Disorders of the cranial nerves Flashcards
Functions of the Cranial nerves (4)
“Special” senses
“Ordinary” sensation
Control of muscle activity
Autonomic functions
What are the ‘special’ senses?
Olfaction I
Vision II
Taste VII, IX and X
Hearing and balance VIII
Control of eye muscle movement is via which cranial nerves?
III
IV
VI
Muscles of mastication are innervated by which cranial nerve
trigeminal V
Muscles of facial expression are innervated by which cranial nerve
VII facial
Muscles of larynx and pharynx are innervated by which cranial nerve
mainly X vagus
Sternocleidomastoid and trapezius muscles are innervated by which cranial nerve
XI accessory
What are the autonomic functions of the cranial nerves (all parasympathetic?
Pupillary constriction - III
Lacrimation - VII facial
Salivation
Vagal - input to organs in thorax and abdomen
Which nerve innervates the submandibular and sublingual glands
Facial VII
Which nerve innervates the parotid gland
IX glossopharyngeal
Cranial nerve reflexes (4)
Pupillary light
Corneal
Jaw jerk
Gag
Where are the nuclei of the Oculomotor and trochlear nerves found?
in the Mid brain
Where are the nuclei of the Trigeminal, Abducent and Facial nerves found?
PONS
Where does the nuclei of the vestibulocochlear nerve lie?
Pontomedullary junction
Where does the nuclei of the Glossopharyngeal, Vagus, Accessory nerves lie?
Medulla
How can cranial nerves be damaged?
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
What is Optic neuritis
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
Describe the effects of complete third nerve palsy
constriction of the pupil
loss of parasympathetic
input results in a fixed, dilated pupil
Pupillary dilatation is a sympathetic response - how can this be damaged?
damage anywhere within the sympathetic pathway can lead to a constricted pupil
Causes for dilated pupils? (7)
Youth Dim lighting Anxiety, excitement Amphetamine, cocaine overdose “Mydriatic” eye drops Third nerve palsy Brain death
Causes of small pupils
Old age
Bright light
Miotic eye drops
Opiate overdose
Horner’s syndrome
Eye Movement Disorders (6)
Isolated third nerve palsy Isolated fourth nerve palsy Isolated sixth nerve palsy Combination of the above Supranuclear gaze palsy Nystagmus
Microvascular causes of 3rd nerve palsy (painless)
diabetes
hypertension
Compressive causes of 3rd nerve palsy (painful, pupil affected)
posterior communicating
artery aneurysm
raised ICP
What can cause isolated 6th nerve palsy (4)
idiopathic
diabetes
meningitis
raised ICP
movement of the lateral rectus muscle affected
Nystagmus causes (6)
Congenital Serious visual impairment Peripheral vestibular problem Central vestibular / brainstem disease Cerebellar disease Toxins (medication and alcohol)
Bell’s palsy
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
Causes of an UMN lesion
Stroke or tumour
What is vestibular neuronitis?
sudden severe attack of disabling vertigo caused by inflammation of the vestibular nerve
can also have vomiting
gradual recovery
Bulbar palsy is what type of motor neuron lesion?
Bilateral LMN lesions affecting IX - XII
due to damage in the medulla oblongata or from lesions of the lower cranial nerves outside the brainstem
Pseudobublbar palsy is what type of motor neuron lesion
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.
