[A preliminary study on cross anastomoses between facial and accessory nerves and reconstruction of motor unit]

In a new operating model, the buccal branch of facial nerve of rabbits, which originally controls the muscles composed of small motor units (MU), was transposed and cross-anastomosed with the accessory nerve which controls the sternocleidocephalic muscle composed of larger MU. One year later, fine filaments of facial nerve were dissected and stimulated, electrophysiological and biomechanic examinations of single MU in sternocleidocephalic muscle were carried out; the total number and percentage of 3 types of muscle fiber were counted according to polyhistochemical and histological methods as we reported formerly; the motor fibers were counted according to nerve AChE direct-coloring method and the innervation ratio was calculated. The results showed that the facial innervation ratio increased by 2.2 to 4.4-fold. That the largest value of TwT recorded in one of single MUs reached to 112.9 mN, suggested that the number of muscle fibers innervated by this facial nerve axon was much more than it did. That there was no type grouping phenomenon appeared in polyhistochemical examination implied that the facial nerve fibers regenerated along the old route offered by original MU, which tended to reneurotize all of muscle fibers of the original MU.