Somatosensory evoked potentials in patients with supraclavicular brachial plexus injuries.

In 12 patients with traumatic lesions of brachial plexus, we studied somatosensory evoked potentials by stimulation of median, radial, and ulnar nerves at the wrist and by recording at the arm, Erb point, cervical spinal cord, and contralateral cortex. Results after median nerve stimulation in patients with upper trunk lesions were normal. Patients with C5/6 root avulsion had either normal, delayed, or absent responses at the cervical cord and cortex, depending on the presence of complicating distal lesions. In patients with particular involvement of C7 root, results were normal after median and ulnar stimulation but were abnormal after radial nerve stimulation. In patients with multiple root avulsions and flail anesthetic arm, no potentials could be recorded from the cervical cord or contralateral cortex, regardless of which nerve was stimulated. For relevant information, it was important to stimulate nerves having roots near the anatomic site of the lesion as determined clinically and electromyographically.