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Flashcards in Cranial Nerve Disorders Deck (34)

What is a cause of anosmia?

A permanent loss of smell may occur after severe head trauma, where the olfactory nerve branches are sheared or torn where they pass through the bony cribriform plate.


Besides trauma what else can cause permanent loss of smell?

A tumor near the olfactory lobe at the skull base, such as a meningioma.


What are some signs of CN III lesion?

- Severe ptosis
- Outward deviation of eye due to unopposed lateral rectus
- Pupil is large and unreactive to light


What is the only nerve that exits the brain stem dorsally?



How are lesions of CN IV best tested for?

Impairment of downward gaze (depression of the eyeball) is best noted when the involved eye is in the adducted position.


What is the effect of CN IV lesion?

Impairment of the downward gaze in the contralateral eye


What is the effect of CN VI lesion?

It affects only the ipsilateral lateral rectus muscle, impairing abduction of the affected eyeball.


Binocular Diplopia

If the eyeballs are not perfectly aligned in primary position or when conjugately moving to other positions, a visual image may appear blurred or doubled


What will resolve binocular diplopia?

Covering of either eye


What can cause binocular diplopia?

It can be caused by lesions of cranial nerves III, IV or VI, or their related extra ocular muscles.


What can cause monocular diplopia?

It is much more rare and can be caused by dislocated lens or detached retina



Repetitive, oscillatory, jerky eye movements


Internuclear Ophthalmoplegia

The paralysis of extraocular muscles ("ophthalmoplegia") from a lesion between the nuclei ("internuclear") involved with lateral gaze (oculomotor and abducens nuclei).


What is interrupted in internuclear ophthalmoplegia?

Medial Longitudinal Fasciculus


What is the most common cause of MLF lesions in young patients?

Multiple Sclerosis


What is the most common cause of MLF lesions in old patients?

Ischemic Infarction


What are classic causes of light- near dissociation?

- Dorsal Midbrain Syndrome
- Argyll Robertson pupils in neurosyphilis


What is light-near dissociation?

Pupil accommodates to the near stimulus but does not react to light with pupillary constriction.


Dorsal Midbrain Syndrome

Pineal tumor compressing the dorsal midbrain but may also occur from an ischemic infarction that leads to light-near dissociation


What is the cause of Horner's syndrome?

It's caused by a a lesion disrupting the occulosympathetic pathway


What syndrome affects the first order neurons of the occulosympathetic pathway?

Wallenberg (lateral medullary infarction)


What can affect the second order neurons of the occulosympathetic pathway?

Tumor at the C8 to T2 levels of the spinal cord


What can affect the third order neurons of the occulosympathetic pathway?

Third-order neurons arising from the superior cervical sympathetic ganglion ascend up the internal carotid artery where they may be affected by neck trauma.


Trigeminal Neuralgia

Trigeminal neuralgia is a painful syndrome of irritation or inflammation of one of the trigeminal nerve sensory branches which "short circuits" or "misfires."


What are the causes of trigeminal neuralgia in the young and the old?

Young - multiple sclerosis
Old - compression by the superior cerebellar artery


What is the drug used to treat trigeminal neuralgia?



What can cause hyper-reflexia of the jaw jerk?

Bilateral upper motor neuron lesions of the trigeminal nerve


What is seen with a LMN lesion in CN VII?

A lower motor neuron facial paralysis involves the nucleus or nerve of CN VII and causes a relatively severe paralysis of the entire ipsilateral half of the face.


What is seen with an UMN lesion in CN VII?

Facial paralysis from an upper motor neuron lesion causes a relatively milder paralysis of only the lower part of the contralateral face, sparing the forehead.


What is a sign of LMN lesion of CN X?

Ipsilateral drooping or sagging of the palatal arch with the uvula pointing toward the normal side if affecting branches of the palate OR hoarseness in voice if affecting branches of the larynx.


What will be seen on a LMN lesion of CN XII?

A lower motor neuron lesion of CN XII on one side causes the protruded tongue to deviate or turn toward the affected or weak side


What will be seen on an UMN lesion of CN XII?

In most patients, ipsilateral and contralateral upper motor neurons control each hypoglossal nucleus, so a frontal lobe lesion on one side would not cause weakness or deviation of the tongue.


Medial Midbrain Syndrome (Weber)

Due to an ischemic infarction from an occluded branch of the posterior cerebral artery which affects CN III and the CST with an ipsilateral oculomotor nerve lesion and upper motor neuron weakness of the contralateral face and limbs.


Lateral Medullary Syndrome (Wallenberg)

Due to an occlusion of PICA that causes pain (pinprick) and temperature impairment in the ipsilateral face (CN V) and contralateral limbs and body (STT).

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