Medial plantar nerve testing facilitates identification of polyneuropathy

Many studies have used sural nerve action potential (NAP) as an electrophysiological marker for distal symmetrical polyneuropathy (DSP). We examined the role of medial plantar nerve testing for identifying DSP by comparing amplitudes from sural, superficial peroneal, and medial plantar nerves in 85 participants with symptoms and clinical signs of DSP and 204 participants without DSP. Receiver-operating characteristic curves were used to determine the sensitivity of all three sensory conduction studies for the diagnosis of DSP. All three nerves could be used to discriminate between subjects with and without DSP with an area under the curve of more than 85% of cases. Sural and superficial peroneal nerve testing sensitivities were about 55%, whereas medial plantar nerve testing sensitivity was more than 90%. These findings suggest that testing the medial plantar nerve may increase the diagnostic yield of nerve conduction studies for DSP.