CRANIAL NERVE EXAM: ABNORMAL EXAMPLES
Cranial Nerve 1- Olfaction
This patient has difficulty identifying the smells presented. Loss of smell is anosmia. The most common cause is a cold (as in this patient) or nasal allergies. Other causes include trauma or a meningioma affecting the olfactory tracts. Anosmia is also seen in Kallman syndrome because of agenesis of the olfactory bulbs.
Cranial Nerve 2- Visual acuity
This patient's visual acuity is being tested with a Rosenbaum chart. First the left eye is tested, then the right eye. He is tested with his glasses on so this represents corrected visual acuity. He has 20/70 vision in the left eye and 20/40 in the right. His decreased visual acuity is from optic nerve damage.
Cranial Nerve 2- Visual fields
The patient's visual fields are being tested with gross confrontation. A right sided visual field deficit for both eyes is shown. This is a right hemianopia from a lesion behind the optic chiasm involving the left optic tract, radiation or striate cortex.
Cranial Nerve 2- Fundoscopy
The first photograph is of a fundus showing papilledema. The findings of papilledema include
1. Loss of venous pulsations
2. Swelling of the optic nerve head so there is loss of the disc margin
3. Venous engorgement
4. Disc hyperemia
5. Loss of the physiologic cup and
6. Flame shaped hemorrhages.
This photograph shows all the signs except the hemorrhages and loss of venous pulsations.
The second photograph shows optic atrophy, which is pallor of the optic disc resulting form damage to the optic nerve from pressure, ischemia, or demyelination.
Cranial Nerves 2 & 3- Pupillary Light Reflex
The swinging flashlight test is used to show a relative afferent pupillary defect or a Marcus Gunn pupil of the left eye. The left eye has perceived less light stimulus (a defect in the sensory or afferent pathway) then the opposite eye so the pupil dilates with the same light stimulus that caused constriction when the normal eye was stimulated.
Cranial Nerves 3, 4 & 6- Inspection & Ocular Alignment
This patient with ocular myasthenia gravis has bilateral ptosis, left greater than right. There is also ocular misalignment because of weakness of the eye muscles especially of the left eye. Note the reflection of the light source doesn't fall on the same location of each eyeball.
Cranial Nerves 3, 4 & 6- Versions
• The first patient shown has incomplete abduction of her left eye from a 6th nerve palsy.
• The second patient has a left 3rd nerve palsy resulting in ptosis, dilated pupil, limited adduction, elevation, and depression of the left eye.
Cranial Nerves 3, 4 & 6- Ductions
Each eye is examined with the other covered (this is called ductions). The patient is unable to adduct either the left or the right eye. If you watch closely you can see nystagmus upon abduction of each eye. When both eyes are tested together (testing versions) you can see the bilateral adduction defect with nystagmus of the abducting eye. This is bilateral internuclear ophthalmoplegia often caused by a demyelinating lesion effecting the MLF bilaterally. The adduction defect occurs because there is disruption of the MLF (internuclear) connections between the abducens nucleus and the lower motor neurons in the oculomotor nucleus that innervate the medial rectus muscle.
Smooth Pursuit
The patient shown has progressive supranuclear palsy. As part of this disease there is disruption of fixation by square wave jerks and impairment of smooth pursuit movements. Saccadic eye movements are also impaired. Although not shown in this video, vertical saccadic eye movements are usually the initial deficit in this disorder.
Optokinetic Nystagmus
This patient has poor optokinetic nystagmus when the tape is moved to the right or left. The patient lacks the input from the parietal-occipital gaze centers to initiate smooth pursuit movements therefore her visual tracking of the objects on the tape is inconsistent and erratic. Patients who have a lesion of the parietal-occipital gaze center will have absent optokinetic nystagmus when the tape is moved toward the side of the lesion.
Vestibulo-ocular reflex
The vestibulo-ocular reflex should be present in a comatose patient with intact brainstem function. This is called intact "Doll’s eyes" because in the old fashion dolls the eyes were weighted with lead so when the head was turned one way the eyes turned in the opposite direction. Absent "Doll’s eyes" or vestibulo-ocular reflex indicates brainstem dysfunction at the midbrain-pontine level.
Vergence
Light-near dissociation occurs when the pupils don't react to light but constrict with convergence as part of the near reflex. This is what happens in the Argyll-Robertson pupil (usually seen with neurosyphilis) where there is a pretectal lesion affecting the retinomesencephalic afferents controlling the light reflex but sparing the occipitomesencephalic pathways for the near reflex.
Cranial Nerve 5- Sensory
There is a sensory deficit for both light touch and pain on the left side of the face for all divisions of the 5th nerve. Note that the deficit is first recognized just to the left of the midline and not exactly at the midline. Patients with psychogenic sensory loss often identify the sensory change as beginning right at the midline.
Cranial Nerves 5 & 7 - Corneal reflex
A patient with an absent corneal reflex either has a CN 5 sensory deficit or a CN 7 motor deficit. The corneal reflex is particularly helpful in assessing brainstem function in the unconscious patient. An absent corneal reflex in this setting would indicate brainstem dysfunction.
Cranial Nerve 5- Motor
• The first patient shown has weakness of the pterygoids and the jaw deviates towards the side of the weakness (without sound).
• The second patient shown has a positive jaw jerk which indicates an upper motor lesion affecting the 5th cranial nerve (with sound).
Cranial Nerve 7- Motor
• The first patient has weakness of all the muscles of facial expression on the right side of the face indicating a lesion of the facial nucleus or the peripheral 7th nerve.
• The second patient has weakness of the lower half of his left face including the orbicularis oculi muscle but sparing the forehead. This is consistent with a central 7th or upper motor neuron lesion.
Cranial Nerve 7- Sensory, Taste
The patient has difficulty correctly identifying taste on the right side of the tongue indicating a lesion of the sensory limb of the 7th nerve.
Cranial Nerve 8- Auditory Acuity, Weber & Rinne Tests
This patient has decreased hearing acuity of the right ear. The Weber test lateralizes to the right ear and bone conduction is greater than air conduction on the right. He has a conductive hearing loss.
Cranial Nerve 8- Vestibular
Patients with vestibular disease typically complain of vertigo – the illusion of a spinning movement. Nystagmus is the principle finding in vestibular disease. It is horizontal and torsional with the slow phase of the nystagmus toward the abnormal side in peripheral vestibular nerve disease. Visual fixation can suppress the nystagmus. In central causes of vertigo (located in the brainstem) the nystagmus can be horizontal, upbeat, downbeat, or torsional and is not suppressed by visual fixation.
Cranial Nerve 9 & 10- Motor
When the patient says "ah" there is excessive nasal air escape. The palate elevates more on the left side and the uvula deviates toward the left side because the right side is weak. This patient has a deficit of the right 9th & 10th cranial nerves.
Cranial Nerve 9 & 10- Sensory and Motor: Gag Reflex
Using a tongue blade, the left side of the patient's palate is touched which results in a gag reflex with the left side of the palate elevating more then the right and the uvula deviating to the left consistent with a right CN 9 & 10 deficit.
Cranial Nerve 11- Motor
When the patient contracts the muscles of the neck the left sternocleidomastoid muscle is easily seen but the right is absent. Looking at the back of the patient, the left trapezius muscle is outlined and present but the right is atrophic and hard to identify. These findings indicate a lesion of the right 11th cranial nerve.
Cranial Nerve 12- Motor
Notice the atrophy and fasciculation of the right side of this patient's tongue. The tongue deviates to the right as well because of weakness of the right intrinsic tongue muscles. These findings are present because of a lesion of the right 12th cranial nerve.