Abstract
BACKGROUND: Among the spectrum of adipose lesions associated with peripheral nerves, complete circumferential encasement of the nerve by the lesion is a very rare entity. The authors report the first case of a giant lipoma that completely and circumferentially encased the radial nerve. OBSERVATIONS: A 57-year-old woman presented with a large left-arm mass that she had noticed over a year following significant weight loss. She had hypersensitivity and dysesthesias in the left posterior arm but no weakness or other symptoms. Magnetic resonance imaging of the left upper limb demonstrated a large lipoma completely encasing the radial nerve, originating at the level of the spiral grove proximally and extending distally to the lateral epicondyle. The lesion was completely resected at surgery with total preservation of radial nerve function. LESSONS: Lipomas encasing peripheral nerves can be difficult to manage while preserving function. This case adds to the intriguing spectrum of adipose lesions associated with peripheral nerves. https://thejns.org/doi/10.3171/CASE24148.