Supinator Syndrome

The supinator syndrome, also known as deep radial nerve syndrome, is a compression palsy of the posterior interosseous nerve of the elbow (continuation of the deep branch of the radial nerve). MRI findings are related to as atrophy of the muscles supplied by the posterior interosseous nerve, namely the supinator muscle (white arrow) and multiple muscles in the hand. A swollen posterior interosseous nerve can apparently also be detected.

The arcade of Frohse, or the supinator arch, is a fibrous arch at the superior end of the superficial layer of the supinator muscle, and covers the posterior interosseous nerve. It is the most frequent site of posterior interosseous nerve entrapment. Entrapment may also occur in humeral fractures and subsequent callus formation (Holstein-Lewis fracture) and a high radial lesion (before origin of the posterior interosseous nerve). Our case had a ganglion (pink arrow) at the distal radial nerve (blue arrow).

References

• Furuta T, Okamoto Y, Tohno E, Minami M, Nishiura Y, Ohtomo K. Magnetic resonance microscopy imaging of posterior interosseous nerve palsy. Jpn J Radiol. 2009 Jan;27(1):41-4.
• Stadnick ME. Posterior Interosseous Nerve Syndrome. MRI Web Clinic - August 2005