and reliably produces conscious sedation mediated through activation of alpha-2 adrenoreceptors in the locus ceruleus, a key modulator for arousal, sleep, and anxiety. This, together with minimal respiratory depression, makes it an attractive agent to use in "awake" functional neurosurgery [34].
Low-dose infusion of dexmedetomidine (0.2 to 0.7 mcg/kg/hour) provides sedation from which patients are easily aroused and cooperative with verbal stimulation. This low-dose infusion does not ameliorate clinical signs of Parkinson disease, and anxiolysis can be achieved with no effect on MER [35,36]. Thus, sophisticated cognitive tests can be successfully carried out.
Dexmedetomidine also attenuates the hemodynamic responses to surgical incision and significantly reduces the concomitant use of antihypertensive medication [34].
We usually avoid administration of a loading dose of dexmedetomidine for these patients. Dexmedetomidine is known to have a biphasic response, causing initial hypertension followed by hypotension. Hypertension and/or oversedation have been reported in some patients with Parkinson disease with loading dose of dexmedetomidine [37]. Hypertension may be due to stimulation of postsynaptic alpha-2B receptors at higher serum concentrations causing peripheral vasoconstriction [38].
We discontinue dexmedetomidine infusion in advance of MER to avoid interference. In a small study of MER during DBS placement, a dexmedetomidine bolus followed by infusion reduced the neuronal burst pattern that helps identify the subthalamic nucleus (STN) target [39].
●Propofol – Propofol may be used as a continuous infusion, either alone or in combination with opioids, especially in cases involving lead placement in the subthalamic nuclei [19]. Propofol affects background neuronal discharges but causes only minor alterations of STN discharge activity [40,41], allowing successful target localization with low dose (25 to 50 mcg/kg/min) propofol sedation [42]. Nonetheless, some centers avoid propofol for sedation or stop it well in advance of MER to avoid interference with recordings.
Propofol has the desirable properties of rapid onset and short duration of action. However, propofol should be titrated carefully in patients with Parkinson disease. The pharmacokinetic and pharmacodynamic profile of propofol may differ in patients with Parkinson disease compared with the population used to develop target-controlled infusion models [43]. Propofol sedation can cause confusion, hallucinations, and disinhibition in some older patients. Addition of opioids to propofol increases the risk of respiratory depression.
●Opioids – Short-acting opioids (eg, fentanyl or remifentanil) are commonly used as analgesics because of their minimal effect on MER [41]. In some centers, low-dose (0.008 to 0.05 mcg/kg/min) remifentanil infusion is used as a sole sedation during surgery. Opioids may cause worsening of rigidity, especially in high doses [16].
●Benzodiazepines – Benzodiazepines should be avoided as these drugs can abolish MER, and also interfere with stimulation testing [32,44].
●Ketamine – Ketamine has been used for sedation as well as an adjuvant during GA in pediatric patients undergoing DBS insertion, with preservation of MER [36,45].
General anesthesia — At our institution, GA is usually induced in the neuroradiology suite, with either inhalation induction (oxygen, sevoflurane) or intravenous (IV) induction (fentanyl [1 to 2 mcg/kg], propofol [1 to 3 mg/kg], and rocuronium [1 mg/kg], doses adjusted for patient factors), depending on the level of patient cooperation. Alternatively, either etomidate or ketamine can be used for induction of anesthesia if indicated. After endotracheal intubation, the stereotactic head frame is placed and MRI is performed to obtain the coordinates for the target nuclei. The patient is then transferred to the operating room, anesthetized, and monitored during transport.
Anesthesia is usually maintained with oxygen, air, and either 0.8 to 1 MAC of sevoflurane or total IV anesthesia (propofol [75 to 200 mcg/kg/minute] and remifentanil [0.02 to 0.1 mcg/kg/minute]). If MER is planned during surgery, a balanced anesthetic with a combination of low-dose inhalation anesthetic (<0.5 MAC), low-dose opioid (eg, remifentanil 0.03 to 0.06 mcg/kg/min) and low-dose propofol (<75 mcg/kg/min) may better preserve recordings than higher doses of anesthetic agents [46].
Neuromuscular blocking agents are usually avoided if movement-related neuronal discharges are elicited during MER.
A postoperative MRI or computed tomography (CT) may be performed, after which the stereotactic frame is removed and the patient is awoken and extubated.
Effect of anesthetic agents on target localization with MER — Some data suggest that both inhalation agents (sevoflurane, desflurane) and IV agents (propofol, ketamine) used to produce GA influence MER, which may affect accurate localization of the target nuclei [26,40,41,46-48]. These effects may be dose-dependent.
GABA-ergic anesthetic agents have been shown to affect both background activity and neuronal spike activity. These effects may not be homogeneous in all regions of the brain [40]. Globus pallidus interna neurons, in particular, are more suppressed by most anesthetic agents than the subthalamic nuclei neurons, possibly due to differences in GABA input [32,46]. Non GABA-ergic drugs (dexmedetomidine, ketamine) and short-acting opioids (fentanyl, remifentanil) have minimal effect on MER [36,41].
Localization of STN using intraoperative MER may still be possible with low doses of a variety of inhalation (sevoflurane, desflurane) and IV (propofol, ketamine) anesthetic agents [33,36,45,46,49,50].
PERIOPERATIVE COMPLICATIONS OF DBS IMPLANTATION — Limited data suggest that perioperative complications occur in 5 to 16 percent of patients undergoing DBS implantation [19,31].
●Airway and respiratory complications occur in 1.6 to 2.2 percent of patients undergoing DBS implantation. Intraoperative loss of airway patency in a patient undergoing the procedure with monitored anesthesia care (MAC) and sedation is of particular concern while the patient's head is immobilized in the stereotactic head frame. Excessive sedation or sudden decreased level of consciousness due to intracranial events such as seizures or hemorrhage may cause airway obstruction. Acute airway obstruction can also occur in a restless awake patient as the body shifts but the head remains fixed to the bed [20,31]. In such cases, it may be necessary to release the frame from the operating room table to relieve the airway obstruction. Prompt insertion of a supraglottic airway may be the most appropriate option to emergently secure the airway. If possible, the airway should be secured without removing the head frame, so that surgery may be completed. In a mannequin study with a stereotactic headframe in situ, it has been shown that both laryngeal mask insertion and tracheal intubation can be performed [51]. However, there are individual variations among different frames with regards to the access to the face and nose.
●Venous air embolism (VAE) can occur at any time during the burr hole procedure, either in the supine or in the semi-sitting position, especially in a hypovolemic patient or spontaneously breathing patient. In a spontaneously breathing patient, sudden vigorous coughing may be a sign of VAE, and is most likely to occur during creation of the burr hole. Other signs include unexplained hypoxia and hypotension.
The true incidence of VAE during DBS insertion is unknown. The reported incidence of VAE in large retrospective studies ranges from 0.6 percent (2 of 324 procedures) to 3.2 percent (9 of 286 procedures) [52-54]. There are no large prospective studies. Early detection may be possible with precordial Doppler monitoring.
Intraoperative VAE is discussed separately. (See "Intraoperative venous air embolism during neurosurgery".)
●Seizures can occur during DBS electrode insertion, with incidence of <1 percent [19,31,55,56]. Patients with multiple sclerosis may be at higher risk of seizures in this setting [55]. Most periprocedural seizures occur during macrostimulation testing and are often self-limited and focal in nature. However, generalized tonic clonic seizures do occasionally occur. Small doses (eg, 10 mg intravenous [IV], repeated as needed) of propofol may be used to treat the seizures and, if seizures are controlled, the procedure may be continued. Postictal airway patency must be ensured.
●Intracranial hemorrhage, although rare (0.5 to 2.8 percent), can be devastating [19,31,56]. Intracranial hemorrhage is suspected in an awake patient when there is a sudden change in mental status or occurrence of a focal neurologic deficit. A magnetic resonance imaging (MRI) or computed tomography (CT) scan confirms the diagnosis.
The only consistent factor associated with the occurrence of hematoma is hypertension [23]. In the absence of hypertension, the number of microelectrode recording (MER) penetrations is weakly correlated with the occurrence of hematoma [57]. Patients undergoing DBS insertion under local anesthesia may be at higher risk, as their blood pressure is often higher intraoperatively when compared with patients under general anesthesia (GA) [58].
●Postoperative delirium may occur after DBS insertion [59,60]. The management of postoperative delirium requires a multidisciplinary approach. Potential underlying causes, namely urinary tract infection, medications, or hemorrhage, should be ruled out first. Treatment with selective dopamine blockers (quetiapine), instead of nonselective blockers (olanzapine, haloperidol) is preferred, particularly for patients with parkinsonism. (See "Delirium and acute confusional states: Prevention, treatment, and prognosis", section on 'Antipsychotic medications'.)
Monitoring for complications should continue in the recovery area. Frequent assessment of neurologic status, control of blood pressure, attention to respiratory status, and prompt treatment of any pain or nausea are important considerations. If therapeutic medications for Parkinson disease have been withheld, these should be resumed as soon as possible to avoid deterioration in neurologic and respiratory function.
ANESTHESIA FOR IMPLANTATION OF THE INTERNAL PULSE GENERATOR — Implantation of the pulse generator and internalization of the electrodes is performed under general anesthesia (GA), either immediately after electrode placement, or as a second-stage surgery. In our experience, there is a higher incidence of hypotension that requires repeated administration of vasopressors when the internal pulse generator (IPG) is implanted with GA in the same setting as the DBS placement.
The generator for the DBS system is often implanted in the pectoral area, similar to placement of a cardiac pacemaker. The cable connecting the DBS electrodes to the IPG is tunneled subcutaneously from the burr hole to the IPG site. Since these procedures involve numerous surgical sites and tunneling that is difficult to anesthetize with local anesthetic, GA is often requested.
There are no specific anesthetic drug considerations. However, as head position is often manipulated during this procedure, the seal of a supraglottic airway may be unpredictable. Thus, endotracheal intubation is usually preferred.
ANESTHESIA FOR PATIENTS WITH PRE-EXISTING DBS — With expanding indications and an increasing number of patients undergoing DBS implantation, patients with pre-existing DBS increasingly require anesthesia for unrelated surgery [4,5].
Many of the issues of perioperative management are similar to those for cardiac pacemakers and automatic implantable cardioverter and defibrillator (AICD) devices, although there are specific differences [61,62]. For example, in contrast with cardiac pacemakers, patients can turn off some devices themselves.
Perioperative considerations — Perioperative preparation includes identification of the specific device and the severity of the patient's symptoms when the DBS system is turned off. If applicable, the anatomic course of the DBS extension cable should be determined.
Perioperative management should be coordinated with the surgeon and the clinician managing the DBS whenever possible. The need for and consequences of turning the device off should be discussed. If deactivation of the device results in severe symptoms, oral medication should be started before turning the device off on the day of surgery. If the device is turned off during the procedure, it should be turned on after the surgery and should be interrogated postoperatively.
DBS systems may interact with multiple medical devices in the operating room, as follows:
●Intraoperative electrocautery can burn neural tissue around the stimulator electrodes or reprogram the device [63,64]. We turn the device off for procedures that require electrocautery to minimize the chance of damaging the device. Bipolar electrocautery is safer than monopolar electrocautery, similar to considerations with implantable cardioverter and defibrillator devices and spinal cord stimulators. If monopolar cautery is required, the return dispersive electrode (grounding pad) should be placed as far as possible from the generator, and the lowest possible source of energy should be used in short irregular pulses. (See "Overview of electrosurgery", section on 'Monopolar versus bipolar'.)
Short-wave diathermy modalities should not be used as they produce radio frequency currents and heating of electrodes [65].
●DBS systems may produce artifacts and/or interfere with the electrocardiogram recording [66].
●Safety of external and internal cardiac defibrillators has not been established in patients with DBS systems [61]. If cardioversion or defibrillation is required, the paddles must be positioned as far as possible from the generator and the lowest clinically-appropriate energy output should be used. The function of the generator must be checked after such treatment.
●Based on a small number of cases, electroconvulsive therapy, radiofrequency neuroablation, and peripheral nerve stimulation are reportedly safe if the implanted pulse generator is turned off and stimulator probes are placed as far as possible from the generator [67,68]. Device manufacturer recommendations should always be followed.
Follow-up MRI examinations — Many patients with DBS systems need magnetic resonance imaging (MRI) to assess disease progress and rule out complications. There are reports of increasing temperature of electrodes leading to brain injury, as well as damage and accidental reprograming of the device [69,70]. Generally, MRI is possible in patients with implanted DBS devices, but manufacturer guidelines must be strictly followed and scan time should be minimized [71,72].
As an example, the Medtronic Activa deep brain stimulator system is listed as MRI Conditional on the manufacturer website, with the stipulation that the website should be consulted or the manufacturer should be contacted for latest MRI information before magnetic resonance (MR) scanning for patients with these implants.
Replacement of the DBS battery unit — Patients with DBS systems may return for battery pack replacement. As this procedure does not involve lead manipulation in the head or the neck, conscious sedation with local anesthesia may be adequate for patient comfort during this procedure. However, general anesthesia (GA) may be required for uncooperative or pediatric patients.
In some patients, rigidity and tremors may worsen during the procedure.
SUMMARY AND RECOMMENDATIONS
●Implantation of deep brain stimulator (DBS) systems are complex procedures involving interactions of multiple specialty teams (neurosurgery, neurology, radiology, anesthesiology). The surgical procedure involves insertion of electrode(s) into the target area of the brain and connection of these electrodes to an extension cable, followed by subcutaneous tunneling of the cable from the cranial area to the programmable internal pulse generator (IPG), which is placed in the infraclavicular area of the chest. (See 'Surgical procedure' above.)
●Meticulous preoperative airway assessment is necessary, since the patient's head will be immobilized in a stereotactic head frame, making conventional laryngoscopy difficult. The anesthesiologist must assess the risk of potential airway compromise and formulate a plan for urgent airway management. (See 'Preoperative evaluation and preparation' above.)
●Extensive preoperative communication is necessary for any patient who will be awake for any part of the procedure. This includes detailed preoperative explanations regarding what to expect, including reassurance regarding the anesthetic care planned for all intraoperative events. (See 'Preoperative evaluation and preparation' above.)
●Lead placement depends on neurophysiologic testing. Both microelectrode recording (MER) and macrostimulation testing may be used to confirm accurate localization of the lead tip in the correct deep brain nucleus. (See 'Placement of stimulating electrodes' above.)
●Monitored anesthesia care (MAC) with sedation is the preferred anesthesia technique during lead implantation for most patients, in order to minimize the effects of anesthetic agents on neuronal background and spike activity during MER localization. This technique allows optimal MER localization as well as macrostimulation testing to assess for efficacy.
For sedation during MAC, we suggest use of a dexmedetomidine infusion with opioids (Grade 2C). Benzodiazepine sedation should be avoided as it may interfere with MER recording. (See 'Monitored anesthesia care' above.)
●For patients unable to tolerate MAC, the procedure can often be performed under general anesthesia (GA). As some anesthetic drugs may make MER difficult to interpret, lead placement in these patients may be based solely on radiologic landmarks. Short-term and long-term outcomes confirm that it is both safe and effective to perform subthalamic nucleus (STN) DBS surgery under GA in patients with Parkinson disease. (See 'Outcomes with MAC versus GA' above.)
Macrostimulation testing is not possible during GA, as it depends upon the patient's ability to report clinical effects and side effects of DBS testing. (See 'General anesthesia' above.)
●Advances in imaging techniques, especially with intraoperative magnetic resonance imaging (iMRI), have enabled DBS insertions to be performed under GA, without MER or macrostimulation. (See 'Interventional MRI-guided technique' above.)
●IPG placement is usually performed under GA. (See 'Anesthesia for implantation of the internal pulse generator' above.)
●For battery changes in the generator that do not involve lead manipulation, conscious sedation with local anesthetic infiltration or GA, are both reasonable options. (See 'Replacement of the DBS battery unit' above.)
●Potential complications of DBS implantation include sudden loss of airway patency (due to excessive sedation, seizures, or hemorrhage), which is particularly problematic with a stereotactic head frame in place.
Also, seizures, hemorrhage, venous air embolism, and post-procedural delirium can occur. (See 'Perioperative complications of DBS implantation' above.)
