Delayed onset of peroneal neuropathy after minor ankle torsion in a 9-year-old boy.

Ankle sprain is only rarely reported as the cause of peroneal nerve palsy and occurs predominantly in adults. Peroneal nerve palsy following an ankle sprain is extremely rare in children. Furthermore, peroneal nerve palsy most commonly results from a severe ankle sprain with considerable pain and edema. Peroneal nerve palsy after minor ankle torsion without major clinical symptoms of ankle sprain is uncommon. Here, we report the case of a 9-year-old boy who developed right peroneal neuropathy, leading to foot drop, following minor ankle plantar flexion/inversion torsion. Electrophysiological findings confirmed a focal neuropathy around the fibular head. The neurologic symptoms resolved completely 4 months after the injury. This case emphasizes that peroneal neuropathy can occur after minor ankle torsion without evident ankle sprain symptoms. Moreover, electrophysiological evaluation is very helpful to confirm the diagnosis and is important for prognostic evaluation.