Clinical Anatomy of Trigeminal through the superior orbital fissure Nerve and courses within the lateral wall of the cavernous sinus on its way The trigeminal nerve is the fifth of to the trigeminal ganglion. the twelve cranial nerves. Often Ophthalmic Nerve is formed by the referred to as "the great sensory union of the frontal nerve, nerve of the head and neck", it is nasociliary nerve, and lacrimal named for its three major sensory nerve. Branches of the ophthalmic branches. The ophthalmic nerve nerve convey sensory information (V1), maxillary nerve (V2), and from the skin of the forehead, mandibular nerve (V3) are literally upper eyelids, and lateral aspects "three twins" carrying information of the nose. about light touch, temperature, • The maxillary nerve (V2) pain, and proprioception from the enters the middle cranial fossa face and scalp to the brainstem. through foramen rotundum and may or may not pass through the • The three branches converge on cavernous sinus en route to the the trigeminal ganglion (also called trigeminal ganglion. Branches of the semilunar ganglion or the maxillary nerve convey sensory gasserian ganglion), which contains information from the lower eyelids, the cell bodies of incoming sensory zygomae, and upper lip. It is nerve fibers. The trigeminal formed by the union of the ganglion is analogous to the dorsal zygomatic nerve and infraorbital root ganglia of the spinal cord, nerve. which contain the cell bodies of • The mandibular nerve (V3) incoming sensory fibers from the enters the middle cranial fossa rest of the body. through foramen ovale, coursing • From the trigeminal ganglion, a directly into the trigeminal single large sensory root enters the ganglion. Branches of the brainstem at the level of the pons. mandibular nerve convey sensory Immediately adjacent to the information from the lateral scalp, sensory root, a smaller motor root skin anterior to the ears, lower emerges from the pons at the cheeks, lower lips, and anterior same level. aspect of the mandible. It is • Motor fibers pass through the formed by the union of the buccal trigeminal ganglion on their way to nerve, lingual nerve, inferior peripheral muscles, but their cell alveolar nerve, and bodies are located in the motor auriculotemporal nerve. nucleus of the fifth nerve, deep within the pons. Motor fibers are • The trigeminal ganglion lies in distributed (together with sensory a depression known as the fibers) in branches of the trigeminal cave (or Meckel's cave). mandibular nerve. The trigeminal nerve exits the trigeminal ganglion and courses Branches of Trigeminal Nerve "backward" to enter the mid-lateral aspect of the pons . • The ophthalmic nerve (V1) • Branchial motor nerves exit enters the middle cranial fossa the mid-lateral aspect of the pons, course within the trigeminal nerve, ganglion, and submandibular pass through the trigeminal ganglion. Within these ganglia, ganglion, and exit the middle pre-ganglionic fibers synapse with cranial fossa within the mandibular post-ganglionic fibers (whose cell nerve through foramen ovale. The bodies make up the bulk of the branchial motor component of the ganglia), which in turn travel to trigeminal nerve consists of lower innervate glands. motor neurons whose cell bodies are located in the motor nucleus of The facial nerve gives rise to two the trigeminal nerve in the important trigeminal hitchhikers - brainstem. (The term "branchial" the Vidian nerve and the chorda refers to structures embryologically tympani nerve. derived from the branchial arches) These nerves exit the mid-lateral The Vidian nerve (nerve of the aspect of the pons, course within pterygoid canal) emerges from the the trigeminal nerve, pass through pterygoid canal carrying pre- the trigeminal ganglion, and within ganglionic fibers to the the mandibular nerve before pterygopalatine ganglion. After branching. The muscles innervated synapse, post-ganglionic fibers exit by the branchial motor component the ganglion and hitchhike along can be remembered as "the trigeminal nerve branches en route muscles of mastication (chewing) to the lacrimal gland and minor plus two tensors." That is, the salivary glands of the palate and temporalis, masseter, medial and mouth. lateral pterygoids, tensor veli palatini, and tensor tympani. • The chorda tympani exits the skull through the petrotympanic Trigeminal Hitchhikers: fissure and courses extracranially to join the lingual nerve. It carries Visceral motor nerves are not a pre-ganglionic fibers to the true component of the trigeminal submandibular ganglion which nerve, but "hitchhike" along its "hangs" from the lingual nerve. branches. (The term "visceral" After synapse, post-ganglionic refers to viscera, including smooth fibers exit the ganglion to muscle and glands). They originate innervate the submandibular gland centrally from other cranial nerves and sublingual gland. and travel along sensory branches of the trigeminal nerve en route to The glossopharyngeal nerve glands. Visceral motor nerves can also contributes an important be subdivided into pre-ganglionic trigeminal hitchhiker - the lesser and post-ganglionic fibers. Pre- petrosal nerve. It carries pre- ganglionic fibers travel from cranial ganglionic fibers to the otic nerve nuclei in the brainstem ganglion. After synapse, post- (where their cell bodies are ganglionic fibers exit the ganglion, located) to peripheral ganglia in hitchhiking along the the head and neck. These include auriculotemporal nerve to the pterygopalatine ganglion, otic innervate the parotid gland.