What is the role of EMG and NCS in the workup of thoracic outlet syndrome?

Updated: Jan 10, 2019
  • Author: Daryl A Rosenbaum, MD; Chief Editor: Sherwin SW Ho, MD  more...
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Answer

Electrodiagnostic studies can be helpful for classic cases of neurogenic thoracic outlet syndrome and therefore can be useful when the results are positive. However, many symptoms are intermittent in neurogenic thoracic outlet syndrome; therefore, negative test results do not rule out this diagnosis. Electrodiagnostic testing can also be helpful in diagnosing other neuromuscular disorders.

Nerve conduction velocity has been used for the diagnosis of thoracic outlet syndrome as defined by a reduction to less than 85 m/s of either the ulnar or median nerves across the thoracic outlet and was found to corroborate the clinical diagnosis. A nerve conduction velocity of less than 60 m/s was considered an indication for surgery. [24] However, as with many aspects of thoracic outlet syndrome, this remains controversial and has not been universally accepted.

Somatosensory evoked potentials are equally controversial, with some studies favoring their use [29] and others not. [30]

Electromyography may be helpful in confirming the presence or absence of a specific alternative diagnosis.

A study reported that intravascular ultrasound detected greater levels of stenosis than venography in the treatment of 14 venous thoracic outlet syndrome patients. [54]

 


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