Disorders of the cranial nerves

Question 1

Functions of the Cranial nerves (4)

Answer 1

“Special” senses
“Ordinary” sensation
Control of muscle activity
Autonomic functions

Question 2

What are the ‘special’ senses?

Answer 2

Olfaction I
Vision II
Taste VII, IX and X
Hearing and balance VIII

Question 3

Control of eye muscle movement is via which cranial nerves?

Answer 3

III
IV
VI

Question 4

Muscles of mastication are innervated by which cranial nerve

Answer 4

trigeminal V

Question 5

Muscles of facial expression are innervated by which cranial nerve

Answer 5

VII facial

Question 6

Muscles of larynx and pharynx are innervated by which cranial nerve

Answer 6

mainly X vagus

Question 7

Sternocleidomastoid and trapezius muscles are innervated by which cranial nerve

Answer 7

XI accessory

Question 8

What are the autonomic functions of the cranial nerves (all parasympathetic?

Answer 8

Pupillary constriction - III

Lacrimation - VII facial

Salivation

Vagal - input to organs in thorax and abdomen

Question 9

Which nerve innervates the submandibular and sublingual glands

Answer 9

Facial VII

Question 10

Which nerve innervates the parotid gland

Answer 10

IX glossopharyngeal

Question 11

Cranial nerve reflexes (4)

Answer 11

Pupillary light
Corneal
Jaw jerk
Gag

Question 12

Where are the nuclei of the Oculomotor and trochlear nerves found?

Answer 12

in the Mid brain

Question 13

Where are the nuclei of the Trigeminal, Abducent and Facial nerves found?

Answer 13

PONS

Question 14

Where does the nuclei of the vestibulocochlear nerve lie?

Answer 14

Pontomedullary junction

Question 15

Where does the nuclei of the Glossopharyngeal, Vagus, Accessory nerves lie?

Answer 15

Medulla

Question 16

How can cranial nerves be damaged?

Answer 16

within the brain - e.g. by ischaemia, tumour

• crossing the sub-arachnoid space - e.g by meningitis
• outside the skull e.g. by base of skull tumours arising in nasopharynx

Question 17

What is Optic neuritis

Answer 17

demyelination within the optic nerve

monocular visual loss

pain on eye movement

reduced visual acuity

reduced colour vision

optic disc may be swollen

often associated with multiple sclerosis

Question 18

Describe the effects of complete third nerve palsy

Answer 18

constriction of the pupil

loss of parasympathetic
input results in a fixed, dilated pupil

Question 19

Pupillary dilatation is a sympathetic response - how can this be damaged?

Answer 19

damage anywhere within the sympathetic pathway can lead to a constricted pupil

Question 20

Causes for dilated pupils? (7)

Answer 20

Youth
Dim lighting
Anxiety, excitement
Amphetamine, cocaine overdose
“Mydriatic” eye drops
Third nerve palsy
Brain death

Question 21

Causes of small pupils

Answer 21

Old age

Bright light

Miotic eye drops

Opiate overdose

Horner’s syndrome

Question 22

Eye Movement Disorders (6)

Answer 22

Isolated third nerve palsy
Isolated fourth nerve palsy
Isolated sixth nerve palsy
Combination of the above
Supranuclear gaze palsy
Nystagmus

Question 23

Microvascular causes of 3rd nerve palsy (painless)

Answer 23

diabetes

hypertension

Question 24

Compressive causes of 3rd nerve palsy (painful, pupil affected)

Answer 24

posterior communicating
artery aneurysm

raised ICP

Question 25

What can cause isolated 6th nerve palsy (4)

Answer 25

idiopathic
diabetes
meningitis
raised ICP

movement of the lateral rectus muscle affected

Question 26

Nystagmus causes (6)

Answer 26

Congenital
Serious visual impairment
Peripheral vestibular problem
Central vestibular / brainstem disease
Cerebellar disease
Toxins (medication and alcohol)

Question 27

Bell’s palsy

Answer 27

Unilateral facial weakness

Lower motor neurone type

Often preceded by pain behind ear

Eye closure affected

Risk of corneal damage

Treated with steroids -Usually good recovery

Can only be diagnosed if other dx diagnoses are ruled out

Question 28

Causes of an UMN lesion

Answer 28

Stroke or tumour

Question 29

What is vestibular neuronitis?

Answer 29

sudden severe attack of disabling vertigo caused by inflammation of the vestibular nerve

can also have vomiting

gradual recovery

Question 30

Bulbar palsy is what type of motor neuron lesion?

Answer 30

Bilateral LMN lesions affecting IX - XII

due to damage in the medulla oblongata or from lesions of the lower cranial nerves outside the brainstem

Question 31

Pseudobublbar palsy is what type of motor neuron lesion

Answer 31

Bilateral UMN lesions e.g. in vascular lesions of both internal capsules, MND

Usually caused by the bilateral damage to corticobulbar pathways, which are UMN pathways that course from the cerebral cortex to nuclei of cranial nerves in the brain stem.