Tarsal tunnel syndrome caused by epineural ganglion of the posterior tibial nerve: report of 2 cases and review of the literature.

Ganglia within the posterior tibial nerve is a rare condition. The authors report 2 cases of epineural ganglion of the posterior tibial nerve, causing tarsal tunnel syndrome. Both cases presented with numbness on the plantar surface of the foot. Magnetic resonance imaging showed the presence of the cyst within the tarsal tunnel. During surgery, these cysts were found within the epineurium of the posterior tibial nerve and were successfully removed without damage to nerve fibers. Both patients were free of symptoms after surgery. Ganglion cysts in the peripheral nerve are either intrafascicular or epineural. Intrafascicular ganglia present beneath the epineurium and involve the nerve fibers, whereas epineural ganglia are located in the epineurium and do not involve the nerve fibers. A review of the literature discusses these concepts. The authors suggest that epineural ganglion should be clinically distinctive from an intrafascicular ganglion because of the differences in surgical treatment, postoperative nerve function, and the recurrence rate.