Tarsal Tunnel Syndrome—A New Way to Diagnose an Old Problem

Abstract

Tarsal Tunnel Syndrome [TTS] is the most common lower limb focal neuropathy but it has a poor pick up rate in most Electrodiagnostic (EXD) Laboratories. There is no gold standard for assessing TTS. The tibial nerve has a complex branching system with 4 main branches and 9 different patterns of division. This study evaluated potential TTS with a similar and extensive assessment of the tibial nerve. The protocol involved 2 tibial motor studies to the Adductor Hallucis Longus (AH) and Adductor Digiti Quinti (ADQ) muscles, assessing amplitudes and distal latencies; medial plantar, lateral plantar and calcaneal sensory studies assessing amplitudes and distal latencies. A needle EMG to the tibial innervated AH and ADQ muscles was also performed. This protocol evaluated 12 different parameters which significantly increased the diagnostic yield. TTS has a low pick up rate using current standard assessment methods accounting for between 0.5% and 0.6% of positive cases referred to electrodiagnostic laboratories. This study had a pick up rate of 3.3% with 40 positive cases identified out of a population of 1210 patients referred to an electrodiagnostic laboratory in a calendar year. A combination of positive findings was observed. There were on average 4.3 positive parameters. The calcaneal sensory study and the needle EMG to the distal AH and ADQ muscles were the most sensitive tests. These 3 tests are not routinely performed in most labs. Of the 40 cases of TTS over 80% had a history of either prior injury or surgery to affected lower limb. This study suggests that this 12 parameter assessment will increase diagnostic sensitivity.