Overview Cranial nerve exits in relation to brainstem anatomy. Illustration by Ava Yap Snapshot A 35-year-old woman presents to the emergency department with left eye vision loss and headache. She was in her usual state of health until 3 hours prior to presentation, when she developed vision loss and eye pain that worsened with eye movement. She reports that approximately 8 months ago she had left arm numbness that self resolved. On physical exam, her visual acuity is 20/185, and a sluggish response to light on the left eye with the swinging flash-light test is noted. (Optic neuritis likely secondary to multiple sclerosis.) Introduction Cranial Nerves Cranial Nerve Type Function Cranial Exit Notes Olfactory nerve (I) Sensory Olfaction Cribiform plate Only CN without thalamic relay to the cortex Cribiform plate fracture can lead to anosmia Optic nerve (II) Sensory Vision Optic canal - Oculomotor nerve (III) Motor Eye movement via the superior, inferior, and medial rectus inferior oblique muscle Pupillary constriction Accomodation Eyelid opening via innervation of the levator palpebrae muscle Superior orbital fissure Center contains output to ocular muscles which is affected primarily 1st by vascular disease Periphery contains parasympathetic output which is affected 1st by compression Trochlear nerve (IV) Motor Eye movement via innervation of the superior oblique muscle Superior orbital fissure - Trigeminal nerve (V) Motor and sensory Mastication via the mandibular nerve (V3) Facial sensation via the ophthalmic nerve (V1) maxillary nerve (V2) mandibular (V3) Ophthalmic nerve (V1)superior orbital fissure Maxillary nerve (V2) foramen rotundum Mandibular nerve (V3) foramen ovale Mediates the jaw jerk reflex Abducens nerve (VI) Motor Eye movement via innervation of the lateral rectus Superior orbital fissure - Facial nerve (VII) Motor and sensory Facial movement Taste from the anterior 2/3 of tongue Lacrimation Salivation via innervation of the submandibular gland sublingual gland Eyelid closing via innervation of the orbicularis oculi muscle Stapedius dampens excessive sound Internal auditory meatus Visceral sensation recieved by nucleus solitarius Vestibulocochlear nerve (VIII) Sensory Hearing Balance Internal auditory meatus - Glossopharyngeal nerve (IX) Motor and sensory Taste from posterior 1/3 of tongue Swallowing Salivation parotid gland Monitoring carotid body and sinus chemo- and baroreceptors Stylopharngeus elevates pharynx and larynx Jugular foramen Motor output orginates in nucleus ambiguus Visceral sensation recieved by nucleus solitarius Vagus nerve (X) Motor and sensory Taste from epiglottic region Swallowing Palate elevation Midline uvula Talking Coughing Thoracoabdominal viscera Monitoring aortic arch chemo- and baroreceptors Can cause vasovagal syncope in response to an emotional stimulus Jugular foramen Motor output originates in nucleus ambiguus Visceral sensation recieved by nucleus solitarius Parasympathetic fibers to heart, lungs, and upper GI orginates from dorsal motor nucleus Gives recurrent laryngeal nerve which innervates all laryngeal muscles except cricothyroid Accessory nerve (XI) Motor Head turning and shoulder shrugging sternocleidomastoid muscle trapezius Jugular foramen Motor output originates in nucleus ambiguus Hypoglossal nerve (XII) Motor Tongue movement Hypoglossal canal -