Cranial Nerve Disorders

Question 1

What is a cause of anosmia?

Answer 1

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.

Question 2

Besides trauma what else can cause permanent loss of smell?

Answer 2

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

Question 3

What are some signs of CN III lesion?

Answer 3

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

Question 4

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

Answer 4

CN IV

Question 5

How are lesions of CN IV best tested for?

Answer 5

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

Question 6

What is the effect of CN IV lesion?

Answer 6

Impairment of the downward gaze in the contralateral eye

Question 7

What is the effect of CN VI lesion?

Answer 7

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

Question 8

Binocular Diplopia

Answer 8

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

Question 9

What will resolve binocular diplopia?

Answer 9

Covering of either eye

Question 10

What can cause binocular diplopia?

Answer 10

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

Question 11

What can cause monocular diplopia?

Answer 11

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

Question 12

Nystagmus

Answer 12

Repetitive, oscillatory, jerky eye movements

Question 13

Internuclear Ophthalmoplegia

Answer 13

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

Question 14

What is interrupted in internuclear ophthalmoplegia?

Answer 14

Medial Longitudinal Fasciculus

Question 15

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

Answer 15

Multiple Sclerosis

Question 16

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

Answer 16

Ischemic Infarction

Question 17

What are classic causes of light- near dissociation?

Answer 17

• Dorsal Midbrain Syndrome

- Argyll Robertson pupils in neurosyphilis

Question 18

What is light-near dissociation?

Answer 18

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

Question 19

Dorsal Midbrain Syndrome

Answer 19

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

Question 20

What is the cause of Horner’s syndrome?

Answer 20

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

Question 21

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

Answer 21

Wallenberg (lateral medullary infarction)

Question 22

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

Answer 22

Tumor at the C8 to T2 levels of the spinal cord

Question 23

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

Answer 23

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

Question 24

Trigeminal Neuralgia

Answer 24

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

Question 25

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

Answer 25

Young - multiple sclerosis

Old - compression by the superior cerebellar artery

Question 26

What is the drug used to treat trigeminal neuralgia?

Answer 26

Carbamazepine

Question 27

What can cause hyper-reflexia of the jaw jerk?

Answer 27

Bilateral upper motor neuron lesions of the trigeminal nerve

Question 28

What is seen with a LMN lesion in CN VII?

Answer 28

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.

Question 29

What is seen with an UMN lesion in CN VII?

Answer 29

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.

Question 30

What is a sign of LMN lesion of CN X?

Answer 30

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.

Question 31

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

Answer 31

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

Question 32

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

Answer 32

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.

Question 33

Medial Midbrain Syndrome (Weber)

Answer 33

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.

Question 34

Lateral Medullary Syndrome (Wallenberg)

Answer 34

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).