[Non-traumatically-induced paralysis of the ramus profundus nervi radialis. Aspects of a rare disease picture].

Both radial tunnel syndrome and posterior interosseous nerve compression syndrome are caused by compression of the posterior interosseous nerve. Posterior interosseous nerve (PIN) compression syndrome is a rare condition--less than 10 percent of our cases of PIN-compression showed signs of palsy--and must be differentiated from tendinous lesions. From 1992 to 1997, we decompressed the PIN using an anterior approach in nine cases because of palsy without a history of trauma. Only one patient was lost to follow-up. Our study indicates that the results of operative decompression of the PIN depend on the time interval between first symptoms of palsy and operation. On the other hand, some cases of posterior interosseous nerve compression syndrome show spontaneous recovery. We recommend operative decompression of the PIN if incomplete palsy worsens or if complete palsy persists for more than 12 weeks.