Disorders of the Cranial Nerves Flashcards
Functions of the cranial nerves
Special senses
Ordinary senses
Control of muscle activity
Autonomic functions
What special senses do cranial nerves provide?
Olfaction (I)
Vision (II)
Taste (VII, IX and X)
Hearing and balance (VIII)
What cranial nerves provide ordinary sensations?
V (trigeminal)
Ear from VII (facial) and IXth (glossopharyngeal)
What control of muscle activity do cranial nerves provide?
Eye muscles - III, IV, VI Muscles of mastication - V Muscles of facial expression - VII Muscles of larynx and pharynx - X Sternocleidomastoid and trapezius muscles - XI
What autonomic functions do cranial nerves provide?
Pupillary constriction - III
Lacrimation - VII
Salvation of submandibular and sublingual glands - VII
Salvation of parotid glands - IX
Input to organs in thorax and abdomen - X
How do we test CN I?
Unilateral or bilateral smell loss
How do we test CN II?
Visual acuity Visual fields Pupillary reactions Fundoscopy Colour vision
How do we test CN III, IV and VI?
Any ptosis
Pupils of equal size
Pupillary reaction
Vertical and horizontal eye movements
How do we test CN V?
Sensation in opthalmic, maxillary and mandibular divisions
Power in muscles of mastication
Corneal reflex
Jaw jerk
How do we test CN VII?
Muscles of facial expression
Corneal reflex
Taste
How do we test CN VIII?
Hearing - rhinnes and webers
Vestibular function
- dix hallpike manouvre
- weinbergers test
How do we test CN IX and X?
Movement of palate
Gag reflex
Quality of speech
Quality of cough
How do we test CN XI?
Head turning and shoulder shrugging
How do we test CN XII?
Appearance, movement and power of the tongue
Which CNs are responsible for the pupillary light reactions? (both afferent and efferent)
Afferent - II
Efferent - III
Which CNs are responsible for the CN reflexes of the corneal reflex? (afferent and efferent)
Afferent - V
Efferent - VII
Which CNs are responsible for the jaw jerk? (Afferent and efferent)
Both V
Which CNs are responsible for the gag reflex? (afferent and efferent)
Afferent - IX
Efferent - X
Causes of dilated pupils
Youth Dim lighting Anxiety Excitement "Mydriatic eye drops" Amphetamine Cocaine overdose Third nerve palsy Brain death
Causes of small pupils
Old age Bright light "Miotic" eye drops Opiate overdose Horner's syndrome
Examples of eye movement disorders
Isolated 3rd nerve palsy Isolated 4th nerve palsy Isolated 6th nerve palsy Combination of above Supranuclear gaze palsy Nystagmus
Causes of isolated third nerve palsy
Microvascular - DM - HTN Compressive - posterior communicating artery aneurysm - rasied ICP
What helps to distinguish between micro vascular and compressive causes of isolated 3rd nerve palsy?
Microvascular - painless, pupil spared
Compressive - painful, pupil affected
Causes of isolated 6th nerve palsy
Idiopathic
DM
Meningitis
Raised ICP
Causes of nystagmus
Congenital Serious visual impairment Peripheral vestibular problem Central vestibular/brainstem disease Cerebellar disease Toxins (medication and alcohol)
What is trigeminal neuralgia?
Paroxysmal attacks of lacinating (stabbing/piercing) pain
Who gets trigeminal neuralgia?
> middle aged patients
Pathology of trigeminal neuralgia
Vascular loop - compression fifth nerve in the posterior fossa
Treatment of trigeminal neuralgia
Carbamazepine
Surgery if medication resistant
Another name for bells palsy
Idiopathic facial nerve palsy
Presentation of bells palsy
Unilateral facial weakness Preceded by pain behind ear Eye closure affected May also have - altered taste - dry eyes - hyperacusis
Which of CNS or PNS is affected in bells palsy?
PNS
What is there a risk of in bells palsy?
Corneal damage
Treatment of bells palsy
Prednisolone (within 72 hours of onset)
Eye care
- artificial tears
- eye lubricants
What would cause an UMN facial palsy?
Stroke
Tumour
What would cause a LMN facial palsy?
Bells palsy
Lyme
Sarcoid
What is vestibular neuritis?
Infection of the vestibular nerve in the inner ear
Presentation of vestibular neuritis
Sudden onset
Disabling vertigo
Vomiting
Gradual recovery
Definition of dysarthria
Disordered articulation, slurring of speech
Definition of dysphagia
Difficulty swallowing
Which of UMN or LMN is affected in bulbar palsy?
LMN
Which of UMN or LMN is affected in pseudobulbar palsy?
UMN
Which of bulbar and pseudobulbar palsy has both dysarthria and dysphagia?
Both
Pathology of pseudobulbar palsy
Bilateral UMN lesions e.g. in vascular lesions of both internal campuses, MND
Presentation of pseudobulbar palsy
Dysarthria Dysphonia Dysphagia Spastic, immobile tongue Brisk jaw jerk Brisk gag reflex
Pathology of bulbar palsy
Bilateral LMN lesions affecting IX-XII e.g. MND, polio, tumours, vascular lesions of medulla, syphillis
Presentation of bulbar palsy
Wasted, fasculating tongue
Dysarthria
Dysphonia
Dysphagia
Where are CNs III and IV found?
Midbrain
Where are CNs V, VI and VIII found?
Pons
Where is the CN VIII found?
Pontomedullary junction
Where are CNs IX, X, XI and XII found?
Medulla
Where can CNs be damaged?
In the brain e.g. by ischaemia, tumour
Crossing the subarachnoid space by e.g. meningitis
Outside of the skull e.g. by base of skull tumour in nasopharynx
What is optic neuritis?
Demyelination within the optic nerve
Presentation of optic neurtis
Monocular visual loss Pain on eye movement Reduced visual acuity Reduced colour vision Optic disc may be swollen
What is optic neuritis usually associated with?
MS
Bilateral CN III signs would indicate a problem where?
Midbrain
A combination of CN II, IV and VI signs would indicate a problem where?
Superior orbital fissure
A combination of CN VI and VII signs would indicate a problem where?
Pons
A combination of CN V and VIII signs would indicate a problem where?
Cerebellopontine angle
Unsual combination of cranial nerve signs may indicate what?
Chronic or malignant meningitis
Pure motor signs by CN may indicate what?
Myastenia gravis
What does a parasympathetic response do to the pupil?
Constricts it
What does loss of a parasympathetic input to the pupil result in?
A fixed dilated pupil
What does a sympathetic response do to the pupil?
Dilates the pupil
What can damage anywhere in the sympathetic pathway to the pupil result in?
A constricted pupil
What causes homonymous hemianopias?
Lesions of
- optic tract OR
- optic radiation OR
- occipital cortex
Homonymous hemianopia and WHAT would indicate damage to the occipital cortex?
Macula sparing
What causes homonymous quadrantanopias?
Lesions of
- temporal lobe (superior)
- parietal lobe (inferior)
What is the pneumonic to remember what homonymous quarantanopias are caused by which lobe?
PITS
- parietal inferior
- temporal superior
What causes bitemporal hemianopia?
Lesion of optic chiasm
Upper quadrant defect vs lower quadrant defect in bitemporal hemianopia
Upper > lower = inferior chiasmal compression, commonly a pituitary tumour
Lower > upper = superior chiasmal compression, commonly a craniopharyngioma
What does a defect in CN VI result in?
Defective eye abduction
Horizontal diplopia
What is facial nerve palsy the most common neurological manifestation of?
Sarcoidosis
Who is bells palsy more common in?
Pregnant women
What CN is susceptible to damage early in the course of raised ICP and why?
Abducens nerve
Long course of the nerve
