Pathophysiology of Charcot-Marie-Tooth disease.

The etiology of the foot deformity in patients with Charcot-Marie-Tooth disease has not previously been discussed in relation to the extrinsic muscle function around the foot and ankle. Eight adult patients with a strong familial history were evaluated, and their foot findings were remarkably similar. All demonstrated a marked cavus deformity that was secondary to a forefoot equinus associated with contracture of the plantar fascia and a varus deformity of the calcaneus. The muscle function demonstrated marked weakness of the tibialis anterior and peroneus brevis muscles, whereas the peroneus longus and posterior calf muscles were rated as good to normal. Based on the relative strengths of these muscles and the progression of weakness, the authors hypothesize that the deformity observed in patients with Charcot-Marie-Tooth disease is secondary to the weakness of the tibialis anterior, peroneus brevis, and the intrinsic muscles, with their natural antagonists, the peroneus longus and the tibialis posterior muscles causing most of the deformity noted in these adult patients.