Electrophysiological assessment in neurogenic thoracic outlet syndrome.

OBJECTIVES: To evaluate the value of different electrophysiological techniques in the diagnosis of neurogenic thoracic outlet syndrome (TOS).
MATERIALS AND METHODS: Two females, aged 22 and 30 years, with progressive weakness and wasting of the right hand with slight sensory disturbances. Needle EMG, motor and sensory conduction along median and ulnar nerves, sensory conduction of medial (MACN) and lateral (LACN) antebrachial cutaneous nerves.
RESULTS: Chronic neurogenic atrophy in small hand muscles, more severe in lateral part of thenar eminency, reduced compound muscle action potentials (CMAPs) more severe by median than ulnar stimulation, and reduced amplitude of the SNAPs of ulnar and MACN were the main findings consistent with neurogenic TOS. Both patients had right cervical rib in radiography.
CONCLUSIONS: Electrophysiological study is useful in the diagnosis of neurogenic TOS. Reduced amplitude of MACN and ulnar nerve SNAPs, predominant denervation in thenar eminency, and reduced amplitude of CMAPs, more by median than by ulnar stimulation, are consistent with the diagnosis.