Complete foot drop due to atypical peroneal ganglion in a 13 ½ year old boy

Peroneal nerve palsy due to compression by an intraneural ganglion is an uncommon entity in the pediatric setting with a need for surgical treatment. Uniquely in this case, the ganglion presented as an elongated instead of a typical round cyst, delaying diagnosis and treatment.

We present the case of a 13 ½ year old boy with increasing peroneal nerve palsy due to an atypically shaped intraneural ganglion. An MRI of the knee revealed an elongated peroneal ganglion compressing the nerve between the lateral insertion of the gastrocnemius muscle and fibular head over a length of 10 cm. After surgical decompression and physiotherapy the peroneal nerve recovered well, achieving M 4-5 one year after surgery.

The atypical shape of the present peroneal ganglion delayed diagnosis and correct treatment. Though rare in the pediatric setting, this entity must be specifically looked for during the diagnostic workup of peroneal palsy, for time to surgery determines neurological outcome.