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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 effecting the olfactory
tracts. Anosmia is also seen in Kallman syndrome because of agenesis of
the olfactory bulbs. |
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Cranial
Nerve 2- Visual acuity
This patientās 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. |
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Cranial
Nerve II- 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. |
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Cranial Nerve II-
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.
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Images
Courtesy Dr. Kathleen Digre, University of Utah
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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. |
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Video
Courtesy of Dr.Daniel Jacobson, Marshfield Clinic
and Dr. Kathleen Digre, University of Utah
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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.
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Video
Courtesy of Dr.Daniel Jacobson, Marshfield Clinic
and Dr. Kathleen Digre, University of Utah
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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.
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Second
Video Courtesy of Dr.Daniel Jacobson, Marshfield Clinic
and Dr. Kathleen Digre, University of Utah
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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. |
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Saccades
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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. |
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Video
Courtesy of Dr.Daniel Jacobson, Marshfield Clinic
and Dr. Kathleen Digre, University of Utah
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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. |
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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. |
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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. |
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Video
Courtesy of Dr.Daniel Jacobson, Marshfield Clinic
and Dr. Kathleen Digre, University of Utah
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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. |
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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. |
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Cranial Nerve 5-
Motor
• The first
patient shown has weakness of the pterygoids and the jaw deviates towards
the side of the weakness.
• The second
patient shown has a positive jaw jerk which indicates an upper motor
lesion affecting the 5th cranial nerve.
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First
Video Courtesy of Alejandro Stern, Stern Foundation
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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.
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Video
Courtesy of Alejandro Stern, Stern Foundation
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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.
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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.
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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. |
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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. |
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Video
Courtesy of Alejandro Stern, Stern Foundation
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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.
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Video
Courtesy of Alejandro Stern, Stern Foundation
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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. |
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Video
Courtesy of Alejandro Stern, Stern Foundation
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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. |
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