An intraneural ganglion cyst of the dorsal cutaneous branch of the ulnar nerve arising from the wrist: support for the articular origin. Illustrative case.

backgroundThe articular theory of the formation of intraneural cysts has significant supporting evidence at common locations but has been less accepted at rarer sites. There have been only 5 cases in the literature documenting an intraneural ganglion cyst in the dorsal cutaneous branch of the ulnar nerve (DCBUN), with only 1 case documenting a joint connection. In this report, the authors present a second case with a proven joint connection in support of the articular theory. OBSERVATIONS: The authors report the case of a 73-year-old man who developed a large intraneural ganglion cyst within the DCBUN along the palmar ulnar aspect of his left wrist. Magnetic resonance imaging demonstrated an articular connection to the distal radioulnar joint. During surgery, the intraneural ganglion cyst was resected and the articular branch was disconnected. The patient recovered and returned to work 4 weeks postoperatively. LESSONS: This case further supports the articular theory as the explanation for intraneural ganglion cysts, even at unusual locations. https://thejns.org/doi/10.3171/CASE24569.