Abstract
Background End-to-side (ETS) neurorrhaphy is a promising procedure for peripheral nerve repair,
yet controversies regarding the efficacy of this repair in facial nerve anastomosis
for facial paralysis still exist.
Materials and Methods Thirty rats were divided into three groups: intact control group, direct facial–hypoglossal
ETS neurorrhaphy, and end-to-end (ETE) neurorrhaphy. Nerve regeneration was assessed
with vibrissae motor performance, electrophysiological tests, retrograde labeling,
and histomorphological analysis at 4 and 8 months postoperatively.
Results Both ETS and ETE neurorrhaphies resulted in axonal regeneration and functional recovery
of the recipient nerve but did not reach the level of intact controls. Significantly
higher numbers of myelinated axons and labeled neurons giving regenerating fibers
were found in group ETE compared with group ETS at both time points, consistent with
the functional and electrophysiological recovery. Group ETS showed significantly smaller
fiber diameter and thinner myelin thickness than group ETE at 4 months, but the difference
became nonsignificant at 8 months. ETS neurorrhaphy had a very slight effect on the
donor nerve, as determined electrophysiologically and histomorphologically. Sparsely
distributed double-labeled neurons and relatively large amounts of single-labeled
neurons contributing to reinnervation were found through double retrograde neuronal
labeling in group ETS. Further quantitative analysis of the percentage of double-labeled
neurons showed a pronounced tendency to decline from 19.8% at 4 months to 6.0% at
8 months postoperatively.
Conclusion Successful reinnervation after ETS neurorrhaphy could be achieved through both collateral
sprouting and terminal sprouting, with the latter seeming to be the principal origin
of motor nerve sprouting.
Keywords
end-to-side neurorrhaphy - facial–hypoglossal neurorrhaphy - nerve regeneration
