Experimental Trigeminal Nerve Injury

Abstract

Abstract:The successful reinnervation of peripheral targets after injury varies with the axonal population of the nerve that is injured and the extent of the dislocation of its central component from the peripheral endoneurial tube. Larger-diameter axons such as those supplying mechanoreceptors recover more readily than narrower axons such as those supplying taste. A complex, bi-directional interaction between lingual epithelium and sprouting nerve results in the redifferentiation of taste buds after denervation. Dentin and the dental pulp provide a strong attraction to sprouting nerves and will become reinnervated from collateral sources if recovery of the original innervation is blocked. The most effective repair technique for transected lingual nerves is one which brings the cut ends together rather than one that provides a temporary bridge.Injuries can result in cell death in the trigeminal ganglion but only if the injury is severe and recovery is prevented. Lesser damage results in chromatolysis and the increased expression of neuropeptides. All nerve injuries bring about changes in the trigeminal nucleus. These occur as changes in receptive field and the incidence of spontaneously active neurons, effects which are consistent with the unmasking of existing afferents. These functional changes are short-lived and reversible. Morphologically, nerve injury results in terminal degeneration in the nuclei and an increased expression of the c-Fos gene and some neuropeptides. Only a chronic constriction injury induces behavioral changes. The adult trigeminal system retains considerable plasticity that permits it to respond successfully to nerve injury. Much remains to be learned about this response, particularly of the trophic factors that control peripheral recovery and the central response to more severe injuries.

Dental neuroplasticity, neuro‐pulpal interactions, and nerve regeneration

“…There are immediate effects of inferior alveolar nerve transection on pulpal blood flow regulation Olgart et al, 1993), immune cell extravasation , and dentin formation (Jacobsen and Heyeraas, 1996;Heyeraas, 1989, 1990;Olgart et al, 1993), as summarized in more detailed reviews (Fristad,1997;Holland, 1996;Olgart, 1996). Similar denervation studies of sympathetic innervation found unusual neurochemistry, nerve sprouting, and immune cell entry in the affected pulps (Haug et al, 2001).…”

“…The nerve fibers also adjust their own functions, cytochemistry, and structure to fit the conditions of their target tissue. These bi-directional tissue-nerve interactions and neuroplasticity are especially prominent in polymodal nociceptive sensory fibers (Kumazawa et al, 1996;Millan, 1999), which are a major component of dental innervation (Byers and Nä rhi, 1999;Cox et al, 2002;Fouad, 2002;Fristad, 1997;Hargreaves, 2002;Heyeraas and Berggreen, 1999;Hildebrand et al, 1995;Holland, 1996;Jontell et al, 1998;Okiji, 2002;Olgart, 1985Olgart, , 1996Olgart and Kerezoudis, 1994;Pashley, 1996;Smith, 2002;Stanley, 2002;Stashenko, 2002;Suda and Ikeda, 2002). All of the features of neural involvement in tooth regeneration are affected by aging, and they are amplified by infection, as noted in studies of replantation, transplantation, or pulp exposure in germ-free conditions (Inoue and Shimono, 1992;Nishioka et al, 1998).…”

Response properties of whisker-associated primary afferent neurons following infraorbital nerve transection with microsurgical repair in adult rats

“…Critical factors thought to underlie discriminative whisking behaviors include spatial accuracy, e.g., topography, and spiketiming precision at millisecond scales, functions established initially in the primary afferent nerves (Shoykhet et al 2000; Stuttgen et al 2006). ION damage in adult animals leads to degeneration of the distal axons innervating the whiskers and to cell death in the trigeminal ganglion (Aldskogius and Arvidsson 1978;Holland 1996). Recovery is associated with partial regeneration of distal processes (Pali and Negyessy 2002).…”

Evaluation of sensitivity of teeth after mandibular fractures

“…Except for the ipsilateral lingual nerve, these do not normally innervate the pulp. Mucosal and skin re-innervation crossing the mid-line has not been demonstrated elsewhere 18 . If the original innervation is allowed to regenerate after such a collateral reinnervation has been formed, the collateral innervation is not withdrawn 37 .…”