Cranial nerve examination
Encyclopedia
The cranial nerve exam is part of the neurological examination
. It is used to identify problems with the cranial nerves
by physical examination
.
Neurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired...
. It is used to identify problems with the cranial nerves
Cranial nerves
Cranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
by physical examination
Physical examination
Physical examination or clinical examination is the process by which a doctor investigates the body of a patient for signs of disease. It generally follows the taking of the medical history — an account of the symptoms as experienced by the patient...
.
Components
| Nerve | Evaluation | Associated conditions |
|---|---|---|
| I: Olfactory nerve Olfactory nerve The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:... |
Smell Olfaction Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates... is tested in each nostril Nostril A nostril is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation... 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 Cinnamon Cinnamon is a spice obtained from the inner bark of several trees from the genus Cinnamomum that is used in both sweet and savoury foods... , cloves and toothpaste Toothpaste Toothpaste is a paste or gel dentifrice used with a toothbrush as an accessory to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it serves as an abrasive that aids in removing the dental plaque and food from the teeth, assists in suppressing... . Bilateral loss can occur with rhinitis Rhinitis Rhinitis , commonly known as a stuffy nose, is the medical term describing irritation and inflammation of some internal areas of the nose. The primary symptom of rhinitis is nasal dripping. It is caused by chronic or acute inflammation of the mucous membrane of the nose due to viruses, bacteria or... , smoking Smoking Smoking is a practice in which a substance, most commonly tobacco or cannabis, is burned and the smoke is tasted or inhaled. This is primarily practised as a route of administration for recreational drug use, as combustion releases the active substances in drugs such as nicotine and makes them... or aging. Unilateral loss indicates a possible nerve lesion or deviated septum. This test is usually skipped on a cranial nerve exam. |
meningioma Meningioma The word meningioma was first used by Harvey Cushing in 1922 to describe a tumor originating from the meninges, the membranous layers surrounding the CNS .... |
| II: Optic nerve Optic nerve The optic nerve, also called cranial nerve 2, transmits visual information from the retina to the brain. Derived from the embryonic retinal ganglion cell, a diverticulum located in the diencephalon, the optic nerve doesn't regenerate after transection.-Anatomy:The optic nerve is the second of... |
Visual acuity Visual acuity Visual acuity is acuteness or clearness of vision, which is dependent on the sharpness of the retinal focus within the eye and the sensitivity of the interpretative faculty of the brain.... is tested in each eye Human eye The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth... 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 snelen chart. Visual fields are assess 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 Peripheral vision Peripheral vision is a part of vision that occurs outside the very center of gaze. There is a broad set of non-central points in the field of view that is included in the notion of peripheral vision... . The examiner's visual fields should be normal, since it is used as the baseline. Fundoscopy Pupillary light reflex The patient stares into the distance as the examiner shines the penlight obliquely into each pupil Pupil The pupil is a hole located in the center of the iris of the eye that allows light to enter the retina. It appears black because most of the light entering the pupil is absorbed by the tissues inside the eye. In humans the pupil is round, but other species, such as some cats, have slit pupils. In... . Pupillary constriction should be noted on the eye examined (direct response) and on the opposite eye (consensual response). 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. |
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| III, IV, VI: Oculomotor nerve Oculomotor nerve The oculomotor nerve is the 3rd of 12 paired cranial nerves. It enters the orbit via the superior orbital fissure and controls most of the eye's movements, including constriction of the pupil and maintaining an open eyelid by innervating the Levator palpebrae superiors muscle. The optic nerve is... , Trochlear nerve Trochlear nerve The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye.... , Abducens nerve |
Extraocular movements: First, inspect for ptosis Ptosis (eyelid) Ptosis is a drooping of the upper or lower eyelid. The drooping may be worse after being awake longer, when the individual's muscles are tired. This condition is sometimes called "lazy eye", but that term normally refers to amblyopia... , eye position and nystagmus. The pupil size should be measured, its shape and any asymmetry should be noted. A commonly used abbreviation to describe normal pupils is PERRLA PERRLA Perrla: Pupils equal, round & reactive to light & accommodationAccording to several articles Perrla is no longer used. Doctors don't find it valuable . According to Levin there are perils to using Perrla... (pupils equal, round and reactive to light and accommodation). The examiner tests ocular movements 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 targets is moved in an "H" shape and the patient is asked to report any diplopia Diplopia Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other... . Then, the target is held at the lateral ends of the patient's visual field. Nystagmus should be noted. One or two beats is a normal finding. The accommodation reflex Accommodation reflex The accommodation reflex is a reflex action of the eye, in response to focusing on a near object, then looking at distant object , comprising coordinated changes in vergence, lens shape and pupil size... 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 moving strip of horizontal lines. Nystagmus is normally observed. |
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| V: Trigeminal nerve Trigeminal nerve The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system... |
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 (C2 and C3). 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 Corneal reflex The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea , or bright light, though could result from any peripheral stimulus. Stimulation should elicit both a direct and consensual response... is conducted along with the facial nerve Facial nerve The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity... section of the test. Note the sensory innervation of the cornea is provided by the trigeminal nerve Trigeminal nerve The trigeminal nerve contains both sensory and motor fibres. It is responsible for sensation in the face and certain motor functions such as biting, chewing, and swallowing. Sensory information from the face and body is processed by parallel pathways in the central nervous system... while the motor innervation for blinking the eye is provided by the facial nerve Facial nerve The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity... .- Muscles of mastication Muscles of mastication During mastication, four muscles of mastication are responsible for adduction and lateral motion of the jaw. Other muscles, usually associated with the hyoid such as the sternohyomastoid, are responsible for opening the jaw.-Muscles:*The masseter... (temporalis, masseter) 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 Jaw jerk reflex The jaw jerk reflex or the masseter reflex is a stretch reflex used to test the status of a patient's trigeminal nerve . The mandible—or lower jaw—is tapped at a downward angle just below the lips at the chin while the mouth is held slightly open. In response, the masseter muscles will jerk the... 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. |
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| VII: Facial nerve Facial nerve The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity... |
Inspect for facial asymmetry and involuntary movements.
1) Raise both eyebrows 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
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| VIII: Vestibulocochlear |
Rinne test The Rinne test is a hearing test. It compares perception of sounds transmitted by air conduction to those transmitted by bone conduction through the mastoid... and Weber test Weber test The Weber test is a quick screening test for hearing. It can detect unilateral conductive hearing loss and unilateral sensorineural hearing loss... . |
acoustic neuroma Acoustic neuroma A vestibular schwannoma, often called an acoustic neuroma, is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve . The term "vestibular schwannoma" involves the vestibular portion of the 8th cranial nerve and arises from Schwann cells, which are... |
| IX and X: Glossopharyngeal and Vagus |
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Lateral medullary syndrome Lateral medullary syndrome Lateral medullary syndrome is a disease in which the patient has a constellation of neurologic symptoms due to injury to the lateral part of the medulla in the brain, resulting in tissue ischemia and necrosis.-Signs and symptoms:This syndrome is characterized by sensory deficits affecting... (IX) |
| XI: Accessory nerve Accessory nerve In anatomy, the accessory nerve is a nerve that controls specific muscles of the shoulder and neck. As part of it was formerly believed to originate in the brain, it is considered a cranial nerve... |
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| XII: Hypoglossal |
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See also
- Cranial nervesCranial nervesCranial nerves are nerves that emerge directly from the brain, in contrast to spinal nerves, which emerge from segments of the spinal cord. In humans, there are traditionally twelve pairs of cranial nerves...
- Cranial nerve nucleusCranial nerve nucleusA cranial nerve nucleus is a collection of neurons in the brain stem that is associated with one or more cranial nerves. Axons carrying information to and from the cranial nerves form a synapse first at these nuclei. Lesions occurring at these nuclei can lead to effects resembling those seen by...
- List of mnemonics for the cranial nerves