24/04/2026
Pay attention to what’s lost and what’s preserved — that’s your pivot.
Three losses point directly to the common peroneal nerve (CPN):
Foot drop — paralysis of all dorsiflexors (anterior compartment: tibialis anterior, EHL, EDL, peroneus tertius) due to loss of the deep peroneal branch
Loss of eversion — paralysis of peroneus longus and brevis due to loss of the superficial peroneal branch
Sensory loss over the anterolateral leg + dorsum of foot — combined territories of both branches
Now the critical clue: the web space between the 1st and 2nd toes is preserved. This is the exclusive territory of the deep peroneal nerve — yet students often think, “if both branches are lost, why is this preserved?” The answer is contextual: the question states sensory loss is over the “anterolateral leg and dorsum except the web space” — which can also reflect an incomplete lesion at the neck of fibula — but more fundamentally,
