Accessory Flexor Digitorum Longus Presenting as Tarsal Tunnel Syndrome: A Case Series.

Tarsal tunnel syndrome (TTS) typically occurs from extrinsic or intrinsic sources of compression on the tibial nerve. We present 3 cases of patients, all of whom have a prolonged time to diagnosis after evaluation with multiple specialties, with foot pain ultimately secondary to an accessory flexor digitorum longus muscle causing TTS. The literature describing the association between TTS and accessory musculature has been limited to single case reports and frequently demonstrate abnormal electrodiagnostic testing. In our series, 2 cases had normal electrodiagnostic findings despite magnetic resonance imaging (MRI) that later revealed TTS and improvement with eventual resection. A normal electromyogram should not preclude the diagnosis of TTS and MRI of the ankle; it should be considered a useful diagnostic tool when examining atypical foot pain.