Cranial nerves Flashcards
What is CN I and what is its function?
Olfactory nerve
Sensory (smell)
What is CN II and what is its function?
Optic nerve
Sensory (vision)
What is CN III and what is its function?
Oculomotor nerve
Motor (eye movement)
What is CN IV and what is its function?
Trochlear nerve
Motor (eye movement)
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
What is CN VI and what is its function?
Abducent nerve
Motor (eye movement)
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
What is CN ViII and what is its function?
Vestibulocochlear nerve
Sensory (hearing and balance)
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
What is CN X and what is its function?
Vagus nerve
Motor control of pharyngeal muscles
Parasympathetic fibres
Visceral sensory fibres
What is CN XI and what is its function?
Accessory nerve
Motor (soft palate throat and neck)
What is CN XII and what is its function?
Hypoglossal nerve
Motor (tongue)
Which three cranial nerves are tested together during clinical examination? why?
Oculomotor (III), Trochlear (IV), Abducens (VI)
They all control eye movement
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)
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
Describe how to examine the Oculomotor nerve (III) and the potential abnormalities/symptoms
Test the accommodation reflex
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)
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
