Short latency somatosensory evoked potentials in patients with neurological lesions.

Short latency somatosensory potentials following median nerve stimulation were recorded in patients grouped according to anatomic location of neurological lesion. Patients with cerebral lesions causing severe sensory deficit lacked a major positive wave of cortical origin that in normal subjects peaked at a mean latency of 20.5 ms. Patients with severe cervical spinal cord disease lacked all of the normal somatosensory response except for the earliest component attributed to peripheral nerve activity. Patients with brain-stem lesions showed delayed latencies of later waves and prolonged interwave latencies. However, auditory evoked potentials measured in the group with brain-stem lesions were more helpful in localization. Analysis of short latency somatosensory potentials can discriminate between peripheral nerve, spinal cord, brain-stem, and cerebral lesions. Further experience and refinement of technique of measurement should increase the value of this procedure.