Cranial nerves
i- olfactory
ii- optic
iii- oculomotor
iv- trochlear
v- trigeminal
vi- abducens
vii- facial
viii- vestibulocochlear
ix- glossopharyngeal
x- vagus
xi- accessory
xii- hypoglossal
Sensory nerves : 1, 2, 8
Motor nerves : 3,4,6,11,12
Mixed nerves : 5, 7,9,10
Examination of the Cranial Nerves
The following is a summary of the cranial nerves and their respective functioning.
• I - Smell
• II - Visual acuity, visual fields and ocular fundi
• III,IV,VI - Extra-ocular movements, including opening of the eyes
• V - Facial sensation, movements of the jaw, and corneal reflexes
• VII - Facial movements and gustation
• VIII - Hearing and balance
• IX,X - Swallowing, elevation of the palate, gag reflex and gustation XI - Shrugging the shoulders and turning the head
• XII - Movement and protrusion of tongue
Cranial Nerve I
Evaluate the patency of the nasal passages bilaterally by asking the patient to breath in through their nose while the examiner occludes one nostril at a time. Once patency is established, ask the patient to close their eyes. Occlude one nostril, and place a small bar of garlic or something with peculiar smell near the patent nostril and ask the patient to smell the object and report what it is. Making certain the patient's eyes remain closed. Switch nostrils and repeat. Furthermore, ask the patient to compare the strength of the smell in each nostril.
Cranial Nerve II
First test visual acuity by using a pocket visual acuity chart. Perform this part of the examination in a well lit room and make certain that if the patient wears glasses, they are wearing them during the exam. Hold the chart 14 inches from the patient's face, and ask the patient to cover one of their eyes completely with their hand and read the lowest line on the chart possible. Have them repeat the test covering the opposite eye. If the patient has difficulty reading a selected line, ask them to read the one above. Note the visual acuity for each eye.
Next evaluate the visual fields via confrontation. Face the patient one foot away, at eye level. Tell the patient to cover their right eye with their right hand and look the examiner in the eyes. Instruct the patient to remain looking you in the eyes and say "now" when the examiner's fingers enter from out of sight, into their peripheral vision. Once this is understood, cover your left eye with your left hand (the opposite eye of the patient) and extend your arm and first 2 fingers out to the side as far as possible. Beginning with your hand and arm fully extended, slowly bring your outstretched fingers centrally, and notice when your fingers enter your field of vision. The patient should say now at the same time you see your own fingers. Repeat this maneuver a total of eight times per eye, once for every 45 degrees out of the 360 degrees of peripheral vision. Repeat the same maneuver with the other eye.
Cranial Nerves III, IV and VI
Move the penlight slowly at eye level, first to the left and then to the right. Then repeat this horizontal sweep with the penlight at the level of the patient's forehead and then chin. Note extra-ocular muscle palsies and horizontal or vertical nystagmus.
Cranial Nerve V
First, palpate the masseter muscles while you instruct the patient to bite down hard. Also note masseter wasting on observation. Next, ask the patient to open their mouth against resistance applied by the instructor at the base of the patient's chin.
Finally, test the corneal reflex using a large Q-tip with the cotton extended into a wisp. Ask the patient to look at a distant object and then approaching laterally, touch the cornea (not the sclera) and look for the eye to blink. Repeat this on the other eye.
Cranial Nerve VII
Initially, inspect the face during conversation and rest noting any facial asymmetry including drooping, sagging or smoothing of normal facial creases. Next, ask the patient to raise their eyebrows, smile showing their teeth, frown and puff out both cheeks. Note asymmetry and difficulty performing these maneuvers. Ask the patient to close their eyes strongly and not let the examiner pull them open. When the patient closes their eyes, simultaneously attempt to pull them open with your fingertips. Normally the patient's eyes cannot be opened by the examiner. Once again, note asymmetry and weakness.
Cranial Nerve VIII
Assess hearing by instructing the patient to close their eyes and to say "left" or "right" when a sound is heard in the respective ear. Vigorously rub your fingers together very near to, yet not touching, each ear and wait for the patient to respond. After this test, ask the patient if the sound was the same in both ears, or louder in a specific ear. If there is lateralization or hearing abnormalities perform the Rinne and Weber tests using the 256 Hz tuning fork.
The Weber test is a test for lateralization. Wrap the tuning fork strongly on your palm and then press the butt of the instrument on the top of the patient's head in the midline and ask the patient where they hear the sound. Normally, the sound is heard in the center of the head or equally in both ears. If their is a conductive hearing loss present, the vibration will be louder on the side with the conductive hearing loss. If the patient doesn't hear the vibration at all, attempt again, but press the butt harder on the patient's head.
he Rinne test compares air conduction to bone conduction. Wrap the tuning fork firmly on your palm and place the butt on the mastoid eminence firmly. Tell the patient to say "now" when they can no longer hear the vibration. When the patient says "now", remove the butt from the mastoid process and place the U of the tuning fork near the ear without touching it.
Tell the patient to say "now" when they can no longer hear anything. Normally, one will have greater air conduction than bone conduction and therefore hear the vibration longer with the fork in the air. If the bone conduction is the same or greater than the air conduction, there is a conductive hearing impairment on that side. If there is a sensineuronal hearing loss, then the vibration is heard substantially longer than usual in the air. Make certain that you perform both the Weber and Rinne tests on both ears. It would also be prudent to perform an otoscopic examination of both eardrums to rule out a severe otitis media, perforation of the tympanic membrane or even occlusion of the external auditory meatus, which all may confuse the results of these tests. Furthermore, if hearing loss is noted an audiogram is indicated to provide a baseline of hearing for future reference.
Cranial Nerves IX and X
Ask the patient to swallow and note any difficulty doing so. Ask the patient if they have difficulty swallowing. Next, note the quality and sound of the patient's voice. Is it hoarse or nasal? Ask the patient to open their mouth wide, protrude their tongue, and say "AHH". While the patient is performing this task, flash your penlight into the patient's mouth and observe the soft palate, uvula and pharynx. The soft palate should rise symmetrically, the uvula should remain midline and the pharynx should constrict medially like a curtain. Often the palate is not visualized well during this manuever. One may also try telling the patient to yawn, which often provides a greater view of the elevated palate. Also at this time, use a tongue depressor and the butt of a long Q-tip to test the gag reflex. Perform this test by touching the pharynx with the instrument on both the left and then on the right side, observing the normal gag or cough.
Cranial Nerve XI
This cranial nerve is initially evaluated by looking for wasting of the trapezius muscles by observing the patient from the rear. Once this is done, ask the patient to shrug their shoulders as strong as they possible can while the examiner resists this motion by pressing down on the patient's shoulders with their hands. Next, ask the patient to turn their head to the side as strongly as they possibly can while the examiner once again resists with their hand.
The hypoglossal nerve controls the intrinsic musculature of the tongue and is evaluated by having the patient "stick out their tongue" and move it side to side. Normally, the tongue will be protruded from the mouth and remain midline. Note deviations of the tongue from midline, a complete lack of ability to protrude the tongue, tongue atrophy and fasciculations on the tongue.
Cranial Nerve XII
The hypoglossal nerve controls the intrinsic musculature of the tongue and is evaluated by having the patient "stick out their tongue" and move it side to side. Normally, the tongue will be protruded from the mouth and remain midline. Note deviations of the tongue from midline, a complete lack of ability to protrude the tongue, tongue atrophy and fasciculations on the tongue.
-SUMAN
