[Intraneural synovial cyst of the external sciatic popliteal nerve].

The authors report a case of an intraneural ganglion of the peroneal nerve. The cystic material was found to expand the neural sheath, while the neural fasciculi were few and atrophic. A communication between the intraneural cyst and the proximal tibio-peroneal joint was demonstrated. An hypothesis for the pathogenetic basis of intraneural ganglia is presented.