The influence of the trigeminal nerve on facial growth and development

For the past twenty years it has been argued that the growth of the face is governed by the growth of a variety of contiguous soft tissues and functioning spaces (functional matrices). Recently, extensive data have been marshalled to suggest that the growth of the functional matrices is controlled by "trophic" influences from nerves. Accordingly, the present study sought to evaluate the role of the trigeminal nerve in the regulation of facial growth by placing unilateral stereotaxic lesions in the trigeminal nerve (root, ganglion, or major sensory branch) of the 10- to 20-day-old rat. The unoperated side and a number of sham animals served as controls. In all, 323 operations were performed, with 119 animals surviving until the age of 50 days. The location and extent of the lesions were controlled histologically. Cephalometric analysis revealed subtle but statistically significant distortions of the facial skeleton; however, the magnitude of the effect was quite small. Thus, although a modest case can be made for the contention that the trigeminal nerve exerts a trophic influence on the craniofacial complex, the conclusion that trophic effects constitute a major factor in the regulation of craniofacial growth cannot be supported.