Median intraneural ganglion cyst at the elbow: the first known example of a joint connection and a reflection on the past. Illustrative case.

Background: The articular origin of intraneural ganglion cysts has been previously described and well supported, except for the median nerve at the level of the elbow.

Observations: The authors present a patient with a median intraneural ganglion cyst at the elbow region and magnetic resonance imaging (MRI) evidence of a joint connection to the proximal radioulnar joint. A 63-year-old man presented with thumb flexion weakness and dysesthesias in the thumb, index, and middle fingers. Electromyography confirmed a median nerve lesion at the elbow. MRI demonstrated a median intraneural cyst as well as an extraneural cyst, both arising from the proximal radioulnar joint. The articular branch between the cyst and the proximal radioulnar joint was identified preoperatively on MRI and intraoperatively using indocyanine green. Following disconnection of the articular branch and pedicle and decompression of the intra- and extraneural cysts, the patient recovered grade M4 motor function after 6 months, with resolution of neuropathic pain immediately after surgery.

Lessons: The authors present the first case of a median intraneural cyst with a joint connection to the proximal radioulnar joint. The authors believe that this report along with other historical data strengthens the articular theory for intraneural ganglion cysts not only at this site but at all sites. https://thejns.org/doi/10.3171/CASE24564.