This section discusses the anatomic structures of the fifth cranial nerve (trigeminal nerve), and symptoms and signs caused by its impairment, and representative diseases or syndromes. The trigeminal nerve innervates facial sensation and jaw movement. Anatomically the nerve consists of three branches: the first branch (ophthalmic nerve), the second branch (maxillary nerve), and the third branch (mandibular nerve). Sensory nerves of the trigeminal nerve innervate skin of the face and forehead, a part of the oral mucosa, and a large part of meninges. The primary neurons are in the semilunar ganglion (gasserian ganglion) which is located in the middle cranial fossa.