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Overview of thoracic outlet syndromes

Overview of thoracic outlet syndromes
Author:
Kaoru Goshima, MD
Section Editors:
Joseph L Mills, Sr, MD
John F Eidt, MD
Jeremy M Shefner, MD, PhD
Deputy Editor:
Kathryn A Collins, MD, PhD, FACS
Literature review current through: Dec 2022. | This topic last updated: Sep 23, 2022.

INTRODUCTION — Thoracic outlet syndrome (TOS) refers to a constellation of signs and symptoms that arise from compression of the neurovascular bundle by various structures in the area just above the first rib and behind the clavicle, within the confined space of the thoracic outlet [1-5]. The term "thoracic outlet syndrome" was coined to collectively encompass the spectrum of syndromes related to the general region of the thoracic outlet [6].

Distinct terms are used to describe the predominantly affected structure, including neurogenic (nTOS) from brachial plexus compression, venous (vTOS) from subclavian vein compression, and arterial (aTOS) from subclavian artery compression [7]. Neurogenic TOS accounts for greater than 95 percent of cases of thoracic outlet syndrome, whereas vTOS accounts for 3 percent and aTOS accounts for 1 percent of cases. Compression of the brachial plexus leads to upper extremity numbness, dysesthesia, and weakness, venous compression may cause deep vein thrombosis and extremity swelling, and arterial compression can lead to distal thromboembolism, arm pain with exertion ("claudication"), or acute arterial thrombosis [8,9].

Thoracic outlet syndromes are commonly reported in adults and are infrequent in the pediatric population, and thus the literature is sparse. All three types of TOS have been reported in children, but vascular TOS may be more common in the adult population. Common risk factors for children with venous thoracic outlet syndrome include sports-related injuries and hypercoagulable states [10]. Neurogenic TOS and arterial TOS appear to be associated with boney abnormalities more frequently in children compared with adults [11].

An overview of the anatomy, pathogenesis, clinical evaluation, and approach to the management of the thoracic outlet syndromes will be reviewed with an emphasis on the features that distinguish these syndromes from one another.

ANATOMY — The thoracic outlet is bounded by the bony structures of the spinal column, first ribs, and sternum (figure 1). Compromise of the neurovascular structures that traverse the thoracic outlet occurs in three distinct spaces: the scalene triangle, the costoclavicular space, and the pectoralis minor space.

Scalene triangle – The scalene triangle is the space most commonly involved in TOS and is the most common site of brachial plexus compression. The anterior scalene muscle, which originates from the transverse processes of the third through sixth cervical vertebrae (C3-C6) and inserts on the inner borders and superior surfaces of the first rib, forms the anterior boundary of the scalene triangle. The middle scalene muscle, which arises from the transverse processes of the second through seventh cervical vertebrae (C2-C7) and inserts broadly onto the posterior aspects of the first rib, forms the posterior wall of the scalene triangle. The superior border of the first rib forms the base of the scalene triangle. The trunks of the brachial plexus and the subclavian artery pass between the anterior and middle scalene muscles while the subclavian vein courses anteromedial to the scalene triangle. Cervical ribs and anomalous first ribs may compress the scalene triangle (figure 2).

Costoclavicular space – The costoclavicular space consists of the area between the first rib and the clavicle. The brachial plexus, subclavian artery, and subclavian vein pass through this space. Of these, the subclavian vein is most likely to be compressed at this site.

Pectoralis minor space – The pectoralis minor space is bounded by the pectoralis minor muscle anteriorly and the chest wall posteriorly. Although this space is not technically a part of the thoracic outlet, the brachial plexus, subclavian artery, and subclavian vein pass through the pectoralis minor space to the upper arm. Compression of the neurovascular structures within the pectoralis minor space may be nearly as common as compression within the scalene triangle [12].

PATHOGENESIS — Compression of the neurovascular bundle as it traverses the thoracic outlet can result from a combination of developmental abnormalities, injuries, and physical activities that predispose to neurovascular compression. Variants in thoracic outlet anatomy, both congenital and acquired, are common and include primarily variations in bony and muscular anatomy. A study that examined 200 consecutive patients undergoing thoracic outlet surgery found that 8.5 percent of patients had a cervical rib articulating with the first thoracic rib, 10 percent had supernumerary scalene muscles, and 43 percent had variations in scalene muscle attachments [13]. Alterations in brachial plexus anatomy and muscle histology may also contribute.

Anomalous ribs – Cervical ribs were first described in the 18th century and subsequently classified in the 19th century into four types based upon length and union with the first rib [14]. These rib abnormalities have long been associated with symptoms of neurovascular compression [14-16]. A higher incidence of bony abnormalities, such as a cervical rib or anomalous first rib, is found in patients with TOS. In a systematic review that included 141 studies and over 77,000 patients, a cervical rib was more prevalent in patients with symptoms of thoracic outlet syndrome compared with those who had no such symptoms (29.5 versus 1.1 percent) [17]. Cervical ribs can be bilateral [18-20]. About 70 percent of patients with cervical ribs are women [1]. The presence of a cervical rib predisposes the patient to develop TOS after hyperextension-flexion (whiplash) injury [21].

Congenital cervical fibro-cartilaginous bands associated with an incomplete cervical rib have also been associated with TOS. The pathologic problem in true neurogenic TOS is not the cervical rib itself but a radiolucent band that extends from the tip of the rudimentary cervical rib to the first thoracic rib and compresses the proximal lower trunk of the brachial plexus [22].

Muscular anomalies – Preexisting variations in muscle anatomy can narrow the space between the anterior and middle scalene muscles. The insertions of these muscles are variable, and overlap of these muscle insertions can narrow the space through which the brachial plexus and subclavian artery pass. Supernumerary scalene muscles can be present. Occasionally, there is complete fusion of the anterior and middle scalene muscles. Cervical fibro-cartilaginous bands may predispose a patient to TOS. Subclavius muscle variations have also been associated with TOS. Acquired variations in muscle anatomy include hypertrophy of the scalene, subclavius, or pectoralis minor muscles, as might be seen in weight lifters. Histologic variations in muscle fiber anatomy may also contribute to TOS. One study demonstrated a type 1 fiber predominance and fiber hypertrophy in the anterior scalene muscles of TOS patients [23]. In another study, increased scalene connective tissue content with fibrosis surrounding individual muscle fibers was found in TOS patients [24].

Injury – Chronic inflammatory change due to trauma is the most common etiology of acquired variant anatomy in TOS. The most common injury associated with neurogenic TOS is hyperextension/flexion injury of the neck, such as might occur in a motor vehicle accident. Other etiologies of injury include bony fracture (first rib, clavicle) [25], a fall from standing (such as onto an icy surface), repetitive neck movement, repetitive occupational overhead arm movements (eg, box stacking), or repetitive athletic arm movements (eg, pitching, swimming). Repetitive injury can lead to any of the three types of TOS (neurogenic, arterial, venous) [26,27]. Patients with first-rib or clavicular fractures can develop callous formation or pseudoarthrosis that can lead to neurovascular compression.

CLINICAL EVALUATION — The clinical manifestations, diagnosis, and approach to management of each type of TOS, including neurogenic (nTOS), venous (vTOS) and arterial (aTOS), are unique, reflecting compression of a specific structure, although there may be some overlap in symptoms if more than one structure is affected. A thorough physical examination that includes a complete neurologic and vascular evaluation should be performed on all patients.

Compression maneuvers on physical examination (ie, Adson test) may demonstrate a decrease in the radial or ulnar pulse with abduction of the upper extremity overhead. The Adson test is prone to false positive results, and the use of duplex ultrasound with these maneuvers has done little to improve its specificity [28]. Thus, the Adson test is of little clinical value and should not be relied upon to make the diagnosis of any of the three types of TOS [1].

Neurogenic TOS — Symptoms of neurogenic thoracic outlet syndrome (nTOS) include pain, dysesthesia, numbness, and weakness, which may not be localized in specific peripheral nerve distribution. Symptoms are reproducibly aggravated by any activity that requires elevation or sustained use of the arms or hands. These activities include reaching overhead (eg, brushing the hair, holding a telephone to the ear, getting objects from a cabinet), overhead lifting, and prolonged typing or working at a computer, or driving. Provocative maneuvers, including neck rotation, head tilting, arm abduction, external rotation, and the upper limb tension test may duplicate the patient's symptoms. (See "Evaluation of the adult patient with neck pain", section on 'Provocative maneuvers'.)

Prolonged, severe compressions of brachial plexus can lead to muscle weakness and atrophy, but this finding is extremely rare. When present, symptoms include slowly progressive unilateral atrophic weakness of the intrinsic hand muscles that is more evident on the thenar aspect of the hand rather than the hypothenar aspect. Sensory abnormalities in the T1 distribution (figure 3) are common. The syndrome may be caused by a taut congenital band from the first rib to the tip of an elongated C7 transverse process. The lower portion of the plexus is stretched over this band, and chronic traction injury can result in a lower trunk plexopathy. (See "Brachial plexus syndromes", section on 'Thoracic outlet syndrome'.)

Venous TOS — Symptoms of venous compression are the second most common clinical finding of TOS, accounting for about 3 percent of cases. Venous TOS (vTOS) typically occurs in individuals who perform vigorous repetitive exertion of the upper extremities, usually with the arms above shoulder level [1]. Forearm fatigue within minutes of using the arm may be present in vTOS.

Swelling can be accompanied by pain and cyanosis of the affected extremity; paresthesias in the fingers are common but are a manifestation of swelling in the hand rather than nerve compression [1]. Collateral venous patterning may be seen in the skin overlying the ipsilateral shoulder, neck, and chest wall and indicates compensatory superficial venous flow due to subclavian vein stenosis or occlusion.

Upper extremity edema due to varying degrees of venous compression or overt deep vein thrombosis is the hallmark of vTOS. Upper extremity venous thrombosis due to thoracic outlet compression is termed "spontaneous" to distinguish it from instrumentation-related or "catheter-induced" venous thrombosis. Spontaneous upper extremity venous thrombosis is historically referred to as Paget-Schroetter syndrome or "effort" thrombosis. Spontaneous upper extremity venous thrombosis is discussed elsewhere. (See "Primary (spontaneous) upper extremity deep vein thrombosis".)

Arterial TOS — Symptoms of arterial compression are the least common type of thoracic outlet syndrome, accounting for only about 1 percent of cases. Symptoms develop spontaneously unrelated to work or trauma [1]. Arterial TOS (aTOS) is almost always associated with a cervical rib or anomalous rib. It occurs in young patients without typical atherosclerotic risk factors distinguishing it from peripheral artery disease. (See "Overview of upper extremity peripheral artery disease".)

Hand ischemia with symptoms of pain, pallor, paresthesia, and coldness is the most common presentation. These symptoms are due to arterial thromboembolization arising from mural thrombus from the subclavian artery or a subclavian aneurysm. In young women, this etiology must be differentiated from the Raynaud phenomenon. (See "Clinical manifestations and diagnosis of Raynaud phenomenon".)

Other presentations include upper extremity pain with activity due to subclavian artery stenosis or occlusion. Rarely, thrombus from the subclavian artery can propagate and embolize retrograde, causing stroke [29]. However, because of the rich collateral circulation around the shoulder (figure 4), arm ischemia is uncommon.

On physical examination, patients may have a lower systolic blood pressure in the affected arm and distal pulses at the wrist may be diminished or absent. In patients with thromboembolism, finger ischemia or patchy ischemic skin may be present. A bruit or a thrill may be appreciated over the subclavian artery, and in patients who have developed post-stenotic aneurysmal changes, a pulsatile supraclavicular mass may be palpable. In contrast to patients with nTOS, the scalene muscles will not be tender and provocative maneuvers will not elicit any symptoms. (See 'Neurogenic TOS' above.)

DIAGNOSIS — The predominant clinical symptoms and signs direct the nature of further evaluation depending on the type of TOS.

For arterial and venous TOS, the diagnosis is supported by the demonstration of stenosis or occlusion of the corresponding subclavian vessel in a patient with an appropriate clinical history. Diagnostic tests are often negative or equivocal in neurogenic thoracic outlet syndrome (nTOS). Further imaging is primarily used to exclude other conditions, such as degenerative cervical disk or spinal column disease, shoulder disease, and various forms of intracranial disease.

Electrodiagnostic testing — Electrophysiological evaluation is indicated in anyone with suspected neurogenic TOS, although the majority of nTOS patients test negative. When positive, the electrophysiological signature of neurogenic TOS is quite specific, though not sensitive. Because of the lack of objective and reliable electrodiagnostic testing for the majority of patients with nTOS, some authors distinguish nTOS as either true or disputed nTOS. The electrodiagnostic testing criteria for nTOS are discussed elsewhere. (See "Brachial plexus syndromes", section on 'Thoracic outlet syndrome'.)

Scalene muscle test injection — Local anesthetic injected into the anterior scalene muscle may be a helpful diagnostic maneuver for nTOS; a positive response (relief of symptoms) helps predict success with surgical decompression [30-36].

Reporting standards from the Society for Vascular Surgery include the response to scalene injection in their criteria to define nTOS [37]. Three out of the four following criteria must be present.

Signs and symptoms of pathology occurring at the thoracic outlet

Signs and symptoms of a nerve compression

Absence of other pathology potentially explaining the symptoms

Positive response to a properly performed scalene muscle test injection

Physiologic vascular studies — Upper extremity vascular studies may be useful in patients with suspected aTOS. In the setting of embolization, segmental pressures or pulse volume recordings can be used to localize the site of obstruction. (See "Noninvasive diagnosis of upper and lower extremity arterial disease", section on 'Physiologic testing'.)

Imaging — Imaging studies can help confirm a suspected diagnosis of thoracic outlet syndrome. Chest x-rays are important to identify bony abnormalities such as cervical ribs (image 1), long transverse cervical processes, or rib/clavicular fracture calluses [22]. Because more than 90 percent of aTOS patients will have a bony abnormality, the absence of rib abnormalities nearly eliminates a diagnosis of aTOS [1].

Ultrasound – Ultrasonography is the initial imaging test to evaluate aTOS or vTOS because it is inexpensive and noninvasive. Duplex ultrasound is a highly sensitive and specific test for venous stenosis or occlusion when performed by an experienced vascular ultrasound technician [38,39]. A positional test can be easily performed to assess patency of the involved vessels with provocative maneuvers. For aTOS, duplex ultrasonography may demonstrate an increased flow velocity in the subclavian artery at the site of a stenosis or aneurysmal degeneration of the artery distal to a stenosis. These findings in a patient with a typical clinical history and no risk factors for atherosclerosis support a diagnosis of aTOS. Equivocal duplex studies are followed up with additional imaging.

Computed tomography – For further anatomic detail, computed tomography (CT) demonstrates the relationship of vascular structures to surrounding bone and muscle (image 2). CT angiography and venography produce high-quality images of the central vasculature and extremity vessels, and three-dimensional reconstruction is increasingly being used to identify the point of vascular compression and assess the extent of pathology.

Magnetic resonance – Contrast-enhanced magnetic resonance (MR) angiography using provocative arm positioning can allow excellent imaging to the vessels and can be a useful diagnostic tool [40]. MR neurogram can also be used to detect compression of the brachial plexus, which may further aid the diagnosis of neurogenic TOS [41].

Conventional arteriography/venography – In many centers, conventional arteriography has been supplanted by CT angiography for the diagnosis of aTOS; however, arteriography may still be needed for patients who have signs and symptoms of acute arterial insufficiency or ischemia, and to plan surgical reconstruction. The advantage of arteriography and venography is the ability to obtain dynamic studies in which the patient performs upper extremity maneuvers during imaging to assist in identifying arterial or venous compression (image 3), or to initiate thrombolytic therapy, if indicated. Although contrast venography is not always needed to establish a diagnosis of vTOS, early intervention with catheter-based thrombolytic therapy appears to be associated with improved outcomes. (See 'Anticoagulation/thrombolysis' below.)

APPROACH TO MANAGEMENT — The treatment approach depends upon the type of TOS. Treatment is indicated only for symptomatic patients. The mere presence of a cervical rib or other rib anomalies does not indicate a need to intervene [1]. Autopsy series demonstrate that about 0.5 percent of the population have cervical ribs, and only a fraction of these patients ever develop symptoms of TOS [42].

Physical therapy — Neurogenic TOS should initially be managed with physical therapy for a period of at least four to six weeks. Patients need to be referred to physical therapists with specific expertise in treating nTOS, given that this entity is distinct from other disorders that affect the neck, shoulder, and arm. Exercises strengthen the muscles surrounding the shoulder, and postural exercises help the patient to sit and stand straighter, potentially lessening pressure on neurovascular structures in the thoracic outlet. Other conservative measures include passage of time and weight reduction [43].

Medical therapy — Interscalene injection of anesthetic agents, steroids, or botulinum toxin type A (BTX-A) have all been used in patients with nTOS with reported success in observational studies [44-48]. However, a randomized trial failed to detect a significant improvement for BTX-A [36].

Anticoagulation/thrombolysis — Management of vTOS historically involved only systemic anticoagulation combined with extremity rest and elevation; however, this approach resulted in long-term morbidity in up to 75 percent of patients [49,50]. Treatment of subclavian thrombosis with catheter-directed thrombolysis is the preferred initial treatment for vTOS for patients with severe symptoms. Success rates for reestablishing subclavian vein patency are nearly 100 percent provided thrombolysis is performed within two weeks of the onset of symptoms [51-53]. (See "Primary (spontaneous) upper extremity deep vein thrombosis", section on 'Approach to treatment'.)

Following restoration of venous patency, persistent venous stenosis and evidence of residual external compression are typical. Some clinicians favor anticoagulation for one to three months following successful thrombolysis to allow endothelial healing and resolution of acute inflammation before definitive thoracic outlet decompression surgery [54]. However, given the significant risk of reocclusion, most advocate surgical decompression during the same hospitalization as thrombolytic therapy. Decompression as early as four hours after thrombolysis appears to be safe and reduces reocclusion of the subclavian vein [55]. (See 'Thoracic outlet decompression' below.)

Managing ischemia — For patients with mild degrees of acute arterial ischemia due to distal embolization from aTOS, catheter-directed thrombolysis may be appropriate before surgical repair. However, more severe ischemia usually requires surgical embolectomy (with or without intraoperative thrombolysis) in conjunction with thoracic outlet decompression. A conduit is usually required, but occasionally, the subclavian artery has a short injury amenable to resection and primary anastomosis. Acceptable conduits include the great saphenous vein, femoral vein, ringed polytetrafluoroethylene, and polyester (ie, Dacron). Distal bypass may be necessary for patients with distal vascular occlusions due to chronic embolization. (See "Subclavian steal syndrome", section on 'Introduction' and "Overview of upper extremity peripheral artery disease".)

Acute ischemia of the upper extremity of sufficient duration may lead to a compartment syndrome; upper extremity fasciotomy may be required. (See "Surgical reconstruction of the upper extremity".)

Timing of intervention during COVID-19 pandemic — The global severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)/coronavirus disease 2019 (COVID-19) pandemic has required a reduction in nonemergency surgical interventions for a variety of disorders, including TOS. The delivery of care during the COVID-19 pandemic should be tailored to the individual clinical situation and availability of institutional resources. An international multidisciplinary consensus group addressed evaluation and treatment of patients with different types of TOS for the three different phases of the COVID-19 pandemic as described below. The phases of local and institutional conditions in response to the COVID-19 pandemic have been defined as: phase 1, preparation phase without hospital resource exhaustion; phase II, limited intensive care unit and ventilator capacity; and phase III, all hospital resources are routed to COVID-19 patients [56].

aTOS – Evaluation and treatment should be reserved for limb-threatening situations, such as acute arm ischemia or digital embolization in all phases of pandemic responses. In late pandemic phases, surgery should be restricted to thrombolysis or thromboembolectomy, with definitive treatment delayed until the pandemic has resolved.

vTOS – Non-occlusive venous TOS treatment and evaluation are postponed. For patients presenting with acute thrombosis, anticoagulation and percutaneous intervention are considered in early phases. Surgical decompression is recommended to be delayed until pandemic conditions resolve.

nTOS – In-person evaluation and treatment are generally postponed during all pandemic phases. Telemedicine visits and at-home physical therapy exercises are recommended when feasible.

THORACIC OUTLET DECOMPRESSION — The first operations for thoracic outlet compression described treatment of subclavian artery aneurysms in patients with cervical ribs [57]. Anterior scalenotomy [58] and, later, other operative approaches to rib resection in TOS were described, including a posterior thoracotomy approach (no longer used), transaxillary approach, supraclavicular approach, and infraclavicular approach [59-61].

Indications for surgery — Thoracic outlet decompression is indicated for symptomatic patients with:

Vascular TOS (aTOS, vTOS) to manage or to prevent complications in patients who are not at high risk for surgery. (See 'aTOS' below and 'vTOS' below.)

Selected patients with nTOS who have acute or subacute progressive neurologic weakness or disabling pain and paresthesia, or who failed nonoperative therapy [62]. (See 'nTOS' below.)

Approaches — There are multiple surgical approaches for thoracic outlet decompression, including the transaxillary, supraclavicular, and infraclavicular approaches. The choice of procedure depends upon the anatomic abnormalities that are identified and surgeon preference.

The transaxillary approach to thoracic outlet decompression has the advantage of more complete visualization of the rib during resection, but it does not allow for vascular reconstruction. The approach requires a limited amount of dissection, and external scarring is minimized. A transverse incision is made at the inferior margin of the axilla from the pectoralis major anteriorly to the latissimus dorsi posteriorly. The incision is deepened to identify the lateral chest wall and continued superiorly to the thoracic outlet with care to avoid injury to the long thoracic and intercostal brachial nerve. The first rib is seen following identification of the axillary vessels and first thoracic nerve root. The subclavius and anterior scalene muscles are divided to free the first rib. Once the periosteum is cleared from the first rib, the rib is resected, which usually requires removing the rib in multiple pieces due to the confined space. The edges of the bone are smoothed with a file or rongeur.

The supraclavicular approach to thoracic outlet decompression provides a wider exposure of the ribs, and the site of compression can be directly identified; arterial reconstruction can be performed, as needed. The anterior and middle scalene muscles can be completely resected with this approach, and brachial plexus neurolysis can also be performed. Resection of the first rib may not be needed to achieve sufficient decompression.

The infraclavicular approach is particularly useful in cases of vTOS. It allows an excellent exposure for surgical venous reconstruction. Exposure of the central veins can be achieved by extending the incision medially and performing a transverse sternotomy. (See "Primary (spontaneous) upper extremity deep vein thrombosis".)

Outcomes — The prognosis of surgical decompression for thoracic outlet syndrome varies depending upon the clinical type [63].

Derkash's classification is commonly used to rate the outcomes of surgery as follows [64]:

Excellent result: No pain, easy return to preoperative professional and leisure daily activities.

Good result: Intermittent pain well tolerated, possible return to preoperative professional and leisure daily activities.

Fair result: Intermittent pain with bad tolerance, difficult return to preoperative professional and leisure daily activities.

Poor result: Symptoms not improved or aggravated.

The Disabilities of the Arm, Shoulder and Hand (DASH) score is another measure of upper extremity function that is commonly used to follow outcomes of orthopedic treatments. A calculator can be found at the orthopedic scores website [65]. The DASH questionnaire covers symptoms and physical, social, and psychological function with a score from 0 to 100, with 0 reflecting no disability and 100 reflecting maximum disability.

nTOS — We generally advocate a conservative approach to nTOS, taking into account the potential benefits and risks of surgical decompression. Given the rate of recurrence and potential surgical complications, the utility of surgical decompression for nTOS remains debated. Unlike patients with aTOS or vTOS, clinical signs or diagnostic imaging cannot objectively gauge resolution of symptoms in patients with nTOS. Surgical success is somewhat subjective and based upon an individual's perception of disability before and after decompression. Use of commonly used functional measurements/quality-of-life scores such as the DASH score and Derkash classification system is particularly useful for evaluating the outcome of surgical intervention in nTOS patients.

Studies evaluating surgical outcomes of thoracic outlet decompression for nTOS are from institutions specialized in the treatment of these patients and predominantly retrospective in nature [66-70]. However, one trial (STOPNTOS) randomly assigned 50 patients with a diagnosis of nTOS refractory to conservative therapy to transaxillary thoracic outlet decompression or continued conservative treatment [71]. At three months, mean DASH scores were significantly improved for those who underwent thoracic outlet decompression compared with continued conservative treatment (45.2 versus 64.9). All patients in the conservative treatment group applied for surgery three months after randomization. While functional and quality-of-life scores were lower for the conservative treatment group who crossed over to surgical treatment compared with those initially randomized to surgical decompression, the observed difference was not statistically significant. Postoperatively, transient neurologic complications occurred in 7 of 46 patients analyzed, and the overall failure rate after one year was 20 percent (6 with recurrence at one year, 3 with persistent nTOS). The outcomes of decompression surgery in this trial are overall consistent with those reported in prior observational studies. Further larger trials with longer-term follow-up are needed to better compare surgery with ongoing conservative management (beyond three months).

In comparative reviews, the outcomes for the various surgical approaches to nTOS (eg, transaxillary, supraclavicular, infraclavicular, combinations) were overall similar with initial high success rates of 91 to 93 percent [66-69]. However, over time, success rates waned [70,72-77]. In one early review, at 10 years, the success rate among all approaches ranged from 64 to 71 percent [68]. In a later systematic review, preoperative DASH improved by 28.3 points after surgery for nTOS, and 56 to 89 percent of patients had improved symptoms (mean follow-up 12 to 150 months) [63].

Factors that predict surgical failure include major depression, chronic symptoms, work-related injury, lack of response to anterior scalene muscle blocks, and diffuse arm symptoms [21,43,78-80].

aTOS — Results following treatment of aTOS are measured by resolution of ischemic symptoms, improvement in quality of life, and vessel patency. For aTOS, long-term outcomes following thoracic outlet decompression correlate with the status of the distal circulation. Upper extremities with ischemia due to embolization have a worse prognosis. In a systematic review that included two studies, improvement to Derkash's classification category excellent/good was achieved in >90 percent of the aTOS patients [63]. One report of 55 cases of aTOS found at a mean follow-up of 5.7 months, 91 percent of patients were asymptomatic, and 9 percent had exertional symptoms [8]. Three of the four patients who were symptomatic at follow-up required embolectomy for brachial artery occlusion, which was associated with hand ischemia. Others report successful long-term outcomes following intervention in 18 patients with arterial reconstruction and decompressions operations. Only 1 of 18 patients required reintervention at four months for bypass occlusion [81].

vTOS — Outcomes for surgical therapy of vTOS are measured by resolution of venous thrombotic symptoms, improvement in quality of life, vessel patency, and technical success. Most patients undergoing successful thrombolysis followed by decompression have five-year secondary vein patency rates greater than 95 percent with successful clinical outcomes [50-53,82]. In a systematic review that included three studies, improvement to Derkash's classification category excellent/good was achieved in 90 percent of the vTOS patients. (See "Primary (spontaneous) upper extremity deep vein thrombosis".)

SUMMARY AND RECOMMENDATIONS

Thoracic outlet syndrome – Thoracic outlet syndrome (TOS) refers to a constellation of signs and symptoms arising from compression of the upper extremity neurovascular bundle by various structures in the area just above the first rib and behind the clavicle, typically within the confined space of the thoracic outlet. The term thoracic outlet syndrome is not a specific diagnosis, and the appropriate type of TOS, such as neurogenic (nTOS), arterial (aTOS), or venous (vTOS) thoracic outlet syndrome should be used. (See 'Introduction' above.)

Causes –Thoracic outlet syndromes are due to rib anomalies, muscular anomalies, or a result of injury. Cervical ribs predispose the patient to TOS after hyperextension-flexion (whiplash) injury. The absence of a rib anomaly makes the diagnosis of arterial thoracic outlet syndrome less likely. Many patients with nTOS have a prior history of neck trauma or repetitive occupational physical stress. Similarly, vTOS is highly associated with repetitive movements, particularly with repetitive overhead upper extremity movements. (See 'Pathogenesis' above.)

Clinical evaluation – Each type of thoracic outlet syndrome can usually be differentiated with clinical history, physical exam, neurophysiological testing, and imaging. (See 'Clinical evaluation' above.)

Symptoms of nTOS include upper extremity pain, dysesthesia, weakness, and numbness in the hand, arm, or shoulder. Progressive unilateral atrophic weakness of the hypothenar hand muscles and numbness in the distribution of the ulnar nerve and medial antebrachial cutaneous nerves can occur, but very rarely. Tenderness over the scalene muscles is often present.

aTOS typically presents as thromboembolism to the hand or arm. Features of arm/hand ischemia include pain, paresthesia, pallor, and coolness.

vTOS is generally easily differentiated from the other forms of TOS because venous compression leads to upper extremity swelling and cyanosis with or without deep venous thrombosis. Due to swelling, some patients may complain of hand paresthesias.

Diagnosis – Diagnosis of nTOS is often clinical, but electrodiagnostic tests and imaging can exclude other diagnosis. Arterial or venous duplex ultrasounds are the initial diagnostic tests for aTOS or vTOS, respectively. The role for computed tomographic or magnetic resonance imaging is evolving and provides important diagnostic information, especially when ultrasound results are equivocal. Conventional arteriography (aTOS) and venography (vTOS) remain useful diagnostic modalities, especially when initiation of thrombolysis is considered. (See 'Diagnosis' above.)

Treatment of nTOS – Patients with nTOS should be managed conservatively with physical therapy and weight loss supplemented by medical therapy unless they have progressive neurologic weakness or disabling pain and paresthesia. Patients who have not responded to conservative treatment may become candidates for thoracic outlet decompression; however, the patient needs to understand that the long-term success rates for thoracic outlet decompression for nTOS diminish over time. (See 'Physical therapy' above and 'Outcomes' above.)

Treatment of vTOS – For patients with deep vein thrombosis due to vTOS, thrombolysis and early thoracic outlet decompression are performed to relieve extrinsic vein compression. In properly selected patients, long-term outcomes are excellent following thrombolysis and thoracic outlet decompression. (See 'Anticoagulation/thrombolysis' above and 'Outcomes' above and "Primary (spontaneous) upper extremity deep vein thrombosis" and "Primary (spontaneous) upper extremity deep vein thrombosis", section on 'Approach to treatment'.)

Treatment of aTOS – Patients with aTOS are treated according to the nature of their symptoms and initial presentation. Patients with signs and symptoms of upper extremity thromboembolism undergo thoracic outlet decompression in conjunction with embolectomy, thrombolytic therapy, or anticoagulation. Arterial TOS is nearly always associated with a correctable anatomic bony abnormality, and, without decompression, the rate of recurrent thromboembolism is high. The supraclavicular approach offers direct access to the subclavian artery. Occasionally, arterial reconstruction (ie, surgical bypass) may be needed. (See 'Anticoagulation/thrombolysis' above and 'Managing ischemia' above and 'Outcomes' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Matthew L White, MD, who contributed to an earlier version of this topic review.

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