Light- and electron microscopic findings in the distal end of human cross-face sural nerve grafts

In five patients with long-standing facial palsy we have tried to improve the possibility of elevating the angle of the mouth by bringing regenerating axons from the facial nerve on the normal side through a sural nerve graft to a transplanted free muscle in the paralyzed cheek. In order to expect clinical improvement a sufficient number of axons must grow into and through the sural nerve graft, neuromuscular contacts must be formed, and the transplanted muscle must be vascularized and survive. In order to find out if axons had regenerated, light- and electronmicroscopic examinations of a biopsy from the tip of the sural nerve graft were carried out at the time of muscle transplantation. All the cases showed a very large number of unmyelinated axons located within the fascicles of the sural nerve graft. A considerable fraction of myelinated axons were, however, present particularly in biopsies removed 12-13 months after the nerve operation. There was also a marked increase in endoneurial collagen and at the very tip a neuroma was present. This investigation thus shows that regeneration of a substantial number of axons had occurred and that they had reached the zone which was surgically sutured to the transplanted muscle. One essential requirement for reinnervation of the transplanted muscle therefore exists in these patients, but the clinical outcome has not yet been evaluated due to the short follow-up period.