Clinical electrophysiologic studies of HTLV-I-associated myelopathy.

Six patients with human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM) were studied by electrophysiologic methods. Upper-limb short-latency somatosensory evoked potentials showed slight delay of the N9-N20 interpeak latency in one of 12 limbs, while the lower-limb short-latency somatosensory evoked potentials showed prolonged N20-P40 interpeak latency in eight of 12 limbs. Frequent polyphasic potentials and occasional giant spikes were observed in the distal extremities. F-wave conduction velocity was delayed in some patients. Results of the other nerve conduction studies were unremarkable. Our data provide a valuable extension of the clinical examination of HAM and offer encouragement for a more extensive electrophysiologic study of this entity, especially in the spinal cord.