Four cases of posterior interosseus nerve palsy caused by ganglion were reviewed. Patients were 3 females and one male. Tenderness and tumor at the anterior aspect of the radial head and palsy of the muscles innervated by the posterior interosseous nerve were seen in all cases. In two cases, resting reduced both pain and palsy and exercise worsened the pain and palsy. Duration between onset of pain or palsy to operation ranged from 2 weeks to 3 months. All cases received surgery and showed nearly complete recovery. Two patients who received surgery within three weeks of onset of symptoms recovered within three weeks. Two other cases who received surgery more than two months after the onset required four and five months for recovery. Early diagnosis and surgery will shorten the recovery period of posterior interosseous nerve palsy caused by ganglion.
