The tarsal tunnel syndrome is not as commonly diagnosed as is its
counterpart in the hand, the carpal tunnel syndrome. Electrodiagnostic
evaluation has shown that reduced amplitude and increased duration of motor
evoked potentials are more sensitive indicators of the presence of tarsal
tunnel syndrome than is the distal motor latency. The lateral plantar
branch of the posterior tibial nerve is probably affected earlier than is
the nerve's medial plantar branch. Surgical release usually results in
complete relief of the compression neuropathy. Electrodiagnostic evaluation
also may help to separate patients with a tarsal tunnel syndrome from those
with compression of the first sacral-nerve root.