Outcomes of surgery for neurogenic thoracic outlet syndrome (NTOS) in workers’ compensation are poor in a majority of patients, partly due to nonspecificity of diagnosis. Most cases have no objective evidence of the presence of brachial plexus dysfunction. Up to 20% of patients experience a new adverse event. Objective neurologic signs and electrodiagnostic evidence of brachial plexus dysfunction must be present before proceeding with invasive procedures. This guideline includes objective criteria that must be met before thoracic outlet syndrome surgery can be approved in Washington State. Evidence does not support the use of scalene blocks, botulinum toxin therapy, or vascular studies to diagnose NTOS.
Key points
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The diagnosis and treatment of neurogenic thoracic outlet syndrome (NTOS) are highly controversial and associated with surgical interventions based on no clear-cut evidence of presence of true thoracic outlet syndrome (TOS).
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Considering the poor outcomes reported from the surgical management of NTOS in most workers’ compensation cases, this guideline requires objective evidence of brachial plexus disorder, including abnormal electrodiagnostic tests.
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In workers’ compensation, a majority of patients have poor outcomes of surgery for NTOS 1 year after surgery.
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Approximately 20% of patients may have new adverse outcomes, primarily related to new neurologic complaints or lung pathology, the most serious of which is phrenic nerve dysfunction.
Introduction
This guideline is to be used by physicians, claim managers, occupational nurses, and utilization review staff. The emphasis is on accurate diagnosis and treatment that are curative or rehabilitative (see http://app.leg.wa.gov/WAC/default.aspx?cite=296-20-01002 for definitions). An electrodiagnostic worksheet and guideline summary are appended to the end of this document.
This guideline was developed in 2010 by the Washington State Industrial Insurance Medical Advisory Committee (IIMAC) and its subcommittee on Upper Extremity Entrapment Neuropathies. The subcommittee presented its work to the full IIMAC, and the IIMAC voted with full consensus advising the Washington State Department of Labor and Industries to adopt the guideline. This guideline was based on the weight of the best available clinical and scientific evidence from a systematic review of the literature (evidence was classified using criteria defined by the American Academy of Neurology) and a consensus of expert opinion. One of IIMAC’s primary goals is to provide standards that ensure high quality of care for injured workers in Washington State.
TOS is characterized by pain, paresthesias, and weakness in the upper extremity, which may be exacerbated by elevation of the arms or by exaggerated movements of the head and neck. There are 3 categories of thoracic outlet syndrome: arterial, venous, and neurogenic. Arterial and venous thoracic outlet syndromes involve obstruction of the subclavian artery or vein, respectively, as they pass through the thoracic outlet. These vascular categories of TOS should include obvious clinical signs of vascular insufficiency: a cold, pale extremity in cases of arterial TOS, or a swollen, cyanotic extremity in cases of venous TOS. There is a separate surgical guideline for vascular TOS. This guideline focuses solely on nonacute NTOS.
Work-related NTOS occurs due to compression of the brachial plexus, predominantly affecting its lower trunk, at 1 of 3 potential sites. Compression can occur between the anterior scalene muscle (ASM) and middle scalene muscle (or sometimes through the ASM); beneath the clavicle in the costoclavicular space; or beneath the tendon of the pectoralis minor.
The medical literature describes 2 categories of NTOS: true NTOS and disputed NTOS. A diagnosis of true NTOS requires electrodiagnostic study (EDS) abnormalities showing evidence of brachial plexus injury (discussed later). Disputed NTOS describes cases of NTOS for which EDS abnormalities have not been demonstrated. To avoid confusion that has arisen over these categories, this guideline does not use such terms. Rather, it provides guidance regarding treatment of cases of NTOS that have been confirmed by EDS abnormalities compared with those cases for which the provisional diagnosis has not been confirmed by such studies.
In general, work-relatedness and appropriate symptoms and objective signs must be present for the Washington State Department of Labor and Industries to accept NTOS on a claim. EDSs, including nerve conduction velocity studies and needle electromyography (EMG), should be scheduled immediately to confirm the clinical diagnosis. If time loss extends beyond 2 weeks or if surgery is requested, completion of EDSs is required and does not need prior authorization.
Introduction
This guideline is to be used by physicians, claim managers, occupational nurses, and utilization review staff. The emphasis is on accurate diagnosis and treatment that are curative or rehabilitative (see http://app.leg.wa.gov/WAC/default.aspx?cite=296-20-01002 for definitions). An electrodiagnostic worksheet and guideline summary are appended to the end of this document.
This guideline was developed in 2010 by the Washington State Industrial Insurance Medical Advisory Committee (IIMAC) and its subcommittee on Upper Extremity Entrapment Neuropathies. The subcommittee presented its work to the full IIMAC, and the IIMAC voted with full consensus advising the Washington State Department of Labor and Industries to adopt the guideline. This guideline was based on the weight of the best available clinical and scientific evidence from a systematic review of the literature (evidence was classified using criteria defined by the American Academy of Neurology) and a consensus of expert opinion. One of IIMAC’s primary goals is to provide standards that ensure high quality of care for injured workers in Washington State.
TOS is characterized by pain, paresthesias, and weakness in the upper extremity, which may be exacerbated by elevation of the arms or by exaggerated movements of the head and neck. There are 3 categories of thoracic outlet syndrome: arterial, venous, and neurogenic. Arterial and venous thoracic outlet syndromes involve obstruction of the subclavian artery or vein, respectively, as they pass through the thoracic outlet. These vascular categories of TOS should include obvious clinical signs of vascular insufficiency: a cold, pale extremity in cases of arterial TOS, or a swollen, cyanotic extremity in cases of venous TOS. There is a separate surgical guideline for vascular TOS. This guideline focuses solely on nonacute NTOS.
Work-related NTOS occurs due to compression of the brachial plexus, predominantly affecting its lower trunk, at 1 of 3 potential sites. Compression can occur between the anterior scalene muscle (ASM) and middle scalene muscle (or sometimes through the ASM); beneath the clavicle in the costoclavicular space; or beneath the tendon of the pectoralis minor.
The medical literature describes 2 categories of NTOS: true NTOS and disputed NTOS. A diagnosis of true NTOS requires electrodiagnostic study (EDS) abnormalities showing evidence of brachial plexus injury (discussed later). Disputed NTOS describes cases of NTOS for which EDS abnormalities have not been demonstrated. To avoid confusion that has arisen over these categories, this guideline does not use such terms. Rather, it provides guidance regarding treatment of cases of NTOS that have been confirmed by EDS abnormalities compared with those cases for which the provisional diagnosis has not been confirmed by such studies.
In general, work-relatedness and appropriate symptoms and objective signs must be present for the Washington State Department of Labor and Industries to accept NTOS on a claim. EDSs, including nerve conduction velocity studies and needle electromyography (EMG), should be scheduled immediately to confirm the clinical diagnosis. If time loss extends beyond 2 weeks or if surgery is requested, completion of EDSs is required and does not need prior authorization.
Establishing work-relatedness
Work-related activities may cause or contribute to the development of NTOS. Because simply identifying an association with workplace activities is not, in itself, adequate evidence of a causal relationship, establishing work-relatedness requires all of the following:
- 1.
Exposure: workplace activities that contribute to or cause NTOS
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Outcome: a diagnosis of NTOS that meets the diagnostic criteria (discussed later)
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Relationship: generally accepted scientific evidence, which establishes on a more probable than not basis (greater than 50%) that the workplace activities (exposure) in an individual case contributed to the development or worsening of the condition (outcome)
When the Washington State Department of Labor and Industries receives notification of an occupational disease, an occupational disease and employment history form is mailed to the worker, employer, or attending provider. The form should be completed and returned to the insurer as soon as possible. If a worker’s attending provider completes the form, provides a detailed history in the chart note, and gives an opinion on causality, the provider may be paid for this (use billing code 1055M). Additional billing information is available in the Attending Doctor’s Handbook (Available at: http://www.lni.wa.gov/IPUB/252-004-000.pdf ).
Symptoms of NTOS may be exacerbated by certain work-related activities, usually involving elevation or sustained use of the arms. Such activities may include but are not limited to the following :
Lifting overhead
Reaching overhead
Holding tools or objects above shoulder level
Carrying heavy weights
Several occupations have been associated with NTOS. This is not an exhaustive list and is meant only as a guide in the consideration of work-relatedness:
Dry wall hanger or plasterer
Welder
Beautician
Assembly line inspector
Shelf stocker
Dental hygienist
Making the diagnosis
Symptoms and Signs
A case definition of confirmed NTOS includes appropriate symptoms, objective physical findings (signs), and abnormal EDSs. A provisional diagnosis of NTOS may be made based on appropriate symptoms and objective signs, but confirmation of the diagnosis requires abnormal EDSs.
Classic symptoms of NTOS include pain, paresthesias, and weakness in the upper extremity. Paresthesias most commonly affect the ring and small fingers. Symptom severity tends to increase after certain activities and worsens at the end of the day or during sleep.
Signs on examination may include tenderness to palpation over the brachial plexus, the scalene muscles, the trapezius muscles, or the anterior chest wall. Although tenderness may be a useful objective finding, it cannot support the diagnosis of NTOS alone. Advanced cases of NTOS are characterized by objective signs of weakness of the hand, loss of dexterity of the fingers, and atrophy of the affected muscles.
Provocative tests have been described that may help corroborate the diagnosis of NTOS. These tests are based on creating maximal tension on the anatomic sites of constriction. Studies have found a high false-positive rate for these tests in healthy subjects as well as patients with carpal tunnel syndrome. Although they are described for completeness, the sensitivity and specificity of these tests for NTOS have not been established, and these tests cannot replace confirmatory EDS testing (discussed later).
Provocative tests include
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The elevated arm stress test (or Roos test)—patient places the affected arm in full abduction and external rotation and then opens and closes the hands slowly for 3 minutes. This test constricts the costoclavicular space. It is considered abnormal if typical symptoms are elicited and the patient cannot sustain this activity for the full 3 minutes.
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The Adson test—patient extends the neck and rotates the head toward the involved extremity, which is held extended at the side. This test constricts the interscalene triangle. It is considered abnormal if a change in the radial pulse is detected when the patients inhale deeply and hold their breath.
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The Wright test—patient sits or stands with the arm in full abduction and external rotation. This test constricts the costoclavicular space. It is considered abnormal if typical symptoms are elicited and a change in pulse is detected.
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The costoclavicular test—examiner depresses patient’s shoulder. This test constricts the costoclavicular space and creates tension across the pectoralis minor. It is considered abnormal if typical symptoms are elicited.
Every effort should be made to objectively confirm the diagnosis of NTOS before considering surgery. A differential diagnosis for NTOS includes musculoskeletal disease (eg, arthritis or tendinitis) of the cervical spine, shoulder girdle, or arm; cervical radiculopathy or upper extremity nerve entrapment ; idiopathic inflammation of the brachial plexus (also known as Parsonage-Turner syndrome); and brachial plexus compression due to an infiltrative process or space-occupying mass (eg, Pancoast tumor of the lung apex).
Electrodiagnostic Studies
EDS abnormalities are required to objectively confirm the diagnosis of NTOS. Given the uncertainties in diagnostic assessment of NTOS, EDSs should be obtained as soon as the diagnosis is considered. EDSs may help gauge the severity of injury. EDSs can help exclude conditions that may mimic NTOS, such as ulnar nerve entrapment or cervical radiculopathy. EDS evidence that confirms a diagnosis of NTOS requires
- 1.
Absent or reduced amplitude (<12 uV) of the ulnar antidromic sensory nerve action potential (SNAP) or absent or reduced amplitude (<10 uV) of the medial antebrachial cutaneous nerve (MABC) antidromic SNAP, with normal amplitude of the MABC SNAP in the contralateral (unaffected) extremity and
- 2.
Absent or reduced amplitude (<5 mV) of the median nerve compound motor action potential (CMAP) or absent or prolonged minimum latency (>33 ms) of the ulnar F wave (with or without abnormalities of the median F wave) and with normal F waves in the contralateral (unaffected) upper extremity or needle EMG showing denervation (eg, fibrillation potentials, positive sharp waves) in at least 1 muscle supplied by each of 2 different nerves from the lower trunk of the brachial plexus, with normal EMG of the cervical paraspinal muscles and at least 1 muscle supplied by a nerve from the middle or upper trunk of the brachial plexus. And, to exclude the presence of other focal neuropathies or polyneuropathy as a cause for the abnormalities (described previously), the following must also be shown:
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Normal amplitude (≥15 uV) of the median nerve antidromic SNAP and
- 4.
Normal conduction velocity (≥50 m/s) of the ulnar motor nerve across the elbow
Other Diagnostic Tests
Arterial or venous vascular studies may be helpful in the diagnosis of suspected arterial or venous TOS. These tests have poor specificity, however, for NTOS, and there is no substantial evidence that vascular studies can reliably confirm the diagnosis of NTOS. Therefore, vascular studies conducted as a diagnostic tool for NTOS are not authorized.
Some investigators have suggested that MRI neurography may be helpful in the diagnosis of NTOS. This service is not authorized for this condition, however, because the clinical utility of these tests has not yet been proved. Although the IIMAC recognizes that this tests may be useful in unusual circumstances where EDS results are normal but there are appropriate clinical symptoms, the IIMAC believes that at this time the use of these tests is investigational and should be used only in a research setting.
ASM blocks have been used in the evaluation of suspected NTOS. This test has poor specificity for NTOS, however, and there is no substantial evidence that ASM can reliably confirm the diagnosis of NTOS. Therefore, ASM blocks conducted as a diagnostic tool for NTOS are not authorized.
Radiographs of the chest may be useful to evaluate the possibility of an infiltrative process or space-occupying mass (eg, Pancoast tumor of the lung apex) compressing the brachial plexus.
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