Intraepineurial constriction of nerve fascicles in pronator syndrome and anterior interosseous nerve syndrome.

In PS or AINS, if obvious epineurial compression deformity of the median nerve or the AIN is not found at known sites of compression, IeCNF should be considered. IeCNF may occur in one or more nerve fascicles of the median nerve at one of multiple levels in the distal upper arm and proximal forearm. Decompression of the nerve fascicles is achieved by epineurotomy, microsurgical interfascicular dissection, and removal of the constricting outer layer of the perineurium above and below the elbow. Resection of the constricted segments of the nerve fascicles is not necessary. Intraepineurial exploration of the nerve trunk also may be considered if, after surgical decompression of PS and AINS, expected recovery has not occurred and there is no evidence of axonal degeneration.