Photographs, nerve conduction studies and ultrasonogrphic images of the patient. (A) Photographs of the patient’s feet. Only in patient’s left foot, prominent peroneal tubercle is seen on the lateral aspect of the calcaneus (white arrows). (B) Sural sensory nerve conduction studies show relatively slow nerve conduction velocity of affected left sural nerve. Top trace; left sural nerve, bottom trace; right sural nerve. (C) Transverse ultrasonographic view of dorsolateral aspect of the patient’s left foot at the level of peroneal tubercle. Ultrasonographic image shows swelling and internal hypoechogenicity of the left sural nerve located between the skin and the tendon of peroneus brevis muscle (white arrows). (D) Ultrasonographic image of right sural nerve at the same aspect and level of (B). Diameter of right sural nerve is much smaller than affected left sural nerve, and honeycomb-like normal internal echotexture is preserved (white arrows). PB; tendon of peroneus brevis muscle, PT; peroneal tubercle, PL; tendon of peroneus longus muscle.