Somatosensory evoked potentials of the medial and lateral plantar and calcaneal nerves.

The ideal electrodiagnostic procedure to assess possible plantar neuropathies continues to elude investigators. Motor studies are rarely abnormal, pure sensory studies may be difficult to obtain, needle electromyography can demonstrate membrane instability in normal feet. Mixed nerve plantar studies may be more diagnostically valuable than the other techniques but they also have shortcomings. In this report, a technique utilizing somatosensory evoked potentials to assess the medial and lateral plantar and calcaneal nerves is demonstrated. Normative data with respect to latencies, amplitudes, and side-to-side differences are presented. Two illustrative cases are also discussed in which the more standard techniques to evaluate plantar neuropathies fail to do so, but the SEP methodology suggests compromise of the intrinsic foot nerves.