Cranial Nerves (C12)

CN I, Olfactory (Testing)

Usually not tested. Rash, deformity of nose. Test each nostril with essence bottles of coffee, vanilla, peppermint *Extra Notes:* In cases of traumatic brain injury (frequently have disturbances in perceiving odors because area of the brain is frequently affected) Easy to distinguish, but not overwhelming

Testing Cranial Nerves

Various tests are available for testing cranial nerve function both neurological, audiological, etc.

CN VIII, Auditory/Vestibulocochlear

Vestibular system: Corresponds to semicircular system and vestibular sacs Auditory system: Cochlea (information to brain)

CN II, Optic (Sensory vs Motor Function)

Visual reception (very specific function, sensory function)

CN IX, Glossopharyngeal and CN X, Vagus (Testing)

Voice: hoarse or nasal. Pt. swallows, coughs (bovine cough: recurrent laryngeal). Examine palate for uvular displacement. (unilateral lesion: uvula drawn to normal side). Pt says "Ah": symmetrical soft palate movement. Gag reflex [sensory IX, motor X]: • Stimulate back of throat each side. • Normal to gag each time. *Extra Notes:* Simultaneous testing "Ah" phonation Open mouth and will look at pharyngeal area if uvula is located symmetrically in the middle (symmetrical movement or deviate laterally) Tongue depressor, without any warning going to stimulate back of tongue to stimulate gag reflex (normal)

CN II, Optic (Testing)

With patient wearing glasses, test each eye separately on eye chart/ card using an eye cover. Examine visual fields by confrontation by wiggling fingers 1 foot from pt's ears, asking which they see move. • Keep examiner's head level with patient's head. If poor visual acuity, map fields using fingers and a quadrant- covering card. Look into fundi *Extra Notes:* Visual acuity investigation. Person can have difficulties in perceiving information in a specific field of vision. Extent of normal visual field: 180 degrees "Campimetry by Confrontation" 4 points (up-low/left-right) Extinction: Can't perceive when both happening

Cranial Nerves (Numbering)

"The 12 pairs of cranial nerves are traditionally abbreviated by the corresponding Roman numerals. They are numbered according to where their nuclei lie in the brain stem e.g. cranial nerve II is the oculomotor nerve leaving the brainstem at a higher position than the cranial nerve XII, whose origin is located more caudally (lower) than the other cranial nerves" • Named using Roman Numerals (I-XII) • Ordinal number frequently used when talking...First, second, third, fourth, etc. • Numbers correspond to particular position nuclei in brainstem • Not necessarily in order

Cranial Nerves (Listed)

(1) Olfactory (2) Optic (3) Oculomotor (4) Trochlear (5) Trigeminal (6) Abducens (7) Facial (8) Auditory (Vestibulocochlear) (9) Glossopharyngeal (10) Vagus (11) Accessory (12) Hypoglassal

Cranial Nerves (Total Number and Irrigation Locations)

"Conventionally, there are twelve recognized cranial nerves. The nerves from the third onward arise from the brain stem. Except for the tenth and the eleventh nerve, they primarily serve the motor and sensory systems of the head and neck region. However, unlike peripheral nerves which are separate to achieve segmental innervation (dermatome), cranial nerves are divided to serve one or a few specific functions in wider anatomical territories" • Most emerging from brainstem, except for #10 and #11 • Innervating neck and up (sensitivity and motor activity), except 10 (partially corresponds to autonomic/parasympathetic system) and 11 (moving shoulders/neck down) • For the spinal nerves, the sensitivity is taken from specific segment of the skin named dermatome. • For cranial nerves, general motor function (e.g. moving eyes, moving tongue)

CN VIII, Vestibulocochlear (Hearing, Vestibular) (Testing)

Examiner's hands arms length by each ear of pt. • Rub one hand's fingers with noise on one side, other hand noiselessly. • Ask pt. which ear they hear you rubbing. • Repeat with louder intensity, watching for abnormality. Weber's test: Lateralization • 512/ 1024 Hz [256 if deaf] vibrating fork on top of patients head/ forehead. • "Where do you hear sound coming from?" • Normal reply is midline. Rinne's test: Air vs. Bone Conduction • 512/ 1024 Hz [256 if deaf] vibrating fork on mastoid behind ear. Ask when stop hearing it. • When stop hearing it, move to the patients ear so can hear it. • Normal: air conduction [ear] better than bone conduction [mastoid]. If indicated, look at external auditory canals, eardrums. *Extra Notes:* Vestibular: Normal when close eyes to present minor swing without losing the balance. Abnormal: Difficulties in keeping balance Auditory: (1) Audiometry (2) Neurological exam (close eyes and if hear sounds close to eyes). (3) Weber's: Normal to associate in middle. Lateralization is abnormal (4) Rinne: Air conduction is longer than bone conduction in normal.

Cranial Nerves (General Locations)

I: OlfactorySituated at the base of frontal lobe II: Optic NerveCommunication between pathway between eye and the thalamus. III-XII: emerging at level of brainstem: • OculomotorEmerging above the pons (level of midbrain) • TrochlearAlso emerging above the pons (level of midbrain) • TrigeminalThree sensory branches . At level of pons. o The rest are related with the brainstem (originating from medulla oblongata). Named according to particular location according to base of nuclei. o Rest of cranial nerves are named downward with descending sequence according to position nuclei has in brainstem.

CN VII, Facial (Testing)

Inspect facial droop or asymmetry. Facial expression muscles: pt looks up and wrinkles forehead. • Examine wrinkling loss. • Feel muscle strength by pushing down on each side Pt shuts eyes tightly: compare each side. Pt grins: compare nasolabial grooves. Also: frown, show teeth, puff out cheeks. Corneal reflex already done. *Extra Notes:* Sometimes disturbance in facial is observe spontaneously and face is asymmetrical. All people is a little bit asymmetrical (normal, minor) Damage in facial, can become asymmetrical (abnormal, major) Asymmetry will increase when making a movement

CN XII, Hypoglossal (Testing)

Listen to articulation. Inspect tongue in mouth for wasting, fasciculations. Protrude tongue: unilateral deviates to affected side. *Extra Notes:* Dysarthria identification (10-20 second of tongue protrusion/right/left/up/down)

Cranial Nerves (Exceptions)

"All cranial nerves except for the olfactory and optic nerves belong to the peripheral nervous system" "The olfactory and optic nerves are named as such, but are technically not nerves, and are continuations of the central nervous system." • Unusual cranial nerves #1 olfactory and #2 optic (peripheral nervous system) are exceptions as the rest belong to the true cranial nerves. • All of them have a single name, except #8 named both as auditory or the vestibulocochlear (<-better name) • #11 named accessory, spinal, or spinal accessory

CN IX, Glossopharyngeal (Sensory vs Motor Function)

"Glosso-Tongue, Pharyng-Throat" Posterior part of the tongue (sensory function) and also the throat (motor function)

Cranial Nerves (Definition)

"Nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord."

Nervous System

Central (Brain and Spinal Cord) Peripheral (Processes in and out of the CNS: Cranial and Spinal Nerves 12 Cranial Nerves 31 Spinal Nerves

CN VIII, Auditory (Vestibulocochlear) (Sensory vs Motor Function)

Conveying information corresponding to balance (coming from limbic system) and auditory information (coming from cochlear) (sensory function)

CN XI, Accessory (Testing)

From behind, examine for trapezius atrophy, asymmetry. Pt. shrugs shoulders (trapezius). Pt. turns head against resistance: watch, palpate SCM on opposite side. *Extra Notes:* Raise shoulders using hands to push down to test strength equal on both sides and move head when holding in both directions to test strength

CN VI, Abducens (Sensory vs Motor Function)

General sensitivity of the face (sensory function), Moving the jaws-Mastication-Partially for speaking (motor function)

CN I, Olfactory (Sensory vs Motor Function)

Smell (very specific function, sensory function)

CN V, Trigeminal

Three branches: Ophthalamic, Maxillary, and Mandibular No movement of tongue, just sensation (e.g. touch, pain) (1) Ophthalmic: Forehead and corneal sensation, and reflex (2) Maxillary: Infraorbital, palatal, and upper teeth sensation (3) Mandibular: Mandibular, chin, lower teeth and tongue sensation

CN III, Oculomotor CN IV, Trochlear CN VI, Abducens

Three for moving eyes. Must be important ability in order for three to be directed towards this function. In order to understand visual perception, visual image is blurry if not constantly moving the eyes. Function: Constricting of pupil and raises of the eyelid Moving eyeball... 6 muscles! • Rectus: Superior-Inferior, Lateral-Media (4) • Oblique: Superior-Inferior (2) • All movements of the eye except control of two of the muscles are carried out by #3 • Exceptions include: o Superior oblique AKA trochlear when activated moving eyeballs downwards (#4) o Activating lateral rectus AKA abducens moving eyes laterally (#6)

CN X, Vagus

Autonomic function related to parasympathetic system (Most important) Motor function in movements of vocal folds Most important for phonation

CN V, Trigeminal (Testing)

Corneal reflex: patient looks up and away. • Touch cotton wool to other side. • Look for blink in both eyes, ask if can sense it. • Repeat other side [tests V sensory, VII motor]. Facial sensation: sterile sharp item on forehead, cheek, jaw. • Repeat with dull object. Ask to report sharp or dull. • If abnormal, then temperature [heated/ water-cooled tuning fork], light touch [cotton]. Motor: pt opens mouth, clenches teeth (pterygoids). • Palpate temporal, masseter muscles as they clench. Test jaw jerk: Examiner's finger on tip of jaw. Grip patellar hammer halfway up shaft and tap Examiner's lightly. Usually nothing happens, or just a slight closure. If increased closure, think UMNL, esp pseudobulbar palsy *Extra Notes:* Sensory: Piece of cotton and beginning to touch face on left-right in three different levels (high-middle-low). In sensitivity, need to always be asking the question to compare "Do you feel the same on right and left?" Motor: Jaw reflex. (1) Thumb in jaw of patient and take a neurological hammer and tapping own thumb. Jaw is expected to open and close immediately. (2) Tongue depressor. Ask to bite and when have them between teeth will take same hammer-like and see if presents with rapid return to normal position.

CN III, Oculomotor CN IV, Trochlear CN VI, Abducens (Testing)

Look at pupils: shape, relative size, ptosis. Shine light in from the side to gauge pupil's light reaction. • Assess both direct and consensual responses. • Assess afferent pupillary defect by moving light in arc from pupil to pupil. Optionally: as do arc test, have pt place a flat hand extending vertically from his face, between his eyes, to act as a blinder so light can only go into one eye at a time. "Follow finger with eyes without moving head": test the 6 cardinal points in an H pattern. • Look for failure of movement, nystagmus [pause to check it during upward/ lateral gaze]. Convergence by moving finger towards bridge of pt's nose. Test accommodation by pt looking into distance, then a hat pin 30cm from nose. *Extra Notes:* When move finger in any direction, do you see double? Case of "Deplopria"

CN IX, Glossopharyngeal

Motor of tongue and throat muscles

CN X, Vagus (Sensory vs Motor Function)

Movements of laryngeal area including movements of vocal folds (motor function) and autonomic activity some internal organs (sensory function)

CN IV, Trochlear (Sensory vs Motor Function)

Moving eyes (motor function)

CN V, Trigeminal (Sensory vs Motor Function)

Moving eyes (motor function)

CN III, Oculomotor (Sensory vs Motor Function)

Moving eyes (motor function) For moving eyes, using three cranial nerves. Overwhelming in working is due to #3 #4 and #6 has limited function

CN VII, Facial (Sensory vs Motor Function)

Moving face including the lips, rounding lips, cheeks, etc-Participation in speech (motor function), Taste of the two-thirds anterior part of the tongue (sensory function)

CN XII, Hypoglassal (Sensory vs Motor Function)

Moving the tongue-Complex motor organ (motor function) Very specific function Most important articulator Most important function of the tongue rarely mentioned-Tremendous ability to avoid being bitten always.

Nervous System Review

Narrowing region (Internal capsule) Decussation of the pyramids-Level of brainstem (Corticospinal Tract) Brainstem-Brainstem has synapse and second neuron-Second neuron is cranial nerve (Corticobulbar Tract)

CN VII, Facial

Participating on movements of face (motor) and also taste information (anterior 3/4 of tongue)

CN XI, Accessory (Sensory vs Motor Function)

Raising the shoulders and moving the head (motor function) Very specific function Accessory, Spinal, or Spinal Accessory

CN I, Olfactory

Receiving and taking olfactory information to the brain Unusual information (type of sensory system) Received by nose (nasal cavity) In nasal cavity, have superior/middle/inferior nasal concha Receptors situated in olfactory epithelium (mucus where air is activating receptors) and going to be responding to the chemical composition of the air. • Air is circulating in the nasal cavity and according to composition of air, stimulators are activated. • Classification of odors are very complicated (not clear point) Receptors have to cross cribriform plate (has small holes, separates nasal cavity from the brain). • The olfactory nerves are going to be crossing to cribriform plate in order to get to olfactory bulb in skill/brain/cranium. Olfactory information has a type of circulation: • Only type of information that does not go through thalamus to cortex • Pyriform and entorhinal cortex (situated in the temporal lobe) hypothalamusthalamuscortex. Going to become aware. • Considered to be primitive type of information. Doesn't mean that isn't important information.

CN II, Optic

Receptors are situated in retina. Retina three layers of neurons (1) photoreceptors (2) bipolar cells (3) cranial cells. From thalamus projected to cortex EyesBrainThalamusPrimary Visual Cortex (partially crossed and partially un-crossed) Information to nasal hemi-retinas is going to contralateral, whereas information corresponding to lateral hemi-retinas is non-decussated. From functional point of view, visual information is crossing. From left visual field to right hemisphere and vice versa.