Tarsal tunnel syndrome involves compression of the posterior tibial nerve beneath the flexor retinaculum behind the medial malleolus. Which muscles in the foot are typically spared because they are innervated by a branch arising proximal to the tunnel?

• A All intrinsic foot muscles are equally affected
• B Flexor digitorum brevis and abductor hallucis are spared
• C Abductor digiti minimi is spared
• D Extensor digitorum brevis is spared (it is peroneal-innervated) ✓

Explanation

Extensor digitorum brevis is innervated by the deep peroneal (fibular) nerve, not the tibial nerve, and is therefore always spared in tarsal tunnel syndrome. In tarsal tunnel syndrome, the posterior tibial nerve or its medial and lateral plantar nerve branches are compressed, causing intrinsic muscle weakness in the plantar aspect of the foot (abductor hallucis, flexor digitorum brevis, lumbrical muscles) and burning pain/paraesthesia on the plantar surface. EDB lies on the dorsum and is a useful clinical differentiator.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.