Cranial nerve function tests Flashcards
How would you test the function of the olfactory nerve (CNI)?
Offer something familiar for the patient to smell and identify, for example orange/lemon peel, coffee, or vinegar. Check each nostril.
How would you test the function of the optic nerve (CNII)?
Acuity - use a Snellen chart (with and without visual aids.)
Colour - use ishihara plates
Visual field - ask the patient to look at you and wiggle a finger in each of the four quadrants, ask patient to identify finger.
Visual inattention - move two fingers at the same time and check patient identifies this.
Visual reflexes - place one hand along the patients nose to block any light from entering the eye which is not being tested. Shine a pen torch into one eye and check that the pupils on both sides constrict. This should be tested on both sides.
Fundoscopy - should be performed on both eyes.
How would you test the function of the occulomotor nerve (CNIIII), trochlear nerve (IV), abducens nerve (VI)?
Ask the patient to keep their head perfectly still in front of you. Then draw a large H using your finger, asking the patient to follow your finger.
How do you test the function of the three branches of the trigeminal nerve (CNV)?
Sensory - touch the face with a piece of cotton wool followed by a blunt pin around the jawline, on the cheek and on the forehead.
Corneal reflex - lightly touch the cornea with the cotton wool. This should cause the patient to shut their eyelids.
Motor - observe and feel the bulk of the masseter and temporalis muscles as the patient clenches their teeth together.
Ask the patient to then open their mouth against resistance.
Perform the jaw jerk on the patient by placing your left index finger on their chin and striking it with a tendon hammer. This should cause slight protrusion of the jaw.
How would you test the function of the facial nerve (CNVII)?
Ask the patient to crease up their forehead (raise their eyebrows), close their eyes and keep them closed against resistance, puff out their cheeks and reveal their teeth.
How would you test the function of the vestibulocochlear nerve (CNVIII)?
Rinne test - place a sounding tuning fork on the patient’s mastoid process and then next to their ear and ask which is louder. A normal patient will find the second position louder.
Weber test - place the tuning fork base down in the centre of the patient’s forehead and ask if it is louder in either ear. Normally it should be heard equally in both ears.
How would you test the function of the glossopharyngeal nerve (CNIX)?
It can be tested by checking the gag reflex, or touching the arches of the pharynx, though not very comfortable for the patient. Listening to the patient speak (checking for any hoarseness of the voice) may give a clue of an abnormality.
How would you test the function of the vagus nerve (CNX)?
Asking the patient to speak gives a good indication to the efficacy of the muscles. The uvula should be observed before and during the patient saying “aah”. Check that it lies centrally and does not deviate on movement.
How would you test the function of the spinal accessory nerve (CNXI)?
Ask the patient to shrug their shoulders and turn their head against resistance.
How would you test the function of the vagus nerve (CNXII)?
Observe the tongue for any signs of wasting or fasciculations. Ask the patient to stick their tongue out. If the tongue deviates to either side, it suggests a weakening of the muscles on that side.
