Tibial nerve injury

1. What nerve roots does the tibial nerve come from?
2. What muscles are innervated by the tibial nerve? What sensory branches does it give off?
3. How is the tibial nerve injured in the tarsal tunnel? What structures pass through the tarsal tunnel?
4. What is the presentation of tarsal tunnel syndrome?
5. What are the NCS findings?

Answers:
1. L4, L5, S1, S2, which continues on as the sciatic nerve and then the tibial branch.
2. The tibial nerve innervates the plantaris, gastrocnemius, popliteus, and soleus. It then continues as the posterior tibial nerve to innervate the tibialis posterior, FDL, and FHL. It then runs underneath the flexor retinaculum and divides into the medial plantar nerve (adductor hallucis, FDB, FHB, lumbricals, sensory), lateral plantar nerve (lumbricals, ADM, quadratus plantae, sensory), and the calcaneal nerve (sensory).
3. The posterior tibial nerve is injured by compression under the flexor retinaculum. The tendons of the tibialis posterior, FDL, and FHL pass through the tarsal tunnel.
4. There may be symptoms of intrinsic foot weaknesss, perimalleolar pain, numbness, and paresthesias in the toes and soles, reproduced by ankle inversion. There may be a positive Tinel's at the ankle. Heel sensation may be spared due to calcaneal branch departing proximal to the tunnel.
5. SNAP is abnormal in plantar nerves but normal in calcaneal nerve. CMAP is abnormal in the medial and lateral plantar nerves.