A Single Branch Of Neurotomy Trigeminal Nerve Affecting On The Whole Trigeminal System

Primary trigeminal neuralgia is a disease from which patients were suffering severely. There is no satisfied therapy because the pathogenesis is unknown, and the surgery is still an effective therapy to release the patiens?suffering. The surgical procedures for the treatment of trigeminal neuralgia, such as neuragxnia of peripheral nerve, percutaneous techniques (radiofrequency rhizotomy, glycerol rhizotomy, and balloom decompression), posterior fossa exploration (microvascular decompression and partial sensory rbizotomy), have either the high rate of pain recurrence or the high risk of the serious complications and sequelae. We treated patients with the high-level trigeminal neurectomy. Both the surgical danger and recurrence rate of the therapy had decreased significantly. For decreasing the recurrence rate of surgical therapy, it is necessary to probe into the causes of recurrence systematically. So we made a series of experiments. First, we invastigated the mental nerves of the recurrent patients who received the high-level trigeminal neurectomy several years ago for mandibular pain by electron microscopy, and found there were still normal fibers in them. It revealed that the neural pathway which was the pathologic foundation of recurrence still kept well after the high-level trigeminal neurectomy. Obviously, regenerating nerve fibers and intersectional fibers are important factors of the neural pathway reforming. After transecting and ligating the rat infraorbital nerve, we injected HRP(horseradish peroxidase) into the vibrissa pad immediately or two months later. And we found that the ipsilateral mandibular peripheral axons sprouted into the vibrissa pad, while the contralateral trigeminal nerve did not. It implied that the adjacent nerve sprouting compensatory into the vibrissa pad was another important factor reforming the neural pathway. Second, after transecting and ligating the rat infraorbital nerve, we induce HRP(horseradish peroxidase) into the trigeminal nerve system from different sites. And we found: (IL) The ipsilateral mandibular neurons?size had no significant changes after the rat infraorbital nerve being transected and ligated, but its central projecting field changed with time.?The infraorbital neurons?size had enlarged significantly at two weeks after being transected, and resumed two months later. Furthermore, its central projecting field enlarged significantly at two weeks after 4 being transected too, but did not resume two months later. The neurons enlarged, their membrane transmural ability strengthened and the efficiency of HRP transganglionic transporting enhanced after the nerve being transected. And these were major causes of the infraorbital nerve central projecting field enlarging. The facts, that the central projecting field of the mandibular nerve which was little affected by transecting the infraorbital nerve, and that the central projecting field of both the mandibular nerve and the infraorbital nerve had not lessened evidently after their neurons resumed two months later, implied that the trigeminal central system had formed new synapses because of the nerve plasticity caused by neurectomy. Some studies supposed that the myelinated fibers would sprout into lamina II and synapse with unniyelinated fibers, and that the innocuous stimuli would cause pain by the new neural pathway. The factors, such as growth associated protein 43 and FK506, could promote new synapse...