Cranial Nerves

Question 1

What are the 12 cranial nerves (and their roles)

Answer 1

1. Olfactory (smell)
2. Optic (vision)
3. Occulomotor (all eye movement except LR and SO)
4. Trochlear (superior oblique)
5. Trigeminal (V1 ophthalmic, V2 maxillary, V3 mandibular)
6. Abducens (Later rectus)
7. Facial (muscles of face)
8. Vestibulocochlear (auditory + balance)
9. Glossopharyngeal (sensory and motor of tongue, tonsil pharynx)
10. Vagus (motor and sensory of most things below neck)
11. Accessory (sterno-mastoid and trapezius)
12. Hypoglossal (tongue muscles)

Question 2

Which cranial nerves have special senses (6)

Answer 2

smell - Olfactory (I)
vision - Optic (II)
Taste - (VII, IX - posterior 1/3, X - anterior 2/3)
Hearing and balance - (VIII)

Question 3

Which cranial nerves are responsible for “ordinary” sensation

Answer 3

Mainly the trigeminal (V)
The ear from the facial (VII) and glossopharyngeal (IX) nerves

Question 4

Which cranial nerves control muscle activity

Answer 4

eye muscles - occulomotor (III), trochlear (IV), abducens (VI)
Mastication - trigeminal (V)
Facial expression - facial (VII)
Larynx and pharynx - mainly vagus (X)
Sternomastoid and trapezius - accessory (XI)

Question 5

Which cranial nerves control autonomic functions (all parasympathetic) for:

Pupillary constriction
Lacrimation
Salivation (submandibular + sublingual glands)
Salivation (parotid gland)
Input to organs in thorax and abdomen

Answer 5

Pupillary constriction - occulomotor (III)
Lacrimation - facial (VII)
Salivation (submandibular + sublingual glands) - facial (VII)
Salivation (parotid gland) - glossopharyngeal (IX)
Input to organs in thorax and abdomen - Vagal (X)

Question 6

What are the divisions of the trigeminal (V)

Answer 6

Ophthalmic, maxillary, mandibular

Question 7

What is the parasympathetic pupillary response

Answer 7

Constriction of pupils

Question 8

What is third nerve palsy

Answer 8

Loss of parasympathetic input to the pupil = fixed, dilated pupil

Pupil is downward and outwards, ptosis

Question 9

What is the sympathetic pupillary response

Answer 9

Pupillary dilation
(Damage anywhere in sympathetic pathway can lead to a constricted pupil)

Question 10

What are some causes of a dilated pupil (7)

Answer 10

Youth
Dim lighting
Anxiety/excitement
Mydriatic eye drops (make pupil bigger)
Cocaine overdose
3rd nerve palsy
Brain death

Question 11

What are some causes of small pupils (5)

Answer 11

Old age
Bright light
Mitotic eye drops (make pupils smaller)
Opiate overdose
Horners syndrome

Question 12

What are the symptoms of horners syndrome (what often causes it)

Answer 12

Small pupil with ptosis, no sweating in the forehead

Often caused by apical lung tumour

Question 13

What may cause eye movement disorders (5)

Answer 13

Isolated 3rd nerve palsy
Isolated 4th nerve palsy
Isolated 6th nerve palsy

(Combination of the above)

Supranuclear gave palsy
Nystagmus

Question 14

What may cause isolated 3rd nerve palsy (what are the symptoms + signs)

Answer 14

Microvascular problems (diabetes or hypertension) - painless, pupil spared

Compressive (raised ICP, artery aneurysm - thunderclap headache) - painful, pupil affected

Question 15

What may cause 6th nerve palsy (4)

Answer 15

Idiopathic
Diabetes
Meningitis
Raised ICP

Question 16

What is the most common cause of nystagmus

Answer 16

Toxins (medication and alcohol)
Commonly seen on a Friday night from alcohol

Question 17

What is trigeminal neuralgia (and what causes it)

Answer 17

Paroxysmal (very sudden) attacks of lancinating pain
Potential Triggers: chewing, speaking, cold air
Caused by a vascular loop - compression of the 5th nerve in the posterior fossa

Question 18

Who does trigeminal neuralgia affect and what are the treatment options

Answer 18

Affects middle age and older
Treat with carbamazepine
If medication resistant there are surgical options

Question 19

What is Bell’s Palsy (how does it present)

Answer 19

Idiopathic palsy of the FACIAL (VII) nerve - Lower motor neuron type
Unilateral facial weakness often preceded by pain behind the ear - eye closure affected

Question 20

what is the treatment for Bell’s palsy

Answer 20

Treated with steroids - usually good recovery
As eye closure is affect eye has to be kept lubricated to prevent corneal damage

Question 21

What are some causes of upper motor neuron (UMN) and lower motor neuron (LMN) facial paralysis

Answer 21

UMN: e.g. stroke, tumour
LMN: e.g. Bell’s palsy, Lyme, sarcoid

Question 22

How to differentiate between UMN and LMN facial paralysis

Answer 22

UMN: will NOT involve the forehead
LMN: will involve the forehead

Question 23

What is vestibular neuronitis (what are the symptoms + cause)

Answer 23

Sudden onset of DISABLING VERTIGO
Vomitting
Gradual recovery
Causes is potentially viral

Question 24

What is dysarthria

Answer 24

Disordered articulation, slurring of speech

Question 25

What is dysphagia

Answer 25

Difficulty swallowing

Question 26

What is dysphonia

Answer 26

Problem with volume of speech

Question 27

What causes pseudobulbar palsy (what are the symptoms (6))

Answer 27

Bilateral UMN lesions (e.g. vascular lesions in both internal capsules) - often caused by MND

Symptoms:
Dysarthria
Dysphonia
Dysphagia
Spastic, immobile tongue
Brisk jaw jerk
Brisk gag reflex

(Brisk reflexes due to UMN lesion)

Question 28

What is Bulbar palsy (what are the symptoms)

Answer 28

Bilateral LMN lesions affecting IX - XII e.g. MND, polio, tumours, syphilis, vascular lesions of the medulla
Symptoms:
Wasted, fasciculating tongue
Dysarthria
Dysphonia
Dysphagia

BEWARE OF FEEDING THESE PATIENTS - do swallowing assessment