Electrophysiological localization of central somatosensory lesions in patients with multiple sclerosis.

Somatosensory evoked potentials (SEPs) and selected indices of peripheral nerve function were compared in 30 multiple sclerosis (MS) patients and 15 normal controls. A high incidence of delayed SEP onset was observed in the MS patients, correlating with sensory loss--particularly of joint position and vibration sense. Using a method for deriving an indirect estimate of spinal cord conduction velocity, the longitudinal level of the sensory disturbance could in many cases be localized either to the spinal or to the supraspinal segment (or both) of the somatosensory pathway. Abnormally low spinal conduction velocity correlated with clinical judgements of spinal cord malfunction, but abnormalities were encountered also in some cases with no clinical evidence of myelopathy. Electrophysiological studies can contribute to the assessment of patients with suspected MS by demonstrating conduction abnormalities in specific segments of the somatosensory pathway.