StrictlyClinical
—
November 2006 American Nurse Today 21
MANY YEARS AGO when I was in
nursing school, I learned a saying
that was supposed to help me re-
call the cranial nerves. You’ve
probably heard it: On Old Olym-
pus Towering Tops A Finn and German Viewed Some
Hops.It didn’t make much sense to me, and it didn’t
help me remember the cranial nerves.
Afew years ago, a colleague taught me a much
easier way to remember the cranial nerves and their
locations—by drawing a face and using numbers as
the facial features. Each number represents one of
the 12 cranial nerves, and the placement of the
numbers represents the location of or an associa-
tion with them. (See Cranial nerves by the
numbers.)
Olfactorynerve (CN I)
Located in the nose,cranial nerve (CN) I controls
the sense of smell. This nerve isn’t frequently tested,
even by neurologists. However,suspect an abnor-
mality in a neurologic patient who has a poor ap-
petite.
Toassess the nerve, use soap and coffee—both
are easy to find on a unit. Or take a trip to the
kitchen for cloves and vanilla. Don’t use a substance
with a harsh odor, such as ammonia, because it will
stimulate the intranasal pain endings of CN V.
Have the patient close both eyes, close one nos-
tril, and gently inhale to smell the scent. Remember
to do both nostrils.
Optic nerve (CN II)
Located in and behind the eyes,CN II controls cen-
tral and peripheral vision.
The fovea in the center of the retina is responsible
for visual acuity in our central vision. Test one eye at
atime. Ask the patient to read his I.V. bag. Then
have him count how many fingers you are holding
up 6 inches in front of him.
Test peripheral vision one eye at a time, too. Cov-
er one eye and instruct the patient to look at your
nose. Move your index fingers to check the superior
and inferior fields one at a time. Ask the patient to
note any movement in the peripheral visual fields.
Oculomotor nerve (CN III)
Also positioned in and behind the
eyes,CN III controls pupillary con-
striction.
To test the patient’s pupils, dim
the lights, bring the light of the penlight from the
outside periphery to the center of each eye, and
note the response. Use the mm chart to describe
pupil size; descriptions such as “small,” “medium,”
and “large” are too subjective.
Also, check wherethe eyelid falls on the pupil. If
it droops, note that the patient has ptosis.
It’s easy to check cranial nerves III, IV, and VI together.
Trochlear nerve (CN IV)
Cranial nerve IV acts as a pulley to move the eyes
down—toward the tip of the nose.
Toassess the trochlear nerve, instruct the patient
to follow your finger while you move it down to-
ward his nose.
Trigeminal nerve (CN V)
Cranial nerve V covers most of the face.
If a patient has a problem with this nerve, it usu-
ally involves the forehead, cheek, or jaw—the three
areas of the trigeminal nerve. Check sensation in all
three areas, using a soft and a dull object. Check
sensation of the scalp, too.
Test the motor function of the temporal and mas-
seter muscles by assessing jaw opening strength. If
you suspect a problem with cranial nerves VI and
VII, check the corneal reflex with a cotton wisp
since it’s easy to do while you’re checking trigeminal
nerve function.
Abducens nerve (CN VI)
Cranial nerve VI controls eye movement to the
sides.
Ask the patient to look toward each ear. Then
have him follow your fingers through the six cardi-
nal fields of gaze.
Here’s another easy technique you can use: With
your finger, make a big X in the air and then draw a
horizontal line across it. Observe the patient for nys-
tagmus or twitching of the eye.
Strictly Clinical
—
Facing cranial nerve
assessment
By Barbara Bolek, APRN, MSN, CCRN, PCCN
How to remember
and assess the cranial
nerves with ease
