Ultrasound in tarsal tunnel syndrome: Correct diagnosis for appropriate treatment

We have read with interest the study, by Kim and colleagues, entitled “A Case of Lateral Calcaneal Neuropathy: Lateral Heel Pain”, about the utility of ultrasound (US) for diagnosis of entrapment of the lateral calcaneal branch of the sural nerve.1 They performed US examination in a 29-year-old patient, finding increased crosssectional area (CSA) of the aforementioned nerve branch. The patient had a 3-month history of pain in the lateral heel and was treated with extracorporeal shock wave therapy (ESWT), because plantar fasciitis was suspected. After treatment, sensory impairment occurred. The study is very important and stimulating for different reasons. First, the study shows and confirms the ability of US to find lesions even in very small nerves. This is a crucial point, because US is an extension of the clinical examination and allows depiction of morphological changes in peripheral nerves.2,3 We would like to report a similar case, in which ESWT was performed for misdiagnosed tarsal tunnel syndrome, and US was crucial to plan the most appropriate treatment. A 67-year-old man came to our attention from another hospital, because he complained of pain in the right foot plantar region and was suspected to have plantar fasciitis. The patient was treated with 2 cycles of ESWT (3 weekly administrations of 2400 shocks, 0.15 mJ/mm2 , 4HZ on the painful region) without benefits. Clinical history and examination revealed burning pain and paresthesia in the anterior part of the right sole. A Tinel sign was evoked on percussion the area behind the right medial malleolus. Bilateral US evaluation at the level of the tarsal tunnel, in the region of the medial malleolus, revealed increased size of the right tibial nerve in comparison with the contralateral side (right CSA, 17 mm2 , left CSA, 12 mm2 , see Fig. 1).