Recordings from human dorsal column nuclei using stimulation of the lower limb.

Responses from the surface of the dorsal column nuclei and the dorsal surface of the spinal cord were recorded using monopolar electrodes after stimulation of the lower limbs (common peroneal nerve at the knee and posterior tibial nerve at the ankle) in patients undergoing neurosurgical operations for spasmodic torticollis. Those responses were smaller in amplitude than responses to stimulation of the upper limbs (median nerve at the wrist), and the waveforms differed. The negative deflection that is prominent in the response to stimulation of the upper limbs is more variable, broader, and relatively smaller in amplitude than the response to upper limb stimulation. Another difference between responses to upper and lower limb stimulation was that multiple peaks were superimposed on the initial response to stimulation of the lower limbs, but were not as consistently seen in the responses to upper limb stimulation. The negative peak in the response from the dorsal column nuclei to lower limb stimulation was of about the same latency as the P27 peak in the far-field response (somatosensory evoked potential) to stimulation of the peroneal nerve.