THE HYPOGLOSSAL NERVE (XII)

The hypoglossal nerve is motor to the intrinsic and extrinsic muscles of the tongue, which originate in the myotomes of occipital somites. After leaving the ventral aspect of the medulla oblongata (Figure 8-19), the nerve passes through the hypoglossal canal before cross­ing the nerves of the vagus group to continue toward the tongue, which it enters ventral to the glossopharyn­geal nerve. It ramifies within the tongue substance to reach the various muscles.

A destructive lesion of this nerve paralyzes the ipsi­lateral muscles, allowing a deviation of the tongue toward the normal side. A marked atrophy eventually develops.