Unilateral Foot Drop by Bilateral Ganglion Cysts: An Imaging Approach to Diagnosis

Ganglion cysts are pseudocysts with no epithelial lining of their own. These are non- neoplastic lesions filled with gelatinous material and originate from tendon sheath, ligament, bursa, joint capsule or subchondral bone. Rarely, they may present in an intramuscular location, away from the joint with no synovial communication. Upper limb involvement is more common and such lesions are usually found on the hand, wrist and ankle. Despite their common occurrence, peripheral nerve compression due to these cysts is rare with cases of ulnar and median nerve compressions infrequently reported in the literature. In lower limb, dorsal surface of the foot is reported to be the most common site. Occurrence of ganglion cysts in lower limb causing compressive neuropathy is an even rarer combination. We report a case with unilateral common peroneal nerve palsy with incidentally detected bilateral intramuscular ganglion cysts. Even an extensive literature search did not reveal any such case report. The patient underwent high resolution ultrasound imaging for the possible cause of compression of common peroneal nerve. Incidentally, cystic lesions were identified in the intramuscular plane causing nerve compression in the right leg with similar lesions at the same location in the left leg. On the left side, patient was free of neuropathic symptoms as the nerve was seen passing between the cystic lesions, not getting compressed. The patient then underwent MR imaging with contrast and intramuscular ganglion was kept as the provisional diagnosis of the cystic lesion. Operative management was planned to relieve the compressive neuropathy and excision biopsy of the lesion proved it to be a ganglion cyst.