LAUSR

Introduction Ganglion cysts are benign masses that commonly arise adjacent to joint spaces and can interfere with the function of surrounding nerves and vessels. The most common clinical presentation is the presence of an asymptomatic, palpable mass, but some patients may experience paresthesias, pain, and/or motor weakness due to external compression forces on nearby nerves (3,11). In rare circumstances, this external compression by the ganglion cyst can induce a peripheral neuropathy and lead to symptoms of nerve palsies (3,5,6,8,9). The development of foot drop due to ganglion cyst induced common peroneal nerve palsy is relatively uncommon and exceedingly rare in the pediatric population (3). Magnetic resonance imaging (MRI) is the criterion standard for diagnosis of peroneal nerve palsy and periarticular cystic lesions with excellent soft tissue contrast and visualization of regional anatomy (3,5,6). Ultrasound further aids in defining these lesions, especially when used as image guidance for corticosteroid injection and/or cyst aspiration. Electromyographical (EMG) and nerve conduction velocity studies (NCVS) assist in further isolating the neuropathy as well as determining severity and chronicity of the lesion. Standard of care for peroneal nerve palsy due to compression by a ganglion cyst involves surgical decompression and removal of the cyst (2,5,6,9,11). The rate of cyst recurrence following surgery is as high as 30% and is associated with a substantial risk of permanent nerve injury (6,11). To decrease the likelihood of cyst recurrence, the articular branch of the peroneal nerve is often ligated. However, evidence for recurrence remains despite this additional measure (2,3,11). Ultrasound guidance is used frequently for superficial ganglion cyst aspirations, but to our knowledge, only one group has reported successful management of a common peroneal nerve ganglion cyst with this procedure (4,6,8,10). Additionally, nerve hydrodissection has proven useful for treating various entrapment neuropathies, but the application of hydrodissection for treating ganglion cyst-induced nerve palsies has not been described (1,7). We present a case of a pediatric athlete who presented with pain and foot drop due to ganglion cyst-induced common peroneal nerve neuropathy that was managed with ultrasound-guided hydrodissection, cyst aspiration, and corticosteroid injection, allowing the athlete to return to sport.