Cranial Nerves Examination BLOCK 16

Dr. Janet Arcenal-Beltran MODULE 1

August 5, 2015 | 8-10 am LECTURE 07

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Objectives

I. Objectives: 1. To review the cranial nerves -its origin -its motor and sensory distribution -its function (Functional Neuroanatomy) -the associated disorders 2. To demonstrate how to test the Cranial Nerves

Audio- italicized DeMeyer’s The Neurological Examination, 6th edition- blue green box Internet- red font

Overview

Cranial Nerves Origin

I - Sensory -frontal lobe/rhinencephalon II - Sensory -occipital bone III - Motor

IV - Motor midbrain V - Mixed VI - Motor pons VII - Mixed VIII - Sensory IX - Mixed X - Mixed XI - Motor medulla XII - Motor

FUNCTIONS OF CRANIAL NERVES

I Smell

II Visual acuity, visual fields and ocular fundi II, III Pupillary Reactions III, IV, VI Extra-ocular movements, opening of the

eyes; pure motor to the eyes V Facial sensation, movements of the jaw and

corneal reflexes/blink reflex; mastication VII Facial movements and gustation (anterior 2/3

of the tongue; taste); eyelid closure VIII Hearing and Balance IX, X Swallowing, elevation of the palate, gag reflex

and gustation V, VII, X, XII Voice and Speech XI Shrugging of shoulders and turning of head XII Movement and protrusion of tongue (look for

any atrophy or fasciculation)

CN II- afferent to pupillary reaction

CN III- efferent to pupillary reaction; opening of eyelid

CN VII- closing of eyelid; defect=ptosis

CN IX- tongue

CN X- pharyngeal muscles

Weakness on one side of shoulder (Stroke)/ gross weakness- doesn’t mean defect on CN XI; problem may be on the cortex of the brain

CN I – OLFACTORY NERVE

Parts:

Olfactory Receptor

Olfactory Bulb

Olfactory Tract

Olfactory Lobe

1. Olfactory Receptors

Olfactory Membrane - yellowish-brown specialized epithelium in

the upper posterior part of the nasal cavity

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2. Olfactory Tract - located at the orbital surface of the frontal lobe; adjacent to the temporal lobe 3. Olfactory Lobe -Pyriform lobe

Primary Olfactory Cortex Pyriform Periamygdaloid

Secondary Olfactory Cortex Entorhinal areas

TEST OF THE OLFACTORY NERVE

Assess patency of nasal passages

Occlusion of a single nostril (eyes are closed) and demonstrate that air passes freely

The patient inhales thru the open nostril to a common odorant: Vanilla Ground Coffee Peppermint Fresh Orange Soap

EACH NOSTRIL IS TESTED SEPARATELY

Caution: AMMONIA stimulates CN V

Don’t use volatile substances because they can stimulate CN V instead of CN I

It’s okay if the patient could not identify as long as he can smell it (true in the elderly and those with Parkinsonian disorders)

CN II – OPTIC NERVE

Optic Nerve

Optic Chiasm

Optic Tract

Optic Radiations (Geniculocalcarine tract)

Visual Cortex –at the occipital lobe

KEY TO FUNCTION V1: Primary visual cortex: receives all visual input. Begins processing of color, motion and shape. Cells in this area have the smallest receptive fields V2, V3,VP: Continue processing: cells of each area have progressively larger receptive fields V3A: Biased for perceiving motion V4v: Function unknown V5/MT: Detects motion V7: Function unknown V*: Processes color vision LO: Plays a role in recognizing large-scale objects Note: A V6 region has been identified only in monkeys

Areas in the occipital lobe:

a. Small scale images b. Pursuit/motion c. Vision/color

BILATERAL ANOSMIA UNILATERAL ANOSMIA

Blocked nasal passage

Trauma

Aging (>70)

Parkinson’s Dse

Blocked nostril

FRONTAL brain lesion

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TESTS OF THE OPTIC NERVE

A. Visual acuity measurement B. Color vision testing C. Pupil evaluation D. Visual field testing E. Optic nerve evaluation via ophthalmoscopy A. Testing the Visual Acuity

Standardized test: reading of a Wall-mounted or pocket Snellen Eye Chart

Cover one eye under favorable lighting

Patient may use their glasses if needed to obtain best corrected vision

Hold the pocket chart at focal length: 14 inches

Have them read the line with the smallest letters

TEST ONE EYE AT A TIME; examine 1st

the eye with defect

Record smallest size read

Acuity testing by: Snellen’s Chart Near Vision Chart Bedside Material

IF UNABLE TO READ LARGEST LETTERS, see if patient can: (in sequence) Count Fingers Hand Movements* Perceive Light* (*3 correct answers out of 5 means satisfactory)

Does visual acuity improve with PINHOLE TEST? o Test if error of refraction is considered

Pinhole Testing: The pinhole testing device can determine if a

problem with acuity is the result of refractive error (and thus

correctable with glasses) or due to another process. The

pinholes only allow the passage of light which is

perpendicular to the lens, and thus does not need to be bent

prior to being focused onto the retina. The patient is

instructed to view the Snellen chart with the pinholes up

(below right) and then again with them in the down position

(below left). If the deficit corrects with the pinholes in place,

the acuity issue is related to a refractive problem.

Corrected by pinhole: Error of Refraction

Not corrected: Ophthalmologic Problems: Cataract, Corneal lesion,

Retinal Hemorrhage/ infarct, Macular Degeneration

Optic Neuropathy: Inflammation, Ischemic,

Compressive Bilateral Occipital Lesions:

Cortical Blindness

B. Color vision testing C. Testing the Pupillary Light Reflex

Ensure that patient is looking into the distance

Dim the room and make sure to use good light; preferably yellow and strong light to elicit papillary contraction

Look at the pupils

Before checking for reflex, make sure to ask the patient if he/she had previous eye surgeries, i.e., cataract extraction= pupils are irregular, some pupils do not react at all o Are they equal in size (estimate)? o Are they irregular in size?

Check for direct or consensual light reflex o Direct reflex – Ipsilateral eye constricts o Consensual reflex – contralateral eye constricts

Findings: equal, large, small (size in mm) pupils, +/-

reaction to light (brisk, sluggish, non-reactive), +/- accommodation

Pupillary Light Reflex Pathway (study the pathway)

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Review of the Visual Pathway When both eyes focus on the arrow, the real images fall on corresponding parts of the retina. Then proceed through the retinal rods and cones; bipolar layer; multipolar layer, optic nerve, optic chiasm; optic tract; geniculate body synapse; and geniculocalcarine tract to the primary visual cortex around the calcarine fissure. PUPILLARY LIGHT REFLEX

Normal Both pupils constrict

CN II Lesion Loss of direct papillary light reflex

CN III Lesion Loss of consensual papillary light reflex

Anisocoria: Left or Right? (Name after the pupil that is bigger)

Pupils equal and normally reacting: normal variant

Senile Miosis: Normal age-related change; not so much in accommodation

10% of normal patients have unequal eye dilatation

Know reactions whether briskly reactive, reactive or non-reactive(problem with CN II and III –mostly in coma patients)

HORNER’S SYNDROME TRIAD

Miosis – small-sized eye

Partial Ptosis

Enopthalmos and loss of hemifacial sweating Central cause: Stroke (Wallenberg), demyelination Peripheral cause: Pancoast’s tumor (apical bronchial Ca), trauma, carotid dissection CORTICAL BLINDNESS

a blind patient with briskly reactive pupils

occipital or post-geniculate ganglion D. Visual Field Testing

Test each eye individually

Use your fingers in the four quadrants of the visual field. Ask the patient to count fingers held up or point to the hand when a finger wiggles.

To test the extraocular muscles (CN III, IV, VI), have the patient follow a target through the 6 principal positions of gaze (“H” pattern)

Patient identifies the moving finger/fingers

Distance between the examiner and examinee should be equal (about 14-15 inches)

Use peripheral vision

Visual Field Defects (study this)

E. Optic nerve evaluation via ophthalmoscopy (Fundoscopy)

Observe the optic disc, physiological cup, retinal vessels and fovea

Note for the: o Pulsations of the optic vessels o Blurring of the optic disc margin o Change in the optic disc’s color

(normal: yellowish-orange)

Possible Findings: o Red orange reflex o Media – clear, hazy o Disc borders – distinct, blurred o Cup disc ration = 0.4 to 0.5 o Arteriole/ Venule Ratio (AVR) = 2:3

If more veins, consider malformations like AVM o Note for hemorrhage, exudates, papilledema

CN III, IV, VI – OCULOMOTOR, TROCHLEAR, ABDUCENS

Formed by diverging fibers of the medial longitudinal fasciculus (MLF) MLF is one of a pair of crossed fiber tracts (group of axons), on each side of the brainstem. These bundles of axons are situated near the midline of the brainstem and are composed of both ascending and descending fibers that arise from a number of sources and terminate in different areas. MLF is the main central connection for the oculomotor nerve, trochlear nerve, and abducens nerve.

Monocular Field Defects (scotoma)

Anterior to Optic Chiasm

Bitemporal Field Defects Optic Chiasm

Homonymous Field Defect Behind Optic Chiasm

Congruous Homonymous Field Defect

Behind Lateral Geniculate Bodies

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You will meet this MLF in eye movement problems (related to CN III)

Lies ventral to periaqueductal gray

V-shaped trough

To test for extraocular muscles, let the patient look on extremes

o Conjugate movement detects muscle palsy

Aneurysm- 1st

sign is ptosis/anisocoria

CN III palsy secondary to compression of aneurysm- presents with dilatation

CN III palsy secondary to stroke/ischemia- presents with exaggerated constriction with slight ptosis

CN III – OCULOMOTOR NERVE

Functions:

Superior Division Levator palpebrae

Superior rectus

Inferior Division Inferior rectus

Medial rectus

Inferior Oblique

For pupillary constriction and accommodation

CN IV- TROCHLEAR NERVE

Small cell group at ventral border of Periaqueductal gray

Curve dorsolaterally and caudally, decussate in the superior medullary velum

Supplies the SUPERIOR OBLIQUE -Downward, inward movement of eyes

CN VI – ABDUCENS NERVE

Innervates the LATERAL RECTUS muscle

Abduct or lateral deviation of the eyes

Defect- can’t look laterally

Inferior oblique- upward and inward

Superior oblique- downward and inward

Superior rectus- upward (and opening of eyelid)

Inferior rectus- downward

Medial rectus- medially

Lateral rectus- laterally

All eye muscles supplied by CN III except Lateral rectus (CN VI) and Superior Oblique (CN IV)

Test of Oculomotor, Trochlear, and Abducens Nerves

Inspect the eyes. Note for ptosis (lagging of an eyelid). Check for ocular alignment.

Versions - Test extraocular range of motion with both eyes open and following the target (conjugate gaze) –if eyes have the same movement - Follow a target trough the “H” pattern –six principle positions of gaze - Note for misalignment of eyes and complaint of diplopia (double vision)

Ductions - If there is any misalignment of the eyes or diplopia on versions then examine each eye with the other covered (ductions) -done one eye at a time if with complains of diplopia

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Vestibulo-ocular reflex (Doll’s eye movement) - Have the patient visually fixate on an object straight ahead, then rapidly turning the patient’s head from side to side and up and down - The eyes should stay fixed on the object and turn in the opposite direction of the head movement -usually done on coma patients

Vergeance - Eye movements occur when the eyes move simultaneously inward (convergence) or outward (divergence) - When the patient is asked to follow an object that is brought from a distance to the tip of their nose the eyes converge, the pupil will constrict and the lens will round up (accommodation)

Misalignment of Eyes

If there is paralysis of 1 of the eye muscle, the opposite

muscle pulls the eye into its direction. Ex. Medial rectus

palsy of the right eye (paralysis of medial rectus, the right

eye is pulled by lateral rectus and goes laterally)

Control of Eye Movements

Type of Eye Movement Site of Control

Saccadic (command) (fast phase, awareness)

Frontal Lobe

Pursuit/motion Ex. Seeing a moving car

Occipital Lobe

Vestibular-Positional Cerebellar, Vestibular Nuclei

Convergence, divergence Midbrain

*Eye field- eye gazes to the direction of the lesion

CN V – TRIGEMINAL NERVE

V, VII, X and XII nerves responsible for speech production.

Largest cranial nerve

Sensory and motor components

Sensory - Exteroceptive – pain, thermal, tactile sensation

from face, forehead, mucous membranes of the nose and mouth, teeth, large parts of cranial dura

- Proprioceptive – deep pressure and kinesthesis from the teeth, periodontium, hard palate and temporomandibular joint

Motor – muscle of mastication

Motor-wise, cranial nerve V only chews. Its motor axons

innervate all and, for clinical purposes, only the chewing

muscles: masseter, temporal, and lateral and medial

pterygoids. CN V conveys no efferents to glands or smooth

muscle and no special sensory afferents.

Unilateral destruction of the perikarya or axons of CN V causes complete paralysis of all ipsilateral chewing muscles.

Atrophy and paralysis are the two outstanding signs of lower motoneuron (LMN) lesions of CN V.

Masseter is the most readily palpable muscle to check for atrophy.

Many proximal (axial) muscles that ordinarily contract symmetrically have bilateral upper motor neuron innervation.

The distal muscles that contract unilaterally have mainly contralateral upper motor innervation.

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Ophthalmic Division (V1) Branches

Tentorial Dura of cavernous sinus, sphenoid wing, anterior fossa, petrous ridge, Meckel’s cave, tentorium cerebella, post falx cerebri and dural venous sinuses

Lacrimal Conjunctiva and skin at area of lacrimal gland; reflex lacrimation

Frontal - Supraorbital

Medial upper lid and conjunctiva, frontal sinuses, forehead and scalp

Frontal - Supratrochlear

Conjunctiva, medial upper lid, forehead and side of nose

Nasociliary Nasal nerves- mucosa of nasal septum, lateral nasal wall, inferior and mid turbinates, top of nose Infratrochlear branch- lacrimal sac, caruncle, conjunctiva, and skin of medial canthus Ciliary nerves- ciliary body, iris and cornea, papillary dilator

Maxillary Division (V2)

Leaves the skull through the foramen rotumdum and enter

the sphenopalatine fossa

Reaches the face by infraorbital foramen

Palatine nerves

Alveolar Nerves

Inferior Paplpebral branch Lower lid

Nasal branch Side of the nose

Superior labial branch Upper lip

Zygomaticofacial branch Cheek

Mandibular Division (V3)

Lingual nerve Lower gums and papillae and mucous membrane of the anterior 2/3 of tongue

Inferior dental branch Lower gums, teeth and mandible

Mental branch Skin, mucous membrane of the lower lip

TEST FOR TRIGEMINAL NERVE

Sensory

Test for both light touch (cotton tip applicator, finger) and pain (sharp object ex. toothpick) in the sensory divisions:

o Forehead - ophthalmic o Cheek - maxillary o Jaw or chin- mandibular

Corneal reflex

Limbal junction of the cornea is lightly touched with a cotton observing the reflex blink

Sensory or afferent limb – ophthalmic division (V1) of CN V

Motor or efferent limb – branch of CN VII to the orbicularis oculi muscle

Motor

Palpate the temporalis and masseter muscles as the patient bites down hard

Have the patient open their mouth and resist the examiner’s attempt to close the mouth

If there is weakness of the pterygoids, the jaw will deviate towards the side of the weakness

Muscles of mastication (temporalis, masseters, and pterygoids

JAW JERK o A stretch reflex o Tested by placing a finger over the

patient’s chin and then tapping the finger with a reflex hammer

o Normal: the jaw moves minimally o Most prominent is patients with

parkinsonism

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CN VII – FACIAL NERVE

Except for the mandible and eyelid elevation, CN VII innervates every other movement that the face can make.

The pontine tegmentum contains motor nuclei for

three CNs: V, VI and VII.

Through the basis of the pons run the corticospinal (pyramidal tract) to the lower motor neurons of the spinal cord.

Before exiting from the pons, the VII nerve fibers loop around the nucleus of the CN VI.

Three CrNs exit at the pontomedullary sulcus. In ventrodorsal order, these nerves are VI, VII, and VIII.

As typifies peripheral nerves, the VII nerves do not cross the midline.

If a lesion destroys the VII nerve nucleus, the intra-axial course of the axons, or the peripheral nerve trunk, the result is paralysis of all facial muscles ipsilaterally.

The only sensory function of CrN VII tested clinically is taste

Remember that, in addition to moving the face, CN VII innervates: (A) Tasting: taste from the anterior two-thirds of the tongue via the geniculate ganglion; (B) Snotting: parasympathetic axons to the nasal mucosa via the pterygopalatine ganglion, (C) Tearing: parasympathetic axons to the lacrimal gland via the pterygopalatine ganglion and (D) Salivating: parasympathetic axons via the submandibular ganglion.

Mnemonic summary of the clinically important functions of CrN VII: It tears, snots, tastes, salivates, moves the face, and dampens sounds.

Cranial Nerve Seven This is the nerve that lets you cry

And wets your mouth when it is dry Dampens noise when you are young Tastes on two-thirds of your tongue And lastly—now, just let me think Lets you give a smile—and wink!

—Meredith Rose Golomb,MD

The freest unilateral facial movement normally is lip retraction.

The least free unilateral facial movement normally is forehead elevation.

4 COMPONENTS AND FUNCTIONS

Branchial Motor

Muscles of facial expression: digastrics, stylohyoid and stapedius Test: frontal, buccinators, oris, ocular

Visceral Motor

Lacrimal, submandibular and sublingual glands and mucous membranes of nasopharynx, hard and soft palate

Special Sensory

Taste sensation – anterior 2/3 of tongue; hard and soft palates

General Sensory

Concha of the auricle and small area behind the ear

Diagram of the complete distribution of cranial nerve VII. (Reprinted with permission from DeMyer W.Neuroanatomy, 2nd ed. Baltimore: Williams & Wilkins, 1998.)

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TEST FOR FACIAL NERVE

Inspect the face during conversation noting any facial asymmetry including drooping, sagging or smoothing of normal facial creases

-be discrete that you are observing

Motor division. It supplies the muscles of facial expression

o Wrinkle forehead – frontalis muscle o Close eyes tight - orbicularis oculi o Smile and Show teeth – buccinators o Purse lips or blow a kiss – orbicularis oris

Should not give way when you poke the puffed cheek

Sensory division: Taste o Use a cotton tip applicator dipped in a solution that is sweet, salty, sour or bitter o Apply to one side then the other side of the extended tongue and have the patient decide on the taste

Use salt, sugar, vinegar, and bitter gourd/coffee

Bell’s Palsy

Px’s left face is abnormal Several times ER residents get this wrong; they admit

Bell’s palsy patients because they thought it was stroke Differentiate bell’s palsy from stroke

Bell’s palsy- is a peripheral Cranial nerve 7 palsy; from forehead-eyelid-down to the face; unable to close eyes full; no forehead crease; facial asymmetry; We don’t admit bell’s palsy px vs.

Stroke- only the cheek part (paralysis); able to close eyes fully, nasolabial flattening, intact forehead crease L&R; we admit

CN VIII – VESTIBULOCOCHLEAR NERVE

CrN VIII consists of cochlear (auditory) and vestibular divisions. Each division has its own specialized receptors, its own bundle within the trunk of VIII, and its own brainstem nuclei and central pathways.

The cochlear division mediates hearing only. It detects sound vibrations between 20 and 20,000 cps. By its design, the ear is the most sensitive vibration detector in the human body.

TEST FOR VESTIBULOCOCHLEAR NERVE

Screen Hearing: 1. Face the patient and hold your arms with your

fingers near each ear - Px eyes should be closed so that there will

be no visual clue 2. Rub your fingers together on one side while moving

the finger noiselessly on the other 3. Increase intensity as needed and note any

asymmetry 4. If abnormal, proceed with the Weber and Rinne’s

tests.

Weber Test o Test for lateralization o Place vibrating tuning fork on the middle of the head

and ask if the patient feels or hears it beast on one side or the other

o Use tuning fork with ears (256 Hz)

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o Normal: the same in both ears o Unilateral neurosensory hearing loss: hear best in

the normal ear o Unilateral conductive hearing loss: hear best in the

abnormal ear

Rinne test

A tuning fork is held against the mastoid process until it can no longer be heard.

It is then brought to the ear to evaluate patient response.

Consists of comparing bone conduction versus air conduction

- Normal: AC > BC - Neurosensory hearing loss: AC> BC - Conduction Hearing Loss: BC > AC

TYPE OF DEAFNESS

CONDUCTIVE SENSORINEURAL

RINNE’S TEST Bone Conduction > Air Conduction

AC > BC

WEBER’S TEST Deaf Ear Good Ear

WHAT IT MEANS External ear obstruction Middle ear disease

Cochlear lesion: Otosclerosis, Meniere’s, drug, noise-induced, damage Auditory nerve lesion: meningitis, CPA, tumor, trauma Pontine lesion

CN IX, X – GLOSSOPHARYNGEAL AND VAGUS NERVES

CN IX – GLOSSOPHARYNGEAL NERVE

Supplies motor fibers: parotid gland and pharynx

Carries sensory fibers: from carotid body and taste fibers from the posterior third of tongue

Motor: gag reflex

Sensory: taste posterior 1/3 of tongue

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CN X – VAGUS NERVE

Test: performed by the gag reflex and “ahh’ test

Unilateral lesion: produce hoarseness and difficulty swallowing due to loss of laryngeal function

Skeletal muscle innervated by CN X: It innervates the palatal

muscles, aided by CN V, the pharyngeal constrictors, aided by

CN IX, and the laryngeal muscles unaided: the palate,

pharynx, and larynx, in rostrocaudal order.

TEST FOR GLOSSOPHARYNGEAL AND VAGUS NERVES

Motor

Ask the patient to say “ah” or “kah”

The palate should rise symmetrically and there should be little nasal air escape

Unilateral weakness, the uvula will deviate toward the normal side (side of the palate is pulled up higher)

Bilateral weakness neither side of the palate will elevate and there will be marked nasal air escape

Ask the patient to swallow and note any difficulty

Note the quality and sound of the patient’s voice Sensory and Motor

Gag reflex

This involuntary reflex is done by touching the back of the pharynx with the tongue depressor and watch for the elevation of the palate

1. Speech 2. Dysphagia 3. Examine Palate and Larynx 4. Hoarseness 5. Rhythm, force (dysprosody), and timber of voice

CN XI – SPINAL ACCESSORY NERVE

CN XI has two parts, spinal and accessory.

The spinal part supplies the sternocleidomastoid (SCM) and rostral portions of the trapezius muscles.

The accessory part is accessory to the vagus. The accessory fibers arise in the nucleus ambiguous of the medulla and merely hitchhike along the proximal part of CN XI before joining CN X for distribution to the pharynx and larynx.

TEST FOR SPINAL ACCESSORY NERVE

Patient is instructed to shrug shoulders against resistance. For Trapezius

Patient is instructed to turn head against the examiner’s hand while the sternocleidomastoid muscle is palpated.

The muscle tone on both sides is compared. 1. Inspect the SCM and trapezius muscles for size and asymmetry. 2. Next palpate the muscles at rest and as they exert their actions. 3. To test the strength of SCM and trapezius muscles,

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CN XII – HYPOGLOSSAL NERVE

TEST FOR HYPOGLOSSAL NERVE

Patient is instructed to stick out the tongue as far out as possible, and then move it laterally against resistance.

Have the patient stick out their tongue and move it side to side

Further strength testing: have the patient push the tongue against a tongue blade

Inspect the tongue for atrophy and fasciculation

Unilateral weakness: the protruded tongue will deviate towards the weak side; uvula will deviate towards normal side

By having the patient say lah-pah-kah, the examiner is testing the motor components of CN 7, 9, 10 and 12

Lower motor neuron lesion of CNs XI to XII is termed bulbar paralysis.

Paralysis of speech and swallowing after UMN (upper motor neuron) lesions “pseudobulbar,” or “false bulbar” paralysis, because the lesion was not truly in the bulb (medulla) or its nerves.

1. Inspect tongue at rest 2. Testing tongue motility and deviation 3. Tongue strength 4. Involuntary movements 5. Dysarthria

References:

SGD notes Audio- italicized DeMeyer’s The Neurological Examination, 6

th edition- blue

green box Internet- red font CATOLICO |DAVIS | DE GUZMAN | DOMINADO

Motor examination of all of the cranial nerves in 45 seconds The formal examination of CrN motor function begins with the eyes. The NE outline at the beginning of the text lists motility last in the ocular sequence for a reason. The Ex can then flow smoothly through the entire CrN motor examination, yes, III to XII, in just 45 seconds, in a normal cooperative Pt. No, the 45 seconds is not a misprint.

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