Electrophysiologic signs of sensory fiber lesion in spinal amyotrophies and the role of physiologic variations of sensory finger innervation pattern.

In 33 patients, 30 to 64 years old, with spinal amyotrophy and brachial paresis, the sensory symptoms and electrophysiologic signs were analyzed. The paresthesias were felt most often in the ulnar nerve innervation region. The motor conduction velocities, terminal latency quotient, sensory conduction on direct nerve stimulation were within the limits of normal in both median and ulnar nerve. On percutaneous stimulation normal values were obtained for median nerve, and significantly slower for ulnar nerve innervation region. In four cases no nerve potential was obtained over the ulnar nerve with stimulation of the fifth finger. The nerve potential over the ulnar nerve was elicited mostly by stimulation of median nerve innervated fingers. Congenital variations of sensory innervation pattern were considered, which may increase the liability to destruction.