Intraoperative spinal root stimulation to detect most proximal site of leprous ulnar neuritis

In 10 patients with leprous ulnar neuritis, we investigated the most proximal site of lesion in the affected nerves. Spinal roots C8 and T1 were stimulated intraoperatively to evoke efferent mixed compound nerve action potentials which were recorded from the exposed ulnar nerves. The site at which amplitudes reached a maximum was considered the most proximal site of lesion. Nerve damage was found far proximally from the thickened segments in otherwise inconspicuous sections. Epineuriotomy within these apparently unaffected segments revealed fibrosis of the interfascicular epineurium in 9 patients, which is an indication for microsurgical interfascicular neurolysis.