On the electrophysiological basis, extensor digitorum brevis(EDB) muscle is innervated electrophysiologically not only by deep peroneal nerve(
DPN) but also by
accessory deep peroneal nerve(ADPN), an anomalous branch of superficial peroneal nerve, with a prevalence of 17-28%. We investigated 23 patients who had both
DPN and sufficient ADPN innervation to the EDB on the intramuscular distribution of
DPN and ADPN innervation to the medial and lateral side of the EDB. Recording
electrodes were placed on the medial and lateral edges of the EDB with a supramaximal stimulation to the anterior or lateral ankle, compound muscle action potential (CMAP) of
DPN or ADPN innervation was recorded. In 19 patients (83%) the
DPN innervation was larger than or equal to the ADPN innervation. Only in 4 patients (17%) the ADPN innervation obviously exceeded the
DPN innervation.
DPN enters to the EDB from the medial side, and ADPN from the lateral side of the EDB. In 16 patients(70%) the
DPN innervation was relatively large and the ADPN innervation was relatively small at the medial side of the EDB, and vice versa at the lateral side of the EDB. These distributions were almost uniform in 5 patients(22%). This study clarified that a biased larger
DPN innervation and smaller ADPN innervation to the medial side of the EDB, and vice versa to the lateral side of the EDB in the majority cases. In some cases diffuse innervation to the EDB was found.