Synovial Cysts as a Rare Cause of Tarsal Tunnel Syndrome Discovered Using Ultrasound: A Case Report.

Background: Tarsal tunnel syndrome (TTS) describes a compression neuropathy of the tibial nerve or its branches as they pass under the flexor retinaculum of the ankle. TTS is a clinical diagnosis, but often involves needle electromyography, nerve conduction studies (NCS), and magnetic resonance imaging. To our knowledge, the use of ultrasound to diagnose tibial nerve compression from synovial cysts (SCs) in the tarsal tunnel has been sparsely reported upon.

Case report: A 50-year-old male patient suffering from TTS whose diagnosis of SC-related compression was confirmed via ultrasound. Patient underwent excision confirming an intraneural ganglion cyst secondary to subtalar joint synovial fluid extension. At follow-up, the patient endorsed improvement in painful paresthesias and NCS indicated improving symmetry of tibial nerve function.

Conclusions: Our report demonstrates the successful evaluation and treatment of a rare cause of TTS utilizing ultrasound as the primary imaging modality. Ultrasound provides a rapid, cost-effective imaging method of the tarsal tunnel.