Somatosensory central conduction time after sural and tibial nerve stimulation.

We recorded spinal and cortical somatosensory evoked potentials (SEPs) after sural and tibial nerve stimulation at the ankle in 34 normal subjects. Spinal SEPs were reproducible with sural nerve stimulation in only 65% of normal subjects. The spinal amplitudes were significantly smaller after sural nerve stimulation. Central conduction time (CCT) was significantly shorter when measured from onset instead of peak latencies. There was a significant difference between CCT with tibial nerve and sural nerve stimulation. Our results are consistent with the idea that CCT measures from onset and peak latencies do reflect the travel of the afferent volley in different spinal fiber populations.