Assessing the Cranial Nerves

©2008 By Kathy Quan RN BSN
All Rights Reserved

What Are the Cranial Nerves?
The Cranial Nerves are made up of 12 pairs of nerves which are located on the ventral surface of the brain. Some
control muscles. Some transmit information from the sensory organs to the brain. Others still are connected to
glands or organ such as the lungs and heart.

Examining the function of the cranial nerves will provide you with pertinent information about your patient's
nervous system. The cranial nerves are numbered using Roman Numerals I-XII. There are a number of
rhymes
or mnemonics
to help you remember the names of the nerves. You might also find this graphic helpful.

I. Olfactory Nerve
Its modality is Special Sensory and its function is smell.
In routine examinations this is not usually tested unless the patient complains of loss or changes in a sense of
smell. Each nostril should be patent. Have the patient occlude on and then the other during testing. With the eyes
closed, a patient should be able to identify common smells such as cinnamon, coffee, vanilla or cloves.

II. Optic Nerve
Its modality is Special Sensory and its function is vision. To test visual acuity, have the patient read a Snellen
Eye Chart from a distance of 20 feet (6 meters). The patient covers one eye at a time and reads to smallest line
possible.

To test visual fields, stand about 2 feet (60 cm) away from the patient. Ask the patient to concentrate his gaze on
your nose or directly into your eyes. Spread your arms so that your hands are about 2 feet apart and lateral to the
patient's ears. Wave your fingers as you slowly draw your hands in towards the patient's line of gaze. Ask him to
tell you when he first visualizes your wiggling fingers. DO this from all quadrants of the visual field. The patient
should see both hands simultaneously and from all directions.

Cranial Nerves III, IV and VI are tested together. They each control the extraoccular muscles involved in eye
movement.

III. Oculomotor Nerve
Its modality is two-fold; Somatic Motor and Visceral Motor. The Somatic Motor function is eye movement and
the Visceral Motor function is pupil dilation.

IV. Trochlear Nerve
Its modality is Somatic Motor and its function is eye movement.

VI. Abducens Nerve
Its modality is Somatic Motor and its function is eye movement.

To test these nerves, have the patient hold his head steady while you move your finger about 1 foot (30 cm) from
his nose to watch his eyes move peripherally and up and down. First move your finger out to the right side then
up and down; and back in towards the nose and up and down. Then outward from the left side and up and down;
back in towards the nose and up and down. Have the patient follow your finger with his eyes without moving his
head.

V. Trigeminal Nerve
This nerve has two modalities Brachial Motor and General Sensory. Its function is also two-fold. The Brachial Motor
controls the muscles of mastication (chewing). The General Sensory provides sensory information regarding touch
and pain in the face to the brain.

To test this nerve first have the patient clench jaw muscles by clenching his teeth. Muscle strength in the
temporal and masseter muscles of the face should be felt and should be symmetrical.
Touch the patient's face at the forehead cheek and chin on each side. The patient should report the sensation as
being symmetrical. You can use a clean safety pin or suitable sharp object) for testing pain sensation.
A cotton swab can be used to test for dull sensation. You can also test for sensation of temperature using test
tubes filled with warm water and ice water.

VII. Facial Nerve
This nerve has four modalities and functions. The modalities are Brachial Motor, Visceral Motor, General
Sensory and Special Sensory. The functions include taste on the anterior 2/3 of the tongue and salivary glands,
transmission of somatosensory information from the ear to the brain, control of muscles used in facial
expression.

To test this nerve, have the patient repeat a sentence. Observe his facial expression during normal conversation
check for any asymmetry, tics, or other facial movements. Next ask the patient to smile, frown, puff out his
cheeks. Look for symmetry especially in the nasolabial folds.

Ask him to close his eyes tightly and you try to open them by pulling upward on the eyebrows and downward on
the cheeks just below the eyes checking for strength and symmetry. To test for taste, drop a few drops of sweet
or salty water on the front part of the tongue and see how it tastes to your patient.

VIII. Acoustic Nerve (also known as Vestibulocochlear or Auditory Nerve)
This nerve has one modality; Special Sensory. It has two branches; the Cochlear which transmits sound
messages to the brain; and Vestibular which controls balance or equilibrium.
To Test this nerve have the patient occlude one ear with a finger. Stand about 1 to 2 feet away (30-60 cm) and
softly whisper a word with two distinct syllables such as football, baseball, or doorbell. Make sure the patient
can't read your lips. Repeat with the other ear and a different word. Repeat the word slightly louder if necessary
and observe for difficulties distinguishing words.

Equilibrium can be tested using the Romberg test: Have the patient stand erect with his feet close together and
his eyes closed. He might sway slightly, but should not fall. (Stay close to the patient in case he does begin to
fall.)

Cranial Nerves IX and X are tested together as they both have a function that innervates the pharynx.

IX. Glossopharyngeal Nerve
This nerve has four mobilities Brachial Motor, Visceral Motor, General Sensory and Special Sensory. Its
function includes taste on the posterior 1/3 of the tongue, some swallowing muscle function, and transmitting
somatosensory information from the tongue, tonsils and pharynx.

X. Vagus Nerve
This nerve also has four modalities: Brachial and Visceral Motor as well as Visceral Sensory and Special
Sensory. Its functions include autonomic, sensory and motor functions of viscera such as glands, heart rate and
digestion.

To test these nerves have the patient swallow some sweet or salty water and test for taste sensation as well as
ability to swallow. Then ask the patient to open wide and say "ah" while you observe the uvula and palate. These
should move symmetrically and without deviation to one side. Next tell the patient you're going to test his gag
reflex. Lightly stimulate the back of the throat on each side with a swab or tongue depressor. The reflex should
be present or symmetrically diminished.

XI. Spinal Accessory Nerve (also known as Accessory Nerve)
The modality is Brachial Motor and the function is control of the trapezius and sternocleidomastoid muscles in
movement of the head.

Place your hands on the patient’s shoulders from the back. Have him shrug his shoulders upward while you exert
slight resistance. The strength and contraction of the trapezius muscles should be symmetrical. Next place one
hand on the side of the patient's jaw and the other on the opposite sternocleidomastoid muscle. Have the patient
turn his head towards the hand on his jaw while you apply slight resistance. Observe the strength in both
muscles. Repeat to the other side.

XII. Hypoglossal Nerve
The modality is Somatic Motor and the function is control of the muscles of the tongue.
This nerve is tested by listening to the patient's articulation as he speaks as well as observing for any atrophy or
deviation of the tongue while speaking. Have the patient stick his tongue out and move it from side to side.
Check for symmetry of movement. Have the patient push his tongue against the inside of each cheek and you
palpate for strength from the outside of his cheek.

Document your assessment carefully and report all abnormal findings to the physician or other practitioner.

Resources:
Lippincott Manual of Nursing Practice, 8th Edition. Philadelphia: Lippincott, Wilkins & Wilkins, 2006
"Assessing the Cranial Nerves" Nursing 2006 November 2006:47-49

Neuroscience for Kids- Cranial Nerves




©2008-present by Kathy Quan RN BSN PHN, all rights reserved. No portion of this document may be used in any
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