Aberrant peripheral nerves and neuromas in normal and injured spinal cords.

Spinal cords from 20 patients (13-78 years of age) were studied for the occurrence of peripheral nerve fibers within the cord. Peripheral nerve fibers were observed in all but two younger patients, 13 and 24 years old, respectively, but all the spinal cords were otherwise normal. The nerve fibers were thin and predominantly myelinated. They were seen in two forms, small parallel bundles resembling normal nerve fascicles and larger interlacing bundles or whorled masses indistinguishable from traumatic neuromas. They almost always occurred in the perivascular spaces of the major parenchymal branches of the anterior sulcal artery and/or in the anterior median sulcus. The neuromas in the otherwise normal cords were identical with those occurring in the cord with old traumatic injury in three patients studied, but they were few in the former, while numerous and widespread in the injured segments of the latter. Accumulating evidence suggests 1. that most, if not all, of the parallel nerve bundles about the anterior sulcal artery in otherwise normal spinal cords represent aberrant, regenerated nerve fibers originating from ventral spinal nerve roots which are severed by clinically occult injuries in adult life, and 2. that the regenerated nerve fibers continue to grow into the anterior median sulcus and perivascular spaces and may become entangled or return upon themselves, forming neuromas as their way is blocked by the pia-glial barrier.