Tarsal tunnel ganglion cyst: intraneural or extraneural site?

Intraneural ganglion cysts are very uncommon lesions, whose diagnosis has increased since the articular theory and the description of the MRI findings were established. We present a case report of a 59-year-old man with symptoms of tarsal tunnel syndrome. Foot and ankle MRI demonstrated the presence of an intraneural cystic lesion in the posterior tibial neve and its connection with the subtalar joint through an articular branch. The identification of the specific radiological signs like the «signet ring sign» allowed establishing an adequate preoperative diagnosis, differentiating it from an extraneural lesion and facilitating the articular disconnection of the nerve branch during surgery.