Download Nervous System

Cranial Nerve Function- A&P Review
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12 pairs of cranial
nerves originate from
brain & brainstem
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Have sensory, motor
or mixed functions.
Enter and exit the
brain rather than
spinal cord
Essentially reflects
brainstem activity
Cranial Nerve I- Olfactory Nerve

Not routinely tested.

Test with:
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Report of loss of smell
Head trauma
Abnormal mental status
Suspected intracranial
lesion
Sensory function

With eyes closed occlude nares
and present aromatic substance
Able to correctly identify aromatic
substance
Cranial Nerve II- Optic Nerve

Sensory Function

Visual acuity


Visual fields by
confrontation
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Snellen: 20/20 OS,
20/20 OD, 20/20 OU
Peripheral fields
intact by
confrontation
Assess optic disc


Color & shape
Optic disc creamy
yellow, round, with
distinct margins
Cranial Nerve III, IV, VI

CN III- Oculomotor

Motor Function
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Medial, superior, inferior rectus muscles
& inferior oblique muscles
Levator palpebrae muscles (elevate
eyelids)
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Parasympathetic
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Muscles of iris & ciliary body
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PERRLA
CN IV- Trochlear

Motor Function
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Palpebral fissures symmetrical, no ptosis
Superior oblique
CN VI- Abducens

Motor Function

Lateral rectus
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EOMS intact without nystagmus
Cranial Nerve V- Trigeminal

Motor Function

Palpate temporal & masseter
muscles as patient clenches
teeth
Try to separate jaw by pushing
down on chin
Jaw strength equal bilaterally


Sensory Function

Test light sensation with
cotton ball over
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Forehead (ophthalmic)
Cheeks (maxillary)
Chin (mandibular)
Sensation intact and equal bilaterally
Cranial Nerve VII- Facial

Motor Function
Smile, frown, close eyes
tightly(against attempt to open,
lift eyes, show teeth & puff
cheeks
Facial muscles intact & symmetrical
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Sensory Function
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Not tested routinely
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Test only if suspect facial nerve
injury
Taste on anterior 2/3rds of tongue
Apply cotton applicator to
tongue with solution of sugar,
salt, or lemon juice
Able to correctly identify sweet, salty
& sour

Corneal Reflex
Only perform if patient
with abnormal facial
sensation or movement
 Remove contact lenses
 Lightly touch cornea
with wisp of cotton
from side
 Tests the sensory
afferent in CN V &
motor efferent CN VII
Corneal Reflex Intact

Cranial Nerve VIII- Acoustic

AKA
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Vestibulocochlear Nerve
Sensory Function
 Assess hearing acuity:
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Ability to hear normal
conversation
Whispered voice test
Whispered words heard
bilaterally
Weber tuning fork test
Tone heard midline
without lateralization
Rinne tuning fork test
AC >BC
Cranial Nerve IX and X
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CN IX- Glossopharyngeal
CN X- Vagus
Motor Function
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Swallow
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Depress with tongue blade & note
pharyngeal movement as patient says
“ahhh”
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Uvula rises midlines with phonation
Touch posterior pharyngeal wall to illicit
gag reflex
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Swallowing intact
Gag reflex intact
Note sound of voice
Sensory Function
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Taste on posterior 1/3 of tongue
Not routinely tested
Cranial Nerve XI- Spinal Accessory
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Motor Function
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Rotate head against
resistance
Shrug shoulders
against resistance
Shoulder shrug and head
movement
intact and
equal
bilaterally
Cranial Nerve XII-Hypoglossal
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Motor Function
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Have patient protrude tongue
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No wasting or tremors
Tongue midline
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Tongue protrudes midline without tremors
Say “light, tight, dynamite”
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Note if clear and distinct
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“Light, tight, dynamite” clear and distinct