Microanatomic analysis of the trigeminal nerve and potential nerve graft donor sites

A histologic study was undertaken to define the microanatomic characteristics of two commonly injured peripheral trigeminal nerve branches (lingual and mandibular nerves) and the two nerves most frequently procured for use in their interpositional graft repair (sural and greater auricular nerves). Nerves, obtained from fresh human cadavers, were evaluated for total fascicular area, fascicle number, axon number, axon size, and axon density. The peripheral branches of the trigeminal nerve (third division) were morphometrically similar, with only a slight decrease in axon density in the lingual nerve. Comparisons between the donor nerves, however, showed numerous discrepancies at the axonal level. While the fascicular area of the sural nerve was only slightly smaller, axon numbers and densities were only one-half that of the trigeminal nerves. Although the greater auricular nerve was appreciably smaller in overall size, a much better correlation existed with the trigeminal nerve in axonal qualities. These microanatomic findings raise questions about the potential capability of these graft choices to optimally restore axonal connections between nerve ends in trigeminal nerve repair.