Cranial nerve examination
The cranial nerve exam is a type of neurological examination. It is used to identify problems with the cranial nerves by physical examination. It has nine components. Each test is designed to assess the status of one or more of the twelve cranial nerves. These components correspond to testing the sense of smell, visual fields and acuity, eye movements and pupils, sensory function of face, strength of facial and shoulder girdle muscles, hearing, taste, pharyngeal movement and reflex, tongue movements.
Components
| Nerve | Function | Evaluation | Associated conditions |
| I: Olfactory nerve | Sense of smell | Smell is tested in each nostril separately by placing stimuli under one nostril and occluding the opposing nostril. The stimuli used should be non-irritating and identifiable. Some example stimuli include cinnamon, cloves, and toothpaste. Bilateral loss can occur with rhinitis, smoking, or aging. Unilateral loss indicates a possible nerve lesion or deviated septum. This test is usually skipped on a cranial nerve exam. | meningioma |
| II: Optic nerve | Visual fields and acuity | Visual fields are assessed by asking the patient to cover one eye while the examiner tests the opposite eye. The examiner wiggles the finger in each of the four quadrants and asks the patient to state when the finger is seen in the periphery. The examiner's visual fields should be normal, since it is used as the baseline. Visual acuity is tested in each eye separately. Ensure the patient's vision is corrected with eyeglasses or a pinhole. The patient is asked to read progressively smaller lines on the near card or Snellen chart. Fundoscopy | Optic neuritis |
| III, IV, VI: Oculomotor nerve, Trochlear nerve, Abducens nerve | Ocular and extraocular movements, pupillary response | Ocular movements are tested by standing one meter in front of the patient and asking the patient to follow a target with eyes only, and not the head. The target is moved in an "H" shape and the patient is asked to report any diplopia. Then, the target is held at the lateral ends of the patient's visual field. Nystagmus is tested for. One or two beats is a normal finding. The accommodation reflex is tested by moving the target towards the patient's nose. As the eyes converge, the pupils should constrict. The optokinetic nystagmus test is optional and involves asking the patient to look at a strip of vertical lines moving horizontally across visual field. Nystagmus is normally observed. Extraocular movements is tested by inspecting for ptosis, eye position and nystagmus. The pupil size is measured, its shape and any asymmetry is tested. A commonly used abbreviation to describe normal pupils is PERRLA. Pupillary light reflex is tested by having the patient stare into the distance as the examiner shines the penlight obliquely into each pupil. Pupillary constriction is tested for on the eye examined and on the opposite eye. The swinging flashlight test involves moving the light between the two pupils. Normally both direct and consensual responses are ellicited when the light shines on an eye, and some dilation will occur during the swing between. | |
| V: Trigeminal nerve | Facial sensation | Light touch is tested in each of the three divisions of the trigeminal nerve and on each side of the face using a cotton wisp or tissue paper. The ophthalmic division is tested by touching the forehead, the maxillary division is tested by touching the cheeks, and the mandibular division is tested by touching the chin. Be careful not to test the mandibular division too laterally, as the mandible is innervated by the great auricular nerve. A common mistake is to use a stroking motion, which will trigger pain and temperature nerves. Instead, a point stimulus should be applied. For pain and temperature repeat the same steps as light touch but use a sharp object and a cold tuning fork respectively. Corneal reflex is conducted along with the facial nerve section of the test. Note the sensory innervation of the cornea is provided by the trigeminal nerve while the motor innervation for blinking the eye is provided by the facial nerve.- Muscles of mastication should be inspected for atrophy. Palpate the temporalis and masseter as the patient clenches the jaw. The pterygoids can be tested by asking the patient to keep the mouth open against resistance, and move from side to side against resistance. A jaw jerk reflex can be tested by placing a finger over the patient's chin and then tapping the finger with a reflex hammer. Normally the jaw moves minimally. | trigeminal neuralgia |
| VII: Facial nerve | Facial muscles | Inspect for facial asymmetry and involuntary movements.
2) Frown 3) Close both eyes tightly so that you can not open them. Test muscular strength by trying to open them 4) Show both upper and lower teeth 5) Smile 6) Puff out both cheeks
| Bell's Palsy, Ramsay Hunt syndrome |
| VIII: Vestibulocochlear | Hearing | acoustic neuroma | |
| IX and X: Glossopharyngeal and Vagus | Taste, pharyngeal movement | Lateral medullary syndrome | |
| XI: Accessory nerve | Shoulder girdle muscles | ||
| XII: Hypoglossal | Tongue movements |