Morphometric study of the hypoglossal canal

Abstract

The hypoglossal nerve, cranial nerve XII, is a motor nerve responsible for extrinsic and intrinsic control of the tongue musculature. At the skull base, it passes through the hypoglossal canal and when crossing it, enters the nasopharynx and the carotid space. It emits small branches which descend into contact with the vagus nerve, passing between the internal carotid artery and the internal jugular vein. It forms the hypoglossal handle around the root of the occipital artery. Hypoglossal canal variations in shape, diameter, and angle are of extreme importance to neuroradiologists and neurosurgeons, once in surgeries at the skull base, such anatomical elements serve as a reference point. The aim of this work is to carry out a study on the prevalence, shape, and angle of the hypoglossal canal, also showing their possible clinical implications. 400 dried intact human skulls (800 sides), without sex or race identification which belong to the Discipline of Anatomy of FOSJCampos - UNESP will be used. From each skull will be obtained linear measures (diameter maximum transverse and anteroposterior maximum) and then each will be classified according to the cranial index. Once the classification is finished, the following studies will be done: the presence or absence of the hypoglossal canal, incidence according to the side of the skull, and then, each canal shall be classified according to the types proposed by Hauser and Stefano (1985): type I (single canal without division), type II (canal showing small bony inside), Type III (canal with two or more spicules), type IV (presence of complete bone bridge on the inside or outside of the canal without breaking it down into two distinct canals), type V (presence of bone bridge throughout the internal orifice to the external canal, dividing it into two distinct canals). After this classification is completed with the aid of a drypoint compass, the diameters of internal and external holes of each canal will be obtained. Such measures will be transferred to a high-precision digital pachymeter of the brand Mitutoyo. All the data found will be stored in appropriate files for subsequent submission of statistical analysis.(AU)