Transcript One1_05_Cranial_Nerve_Evaluation

Dr. Michael P. Gillespie
 Between the brain and spinal cord.
 3 regions.
 Medulla oblongata.
 Pons.
 Midbrain.
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 A continuation of the spinal cord.
 Sensory (ascending) tracts and motor (descending)
tracts travel through the white matter of the medulla.
 Many nerves decussate (cross over) in the medulla.
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 Cardiovascular center regulates the heartbeat and the
diameter of the blood vessels.
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 The medullary rhythmicity area adjusts the rhythm of
the breathing and controls reflexes for vomiting,
coughing, and sneezing.
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 The nuclei for the following cranial nerves reside in
the medulla:
 VIII (vestibulocochlear).
 IX (glossopharyngeal).
 X (vagus).
 XI (accessory).
 XII (hypoglossal).
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 Pneumotaxic area and apneustic area regulate
breathing.
 Nuclei for cranial nerves V (trigeminal), VI
(abducens), and VII (facial).
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 The midbrain or mesencephalon contains the
superior colliculi (visual actvities) and inferior
colliculi (auditory pathways).
 The midbrain contains the substantia nigra which
release dopamine to help control subconscious
muscle activities. Loss of these neurons results in
Parkinson disease.
 Cranial nerves III (oculomotor) and IV (trochlear)
originate here.
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 Type: sensory.
 Function: smell.
 Anosmia – loss of sense of smell.
 Does not connect with the brainstem.
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 Type: sensory.
 Function: vision.
 Anopia – blindness in one or both eyes.
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 Type: mixed (mainly motor).
 Function: movement of the upper eyelid and
eyeball. Accomodation of the lens for near vision
and constriction of the pupil.
 Strabismus – deviation of the eye in which both
eyes don’t focus on the same object.
 Ptosis – drooping of the upper eyelid.
 Diploia – double vision.
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 Type: mixed (mainly motor).
 Function: movement of the eyeball.
 Diplopia and strabismus occur with trochlear nerve
damage.
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 Type: mixed.
 Function: conveys impulses for touch, pain,
temperature and proprioception. Chewing.
 Trigeminal neuralgia (tic douloureux) – pain to
branches of the trigeminal nerve.
 Dentists apply anesthetic to branches of this nerve.
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 Type: mixed (mainly motor).
 Function: movement of the eyeball.
 With damage to this nerve the eye cannot move
laterally beyond the midpoint and usually points
medially.
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 Type: mixed.
 Function: Propriception and taste. Facial expression.
Secretion of saliva and tears.
 Injury produces bell’s palsy (paralysis of facial
muscles).
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 Type: mixed (mainly sensory).
 Function: conveys impulses for equilibrium and
hearing.
 Injury can cause vertigo, ataxia (muscular
incoordination), nystagmus (rapid movement of the
eyeball), and tinnitus.
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 Type: mixed.
 Function: taste and somatic sensations from the
posterior 1/3 of the tongue. Elevates the pharynx
during swallowing and speech. Stimulates the
secretion of saliva.
 Injury causes decreased salivary secretion, loss of
taste, and difficulty swallowing.
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 Type: mixed.
 Function: taste and somatic sensations. Swallowing,
coughing, and voice production. Regulates GI tract
and heart rate.
 Injury interferes with swallowing, paralyzes vocal
cords, and causes the heart rate to increase.
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 Type: mixed (mainly motor).
 Function: Proprioception. Swallowing, movement of
head and shoulders.
 If the nerves are damaged the SCM and Trapezius
become paralyzed.
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 Type: mixed (mainly motor).
 Function: Proprioception. Movement of the tongue
during speech and swallowing.
 Injury results in difficulty in chewing, speaking, and
swallowing. When protruded, the tongue curls
towards the affected side and atrophies on the affected
side.
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 I – Olfactory
 VII – Facial
 II – Optic
 VIII – Auditory
 III – Oculomotor
 IV – Trochlear
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 V – Trigeminal
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 VI – Abducens
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(Vestibulocochlear)
IX – Glossopharyngeal
X – Vagus
XI – Spinal accessory
XII - Hypoglossal
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 On Old Olympus’ Towering Tops A Fin And German
Viewed Some Hops.
 This mnemonic device helps you memorize the names
of the cranial nerves.
 The first letter from each word corresponds to the first
letter of each cranial nerve.
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 Some Say Marry Money, But My Brother Says Big
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Brains Matter Most.
This mnemonic device helps you memorize the
sensory / motor distribution of the cranial nerves.
S = sensory
M = Motor
B = Both
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 Twelve pairs of cranial nerves exit from the brain and
brainstem.
 These nerves innervate the face, head, and neck.
 They control all sensory and motor functions in these
areas including the special senses of vision, hearing,
smell, and taste.
 Cranial trauma, infections, aneurysm, stroke,
degenerative diseases (i.e. multiple sclerosis), upper
motor neuron lesions, lower motor neuron lesions,
increased intracranial pressure, and abnormal masses
or tumors can all affect the cranial nerves.
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 Some facial movements are performed in bilateral
synchrony such as swallowing and moving the
forehead and are thus innervated bilaterally.
 Fine movements of the face are unilateral. The
contralateral hemisphere innervates the affected area.
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 To test this nerve, obtain some aromatic substance
such as coffee, tobacco, or peppermint oil.
 Instruct the patient to close one nostril.
 Place the substance under the open nostril and ask
what the patient smells if anything.
 Repeat the procedure for the opposite nostril.
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 If the patient cannot smell or identify the smell
unilaterally, suspect a lesion of the olfactory nerve.
 If the patient cannot smell or identify the smell
bilaterally, consider a nonorganic problem or a
bilateral cranial nerve I lesion.
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 A diminished or almost absent sense of smell is
common in the elderly. This will be apparent if the
loss of sense of smell is bilateral and the cranium has
not undergone a trauma.
 Other nonneurogenic lesions such as a sinus infection,
deviated septum, and lesions caused by smoking nay
also cause a loss of smell.
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 The optic nerve is responsible for visual acuity and
peripheral vision.
 To test for visual acuity, ask the patient to cover one
eye and read the smallest print possible on a Snellen
chart.
 Repeat the test with the opposite eye.
 This is not a test for visual acuity and refractive errors
of the eye. We are testing the acuity for optic nerve
involvement. Consequently, we can perform the test
with the patient wearing glasses or contact lenses.
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 To test for peripheral vision, ask the patient to cover
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one eye with the hand and keep a fixed gaze on your
nose with the uncovered eye.
Directly motion a large cross with your finger from
superior to inferior and from right to left.
Instruct the patient to tell you when he or she begins
to see your finger.
Repeat with the opposite eye.
Record results.
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 Any loss of vision from a complete unilateral or
bilateral loss of vision, loss of half fields of vision
(hemianopsia), or a partial defect in the field of vision
(scotoma) indicates an optic nerve lesion.
 A temporal lobe lesion can produce a superior
contralateral quadrantanopsia.
 An occipital lobe lesion can produce a contralteral
homonymous hemianopsia with macula sparing.
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 Cranial nerves III, IV, and VI are all associated with
ocular and pupillary motility.
 They are testing together for simplicity.
 Cranial nerve II also innervates the levator palpebrae
muscles, which are responsible for movement of the
eyelids.
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 First, look at your patient and observe for any ptosis.
 Next inspect the eye globes for alignment.
 Next, inspect the pupils and determine their size and
shape.
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 Test the pupillary reflex by flashing a light into one of
the patient’s eyes. Look at the pupils one at a time for
dilation and contraction.
 Test ocular movements. Have the patient follow either
your finger or a moving object through the entire field
of vision in all axes.
 Observe for nystagmus and / or the inability to move
the eye on a particular direction.
 Test for convergence by having the patient look at a
distant object and continue to focus on it as you move
it closer to the patient.
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 Oculomotor nerve lesion
 Causes ptosis of the eyelid with inability to open the lid.
 Eye alignment may be down and lateral.
 The patient will be unable to move the eyeball upward,
inward, or downward due to weakness of the medial,
superior, and inferior rectus muscles.
 Pupil is usually dilated and the pupillary reflex is absent.
 The most frequent cause is an aneurysm in the circle of
Willis.
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 Trochlear nerve lesion
 Causes superior and lateral deviation of the eye with
inability to move the eyeball downward and inward
because of weakness of the superior oblique muscle.
 Aducens nerve lesion
 Causes inability to move the eyeball outward because of
weakness of the lateral rectus muscle.
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 The trigeminal nerve is composed of motor and
sensory portions.
 The motor portion innervates the muscles of
mastication (masseter, pterygoid, and temporal
muscles).
 The sensory portion is divided into three branches:
opthalmic (V1), maxillary (V2), and mandibular (V3).
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 Motor
 Masseter – instruct the patient to simulate a bite while
you palpate the masseter and attempt to open the
patients jaw with your thumbs.
 Pterygoid – instruct the patient to deviate the jaw
against your resistance.
 Temporalis – instruct the patient to clench the jaw while
you palpate the temporalis with your fingers.
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 A weak masseter or pterygoid may indicate a trigeminal
nerve lesion. A difference in tension in the temporalis may
indicate a lesion.
 In b/l paralysis, the jaw may not close tightly.
 In unilateral paralysis, the jaw deviates towards the side of
the lesion.
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 Reflex
 Corneal reflex – instruct the patient to gaze upward and
inward while you touch the cornea with a strand of
cotton, approaching from the lateral side. Do not touch
the eyelash or conjunctiva.
 The patient should blink when the cornea is touched.
 Sensory from trigeminal nerve, from the facial nerve.
 Jaw reflex – instruct the patient to open the mouth
slightly. Place your thumb or index finger just lateral to
the midline. Tap down to open the jaw with your reflex
hammer.
 The patient should close the jaw rapidly.
 Sensory and motor from trigeminal nerve.
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 Sensory
 Patient eyes closed. Touch the forehead, cheek, and
chin with a pin for pain sensation; a piece of cotton for
the sensation of light touch; small test tubes of hot an
cold water for thermal sensations. Compare b/l.
 Touch the tongue, inside of both cheeks, and the hard
palate with a tongue depressor. Have the patient give a
signal upon feeling the sensation.
 Decreased sensation indicates a lesion of that sensory
branch of the trigeminal nerve in the affected region.
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 Motor
 The facial nerve has both motor and sensory fibers.
 The motor fibers innervate the muscles of the face and
the platysma.
 Observe for abnormal movements, tics or tremors. Note
the degree of change or lack of change of expression.
 Observe the face in repose. Instruct the patient to
frown, raise the eyebrows, close the eyes, show the teeth,
smile, and whistle or puff the cheeks.
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 Sensory
 Instruct the patient to close the eyes and protrude the
tongue. Apply solutions of sugar, salt, and/or vinegar to
one side and on the anterior two-thirds of the tongue.
Ask the patient to identify each substance without
retracting the tongue (point to a list). Rinse the mouth
and apply on opposite side.
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 Weber’s Test: Cochlear Nerve
 Place a tuning fork on top of the patient’s head. Ask if the
patient hears it the same in both ears. If it is louder in one
side than the other suspect a conduction problem. If it is
heard only in one side, suspect a cochlear nerve lesion.
 Rinne’s Test: Cochlear Nerve
 Place a vibrating tuning fork on the mastoid process. Ask the
patient to say when the sound disappears. After the sound
disappears place the tuning fork next to, but not touching the
ear. See when the sounds fades out.
 Normally, air conduction is twice as loud as bone conduction
(Rinne positive). In conduction lesions and non-neurogenic
lesions, bone conduction is greater than air conduction
(Rinne negative).
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 Veering Test: Vestibular nerve
 Instruct the patient to walk with eyes closed.
 Veering on walking or a positive Romberg’s test indicates
a unilateral vestibular lesion.
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 Sensory
 Patient closes eyes and protrudes tongue. Apply a bitter
tasting solution to the posterior third of the tongue.
Have the patient identify each substance without
retracting the tongue.
 Reflex (Gag reflex)
 With a throat stick, touch the posterior pharyngeal wall,
first on one side, then on the other. Observe the
moment when the patient gags and ask him whether the
sensation is stronger on one side or the other.
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 The spinal accessory nerve innervates the trapezius
and the sternocleidomastoid muscles. To test the
nerve, test these muscles.
 Trapezius
 Patient seated, apply pressure to the patient’s shoulders
bilaterally and ask him to shrug against resistance.
 SCM
 Patient seated, place your hand on the lateral aspect of the
patient’s jaw, instruct him to turn the head toward your hand
against resistance.
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 The hypoglossal nerve is purely motor and is
responsible for movement of the tongue.
 Place your hand on the patient’s cheek and instruct
him to press the tip of the tongue against the cheek
under your hand. Repeat b/l. Instruct the patient to
protrude the tongue.
 If the pressure is unequal, suspect a unilateral
hypoglossal nerve lesion. The tongue will deviate
towards the side of the lesion.
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