Minimally Invasive Approach to the Lingual and Hypoglossal Nerves in the Adult Rat

Surgical manipulation of the sensory and motor nerves of the rat tongue is often employed in studies evaluating the oral cavity functions of mastication and deglutition. A noninvasive, atraumatic approach that will then facilitate sufficient manipulation of these structures is required. In this study, we detail an approach that consistently allows identification of the hypoglossal (motor) and lingual (sensory) nerves of the rat. Six Wistar rats (250-500 g) were anesthetized and dissected either as fresh tissue (N = 3) or following transcardial perfusion with 4% paraformaldehyde (N = 3). Both fixed and non-fixed specimens of the rat head and neck were incised in the right submandibular region. The first animal in each group was used to gain a basic understanding of the regional muscular anatomy with reference to the hypoglossal and lingual nerves. Subsequent animals were used for the development of an efficient and minimally invasive approach to these nerves. The resultant approach begins as an incision through skin and platysma, followed by medial reflection of the digastric muscle. This allows visualization of the hypoglossal nerve in the region of the bifurcation of the common trunk into medial and lateral subdivisions. Next, the lingual nerve dissection is approached by reflection rostrally of the transversus mandibularis muscle and a caudal reflection of the mylohyoid muscle. This dissection reveals the geniohyoid muscle which when separated bluntly using forceps, exposes the lingual nerve. The anatomical approach described and illustrated herein will aid investigators in consistent identification of these two nerves as fundamental methods of their projects.