Bilateral tarsal tunnel syndrome related to intense cycling activity: proposal of a multimodal diagnostic approach

Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve or its branches (medial plantar, lateral plantar and calcaneal nerves) within its fibro-osseous tunnel beneath the flexor retinaculum on the medial side of the ankle. TTS is a rare and likely underdiagnosed condition due to extrinsic (e.g. space occupying lesions, traumas) or intrinsic causes. Symptoms depend on the involved branch, but usually patients complain of burning, tingling and pain along the foot plantar region, sometimes radiated to the distal part of the medial region of the leg. Symptoms often worsen walking or after prolonged standing or using high-heeled shoes. TTS diagnosis is often difficult and no gold standard test is available. A recent review of the literature highlights the lack of high-quality evidence-based data and the still controversial role of nerve conduction studies, where false-positive and false-negative data are frequent [1]. Neurophysiology and neuroimaging may provide useful information but rarely diagnostic certainty. The combination of neurophysiology and nerve ultrasound (US) has been shown to improve diagnosis and therapeutic approach in other entrapment neuropathies and a recent paper presents the results of ultrasound examination in 81 patients with TTS. There are no reference values in US diagnosis of TTS because of the high variability of compression sites.