The two locations of ganglions causing radial nerve palsy.

Ganglions associated with radial nerve palsy at two different locations were identified at the elbow in 14 patients. The first type, found in 13 patients, arose from the anterior capsule of the proximal radioulnar joint and was located proximal to the proximal edge of the supinator muscle. It compressed the main radial nerve anteriorly. The second type, which has not been reported before in patients without abnormalities in the elbow joint, was found in the remaining patient. It was located in the supinator muscle, distal to the proximal edge of the supinator muscle, and compressed the posterior interosseous nerve against the proximal radius. Magnetic resonance imaging makes it possible to identify ganglions in a wide area around the elbow. This examination should be carried out in view of the possible presence of both types of ganglion. Magnetic resonance imaging also provides more accurate information than computed tomography or ultrasonography about the location and characteristics of the mass.