Preoperative Electrophysiological Findings Predicting Surgical Outcomes in Tarsal Tunnel Syndrome

Tarsal tunnel syndrome is an entrapment neuropathy caused by the compression of the tibial nerve and its terminal branches in the tarsal tunnel. Electrophysiological examinations are often used to diagnose tarsal tunnel syndrome. Surgical decompression of the tibial nerve is performed in patients who are resistant to conservative treatment. However, the preoperative electrophysiological findings that predict surgical outcomes remain unknown. This study aimed to clarify the preoperative electrophysiological findings that predict the surgical outcomes of tarsal tunnel syndrome. We reviewed 28 feet of 23 patients who underwent preoperative electrophysiological examinations between November 2021 and October 2024, were diagnosed with tarsal tunnel syndrome, and subsequently underwent surgery. Electrophysiological examinations included nerve conduction study and needle electromyography. We reviewed patient characteristics and electrophysiological findings prior to surgery. Sensory plantar symptoms, such as numbness and pain, were evaluated using the Numerical Rating Scale before and after surgery. Patients were divided into the improvement and non-improvement groups based on the Numerical Rating Scale improvement rate after surgery. A comparative analysis of patient characteristics and preoperative electrophysiological findings was performed between the improvement and non-improvement groups. In a motor nerve conduction study of the tibial nerve, the amplitude of the compound motor action potential evoked by stimulation at the ankle was significantly lower in the non-improvement group than in the improvement group. In tarsal tunnel syndrome, a low compound motor action potential amplitude of the tibial nerve on preoperative motor nerve conduction study may indicate poor symptomatic improvement after surgery. Electrophysiological examinations may be useful for predicting the surgical outcomes of tarsal tunnel syndrome.