Ulnar F-wave conduction velocity in epidural metastatic root lesions.

In 40 controls and 19 patients with neoplastic lesions of the eighth cervical and first thoracic nerve roots confirmed by myelography, ulnar F-wave conduction velocity (FWCV) was estimated using the shortest F-wave latency (FWL). F-waves were recorded from needle electrodes inserted in the abductor digiti minimi manus muscle after stimulation of the ulnar nerve at the wrist. Motor nerve conduction velocities of distal ulnar segments were normal. It was found that the ulnar FWCV decreases significantly with increasing age. This is not true for FWL. During the initial examinations ulnar FWCV was delayed in 18 patients. At follow-up, ulnar signs correlated well with changes in FWCV. Low F-wave frequency and wide FWL differences are also important features in ulnar root disease.