Cranial Nerve Disorders

Question 1

What Cranial nerve(s) would be affected by a midbrain lesion?

Answer 1

Oculomotor Bilaterally

Question 2

What Cranial nerve(s) would be affected by a lesion in the Sup Orbital fissure? [4]

Answer 2

Oculomotor
Trochlear
Abducens
Opthalmic (V1)

Question 3

What Cranial nerve(s) would be affected by a lesion in the Pontomedullary junction? [3]

Answer 3

VI
VII
VIII

Question 4

What Cranial nerve(s) would be affected by a lesion at the cerebellopontine angle? [2]

Answer 4

Trigeminal & Vestibulocochlear

Question 5

Describe some lesions that could damage a cranial nerve? [3]

Answer 5

ISchaemia or tumour within the brain

Meningitis or SAH whilst crossing the subarachnoid space

Skull tumours outside the cranium

Question 6

Name a condition that can cause optic neuritis?

Answer 6

MS

Question 7

What are the symptoms of optic neuritis? [4]

Answer 7

• Monocular visual loss
• Pain on eye movement
• Reduced visual acuity & Colour vision
• Papilloedema

Question 8

What could cause a dilated pupil?
Physiological [3]
Pathological [4]

Answer 8

Physiological:

• Youth
• Dim lighting
• Anxiety or Excitement

Pathological:

• Mydriatic eye drops
• Amphetamines/cocaine
• third nerve palsy
• Brain death

Question 9

What could cause a constricted pupil?
Physiological [2]
Pathological [3]

Answer 9

Physiological:

• Old Age
• Bright Light

Pathological:

• Miotic Eye Drops
• Opiates
• Horners Syndrome (comes with anhydrosis and ptosis)

Question 10

Define Horner’s Syndrome

Answer 10

Something cutting off or compressing the sympathetic innervation to the eye and face (unilateral)

Can be intracranial lesions at the point where the sympathetic fibres leave thalamus and enter brainstem or in spinal cord or after they leave the spinal cord (e.g. pancoast tumour)

It causes:

• Miosis (Constricted pupil)
• Anhydrosis
• Ptosis

Question 11

What type of cranial nerve palsies can cause eye movement disorders? [4]

Answer 11

• Isolated nerve palsy to III, IV or VI
• Any combination of the above
• Supranuclear gaze palsy
• Nystagmus (VIII)

Question 12

What is a supranuclear gaze palsy?

Answer 12

An inability to look in a particular direction due to impairment in the cerebrum (Above the cranial nerve nuclei)

Question 13

What could cause an Isolated III nerve palsy? [2]

Answer 13

Microvascular conditions like diabetes or hypertension could cause a painless, pupil sparing III palsy

Compressive conditions like raised ICP or a Post. Comm. Art. Aneurysm could cause a a painful III palsy with a dilated pupil

Question 14

What could cause an isolated VI nerve Palsy? [4]

Answer 14

• Idiopathic
• Diabetes
• Meningitis
• Raised ICP

Question 15

What are the common causes of pathological nystagmus?

Answer 15

• Congenital (may never notice visual problems)
• Visual impairment
• Vestibular problems
• Brainstem disease (Affecting VIII)
• Cerebellar Disease
• Alcohol
• Toxic Med

Question 16

Name 2 meds that can cause pathological nystagmus?

Answer 16

• Phenytoin
• Carbamazepine

Both are epileptic medications

Question 17

What causes Trigeminal Neuralgia?

Answer 17

A vascular loop compressing the V nerve in the posterior fossa

Question 18

What is trigeminal neuralgia?

Answer 18

Paroxysmal attacks of Lancinating pain (Stabbing/piercing) in the face

Brought on my temp changes, wind, touch or chewing

Question 19

Define Bell’s Palsy? [4]

Mx

Answer 19

A LMN idiopathic facial nerve palsy:

• Unilateral facial weakness
• Often preceded by ear pain
• Risk of corneal damage form open eye

Mx: steroids

Question 20

Whats different about an UMN and LMN Facial nerve palsy?

Answer 20

Facial nerve fibres to lower face (below zygomatic arch) have UMNs from the contralateral cortex
So in an UMN or LMN lesion the lower face is always affected

However the facial nerve fibres to the upper face recieve UMNs from both hemispheres
Meaning if theres an UMN lesion the forehead is spared but a LMN will affect that entire side of the face

Question 21

Examples of UMN vs LMN facial palsies?

Answer 21

UMN - Stroke or tumour

LMN - Bells Palsy, Lymes disese or sarcoid

Question 22

What is Vestibular Neuronitis? [3]

Prognosis?

Answer 22

Sudden onset VIII palsy causing:

• Vomiting
• Disabling Vertigo

They tend to recover fully over a few weeks

Question 23

What are bulbar and pseudobulbar palsy?

Answer 23

Palsies afffecting the 9th-12th cranial nerves causing Inability to control movements (such as chewing and speaking)

Due to bilateral lesions of the:
- corticobulbar tracts i.e.
UMNs (Pseudobulbar)
- Motor Cranial Nerves i.e. LMNs (Bulbar)

Question 24

What could cause pseudobulbar palsy? [3]

Answer 24

Bilateral UMN lesion

• Vascular lesions of both internal capsules
• Motor Neuron Disease

Question 25

Difference between pseudobulbar [3] and bulbar palsy [4] presentations?

Answer 25

Bulbar (LMN):

• wasted, fasciculating tongue
• dysarthria (slurred Speech)
• dysphonia (Abnormal sound production)
• dysphagia

Pseudobulbar (UMN):

• Hyperreflexia (Gag, Jaw Jerk)
• Dysarthia, Dysphonia, Dysphagia
• Spastic Immobile Tongue

Question 26

What should you be careful of in patients with bulbar or pseudobulbar palsies?

Answer 26

Feeding them, they will likely choke

Question 27

What could cause Bulbar Palsy? [6]

Answer 27

Bilateral LMN lesions affecting IX-XII

• MND
• Polio
• Tumour
• Vascular lesion of medulla
• Syphilis

Question 28

Internuclear ophthalmoplegia
Pathophysiology [2]
Causes [2]

Answer 28

Ax

• a cause of horizontal disconjugate eye movement
• due to a lesion in the medial longitudinal fasciculus, which connects the IIIrd, IVth and VIth cranial nuclei

Causes

• multiple sclerosis
• vascular disease

Question 29

Internuclear ophthalmoplegia presentation [2]

Answer 29

impaired adduction of the eye on the same side as the lesion

horizontal nystagmus of the abducting eye on the contralateral side