Collateral Sprouting Occurs following End-to-Side Neurorrhaphy

Abstract

Recent evidence supports the use of end-to-side neurorrhaphy for the treatment of certain peripheral nerve disorders. However, the mechanism by which nerves regenerate following this procedure is still unclear. To address this question, the authors designed a new end-to-side coaptation model in rats in which the donor nerves were uninjured. The regenerated axons at the coaptation site were observed directly using fluorescent dye as the neural tracer. The sciatic nerve from adult Wistar rats was transplanted between the left and right median nerves. Fifteen rats were divided into three groups. In group I, the donor (right median) nerve was sutured end to side to the divided grafted nerve using a noninjury technique. In group II, the aponeurosis of the spinal muscles was harvested and the sciatic and right median nerves were coapted end to side noninjuriously by wrapping them in the excised aponeurosis. In group III, a perineurial window was created and a partial neurectomy was carried out at the suture site, after which the sciatic and right median nerves were sutured end to side. Sixty days after the operation, nerve regeneration was evaluated by recording action potentials in the grafted nerve, by performing electromyography in the flexor muscles in the forearm, and by histological examination. The grafted nerves were fixed and sectioned, the number of regenerated nerve fibers was counted, and axonal diameters were measured. Fluorescent dye crystal was used, in conjunction with confocal microscopy, to observe the regenerated axons at the co-aptation site. The results showed that nerve regeneration had occurred in the animals, as determined electrophysiologically and histologically. Both the right and left flexor muscles of the forearm contracted simultaneously as a result of indirect electric stimulation of the grafted nerve, which suggests that the regenerated nerve was physiologically connected with the donor nerve. Nerve fiber counts did not show any differences among groups (p > 0.05), but axonal diameters were significantly greater in group III than in the other two groups. Fluorescent dye staining revealed the presence of regenerated nerve fibers beyond the coaptation site. In group III, the regenerating nerves were observed within the whole section of the coaptation site and collateral sprouting was found to occur even at a site distal to the suture. From these results, the authors conclude that in end-to-side neurorrhaphy, nerve regeneration occurs by collateral sprouting from the donor nerve.

Functional Recovery following an End to Side Neurorrhaphy of the Accessory Nerve to the Suprascapular Nerve: Case Report

“…The precise mechanism of axonal regeneration following end-to-side neurrorhaphy remains controversial with both experimental and clinical studies reporting mixed results [4,6,8,11,12,19,20,[23][24][25][33][34][35][36][37]. Several authors have concluded that axonal damage to the donor nerve is required to induce motor collateral sprouting but may not be required to induce sensory sprouting in end-to-side neurorrhaphy [1,12,28,29].…”

Terminolateral Neurorrhaphy between Somatic Nerve and Autonomic Nerve

“…The other is that regenerated nerve derived from terminal sprouting of donor nerve due to the damage to the donor nerve during suturing process [56][57][58]. Zhang, et al [59] and Hayashi, et al [60] demonstrated that the nerve regeneration through the terminolateral neurorrhaphy originated from the collateral sprouting from the intact donor nerve by using immunofluorescence tracing technique. However, Hastert, et al [61] founded that nerve regeneration not only originated from collateral sprouting from noninjurious donor nerve, but also originated from terminal sprouting from the damaged donor nerve when retrograde nerve tracing of neurons performed with DiI and FluoroGold to reveal the origin of regenerated axons through sciatic nerve in a rat model.…”

Influence of Breaching the Connective Sheaths of the Donor Nerve on Its Myelinated Sensory Axons and on Their Sprouting into the End-to-Side Coapted Nerve in the Rat

“…1), any mechanical damage to the donor nerve was avoided by employing a non-injurious technique of endto-side nerve coaptation previously described by Hayashi et al 55 Proximal end of the recipient nerve segment was split longitudinally by microscissors, and its split ends were completely wrapped around the donor nerve and then sutured together by four No. 11-0 Ethilon sutures.…”