Lumbosacral spinal evoked potentials in patients with multiple sclerosis.

Lumbosacral spinal evoked potentials were recorded percutaneously in 22 MS patients with spinal symptoms and in 24 age-matched normal volunteers. Latencies, durations, and areas of waves R and A (level S1) as well as S and P2 (level Th12) were analyzed. The most significant result observed in the MS group was a reduction of the ratio between the areas of P2 and S. The reduction was strongly correlated with intensity of spasticity, but not with other clinical features. The P2/S ratio can thus be proposed as an electrophysiologic measure of spasticity.