Cranial Nerves

Cranial nerves Things I’m going to cover and you’re going to understand • General informaon about cranial nerves • Systemac explanaon about cranial nerves I-IV and VI • Visual pathway • Annulous of Zinn and Cavernous Sinus • Extraocular muscles • Systemac explanaon of cranial nerves V and VII-XII • Summary of reflexes The cranial nerves

I. Olfactory nerve VI. Abducens nerve II. Opc nerve VII. Facial nerve III. Oculomotor nerve VIII. Vesbulocochlear nerve IV. Trochlear nerve IX. Glossopharyngeal nerve V. Trigeminal nerve X. Vagus nerve I. Opthalmic XI. Accessory nerve II. Maxillary I. Cranial III. Mandibular II. Spinal XII. Hypoglossal nerve Sensory, motor or both?

I. Some VII. Brother II. Say VIII. Says III. Marry IX. Big IV. Money X. Brains V. But XI. Maer VI. My XII. More Olfactory nerve

• Sensory • Exits via the cribriform plate • An extension of telencephalon • Clinical: • Anosmia • Ethmoidal fracture or Foster-Kennedy syndrome • Rhinorrhea • Can lead to life threatning infecon Optic nerve

• Sensory nerve • Exits via the opc canal • Extension of diencephalon • Reflexes associated with CN. II: • Pupillary light reflex • Accommodaon reflex • Clinical: • Papilledema (increase in intercranial pressure) • Opc atrophy (greater wing of sphenoid fracture) • Glaucoma (Excess of fluid in anterior poron of eye) Visual Pathway

• I’m going to draw, despite lacking the ability! Oculomotor, Trochlear and Abducens nerve • Motor nerves • Oculomotor has parasympathec fibers (sphincter pupillae and ciliary muscles) • Levator palpebra superioris • All exit via the superior orbital fissure • Reflexes associated with CN. III • Pupillary reflex • Accommodaon reflex Extraocular muscles • Superior oblique • Inferior oblique • Superior rectus • Inferior rectus • Medial rectus • Lateral rectus Lesions of CN. III, IV or VI Summary of palsies affecting the eye

• Trochlear (IV) nerve palsy • Vercal diplopia and nystagmus • Difficulty walking down stairs and reading • Head lt away from damaged side • Abducens (VI) nerve palsy • Damaged eye fixed medially • Horizontal diplopia and nystagmus • Oculomotor (III) nerve palsy • Damaged eye fixed in ”down and out”-gaze • Diplopia and nystagmus • Ptosis (droopy eyelid), constant mydrasis (dilated pupil) and absence of accomodaon reflex Cavernous sinus (O TOM CAT) Annulus of Zinn aka Common tendinous ring • The common origin of the rectus muscles • Contents: • Opc nerve • Oculomotor nerve • Nasociliary nerve of V1 • Abducens nerve • Trochlear nerve does not pass! Trigeminal nerve

• Both sensory and motor • Divided into three divisions • Opthalmic nerve exits skull through the superior orbital fissure • Maxillary nerve exits skull through the foramen rotundum • Mandibular nerve exits skull through the foramen ovale • SRO – Standing Room Only Opthalmic nerve

• Sensory nerve that innervates • Dorsum of nose, upper eyelid, forehead, scalp • Frontal sinuses and ethmoidal sinuses • Afferent poron of the corneal reflex Branches of opthalmic nerve Communicang

branch from Opthalmic Maxillary nerve nerve Pure sensory

Meningeal branch Innervates meninges

Frontal Nasociliary Lacrimal Lacrimal gland

Long ciliary Posterior Anterior Supratrochlear Supraorbital Infratrochlear nerves ethmoidal ethmoidal Forehead Frontal sinus, scalp Dilator pupilae Ethmoidal sinus Part of nasal Upper eyelid and cornea cavity

Maxillary nerve

• Sensory nerve that innervates • From lower eye lid down to upper lip, nasal cavity, nasopharynx, maxillary teeth, gingiva • Maxillary sinuses Branches of Maxillary nerve

Maxillary nerve

Meningeal branch Ganglionic branches

To Pterygopalane ggl

Zygomac Infraorbital Lower eye lid, upper lip

Zygomacofacial Zygomacotemporal Pos sup Mid sup Ant sup Side of Cheek alveolar alveolar alveolar forehead Molars Premolars Incisors Superior dental plexus

Sensory division of the Mandibular nerve • Meningeal branch, lower lip, chin, mandibular teeth and gingiva (enre mandible) • Mucous membranes • General sensaon to anterior 2/3 of tongue (NOT TASTE)

Motor division of Mandibular Nerve

• Muscles of mascaon • Temporalis (elevates mandible) • Masseter (elevates mandible and grind food) • Medial pterygoid (elevates mandible) • Lateral pterygoid (depresses mandible) • Anterior belly of digastric and mylohyoid • Tensor veli palani (tenses so palate while swallowing) • Tensor tympani (dampens noise) Facial Nerve

Facial nerve Greater Bells palsy: Facial nerve palsy petrosal Parasymp Stapedial Motor Chorda tympani Parasymp and taste Petrous part (intracranial) Extracranial Posterior auricular Nerve to Sensory stylohyoid and posterior digastric Facial paralysis Motor

Pes Anserius Motor to face Vestibulocochlear nerve

• Pure sensory • Divided into two parts; The vesbular and the cochlear • Enters the internal acousc meatus and innervates the vesbules and cochlea Glossopharyngeal nerve

• Both sensory, motor and parasympathec • Tympanic nerve • Nerve to stylopharyngeus • Pharyngeal branch • Sensory to oropharynx • Afferent part of the gag reflex • Tonsilar branch • Lingual branch • Posterior 1/3 tongue taste and sensaon • Carod body branch Vagus nerve

• Sensory, motor and parasympathec • The last of the four parasympathec cranial nerves! • The wanderer • Innervates all muscles of larynx, pharynx (except stylopharyngeus), palate (except tensor veli palani) and palatoglossus Vagus

Meningeal Pharyngeal *Damage to vagus will result in branch branches inability to cough and deviaon Pharyngeal muscles + of uvula away from damaged palatoglossus side Internal branch - Accompanied by superior laryngeal artery Auricular Superior laryngeal External branch - Accompanied by branch superior thyroid artery Sensory to parts of external ear External Internal Recurrent branch branch laryngeal Sensory to larynx below Sensory of larynx above vocal chord and motor to all Cricothyroid vocal chord laryngeal muscles except cricothyroid Accessory nerve

• Pure motor nerve • Spinal accessory innervates sternocleidomastoid and trapezius • Lesion results in inability to shrug and lted neck • Cranial accessory joins the vagus and contributes to the pharyngeal plexus Hypoglossal nerve

• Purely somac efferent that innervates all muscles of the tongue, except the palatoglossus • Lesion of the XII result in deviaon of the tongue to the affected side • Due to imbalances of the genioglossus muscles Exceptions!

• Palate • Sensory: V2 • Motor: X, except tensor veli palani (V3) • Tongue • Sensory: V3, IX, VII (taste, not general sensory) • Motor: XII, except palatoglossus (X) • Pharynx • Sensory: V2, IX, X • Motor: X, except stylopharyngeus (IX) • Larynx • Sensory: Internal laryngeal nerve (X) • Motor: Recurrent laryngeal nerve, except Cricothyroid (external laryngeal nerve) Summary of reflexes

• Pupillary light reflex (aII, eIII) • Corneal reflex (aV1, eVII) • Accommodaon reflex (aII, eIII) • Jaw-jerk reflex (aV3, eV3) • Gag reflex (aIX, eX) • Sneeze reflex (aV2, eX) • Cough reflex (aX, eX)

• a= afferent • e=efferent