Video – Screening Examination of Cranial Nerves

Screening Examination of Cranial Nerves

This video will present a screening examination of the cranial nerves.   

Begin with a general inspection of the head and neck and look for symmetry of:

• The creases in the forehead,
• The position of the eyelids,
• The position of the eyes,
• The size of the pupils,
• The nasolabial folds,
• The corners of the mouth,
• The contours of the neck.

CN I – Sense of  Smell

To test cranial nerve one, examine the sense of smell. Ask the patient to close their eyes and block off one nostril. Bring a familiar substance such as coffee towards the patient’s nose and ask them if they can smell and identify the substance. Repeat with the opposite nostril.

CN II

To test Cranial Nerve Two, examine the Visual Acuity and Visual Fields.

Visual Acuity
Visual Acuity is typically assessed using a Snellen eye chart. This video shows a handheld version of the chart being used. Ask the patient to cover the left eye. Give them the chart and ask them to read aloud the smallest line they are able to read. Repeat with the other eye.

Visual fields
There are several methods for examining the visual fields. This video presents the examination of peripheral fields using a moving finger. Position yourself about 1 meter in front of the patient at eye level.

Right Eye – To test the right eye, ask the patient to cover their left eye with their left palm. Now cover your right eye with your right hand and ask the patient to look directly at your left eye.

To test the upper temporal quadrant, hold your left hand with the index finger extended upwards and outwards, equidistant between you and the patient. Ask the patient to report when they can see your index finger wiggling. If the patient is unable to see your wiggling finger, slowly bring your hand towards the centre until they indicate that they can see the movement. Compare the patient’s visual field with yours. Repeat the procedure for testing the lower temporal quadrant. Now cover your right eye with your left hand and perform the procedure for the upper nasal quadrant.  And finally, test the lower nasal quadrant.

Left Eye – Test the patient’s left eye by checking the upper temporal quadrant, the lower temporal quadrant, the upper nasal quadrant, and finally the lower nasal quadrant.

Right Eye – To test the right eye, ask the patient to cover their left eye with their left palm. Now cover your right eye with your right hand and ask the patient to look directly at your left eye.

To test the upper temporal quadrant, with the object in hand extend your left arm upwards and outwards equidistant between you and the patient. Slowly bring your hand towards the centre and ask the patient to indicate when they can see the object. Compare this to your own visual field. Repeat the procedure for testing the lower temporal quadrant. Now cover your right eye with your left hand and perform the procedure for the upper nasal quadrant. And finally, test the lower nasal quadrant.

Left Eye – Test the patient’s left eye by checking the upper temporal quadrant, the lower temporal quadrant, the upper nasal quadrant, and finally the lower nasal quadrant.

CN II and III

To test Cranial Nerves Two and Three, examine the direct light reflex, the Consensual light reflex, and the Accommodation-Convergence reflex. Dim the lights and ask the patient to look at a point on the wall behind you. Place one hand vertically along the patient’s nose to confine the light to one eye. To test for the direct light reflex, shine a bright light into the right eye and observe for pupillary constriction in that eye. To test for the consensual light reflex, shine the light again into the right eye but this time, observe for pupillary constriction in the left eye. Repeat the same procedures on the opposite side.

To test for the accommodation-convergence reflex, hold your finger approximately 6 inches in front of the patient’s face. Ask the patient to look at the wall behind you and then to look at your finger. Observe for the adduction of the eyes and pupillary constriction when they focus on your finger.

CN III, IV, VI

Eye Movements
To test Cranial Nerves Three, Four, and Six, check the movement of the eyes. Hold your index finger approximately 2 feet in front of the patient’s face and have them focus on your fingertip. Ask the patient to watch the movement of your finger without moving their head and report any loss of focus or double vision. Draw an “H” pattern with your finger and observe the smoothness and range of the patient’s eye movements. Pause for several seconds at the maximum range in each position and observe for any nystagmus that might be present.

CN V

To test cranial nerve Five, examine facial sensation, the muscles of mastication, and the jaw jerk.

Facial Sensation
To test facial sensation, with the patient’s eyes closed, lightly stroke both sides of the forehead and ask the patient if the feeling is the same on both sides. Repeat the test on the cheeks and then on the chin.

Muscles of Mastication
To examine the muscles of mastication, first, palpate the temporalis muscles and ask the patient to clench their teeth. Feel the muscle tension and compare each side. Next, palpate the masseter muscles and ask the patient to clench their teeth again. Feel the muscle tension and compare each side. Ask the patient to open their jaw and keep it open while you attempt to close it. Assess the strength of their resistance. Ask them to move the jaw to the right side and hold it there while you press against the jaw. Repeat on the opposite side and compare the strength of resistance.

Jaw Jerk Reflex
To perform the jaw jerk reflex place your finger on the patient’s chin and ask them to slightly open their mouth. Strike your finger with a reflex hammer. Typically this reflex is absent or is only slightly present, therefore, making areflexia or hyporeflexia difficult to detect. However, the presence of a hyperactive reflex with or without clonus suggests upper motor neuron involvement. 

CN VII

To test cranial nerve seven, examine the muscles of facial expression. Ask the patient to raise their eyebrows. Observe the wrinkling of the forehead and compare it on each side. Now, ask the patient to close their eyes tightly while you attempt to open them. Compare the strength of their resistance on each side. Ask the patient to smile and show their teeth. Observe for symmetry. Finally, ask the patient to blow out their cheeks and maintain this while you apply pressure on both cheeks. Compare the strength of their resistance on each side.

CN VIII

To test cranial nerve eight, examine the sense of hearing and balance.

Sense of Hearing
To test the sense of hearing, with the patient’s eyes closed, ask them to indicate in which ear they can hear your fingers rubbing together.  Test each ear separately.

Balance
Another test for Cranial Nerve 8 is to check for balance. Ask the patient to first stand with their feet together. Now ask them to walk across the floor and then turn and walk back.

CN IX and X

To test cranial nerves nine and 10, check for the mobility of the soft palate and examine the patient’s ability to swallow and cough. Ask the patient to open their mouth wide. Shine a torch into the mouth and ask the patient to say ‘ah’. Observe for the symmetrical elevation of the soft palate and uvula. Now, ask the patient to swallow some water. Observe the action and ask them to report any difficulty. Finally, ask the patient to cough and observe and listen for any difficulty.

CN XI

To test cranial nerve eleven, assess the strength of shoulder shrug and neck rotation. Ask the patient to elevate their shoulders and hold them there as you press down. Compare the strength of resistance on each side. Now ask the patient to turn their head to the right and hold it in that position against your pressure. Repeat the procedure on the left. Compare the strength of resistance on each side.

CN XII

To test cranial nerve twelve, assess tongue position and strength. Ask the patient to stick out their tongue. Observe for any deviation or fasciculation. Ask them to move the tongue from side to side. Compare the range and symmetry of the movement. Now ask the patient to press their tongue against their right cheek and resist while you apply pressure. Repeat on the opposite side and compare the strength of resistance on each side.

This concludes our presentation of a screening examination of the cranial nerves. If the case history or examination findings suggest any abnormality, a more thorough examination should be performed including ophthalmoscopy, assessment of the sense of taste, visual inattention, and the use of Ishihara colour charts and an Amsler Grid. 

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