“On Old Olympus Towering Tops A…” Andrea Gianniny Eden Treadway CRANIAL NERVES I-VI “On Old Olympus Towering Tops A…” Andrea Gianniny Eden Treadway

Brief Review CNs : from brain pass through foramina magnum of skull I-XII from ascending – descending CNs 1 & II attach to forebrain I- telencephalon II- diencephalon Other 10 to brainstem Primarily serve head/neck structures Vagus (X) extends to abdomen

Number Name Sensory/Motor/Both I Olfactory On Some II Optic Old Say III Oculomotor Olympus Money IV Trochlear Towering Matters V Trigeminal Tops But VI Abducens A My VII Facial Finn Brother VIII Auditory And Says IX Glossopharyngeal German Big X Vagus Viewed Brains XI Spinal Accessory Matter XII Hypoglossal Hops Most

I - Olfactory Sensory nerve of smell Function: transduce odor molecules Cortical olfactory regions: responsible for olfactory awareness and Limbic olfactory connections: responsible for integrating smell with emotions Connections with hypothalamus play role in feeding behavior. Formed by unmyelinated axons, terminates into two olfactory bulbs located in the inferior surface of the frontal lobe

Clinical Conditions - I Damage: deviations in ability to smell Anosmia/hyposmia- Reduction or loss of ability to smell Hyperosmia- Abnormally acute sensation of smell

II - Optic Sensory nerve of vision Optic nerve endings receive light energy in the form of nerve potentials produced by photoreceptor cells in the retina. Path: axons of the Optic Nerve travel until the optic chiasm and then as the optic tract. The optic tract then terminates in the Lateral Geniculate Body of the thalamus. There, the optic radiations travel to primary visual cortex.

Clinical Conditons - II Ipsilateral blindness: lesion to optic nerve Bitemporal hemianopsia: chiasmatic lesion Unilateral homonymous hemianopsia: post chiasmatic lesions close to lateral geniculate body  Upper & Lower homonymous quadrantopsia: lesions distal to the geniculate ganglion

III - Oculomotor Motor nerve Innervates four of six extrinsic eye muscles Form & Function: composed of two components Somatic: Innervates the four extrinsic eye muscles & levator superioris, which is responsible for movement of eye lids. Visceral: innervates the intrinsic ocular eye muscles and controls parasympathetic functions including light reflex (constriction of pupils) and accommodation- convergence (modification of lens for near vision) CN III is one of only four CNs that are involved in parasympathetic functions (along with VII, IX, and X)

Clinical Conditions - III External Opthalamoplegia: Paralysis of extrinsic eye muscles and levator superiorsis. Lateral Striabismus: deviation of ipsi eye to the lateral side May result in diplopia (double vision) Ptosis: eye lid drooping Internal Opthalamoplegia: Paralysis of intrinsic muscles Mydriasis: permanent dilation of pupil

Mydriasis

IV - Trochlear Motor Eye muscle movement (III, IV, & VI) Innervation: extrinsic muscle Superior oblique Action: abducts and depresses eyeball Moves eye outward and down Only CN that exits posterior side of brainstem

Clinical Conditions - IV Damage: difficulty looking down and out Also, eye fixed in upward, medial gaze

VI - Abducens Motor Innervation: extrinsic eye muscle Lateral rectus Action: abducts eyeball horizontally Runs long intracranial course therefore more susceptible to damage

Clinical Conditions - VI Damage: medial strisbismus (because medial rectus [CN III] is unopposed) which in turn may cause diplopia Medial strasbismus: affected eye turns medially Diplopia: double vision Medial Longitudinal Fasciculus – brainstem tract that helps communication between CNs III, IV, & VI and vestibular system and neck muscles Coordinates eye muscles for gaze control and head position with eye movements doll’s eye reflex

Damage to CN VI – Medial strabismus

V - Trigeminal Largest CN Mixed Sensory innervation: from face Motor innervation: to chewing muscles Sensory & motor components for Jaw Jerk Reflex - lesion causes exaggerated reflex 3 branches (tri) V1. Opthalamic nerve (sensory) V2. Maxillary nerve (sensory) V3. Mandibular nerve (sensory and motor)

V – Trigeminal (cont.) Action: Sensory: cutaneous (touch, pain, temperature) and… proprioceptive (awareness of relative muscle movement) sensations from the: face, head, oral and nasal cavities Sinuses and teeth Anterior 1/3 of tongue Anterior half of pinna, external auditory meatus, and external surface of TM Motor: controls muscles of mastication (chewing) and speech production, tensor veli palatini (soft palate) and tensor tympani (middle ear muscle) CN V: controls muscles involved in chewing but NOT facial expressions

V – Trigeminal (cont.) Mandibular nerve: only carries general sensory sensations from mouth, NOT taste (e.g. touch/position, pain/temperature) Taste fibers from anterior 2/3 of tongue carried by lingual nerve then chorda tympani (branch of CN VII) Taste fibers from posterior 1/3 and pharynx carried by branches of CNs VII, IX, and X

Clinical Testing - V Sensory: lightly touch parts of pt’s face with cotton or blunt object Check for sneezing reflex and corneal reflex (blink in response to touching cornea) Jaw Jerk Reflex Motor: check masseter muscle by asking pt to bite down hard Ask pt to open mouth against resistance at base of chin

Clinical Conditions - V Damage to Sensory portion: Ipsilateral loss of sensation Loss of sneezing and blinking reflexes Trigeminal Neuralgia Sudden intense pain in eyes, lips, nose, scalp, forehead, and jaw Nerve severing in rare cases to treat

Clinical Conditions - V Damage to Motor portion: Ipsilateral muscles of mastication paralyzed Absent Jaw Jerk reflex, muscle tics/twitching Dysarthria – paralyzed mandible and soft palate cause misarticulations

Clinical Conditions - V Wallenberg Syndrome: Believed to be stroke involving Posterior Inferior Cerebellar Artery [PICA] Loss of pain/temperature sensation from Ipsilateral (same) side of face Contralateral (opposite) side of body Reason: the ascending spinothalamic tract in the medulla carries pain/temp info from contralateral side of body is adjacent to descending tract of CN V which carries pain/temp info from ipsilateral side of face A stroke cutting off blood supply in this area (e.g. clot in PICA) destroys both tracts

Questions! At what point do the CNs pass through the skull? a. medulla b. jugular foramina c. foramina magnum d. brainstem

10 of the 12 CNs originate where? a. diencephalon b. brainstem c. cerebellum d. medulla

Of the first 6 cranial nerves, which is the only mixed nerve? a. Trochlear b. Oculomotor c. Abducens d. Trigeminal

Which cranial nerve exits the brainstem posteriorly? a. Vagus b. Trochlear c. Trigeminal d. Spinal Accessory

This cranial nerve innervates an extrinsic eye muscle (superior oblique) and is responsible for abducting and depressing the eyeball. a. CN II b.CN III c. CN IV d. CN VI

This cranial nerve innervates an extrinsic eye muscle (lateral rectus) and is responsible for abducting the eyeball horizontally. a. CN II b. CN III c. CN IV d. CN VI

Damage to the Abducens nerve (VI) will result in what kind of damage? a. medial strabismus b. lateral strabismus c. Wallenberg Syndrome d. hemianopsia (blindness in half of visual field)

is an important tract in the brainstem that facilitates communication between CNs III, IV, and VI as well as the vestibular system and neck muscles. This tract also coordinates muscles for the doll’s eye reflex. a. Medial Longitudinal Fasciculus b. Spinothalamic tract in medulla c. Pyramidal tract d. Lateral Corticospinal Tract

The largest cranial nerve is . a. CN IV b. CN V c. CN X d. CN XII

CN controls muscles of mastication as well as the tensor veli palatini and tensor tympani muscles involved in speech production. a. CN X b. CN VII c. CN V d. CN VI

A rare condition with symptoms of intense pain in a patient’s face (eyes, lips, nose, jaw, etc.) is known as . a. PICA b. Occipital Neuraligia c. Wallenberg Syndrome d. Trigeminal Neuralgia

What branch of the Trigeminal nerve accounts for its motor functions? a. Opthalamic b. Mandibular c. Maxillary d. Facial

Wallenberg Syndrome is a condition characterized by loss of pain/temperature sensation from the side of the body and the side of the face. a. ipsiliateral; contralateral b. ipsiliateral; ipsilateral c. contralateral; contralateral d. contralateral; ipsilateral

The sensory portion of this cranial nerve carries cutaneous and proprioceptive sensations from the anterior 1/3 of the tongue and the anterior half of the pinna, external auditory meatus, and external surface of the TM. a. CN V b. CN VII c. CN IX d. CN IV

A condition that causes a reduction or loss of the ability to smell is known as _____________. a. Hyperosmia b. Neuralgia c. Anosmia d. Wallenberg Syndrome

CN ___ innervates four of the six extrinsic eye muscles. a. CN VI b. CN II c. CN III d. CN IV

A lesion to CN ____ can cause ipsilateral blindness. a. CN I b. CN II c. CN III d. CN IV

Sensory endings of CN ____ are responsible for responding to noxious sensations, such as those associated with mace spray, onions, and mustard oil. a. CN V b. CN IV c. CN II d. CN I  

Connections of Cranial Nerve ___ with the hypothalamus play an important role in feeding behavior. a. CN III b. CN II c. CN IV d. CN I

The visceral portion of CN ____ controls parasympathetic functions such as light reflex and accommodation- convergence reflex. a. CN IV b. CN III c. CN I d. CN II

Which of the following nerves do NOT serve parasympathetic functions of the autonomic system? a. CN III b. CN IX c. CN II d. CN VII

Paralysis of the extrinsic eye muscles and levator superiorsis is known as ____________________. a. External Opthalamoplegia b. Internal Opthalamoplegia c. External Neuralgia d. Internal Neuralgia

All of the following are Motor or Mixed nerves EXCEPT: a. CN III b. CN IV c. CN II d. CN V

Lateral striabismus caused from a lesion to CN III can cause double vision, which is formally known as: a. Mydriasis b. Bitemporal hemianopsia c. Ipsilateral blindness d. Diplopia  

Where are the two olfactory bulbs, where CN I terminates, located? a. Superior surface of Temporal lobe b. Inferior surface of Frontal lobe c. Inferior surface of Occipital lobe d. Superior surface of Occipital lobe