This study was laboratory based and focused on different types of end-to-side neurorraphy, and their effects on treating partial facial paralysis. The ultimate aim of this study was to determine which end-to-side neurorraphy produced the greatest axonal growth across the coaptation. A rat facial nerve model was used and buccal branch neural repair was attempted by coapting an intact marginal mandibular nerve branch end-to-side or side-to-side. The perineural window created in the recipient buccal nerve matched the stump size in end-to-side (in a traditional fashion) whereas the side-to-side repairs had different size windows in the perineurium; 5mm long or the same width as the donor nerve stump. The broad hypothesis was that a larger window would provide more useful axonal growth, better return to facial function, as measured on a scale, and greater linkage to the facial nerve nucleus centrally.
Although the larger window side-to-side did yield more axons and a good return to function this was not significantly different from a standard end-to-side coaptation. Functional significant difference was present at five weeks but not at 12 weeks (the study end-point).This is excellent work that has tried to determine whether different methods of nerve coaptation can produce a differential or incremental effect at the target end-plate. This is primarily aimed at patients who have incomplete facial paralysis and require augmentation of their neural input to the weakened side. However, it is unclear clinically if this could create muscle spasm, worsen synkinesis (if present) and accentuate facial imbalance. Moreover, creating a perineural window does carry the risk of axonal injury potentially creating unnecessary scar at the coaptation. Especially in the side-to-side technique, where a large window would be used, both donor and recipient nerve (which has some residual function) are liable to risk, for no significant benefit over an end-to-side. Overall this paper correctly tries to quantify an improvement in incomplete facial nerve regeneration, but whether this gathers clinical vogue is unclear given the added complexity of the microneural surgical expertise required, for what appears to be little gain.
