ELECTROPHYSIOLOGIC STUDIES IN TARSAL TUNNEL-SYNDROME - DIAGNOSTIC RELIABILITY OF MOTOR DISTAL LATENCY, MIXED NERVE AND SENSORY NERVE-CONDUCTION STUDIES

The tarsal tunnel syndrome (TTS) is an entrapment of the posterior tib ial nerve at the ankle, which, like carpal tunnel syndrome, improves w ith surgery but needs an instrumental diagnosis to exclude other disea ses. This study was performed to evaluate the diagnostic value of nerv e conduction tests proposed for the diagnosis of TTS. Of the 13 patien ts who were investigated 12 had secondary unilateral and 1 idiopathic bilateral TTS. One or more neurophysiologic parameters were abnormal i n all cases. The diagnostic value of each neurophysiologic parameter w as calculated by comparing conduction on the affected side with conduc tion on the healthy side of each patient with TTS. The accuracies of t he sensory nerve action potential and mixed nerve action potential, bo th after stimulation of the plantar nerves, were almost the same, with sensory nerve action potentials more sensitive and less specific and mixed nerve action potentials less sensitive and more specific. Becaus e from the clinical point of view we must be more afraid of false-posi tive results, the mixed nerve action potential is recommended for pres urgical diagnosis of TTS. Coexistence of mixed nerve and sensory nerve action potential abnormalities, especially if asymmetric, are highly indicative of TTS.