Overview Snapshot A 64-year-old man is brought to the emergency department by his son after noticing right eye deviation a few hours prior to presentation. The patient's trouble seeing progressively worsened over the course of a few hours which has never happened before. His medical history is significant for a myocardial infarction that was managed with a coronary artery bypass grafting, type 2 diabetes mellitus, and hypertension. He is currently on an appropriate medication regimen for his chronic illness. On physical examination, the right eye is deviated inferiolaterally with mydriasis of the affected eye. (Oculomotor nerve palsy likely secondary to a posterior communicating artery aneurysm compressing the nerve) Introduction Muscles Innervated by Cranial Nerves Cranial Nerve Muscle Lesion Oculomotor nerve (CN III) Extraocular muscles innervated by CN III are superior rectus (SR) infecrior rectus (IR) medial rectus (MR) inferior oblique (IO) Levator palpebrae superioris Ciliary muscle Sphincter pupillae Diplopia Ptosis Loss of accomodation Dilated pupil and loss of light reflex Trochlear nerve (CN IV) Superior oblique Difficulty looking downHead tilt away from the side of the lesion Mandibular branch of the trigeminal nerve (CN V3) Muscles of mastication which include Mandibular elevators masseter muscle temporalis muscle medial pterygoid muscle Mandibular depressors lateral pterygoid muscle anterior belly of the diagstric muscle mylohyoid muscle Tensor palati Tensor tympani Jaw deviation towards the side of the lesion Abducens nerve (CN VI) Lateral rectus Horizontal diplopia Facial nerve (CN VII) Muscles of facial expression Posterior belly of digastric muscle Stylohyoid muscle Stapedius muscle Bell's palsy Loss of blink reflex Hyperacusis (when the stapedius is involved) Glossopharyngeal nerve (CN IX) Stylopharyngeus muscle - Vagus nerve (CN X) Muscles of the palate and pharynx except tensor palati muscle (CN V3) Stylopharyngeus muscle (CN IX) All muscles of the larynx Palate droop Dysphagia Deviation of the uvula away from the side of the lesion Loss of gag reflex (the sensory component of this reflex is mostly via CN IX) Accessory nerve (CN XI) Sternocleidomastoid muscle Trapezius muscle Weakness with turning of the head Shoulder droop Hypoglossal nerve (CN XII) Muscles of the tongue except for the palatoglossus muscles Tongue deviation towards the side of the lesion