A rare case of intraneural ganglion cyst involving the tibial nerve.

Cystic lesions around the knee are a relatively common occurrence. Several types of cysts have been reported, including synovial, bursal, and ganglion. Ganglion cysts are not lined by synovial cells. Their location is highly variable, with occurrences described in the fat pads near the tibia or femur, muscles, nerves, and arteries. Intraneural ganglia are rare nonneoplastic cysts caused by the accumulation of thick mucinous fluid within the epineurium of peripheral nerves, encased in a dense fibrous capsule. These cysts can cause compression of the adjacent nerve fascicles, resulting in pain, paresthesias, weakness, muscle denervation, and atrophy. They are most commonly manifested by local and radiating pain, but sensory and motor deficits have also been described. Involvement of the tibial nerve is exceptionally rare, with <15 reported cases in the literature. We present a case of intraneural tibial ganglion cyst in a young woman. We also discuss the imaging features, differential considerations, proposed pathogenesis and anatomic origin, and treatment of this rare entity.