Morphometric aspects of the human hypoglossal nerve in adults and the elderly.

AIM Perform a morphometric analysis of the myelinic fibers of the right hypoglossal nerve, in two age groups; to verify quantitative changes as a result of the aging process. STUDY DESIGN Anatomic. MATERIAL AND METHOD A 1 cm fragment of the right hypoglossal nerve was collected from 12 male corpses without any medical history of diseases such as: diabetes, alcoholism, and malignant neoplasia. The sample was divided in two groups: group with six corpses under sixty years old (adult), and another group with six corpses sixty years old or above (elderly). The material was fixed at 2.5% glutaldehyde and 2% paraformaldehyde solution; post-fixed at 2% osmium tetroxide; dehydrated with increasing ethanol concentrations, and included in epoxy resin. Semi-thin sections of 0.3 microm were obtaining, colored in 1% toluidine blue, and evaluated with light microscope combined with image analyzing system. The following morphometric data were quantified: intraperineural transversal section area, number, and diameter of the myelinic fibers. RESULTS The intraperineural area of the hypoglossal nerve was similar in both age groups (p=0.8691). The average area in the adult group was 1.697 mm2 and in the elderly group it was 1.649 mm2. The total number of myelinic fibers of the hypoglossal nerve was similar in both age groups (p=0.9018). The adult group presented an average of 10,286 +/- 2,308 myelinic fibers, and the elderly group presented an average of 10,141 +/- 1,590 myelinic fibers. A bimodal distribution of the myelinic fibers was observed, with a significant peak on the 9 microm fibers, and another smaller peak on the 2 microm fibers. CONCLUSION The intraperineural area and the total number of myelinic fibers of the right hypoglossal nerve are similar in both age groups.