Trigeminal nerve

The trigeminal nerve (the fifth cranial nerve, or simply CN V) is a nerve responsible for sensation in the face and motor functions such as biting and chewing; it is the largest of the cranial nerves. Its name ('trigeminal' = tri-, or three, and - geminus, or twin: thrice-twinned) derives from the fact that each of the two nerves (one on each side of the pons) has three major branches: the ophthalmic nerve (V1), the maxillary nerve (V2), and the mandibular nerve (V3). The ophthalmic and maxillary nerves are purely sensory, whereas the mandibular nerve supplies motor as well as sensory (or 'cutaneous') functions.The three major branches of the trigeminal nerve—the ophthalmic nerve (V1), the maxillary nerve (V2) and the mandibular nerve (V3)—converge on the trigeminal ganglion (also called the semilunar ganglion or gasserian ganglion), located within Meckel's cave and containing the cell bodies of incoming sensory-nerve fibers. The trigeminal ganglion is analogous to the dorsal root ganglia of the spinal cord, which contain the cell bodies of incoming sensory fibers from the rest of the body.The sensory function of the trigeminal nerve is to provide tactile, proprioceptive, and nociceptive afference to the face and mouth. Its motor function activates the muscles of mastication, the tensor tympani, tensor veli palatini, mylohyoid and the anterior belly of the digastric.All sensory information from the face, both touch-position and pain-temperature, is sent to the trigeminal nucleus. In classical anatomy most sensory information from the face is carried by the fifth nerve, but sensation from parts of the mouth, parts of the ear and parts of the meninges is carried by general somatic afferent fibers in cranial nerves VII (the facial nerve), IX (the glossopharyngeal nerve) and X (the vagus nerve).Wallenberg syndrome (lateral medullary syndrome) is a clinical demonstration of the anatomy of the trigeminal nerve, summarizing how it processes sensory information. A stroke usually affects only one side of the body; loss of sensation due to a stroke will be lateralized to the right or the left side of the body. The only exceptions to this rule are certain spinal-cord lesions and the medullary syndromes, of which Wallenberg syndrome is the best-known example. In this syndrome, a stroke causes a loss of pain-temperature sensation from one side of the face and the other side of the body.Diagram of facial sensory nerves (front view)Trigeminal nerve in yellowTrigeminal ganglionCerebrum (deep inferior dissection)