Effect of Perineurial Window Size on Nerve Regeneration, Blood–Nerve Barrier Integrity, and Functional Recovery

Abstract

End-to-side neurorrhaphy is used clinically to reconstruct nerve injuries when the lack of a suitable proximal nerve stump precludes conventional approaches to microsurgical repair. In end-to-side neurorrhaphy, the distal stump of a transected nerve is sutured to the side of an intact nerve that serves as an axon donor. Prior studies suggest that this perineurial window is a prerequisite for effective nerve regeneration into the recipient nerve. However, the optimal size for this perineurial window remains uncertain. This study evaluated the effect of perineurial window size on collateral axonal sprouting, blood-nerve barrier architecture, and functional impairment of the donor nerve. One hundred twenty Lewis rats were randomized to 1 and 5 mm perineurial window groups and examined at serial time points. The 5 mm perineurial window group exhibited significantly greater fiber counts at the repair zone than the 1mm group within 4 weeks (p < 0.005). Marked breakdown of the blood-nerve barrier was present 2 week postoperatively and resolved by 4 weeks regardless of 1 versus 5 mm perineurial window size. Tibial function indices in both groups normalized between 4 and 6 weeks postoperatively. A large (5 mm) perineurial window induced greater collateral sprouting or regenerative response than a small (1 mm) perineurial window without increasing cross sectional nerve injury or delaying functional recovery.

Terminolateral Neurorrhaphy between Somatic Nerve and Autonomic Nerve

“…In fact, when there is no injury to the donor nerve, nerve regeneration can occur following endto-side anastomosis, but several experimental studies have shown that when the donor nerve had a fenestration, the effect of nerve regeneration was better [71][72][73][74]. Although there are still controversies over whether fenestration can damage the donor nerve, many studies have confirmed that the fenestration of the epineurium can cause a slight damage to the donor nerve, but does not affect the donor nerve function [75][76][77]. this approach does not cost the donor function when nerve grafting.…”

Nerve Transfers in the Treatment of Peripheral Nerve Injuries

“…The idea is that the axons of the healthy nerve create lateral sprouts that grow inside the damaged one. Although axons can travel in the epineurial space of rabbit nerves [18], in humans the epineurial window is essential to achieve axonal regeneration [68]. Sensory axons will spontaneously sprout from the healthy into the injured nerve, providing a kind of protective sensation, although it is never fully normal [11,65,66].…”

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

“…16,51,53,64 Interestingly, if epineurial or perineurial windows were enlarged from 1 to 4 or 5 mm, respectively, then, also, the magnitude of axonal ingrowth into the recipient nerve was increased. 65,66 Subepineurial focal degeneration and demyelination of the donor nerve distal to the site of coaptation in experimental groups Notably, bimodality coefficient > 0.555 indicates that a distribution is bimodal 56 (but see Jackson, P.R., Tucker, G.T., and Woods, H.F. (1989). Testing for bimodality in frequency distributions of data suggesting polymorphisms of drug metabolism -hypothesis testing.…”