Common peroneal neuropathy: A study of selective motor and sensory involvement.

We performed a prospective clinical and electrophysiologic study of common peroneal (CP) neuropathy to evaluate the extent of involvement of the muscles and cutaneous areas supplied by this nerve. In 22 patients, seven had more weakness clinically in muscles innervated by the deep peroneal nerve than in those innervated by the superficial peroneal nerve; the reverse never occurred. Statistical paired comparisons confirmed the tendency in the entire group of patients for weakness to be greater in muscles supplied by the deep peroneal nerve. On EMG, denervation was more often present and of more marked degree in muscles supplied by the deep peroneal nerve. Motor nerve conduction studies indicated axonal damage and focal demyelination with similar frequency. Sensory deficits varied in the three areas supplied by the cutaneous branches of the CP nerve: five patients had involvement of all three areas, 11 of two areas, two of one area, and four had no sensory deficit. The most likely explanation for these findings is differing degrees of damage to individual fascicles within the CP nerve.