Cranial Nerve assessment

1. CRANIAL NERVES
Assessment

6. MENTAL STATUS
ASSESSMENT

11. CN I – Olfactory (Sensory)
• Not often checked –
impairment usually due to
other causes (allergies,
colds)
• Impairment will also lead to
decreased taste
• Check each nostril
independently with
patient’s eyes closed
• Use non-toxic substances
such as
– Coffee
– Tobacco
– Mild soap (Ivory)
– Cloves

12. CN II – Optic (Sensory)
• Three tests
1. Visual acuity (sharpness or keenness)
2. Visual fields (peripheral vision)
3. Ophthalmoscope (internal eye inspection of optic
fundus, where CNII joins the eye)

13. CN II – Optic: Checking visual acuity
• Snellen chart may
be used for greater
accuracy
• Simple acuity test
– Patient covers one
eye at a time
– Hold up fingers and
ask how many
he/she sees
– Or simply read a
newspaper at arm’s
length

18. CN II – Optic: Checking visual fields
• Method called confrontation
– Sit 2-3 feet from patient, your left eye
aligned with patient’s right
– Your eye acts as control, so you need
good peripheral vision!
– You close or cover your eye aligned
with patient’s eye
– Holding up your index finger, mid-
distance between the patient and
yourself, just beyond your own
peripheral field, wiggle your finger as
you slowly bring it into the visual field.
– Ask the patient to tell you when he first
sees your finger. It should be at about
the same time that you see it.
– Repeat the test to cover the entire
visual field for each eye, which is to
test at each of the six even-numbered
positions on a clock's face.

19. CN II – Optic: Ophthalmoscope
•Expensive piece of equipment
•Use appropriately

20. All together now …
• Cranial Nerves III, IV, and VI
– III Oculomotor
– IV Trochlear
– VI Abducens
• Observation
– Examine the upper and lower lids by observation.
Look to see that the opening between the eyelids,
or the "palpebral fissures", are equal on both
sides, and that each lid relates symmetrically to
the cornea. Make sure to observe both upper and
lower lids.
– Next, observe the pupils in normal room light to
see if they are symmetric.

21. Cranial Nerves III, IV, and VI (Motor)
• Four tests
1. Direct Light Reflex
2. Consensual Light Reflex
3. Accommodation
4. Six Cardinal Fields of Gaze

22. Cranial Nerves III, IV, and VI
• Direct Light Reflex
– Each pupil should
constrict briskly
when the light
strikes the pupil.
– Move the light in
from the temporal
side.
– Document the
reaction in mm (e.g.,
6mm  4mm).

23. Cranial Nerves III, IV, and VI
• Consensual Light
Reflex
– Perform the
procedure again,
exactly as before for
Direct Light Reflex…
only this time watch
the opposite pupil.
– It should react the
same as the pupil in
which the light is
shined.

24. Cranial Nerves III, IV, and VI
• Accommodation - adaptation of the
eyes for near vision
– Ask the patient to focus on a distant light
(e.g., a wall or door) at their eye level and
maintain that gaze until directed
otherwise.
– Hold an object (pencil, penlight, finger)
about 18" from the patient's nose.
– Ask him to change his focus from the
distant object to the closer one.
– As he does so, observe his eyes as they
converge (turn inward) and the pupils
constrict.

25. Cranial Nerves III, IV, and VI
• Document normal reactions as PERLA!
– Pupils
– Equally
– Reactive to
– Light and
– Accommodation

26. Cranial Nerves III, IV, and VI
• Document abnormal eye movements
– Some key terms to know
1. Nystagmus: constant, involuntary, cyclical
movement
2. Saccadic: jerky, rapid, intermittent movements
3. Tracking: lagging, catching up movement
4. Vergence: turning of one eye without reference
to the other, which may indicate weakness of
oblique muscles.

27. Cranial Nerves III, IV, and VI
• Six Cardinal (primary) Fields of Gaze:
tests for extraocular movement
– Six fields correspond roughly to
12, 2, 4, 6, 8, 10 on a clock face
– Hold an object (pen, penlight,
finger) about 12" from the patient's
nose.
– Instruct the patient to keep his
head still and to follow the object's
movement to the six cardinal fields
with his eyes only.
– Slowly move the object through
each vision field separately,
observing both eyes
simultaneously.

28. CN V – Trigeminal (Sensory AND Motor)
• As the name
suggests, the
trigeminal nerve
innervates 3
sections of the
face:
1. ophthalmic
2. maxillary
3. mandibular

29. CN V – Trigeminal
• Sensory Assessment
– Begin by assessing ability to sense light touch
to the face.
– Ask the patient to close his/her eyes and to tell
you what he/she feels, and when and where
he/she feels it.
– Using a fine wisp of cotton or your fingertip,
gently test the forehead, cheeks, and jaw,
randomly and bilaterally.
– The patient should be able to identify the same
sensation bilaterally, and tell when and where
he/she feels the touch.
– If not, repeat the test using the sharp and blunt
ends of a sterile pin to check sensitivity to pain.
– Sensitivity to temperature may also be tested
using test tubes with warm and cool water.

30. CN V – Trigeminal
• Corneal Reflex Test
– Usually not done if light touch
is intact
– Instruct the patient to look up
and away from you.
– Approaching the patient
laterally, out of his line of
vision, and avoiding the
eyelashes, touch the cornea
lightly with a fine wisp of
cotton.
– Look for blinking of the eyes,
the normal reaction to this
stimulus.
– Be aware that use of contact
lenses frequently diminishes,
or may even eliminate, the
corneal reflex response.
The corneal reflex tests
the afferent (sensory) arc
of CN V, and the efferent
(motor) arc of CN VII.

31. CN V – Trigeminal
• Motor Assessment
– Ask the patient to clench his/her teeth.
– While he/she is clinching, palpate the
temporal muscles.
– You should note symmetrical strength.
Move your hands to the area of the
masseter muscles and ask the patient to
clench again.
– Bilateral contraction should be equally
strong.
– To assess chewing ability, ask the patient
to clench and unclench his/her jaws
several times while you observe for
distorted movements or asymmetry.

32. CN VII – Facial (Sensory and Motor)
• Motor assessment
– Observation during conversation
– Facial symmetry during spontaneous expression
• Wrinkling the nose
• Smiling and frowning
• Closing eyes
• Grimacing
– Intentional expression; ask the patient to
• Raise and lower eyebrows
• Squeeze eyes shut tightly
• Smile showing teeth
• Puff out cheeks

33. CN VII – Facial
• Sensory assessment
– Usually not done unless problems are
noted during motor assessment
– CNVII responsible for taste on anterior 2/3
of the tongue
– With patient’s eyes closed, check for
recognition of common, easily
distinguishable tastes such as chocolate
or lemon

34. CN VIII – Acoustic (Sensory and Motor)
• aka Vestibulocochlear nerve
• Two branches
– Vestibular nerve branch controls balance and equilibrium
– Cochlear nerve branch controls hearing
• Vestibular branch not usually checked unless several
symptoms of abnormality exist
• Vertigo
• N/V
• Nystagmus
• Postural deviation
• Pallor
• Sweating
• Hypotension

35. CN VIII – Acoustic
• Sensory assessment
– To make a gross assessment of
the cochlear division, begin by
instructing the patient to close
his eyes and tell you what he
hears and in which ear.
– Gently rub your fingers together
about 6" away from first one ear,
then the other, then both
simultaneously.
– If deficit is suggested, a more
precise assessment may be
done with a tuning fork.

36. CN IX & X – Sensory and Motor
• CN IX Glossopharyngeal
• CN X Vagus
– Cranial nerves nine and ten are tested
together, because they are closely associated
and similar in function.
– The motor aspect of the glossopharyngeal
nerve innervates the muscle used to swallow.
– Its sensory component supplies sensation to
the pharynx and is responsible for taste
perception on the posterior 1/3 of the tongue,
and for salivation.

37. CN X – VAGUS!
• The vagus nerve controls:
– swallowing
– phonation (the process of uttering vocal
sounds)
– movement of the uvula and soft palate.
• CN X also innervates the thoracic and
abdominal visceral organs!
– Carries sensory impulses from the GI tract,
the heart, and the lungs

38. CN IX & X – Assessment
• Begin assessment of these
2 nerves by inspecting the
soft palate.
• When the patient says "ah",
the palate should rise
promptly and
symmetrically.
• The uvula should NOT be
used to assess symmetry,
because there are many
normally odd-shaped
structures.

39. CN IX & X – Assessment
• The gag reflex assesses the sensory component of
CN IX, and the motor response of CN X.
• Touch the posterior pharynx lightly with a cotton-
tipped applicator.
• Test the palatal reflex, stroke the posterior portion of
the palate on each side with the applicator.
• In both instances, the palate should elevate and a
gag response should be induced.
• However, remember that normal patients frequently
manifest bilateral loss of the gag reflex, especially
patients with a history of smoking or tobacco use.

40. CN XI – Spinal Accessory (Motor)
• The spinal
accessory nerve
supplies the
sternocleidomastoid
muscles and the
upper portion of the
trapezius muscles.

41. CN XI – Spinal Accessory
• To assess sternocleidomastoid strength, apply
resistance to the jaw and have the patient try to turn
his head to the side against your pressure.
• To evaluate the trapezius, watch the patient shrug
his shoulders, which should move at the same speed
and with roughly the same extent of movement.
• Next, ask the patient to shrug his shoulders upward
while you try to hold them down.

42. CN XII – Hypoglossal (Motor)
• Responsible for normal
tongue movements.
• First observe the
tongue at rest on the
floor of the mouth.
• Look for:
– asymmetry
– deviation to one side
– loss of bulk on one side
– fasciculations
(involuntary contractions,
twitching)
• Next, ask the patient to
stick out his tongue.
• It should protrude along
the midline [the
"median raphe" (midline
crease) lines up with
the notch between the
"medial incisors" (two
front teeth)].

43. CN XII – Hypoglossal
• Finally, have the patient
push his/her tongue as
hard as he/she can against
the inside of the cheek,
while you push using your
thumb against the outside
of the cheek.
• Compare right and left
sides.
• Remember that weakness
pushing the tongue into the
right cheek indicates an
abnormality in the left
hypoglossal nerve, and
vice versa.