eMedicine Specialties > Physical Medicine and Rehabilitation > Plexopathy

Thoracic Outlet Syndrome: Differential Diagnoses & Workup

Author: Benjamin M Sucher, DO, FAAPMR, FAOCPMR, Medical Director, EMG Labs of AARA (Arizona Arthritis & Rheumatology Associates)
Contributor Information and Disclosures

Updated: Jul 1, 2009

Differential Diagnoses

Adhesive Capsulitis
Fibromyalgia
Carpal Tunnel Syndrome
Radiation-Induced Brachial Plexopathy
Cervical Disc Disease
Rheumatoid Arthritis
Cervical Myofascial Pain
Rotator Cuff Disease
Cervical Spondylosis
Traumatic Brachial Plexopathy
Cervical Sprain and Strain
Workers' Compensation System
Chronic Pain Syndrome
Complex Regional Pain Syndromes

Other Problems to Be Considered

Cervical myelopathy
Cervical radiculopathy
Double crush syndrome (thoracic outlet syndrome and compression at another distal or proximal site)
Paget-von Schroetter syndrome, effort syndrome (spontaneous venous thrombosis, primary deep venous thrombosis of the upper extremity)
Pancoast (apical lung) tumor
Shoulder tendonitis, bursitis, impingement6
Shoulder (glenohumeral) instability
Raynaud syndrome
Ulnar neuropathy (cubital tunnel syndrome, Guyon canal syndrome)

Workup

Laboratory Studies

  • Laboratory studies are used to rule out other systemic problems.

Imaging Studies

  • In cases of nonspecific thoracic outlet syndrome (TOS), all studies have normal findings; however, testing to evaluate for other treatable problems or to establish true neurogenic or true vascular TOS usually is indicated.
  • Radiographs
    • Radiographs of the chest (with apical lordotic views) and cervical spine should be obtained.
    • Rule out significant cervical spine degenerative changes that may be causing neck/shoulder pain or impingement of the spinal nerve roots; also eliminate the possibility of upper lobe lung masses.
    • Radiographs can also help identify cervical ribs, which may be responsible for plexus injury or have associated fibrous bands.
    • Radiographs may help identify elevated first ribs, caused by tight contracted anterior/middle scalene muscles. Displaced clavicle fractures, nonunion, and exuberant callus also can be identified.
  • Magnetic resonance imaging (MRI) and computed tomography (CT) scanning
    • An MRI of the cervical spine and supraclavicular/brachial plexus area is useful to identify other causes, or a CT scan of the brachial plexus area and apical lung may be indicated.
    • MRI and CT scans can identify cervical root injury from degenerative spurs, disc herniation, or other causes. Some authors have reported that MRI can identify distortion or displacement of the plexus in the thoracic outlet or supraclavicular space, usually from fibrous bands but also from clavicular abnormality (callus, fracture displacement). In addition, MRI has been reported to demonstrate differences in the costoclavicular measurements during provocative stress maneuvers, in patients with thoracic outlet compression.8
  • Doppler and noninvasive blood flow studies
    • Doppler and plethysmography studies can identify interruption of blood flow to the involved extremity. A near-complete cut-off of flow during the stress maneuver with reproduction of the primary symptoms should be noted.
    • Hyperabduction is somewhat controversial, since most normal individuals lose flow with the position and also may develop symptoms.
  • Angiography/venography
    • Angiography and venography can identify blockage of the vessels from thrombi or emboli, which result in vascular symptoms.
    • Angiography can detect aneurysms that may be compressing the plexus and causing neurologic symptoms. This finding documents true vascular TOS.
  • Autonomic assessment (thermography)
    • Autonomic assessment has demonstrated thermal/temperature asymmetry consistent with nerve irritation or some interference with blood flow.
    • Following successful treatment, thermal symmetry usually is restored and should correlate well with reduction or elimination of symptoms. This technique remains controversial, and, although the sensitivity has been considered high, the specificity is low and has not been well established.

Other Tests

  • EMG and nerve conduction studies, also known as electrodiagnostic studies, are necessary to identify true neurogenic thoracic outlet syndrome (TOS) and to rule out other sites of compression neuropathy. With true neurogenic TOS, reported abnormalities include the following:
    • Low-amplitude ulnar sensory response. This finding may be variable, since the fifth digit is believed to be supplied primarily by C8 nerve fibers, whereas the T1 fibers are more deflected, stretched, or angulated by a cervical band (or rib) and thereby more likely to sustain injury in TOS.
    • Low-amplitude median motor response. The thenar muscles are supplied more from the T1 root, whereas the hypothenar muscles receive primarily C8 innervation.
    • Normal median sensory response.
    • Neurogenic motor units within the C7-T1 or lower trunk distribution on needle EMG.
    • Abnormal medial antebrachial cutaneous response (low-amplitude or unobtainable). Some authors believe that this finding can aid in the early diagnosis of neurogenic TOS. This test primarily assesses the T1 fibers.
    • Abnormal C7-T1 root stimulation (prolonged latency).
    • Abnormal F-wave study (prolonged latency, with either full F-wave or axillary F-loop)
    • Absent or attenuated N13 response in ulnar-derived somatosensory evoked potentials
  • The degree of nerve injury determines the abnormalities described above. In severe injuries with massive axon loss all of the above findings are seen. In cases where part of the lower plexus is spared, the findings are less dramatic. In these cases, the needle EMG is more likely to show abnormalities.

Procedures

  • In most patients with nonspecific thoracic outlet syndrome (TOS), there are no indicated procedures. An anterior scalene block can be performed to anesthetize the anterior scalene muscle and to relieve pressure from the brachial plexus. Thus, this type of block is diagnostic but also may be therapeutic.
    • The anterior scalene block is a potentially dangerous procedure because the plexus can be injured directly in the process; however, its reliability, accuracy, and safety may be improved with the use of electrophysiologic guidance to verify needle tip placement.
    • Jordan and Machleder believe that a negative response to this block excludes a surgical treatment option, while a positive response predicts which patients should benefit from surgical decompression.9
    • In a study of patients being tested for neurogenic TOS, Torriani et al concluded that diagnostic injection of anesthetic into the anterior scalene muscle can be safely performed with ultrasonographic guidance.10  The investigators administered injections to 26 patients with suspected neurogenic TOS, reporting technical success (ie, anterior scalene muscle identification, intramuscular needle placement, and intramuscular medication delivery) in all procedures, with no major complications occurring. They concluded that this was a well-tolerated diagnostic test.

Histologic Findings

Biopsy results have not been reported systematically, and the procedure is not indicated unless some other condition is being considered.

More on Thoracic Outlet Syndrome

Overview: Thoracic Outlet Syndrome
Differential Diagnoses & Workup: Thoracic Outlet Syndrome
Treatment & Medication: Thoracic Outlet Syndrome
Follow-up: Thoracic Outlet Syndrome
Multimedia: Thoracic Outlet Syndrome
References
Further Reading
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Keywords

thoracic outlet syndrome, thoracic outlet, thoracic syndrome, outlet syndrome, brachial plexus, brachial plexopathy, brachial plexus injury, cervical rib syndrome, cervicobrachial myofascial pain syndrome, cervicobrachial pain syndrome, costoclavicular mass syndrome, costoclavicular syndrome, scalenus anticus syndrome, scalenus syndrome, thoracic outlet compression syndrome

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Contributor Information and Disclosures

Author

Benjamin M Sucher, DO, FAAPMR, FAOCPMR, Medical Director, EMG Labs of AARA (Arizona Arthritis & Rheumatology Associates)
Benjamin M Sucher, DO, FAAPMR, FAOCPMR is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, American Osteopathic Association, and American Osteopathic College of Physical Medicine and Rehabilitation
Disclosure: Nothing to disclose.

Medical Editor

Robert E Windsor, MD, FAAPMR, FAAEM, FAAPM, President and Director, Georgia Pain Physicians, PC; Clinical Associate Professor, Department of Physical Medicine and Rehabilitation, Emory University School of Medicine
Robert E Windsor, MD, FAAPMR, FAAEM, FAAPM is a member of the following medical societies: American Academy of Pain Medicine, American Academy of Physical Medicine and Rehabilitation, American College of Sports Medicine, American Medical Association, International Association for the Study of Pain, Physiatric Association of Spine, Sports and Occupational Rehabilitation, and Texas Medical Association
Disclosure: Nothing to disclose.

Pharmacy Editor

Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment

Managing Editor

Patrick M Foye, MD, FAAPMR, FAAEM, Associate Professor of Physical Medicine and Rehabilitation, Co-Director of Musculoskeletal Fellowship, Co-Director of Back Pain Clinic, Director of Coccyx Pain Service (Tailbone Pain Service: www.TailboneDoctor.com), University of Medicine and Dentistry of New Jersey, New Jersey Medical School
Patrick M Foye, MD, FAAPMR, FAAEM is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation, American Association of Neuromuscular and Electrodiagnostic Medicine, Association of Academic Physiatrists, and International Spine Intervention Society
Disclosure: Nothing to disclose.

CME Editor

Kelly L Allen, MD, Regional Medical Director, IMX-Medical Management Services
Disclosure: Nothing to disclose.

Chief Editor

Robert H Meier III, MD, Director, Amputee Services of America; Active Medical Staff, Presbyterian/St Luke's Hospital, Spalding Rehabilitation Hospital, Select Specialty Hospital; Consulting Staff, Kindred Hospital
Robert H Meier III, MD is a member of the following medical societies: American Academy of Physical Medicine and Rehabilitation and Association of Academic Physiatrists
Disclosure: Nothing to disclose.

 
 
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