Somatosensory evoked responses as a diagnostic aid in thoracic outlet syndrome. A preoperative study.

Responses evoked in the supraclavicular fossa (Erb's point) were recorded after stimulation of the median and ulnar nerves separately in both arms. The recordings were made in 20 healthy controls and 13 patients with unilateral thoracic outlet syndrome. In 12 of the 13 patients subsequent surgery clearly confirmed the diagnosis. Nine of the 13 patients showed abnormalities in the preoperative recordings at Erb's point. In all of these nine patients the relative amplitude difference on the affected side was outside the normal range. In two patients there was also abnormally low conduction velocity. The differences of amplitudes in the Erb's point responses between patients and controls were statistically significant. The suggestion is made that Erb's point responses evoked by stimulation of the median and ulnar nerves may be of diagnostic value in thoracic outlet syndrome and that the method is suitable as a supplement to conventional electroneurography in routine clinical practice.