Value of Motor Nerve Conduction Studies in the Diagnosis of Idiopathic Tarsal Tunnel Syndrome: A Single-center Prospective Observational Study from India.

Background: Nerve conduction studies are considered to be the gold standard for diagnosing secondary tarsal tunnel syndrome (s TTS), but their utility in the diagnosis of idiopathic tarsal tunnel syndrome (i TTS) is largely unknown.

Objective: We sought to investigate the value of motor nerve conductions studies (MNCS) in the diagnosis of clinically suspected i TTS.

Materials and Methods: Twenty-six (52 limbs) adult patients of clinically suspected i TTS were subjected to motor nerve conductions of posterior tibial nerve, and its branches and motor conduction parameters were compared with those of 45 healthy controls.

Results: Symptoms were bilateral in 70% ( P = 0.02), with heel pain in 95% of symptomatic limbs. MNCS was abnormal in 32 (80%) of symptomatic limbs and 8 (66.6%) of asymptomatic limbs ( P = 0.004). Out of electrophysiologically abnormal nerves ( n = 67), the pathological process could be identified in all the nerves with abnormal MNCS ( P = 0.02). Probable demyelination was seen in 58.2% of the electrophysiologically abnormal nerves.

Discussion: The present study shows that i TTS are gender and Body Mass Index neutral with bilateral symptoms being common. Tinel's sign was inconsistent. Heel pain did not correlate with abnormal inferior calcaneal nerve conductions. Motor nerve conduction study was abnormal in a significant number of symptomatic limbs. "Probable demyelination" was more frequent in symptomatic limbs.

Conclusion: MNCS is significantly abnormal in symptomatic limbs of subjects with i TTS. Demyelination is slightly more common than axonopathy in i TTS. With a sensitivity of 80% and specificity of 33.3%, MNCS seems to be useful as a screening tool in clinically suspected i TTS. This study is Level II: Lesser quality randomized controlled trial or prospective comparative study.