Origin of far-field subcortical potentials evoked by stimulation of the posterior tibial nerve.

Evoked potentials to stimulation of posterior tibial nerves were recorded from cervical-scalp derivation (cervical electrode: surface electrode on spinal process of the fifth cervical vertebrae; scalp: vertex). Four subcortical potentials labeled as N24, P27, N30 and P32 were identified. Evidence indicating that these components are originated in the following structures is presented: N24, posterior columns at the level of C5; P27, high cervical posterior columns or brain stem; N30, medial lemniscus or thalamus; P32, thalamo-cortical radiations.