Testing Cranial Nerves
Cranial Nerve Number | Name | Function | Test |
1st | Olfactory | Smell | The ability to smell is tested by asking the person to identify items with very specific odors (such as soap, coffee, and cloves) placed under the nose. Each nostril is tested separately. |
2nd | Optic | Vision | The ability to see is tested by asking the person to read an eye chart. Peripheral (side) vision is tested by asking the person to look straight ahead while the doctor gradually moves a finger toward the person's center of vision from above, below, left, and right. The person is then asked to say when the finger is first seen. |
Detection of light | The ability to detect light is tested by shining a bright light (as from a flashlight) into each pupil in a darkened room. | ||
3rd | Oculomotor | Eye movement upward, downward, and inward | The ability to move each eye up, down, and inward is tested by asking the person to follow a target moved by the examiner. |
Narrowing (constriction) or widening (dilation) of the pupil in response to changes in light | The pupils’ response to light is checked by shining a bright light (as from a flashlight) into each pupil in a darkened room. | ||
Raising the eyelids | The upper eyelid is checked for drooping (ptosis). | ||
4th | Trochlear | Eye movement downward and inward | The ability to move each eye down and inward is tested by asking the person to follow a target moved by the examiner. |
5th | Trigeminal | Facial sensation | Sensation in areas of the face is tested using a pin and a wisp of cotton. The blink reflex is tested by touching the cornea of the eye with a cotton wisp. |
Chewing | Strength and movement of muscles that control the jaw are tested by asking the person to clench the teeth and open the jaw against resistance. | ||
6th | Abducens | Eye movement outward | The ability to move each eye outward beyond the midline is tested by asking the person to look to the side. |
7th | Facial | The ability to move muscles in the face (for example, in facial expressions), taste in the front two thirds of the tongue, production of saliva and tears, and control of a muscle involved in hearing | The ability to move the face is tested by asking the person to smile, to open the mouth and show the teeth, and to close the eyes tightly. |
8th | Auditory (vestibulocochlear) | Hearing | Hearing is tested with a tuning fork or with headphones that play tones of different frequencies (pitches) and loudness (audiometry). |
Balance | Balance is tested by asking the person to walk a straight line. | ||
9th | Glossopharyngeal | Swallowing, the gag reflex, and speech | Because both the 9th and 10th cranial nerves control swallowing and the gag reflex, they are tested together. The person is asked to swallow. The person is asked to say “ah-h-h” to check movement of the palate (roof of the mouth) and uvula (the small, soft projection that hangs down at the back of throat). The back of the throat may be touched with a tongue blade, which evokes the gag reflex in most people. The person is asked to speak to determine whether the voice sounds nasal (another test of palate movement). |
10th | Vagus | Swallowing, the gag reflex, and speech | |
Control of muscle in some internal organs and the heart rate | This function is not tested as part of the cranial nerve examination. | ||
11th | Accessory | Neck turning and shoulder shrugging | The person is asked to turn the head and to shrug the shoulders against resistance provided by the examiner. |
12th | Hypoglossal | Tongue movement | The person is asked to stick out the tongue, which is observed for deviation to one side or the other. |