Cranial nerves Flashcards by Hannah Thomas

What is CN I and what is its function?

Olfactory nerve

Sensory (smell)

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What is CN II and what is its function?

Optic nerve

Sensory (vision)

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What is CN III and what is its function?

Oculomotor nerve

Motor (eye movement)

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What is CN IV and what is its function?

Trochlear nerve

Motor (eye movement)

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What is CN V and what is its function?

Trigeminal nerve
Mixed; sensation from face and mouth (including general sensation from th anterior 2/3 of the tongue), and motor control of muscles of mastication

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What is CN VI and what is its function?

Abducent nerve

Motor (eye movement)

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What is CN VII and what is its function?

Facial nerve
Motor control of muscles of facial expression
Parasympathetic fibres
Taste; special sensation to anterior 2/3 of tongue

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What is CN ViII and what is its function?

Vestibulocochlear nerve

Sensory (hearing and balance)

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What is CN IX and what is its function?

Glossopharyngeal nerve
Swallowing
Sensation from tongue (general and special sense from the posterior 2/3)
Parasympathetic fibres

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What is CN X and what is its function?

Vagus nerve
Motor control of pharyngeal muscles
Parasympathetic fibres
Visceral sensory fibres

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What is CN XI and what is its function?

Accessory nerve

Motor (soft palate throat and neck)

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What is CN XII and what is its function?

Hypoglossal nerve

Motor (tongue)

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Which three cranial nerves are tested together during clinical examination? why?

Oculomotor (III), Trochlear (IV), Abducens (VI)

They all control eye movement

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Describe how to examine the Olfactory nerve (I) and the potential abnormalities/symptoms

Test sense of smell in each nostril separately and ask about changes in sense of smell

bilateral or unilateral
anosmia (loss of sense of smell)
parosmia (pleasant scents perceived as unpleasant)

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Describe how to examine the Optic nerve (II) and the potential abnormalities/symptoms

AFRO
Acuity - test visual acuity for partial sight or blindness
Fields and inattention - test visual fields for scotoma or hemianopia
Reflexes - examine the size and shape of pupils, looking for anisocoria (unequal size of the pupils). Test the pupil light reflex
Optic disk - use fundoscopy to look at the optic disk and retina

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Describe how to examine the Oculomotor nerve (III) and the potential abnormalities/symptoms

Test the accommodation reflex

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Which nerves are being examined when testing eye movements? What symptoms are you looking for?

III, IV and VI
Strabismus (eyes not aligned properly)
Diplopia (double vision)
Nystagmus (involuntary eye movements)

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Describe how to examine the Trigeminal nerve (V) and the potential abnormalities/symptoms

Test facial sensation with cotton wool and neurotip
Test the corneal reflex
Test the muscles of mastication by palpating the bulk of the masseter muscle and then ask the patient to clench their teeth. Also test the jaw opening against resistance to test the pterygoid muscles
Test the jaw jerk reflex

Describe how to examine the Vestibulocochlear nerve (VIII) and the potential abnormalities/symptoms

Vestibular: check for nystagmus
Hearing: rub fingers together close to each ear one at a time
- see head and neck for more sensitive tests

Describe how to examine the Glossopharyngeal nerve (IX) and Vagus nerve (X). Why are these nerves examined together?

Examined together because they are closely related anatomically
Ask patient to open their mouth and say “ah” - check that palate moved symmetrically and that the uvula remains central
Ask the patient to cough and hear if this sounds normal
Test the gag reflex (not in all patients) to test pharyngeal sensation

Describe how to examine the Accessory nerve (XI) and potential abnormalities/symptoms

Place hands on patient’s shoulders and ask them to shrug - look and feel contraction of trapezius muscle
Ask patient to turn their head, pushing against your fist, to test sternocleidomastoid contraction

Describe how to examine the Hypoglossal nerve (XII) and potential abnormalities/symptoms

Ask the patient to open their mouth - look at tongue at rest for fasciculation, wasting or deviation
Ask the patient to stick out their tongue and move it from side to side
Test speech - e.g. ask patient to say the days of the week

Which cranial nerve would be affected by a lesion in the midbrain?

Oculomotor nerve (bilaterally)

Which cranial nerves would be affected by a lesion in the superior orbital fissure?

Oculomotor (Cr N III)
Trochlear (Cr N IV)
Abducens (Cr N VI)

Which cranial nerves would be affected by a lesion in the pons?

Abducens (Cr N VI) | Facial (Cr N VII)

Which cranial nerves would be affected by a lesion in the cerebellopontine angle?

Trigeminal (Cr N V) | Vestibular (Cr N VIII)

What could cause an unusual combination of cranial nerve signs?

Malignancy | Chronic meningitis e.g. due to sarcoidosis

What is myasthenia gravis and what causes it?

An autoimmune disease with motor signs only | Problems with the NMJ caused by acetylcholine receptor antibodies

What is optic neuritis? How is it tested for?

Demyelination of axons within the optic nerve, meaning that impulses slow down Test visual evoke response

Describe the signs/symptoms of optic neuritis

``` Monocular visual loss Pain on eye movement Reduced visual acuity Reduced colour vision - desaturation of colour, usually red Swollen optic disk ```

What disease can optic neuritis be the first presentation of?

Multiple sclerosis

Describe two types of Cr N III palsy

``` Microvascular - often caused by diabetes or hypotension - painless - pupil is spared Compressive - may be caused by raised ICP or post. com. aa aneurysm - painful - pupil is affected ```

What are the possible causes of nystagmus?

``` congenital serious visual impairment peripheral vestibular problem central vestibular/brain disease cerebellar disease toxins - medication, alcohol ```

What is Bell's palsy? Describe the clinical presentation of this condition

``` Idiopathic facial nerve palsy Presentation: - unilateral facial weakness - lower-motor neurones affected - often preceded by pain behind the ear - eye closure is often affected (risk of corneal damage) ```

How is Bell's palsy treated?

sterioids | usually good recovery

How do you distinguish between UMN and LMN lesions in facial paralysis?

Forehead innervation is affected in LMN lesions but not UMN

What are some causes of UMN facial paralysis vs LMN facial paralysis?

UMN: stroke, tumour LMN: Bell's, lyme disease, sarcoidosis

What is vestibular neuronitis?

Sudden onset, disabling vertigo often causes vomiting recovery is very gradual - can take weeks cause is uncertain, could be viral

What is disarthria?

Slurring of speech

What is dysphagia?

Difficulty swallowing

Name two conditions that can cause disarthria/dysphagia and describe the differences between these two conditions

``` Bulbar palsy - bilateral LMN lesions - tongue is wasted and/or fasiculating Pseudobulbar palsy - bilateral UMN lesions - tongue is spastic and/or immobile - brisk jaw-jerk and gag reflexes ```

Which cranial nerves are affected in bulbar palsy?

Cr N IX - Glossopharyngeal Cr N X - Vagus Cr N XI - Accessory Cr N XII - Hypoglossal

Which cranial nerves are affected in psuedobulbar palsy?

Cr Ns V, VII, IX, X, XI, XII