Sensory and motor evoked potentials findings in patients with thoracic outlet syndrome.
OBJECTIVE
Diagnostic utility of somatosensory and motor evoked potentials in two patients with neurogenic and vascular thoracic outlet syndrome (TOS) were investigated.


METHODS
In two female patients with progressive weakness and sensory disturbance of the arms, mixed nerve somatosensory evoked potentials (SSEP), and motor evoked potentials (MEP) were tested before and after dynamic position of the affected arm.


RESULTS
The cortical and cervical (C7) ulnar SSEPs demonstrated no change in latency of major peaks at rest and after abduction of the shoulder. A slight diminishment of cortical amplitude was noted in the first patient after the dynamic position of the arm. The MEPs demonstrated significant drop in amplitude after dynamic position of the arm in both cases signifying neurovascular compression during elevation of the affected arm. No change in MEP latency was noted. The MEP amplitude completely returned to normal after repositioning the arm.


CONCLUSIONS
Evoked potential studies are helpful in the diagnosis of neurogenic or vascular TOS. Reduced amplitude of MEP occurs after elevation of the arm above the head which improves after normal position of the arm.
Department of Clinical Neurodiagnostic, Sharp Memorial Hospital, San Diego, California 92123, USA. Siavash.haghighi@sharp.com
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Haghighi
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Baradarian
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Bagheri
D000328:Adult; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009431:Neural Conduction / Q000502:physiology*; D013901:Thoracic Outlet Syndrome / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery