The accessory deep peroneal nerve : frequency and electrophysiological findings

ABSTRACT

The accessory deep peroneal(ADP) nerve is known as a common anatomical variant. It may alter the usual clinical and electrophysiological charateristics of peroneal nerve lesions. The purpose of the study was to investigate the frequency of occurrence and the electrophysiologic characteristics of the ADP nerve. We performed peroneal motor nerve conduction studies in 434 patiets with conventional method. When the CMAP amplitudes evoked by distal peroneal stimulation is smaller than that by proximal stimulation, we searched ADP nerve by stimulation at posterior to the lateral malleolus. In 60 patients, we searched ADP nerve regardless of CMAP amplitude difference. Additionally, we routinely stimulated the region of posterior to the lateral malleolus with recording at the medial and lateral extensor digitorum brevis(EDB) muscles using multi channel EMG in 34 patients. In conventional peroneal nerve conduction study, ADP nerves were detected in 27(8.2%) patients out of 330 studied patients(right 7, left 15, both 5). Mean amplitue of ADP nerve was 1. 52mV (right 1. 90, left 1. 84). In routine ADP stimulation study, ADP nerve was detected in 5(21.7%) out of 23 patients(left 2, both 3). In 4 of them, the distal peroneal amplitudes were greater than the proximal. Mean amplitude was 1.86mV(right 1.38, left 1.65). In conclusion, we confirmed that the accessary deep peroneal nerve is a relatively common variant and its presence may not be predicted by the difference of amplitudes between the distal and proximal peroneal segments in conventional peroneal nerve conduction study. So in cases of suspected peroneal nerve lesions, ADP nerve should be searched.