Cranial Nerves

Question 1

Name three distinct symptoms associated with a CN III deficit

Answer 1

1) Severe ptosis
2) Large pupil, unreactive to light
3) Outward deviation (due to unopposed lateral rectus)

Question 2

What do the eyes look like in someone with a CN VI lesion?

Answer 2

Busted lateral rectus –> inability to ABduct in affected eye

Question 3

Which CN is responsible for mediating constriction in response to light?

Answer 3

CN II

Question 4

What are the three components of the near reflex?

Answer 4

Lens accommodation
Pupillary constriction
Convergence

Question 5

Selective disruption of the light reflex (when the pupil constricts as part of the near reflex but now when exposed to light) indicates a lesion in which part of the brain?

Answer 5

the pretectal area of the midbrain

Question 6

Name two pathological processes that lead to a selective disruption of the light reflex

Answer 6

Disruptions of the pretectal area of the midbrain such as:

1) Argyl-Robertson pupil in neurosyphilis
2) Dorsal midbrain tumors such as pineal tumor- Parinaud’s syndrome (associated with poor upgaze)

Question 7

Why does Horner’s syndrome lead to miosis?

Answer 7

A lesion in the sympathetic nerve –> inability for pupil to dilate

Horner’s= ptosis, miosis and anhydrosis

Question 8

Describe the steps necessary for the eyes to both look left

Answer 8

1) Left frontal eye field of the cortex activates the left PPRF
2) PPRF activates the CN VI to contract the left lateral rectus
3) PPRF sends a signal up the right MLF pathway to the right oculomotor nucleus and activates the right CN III. Activated CN III causes the right medial rectus to contract, and both eyes are turned to the left.

Question 9

Describe a left internuclear opthlamoplegia (left MLF syndrome)

Answer 9

a LEFT INO is seen when the left eye is unable to ADduct, but the right eye abducts with nystagmus

(Direction refers to which ascending MLF pathway is compromised)

Question 10

How will the ADduction during a near reflex be affected by someone with a left INO?

Answer 10

It will not- the adduction will be normal because the MLF pathway is not involved

Question 11

What is trigeminal neuralgia?

Answer 11

short-circulating nerve conduction of the trigeminal nerve leads to lightning-like jabs of pain, often in the V2/V3 area.

Question 12

What causes trigeminal neuralgia?

Answer 12

1) Associated with young MS patients

2) Tortuous blood vessels compressing CN V in older patients

Question 13

What is the tx for trigeminal neuralgia?

Answer 13

1) Anticonvulsants
2) Destroy nerve branch, or
3) Move blood vessel

Question 14

What nerve is tested by the corneal blink test?

Answer 14

V1- V1 is sensory only

Question 15

Describe the innervation of the muscles of mastication

Answer 15

bilateral UMN (corticobulbar) control

Question 16

IN lower motor neuron lesions of CN5, how is the

Answer 16

The jaw deviates to the side of the lesion, and the masseter and temporalis muscle are atrophied

Question 17

Describe the effects of left corticobulbar damage of the UM innervating the facial nerve

Answer 17

Weakness of the RIGHT lower face

Question 18

What happens to your face where there is a LMN lesion of facial nerve or facial nerve nucleus?

Answer 18

weakness of entire ipsilateral face

Question 19

What is Bell’s palsy?

Answer 19

Sudden, non-traumatic, isolated CN VII palsy

Question 20

A stylomastoid lesion of the facial nerve leads to what clinical feature?

Answer 20

Ipsilateral facial paralysis

Question 21

A petrous bone lesion of hte facial nerve leads to what clinical feature?

Answer 21

Loss of taste to anterior 2/3rds tongue (and facial paralysis)

Sensitivity to sound ( and facial paralysis)

Question 22

A cerebellopontine angle lesion of CN VII leads to what clinical feature?

Answer 22

Deafness, tinnitus (and facial paralysis)

Question 23

A pontine lesion of CN VII leads to what clinical feature?

Answer 23

Impaired lateral gaze (and facial paralysis)

Question 24

Does the uvula deviate to right or left in a left sided CN X lesion?

Answer 24

Uvula will deviate to the RIGHT.

The uvula deviates to the unaffected side

Question 25

How would an UMN lesion on the right side affect the tongue?

Answer 25

In most patients, an UMN lesion may not cause weakness or tongue deviation, because motor cortex controls both ipsi and contralateral hypoglossal nuclei.

In a few patients, there is unilateral control from the cortex, and the tongue deviates to the affected side.

Question 26

How does a LMN lesion of CN XII affect the tongue?

Answer 26

atrophy, fibrillations and fasciculations of the affected side.

Question 27

What is another name for Medial midbrain syndrome?

Answer 27

Webber Syndrome

Question 28

WHat is webber syndrome?

Answer 28

Webber Syndrome arises from an occlusion of the posterior cerebral artery branch. It leads to ipsilateral CN III lesion and contralateral hemiplegia (due to lesion in the cerebellar peduncle)

Question 29

What is another name for lateral medullary syndrome?

Answer 29

Wallenberg syndrome

Question 30

What is wallenberg syndrome?

Answer 30

occlusion of vertebral or PICA

• Nystagmus (Vestibular nuclei)
• ipsilateral limb dysmetria (ICP)
• Ipsilateral horner’s syndrome (descending sympathetic fibers)
• ipsilateral palatal, vocal cord weakness (nucleus ambiguus)
• Impaired pain and temperature in the ipsilateral face and CONTRALATERAL body (descending tract CN V, Vn and Vt)