REINNERVATION OF AVULSED AND REIMPLANTED VENTRAL ROOTLETS IN THE CERVICAL SPINAL-CORD OF THE CAT

Spinal nerve root avulsions frequently occur in brachial plexus injuri es caused by traction. Such lesions are considered to afflict the cent ral nervous system (CNS) and are, therefore, believed to be beyond sur gical repair. The present experimental study was initiated to challeng e this hypothesis. The ventral rootlets of C-7 were avulsed from the s pinal cord in 28 cats via an anterior approach and subsequently reimpl anted into the cord at the site of origin. In nonoperated central cats and cats undergoing reimplantation, electrophysiological experiments were performed and horseradish peroxidase was administered to the spin al nerve on the reimplanted side after survival times ranging from 6 t o 293 days. Spinal cord sections in all cats were stained for neurofil ament, acetylcholinesterase (AChE), Nissl, and filial fibrillary acidi c protein. Horseradish peroxidase-labeled ventral horn motoneurons wer e found as early as 14 days after reimplantation and their number incr eased with time. On Days 209 and 293, the number of labeled neurons eq ualed the number of labeled ventral horn neurons in the two control ca ts that did not undergo surgery. Starting on Day 6 after reimplantatio n, the appearance of the ventral horn and the white matter in the neur ofilament, AChE, and Nissl-stained sections changed as a result of the CNS response to the injury. A return to their normal appearance could be observed in these stainings from Day 209 onward. Glial fibrillary acidic protein-positive astrocytic tissue was consistently found in th e ventral horn and in the white matter reimplantation area. From Day 6 9 onward, electrophysiological stimulation of the spinal nerve C-7 on the reimplanted side elicited an electromyogram response in the spinod eltoid muscle. The latency and threshold intensity of the C-7 response s were initially increased but equalized to match the nonoperated cont rols between 98 and 122 days after reimplantation. The results of this study show that functional regeneration of ventral horn neurons after root avulsion and subsequent reimplantation in the cat is possible.