An intraneural ganglion cyst is an uncommon occurrence of the peripheral nerves. The most common type is the peroneal intraneural ganglion cyst. Other reported sites of involvement are the radial, ulnar, median, sciatic, tibial, and posterior interosseus nerves. The first case of intraneural ganglion cyst of the tibial nerve was described in 1967.
The differential considerations for cystic intraneural lesions include cystic nerve sheath tumors, atypical Baker's cyst, and extraneural ganglion.
Cystic nerve sheath tumors such as schwannomas and extraneural ganglion can be differentiated from cystic intraneural lesions by MRI. A Baker's cyst classically is more mass-like, with a characteristic location extending from the tibiofemoral joint to within the confines of the medial head of the gastrocnemius and the muscles of the joint capsule 1).
A fifteen-year-old patient with an intraneural ganglion cyst of the common peroneal nerve, with paralysis of the anterior tibial muscles which was subacute in onset. The lesion was radically removed using microtechniques. Such a purely intraneural location has rarely been described. The use of the surgical microscope and pathological study of the peroneal articular branches allows one to reject the possible synovial origin of this lesion 2).