Posterior interosseous nerve palsy caused by parosteal lipoma of proximal radius.

Lipomas are common benign soft tissue tumors which tend to be indolent, and symptoms caused by nerve compression are unusual. However, a parosteal lipoma, occurring adjacent to the proximal radius may easily cause paralysis of the posterior interosseous nerve because of a specific anatomical relationship of these structures in that area. Two cases of parosteal lipoma of the proximal radius causing paralysis of the posterior interosseous nerve are reported. CT and MR imaging demonstrate the characteristic fatty mass around the radius and are specific in making the diagnosis. Surgical excision should be promptly performed to ensure optimal recovery from the nerve paralysis.