The Hypoglossal Nerve: Twelfth Cranial Nerve

The twelfth nerve arises from hypoglossal nucleus in the medulla as a number of rootlets which emerge from the front of the medulla in the anterolateral sulcus which separates the olive and the pyramid. The nerve passes through the subarachnoid space and pierces the dura mater near the hypoglossal canal which is an opening in the occipital bone of the skull. After emerging from the hypoglossal canal, it gives off a meningeal branch and picks up a branch from the anterior ramus of C1. The 12th nerve then travels along the vagus and the accessory nerve and passes between the internal carotid artery and internal jugular vein to supply the extrinsic and intrinsic tongue muscles (Fig. 22.1). CN XII is a nerve with pure motor innervation of tongue muscles.