How do the principles of primary nerve anastomosis apply to nerve grafting for the treatment of spinal accessory nerve (SAN) injury?

Updated: Feb 09, 2018
  • Author: Rohan R Walvekar, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Answer

The principles of primary nerve anastomosis also apply to graft interpositioning. Both proximal and distal nerve ends must be cleanly cut so that the fascicles are visible. The nerve graft is interpositioned in the reverse direction (ie, the proximal graft end attached to the distal free end of the nerve and vice versa). Nerve fascicles progressively branch and diverge distally, so reverse interpositioning promotes "funneling" of the regenerating axons from proximal to distal through the graft. [49]

Because grafting requires nerve axons to regenerate across 2 sites (proximal and distal), outcomes were previously believed to be inferior to those with primary anastomosis (ie, with only one site of end approximation). However, this hypothesis has been disproved; a tension free graft inter-positioning will lead to superior outcomes when compared with a tension-laden primary anastomosis. In addition, thinner nerve grafts such as cutaneous nerve grafts are more easily revascularized than thicker grafts, thus leading to better outcomes. [49]


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