Peroneal nerve anatomy

1. Where do the peroneal nerve fibers originate from?
2. What is the course of the peroneal nerve?
3. What muscles are innervated by the superficial peroneal nerve? What sensory branches does it give off?
4. What muscles are innervated by the deep peroneal nerve? What sensory branches does it give off?
5. What is the accessory peroneal nerve and how is it identified on NCS?

Answers:
1. L4-S2 roots, which becomes the sciatic nerve.
2. It branches from the sciatic nerve in the distal posterior thigh to form the common peroneal nerve. It then travels through the popliteal fossa, winds around the fibular head, then splits into the deep and superficial nerves. Prior to this, it gives off the lateral cutaneous nerve of the calf.
3. Peroneus longus, peroneus brevis. Sensory branches are the medial and lateral cutaneous nerve.
4. Tibialis anterior, EDL, EHL, peroneus tertius, EDB, FDI. Sensory branch is the dorsal distal cutaneous nerve.
5. The accessory peroneal nerve is an anomalous innervation. It branches from the superficial peroneal nerve, traveling behind the lateral malleolus to innervate all or some of the EDB. If there is a deep peroneal nerve injury, the EDB may be spared if there is an accessory peroneal nerve. NCS shows a CMAP with stimulation behind the lateral malleolus.