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neuro year 4 > posterior fossa pathology > Flashcards

posterior fossa pathology Flashcards

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1
Q

what happens to facial weakness in UMN lesion

A

opposite side lower half of face is weak. sparing of frontalis, preserved brow furrowing, eye closure and blinking unaffected

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2
Q

what happens to facial weakness in LMN lesion

A

ipsilateral weakness of all facial expression. angle of mouth falls, frowning and eye closure are weak. impaired taste sensation

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3
Q

what is the commonest cause UMN lesion leading to facial weakness

A

stroke with contralat hemiplegia

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4
Q

what happens if the facial nerve is damaged in the pons

A

loops around CN6 leading to lateral rectus palsy with unilat LMN weakness

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5
Q

what can cause facial weakness in the pons

A

tumour eg glioma, MS, infarction

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6
Q

what can be compressed with facial nerve in the cerebellopontine angle

A

5,6,8.

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7
Q

what can cause facial weakness in the cerebellopontine angle

A

acoustic neuroma, meningioma, mets

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8
Q

causes of facial nerve weakness in the petrous temporal bone

A

bells palsy, trauma, middle ear infection, herpes zoster

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9
Q

signs of damage at the petrous temporal bone

A

loss taste in ant 2/3 tongue. hyperacusis

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10
Q

what is Bells palsy

A

acute facial palsy thought to be due to viral infection causing swelling of the facial nerve in the tight petrous temporal bone facial canal

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11
Q

symptoms Bells palsy

A

unilateral LMN weakness developing over 24-48 hours, sometimes lost/altered sensation on the tongue, hyperacusis. pain behind ear common at onset

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12
Q

what does it mean if other cranial nerves are involved (if suspecting Bells palsy)

A

its not bells palsy

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13
Q

what can cause Bells palsy

A

Lyme disease in endemic areas, HIV seroconversion in Africa

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14
Q

treatment Bells

A

early corticosteroids- prednisolone 1mg/kg for 7 days. acyclovir and valaciclovir can be given in combination

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15
Q

come complications Bells

A

if cant blink can get exposure keratitis- lubricating eye drops. if severe weakness and cant close eye- need ophthal assessment. aberrant reinnervation of facial muscles eg twitching- late complication

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16
Q

prognosis Bells

A

good, 85% completely recover in 3-8 weeks even without specific treatment. rarely recurs

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17
Q

what may be helpful if recovery is not complete in Bells

A

cosmetic surgery

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18
Q

what does the trigeminal nerve do

A

mostly sensory but motor muscles of mastication

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19
Q

what happens in a 5th nerve lesion

A

unilateral sensory loss on the face. disminution of corneal reflex is an early sign

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20
Q

causes trigeminal lesion

A

brainstem- infarction, demyelination; CPA- acoustic neuroma, meningioma; tumour, infection

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21
Q

main risk factor for trigeminal neuralgia

A

hypertension. typically occurs 60-70+

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22
Q

what are the causes

A

ectatic vascular loop. in younger patients can be MS, CPA tumours

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23
Q

features trigeminal neuralgia

A

paroxysms of knife like or electric shock like pain which lasts seconds. in the distribution of the 5th nerve

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24
Q

which branch of V does trigeminal neuralgia commence

A

V3- mandibular. can spread to V2 maxillary and occasionally V1 ophthalmic

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25
Q

when would the TN be bilateral

A

demyelination. rare

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26
Q

what can stimulate TN

A

washing, shaving, cold wind, chewing

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27
Q

treatment TN

A

carbamazepine 600-1200mg a day. alternative- lamotrigine3, gabapentin, oxcarbazine

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28
Q

if medical treatment is not tolerated what can be used to treat TN

A

surgery- percutaneous radiofrequency selective ablation of trigeminal ganglion or microvascular decompressin of the nerve in post fossa

29
Q

what does the oculomotor supply

A

superior, inferior and medial recti, inferior olique, levator palpabrae superioris (lifts eyelid), parasympathetic constriction of the pupil

30
Q

causes of oculomotor lesion

A

aneurysm in posterior communicating artery, infarction of 3rd nerve(diaebetes, atheroma), coning temporal lobe, midbrain tumour or infarction

31
Q

signs complete 3rd lesion

A

unilateral complete ptosis (weakness levator), down and out (unopposed lateral rectus and superior oblique), fixed and dilated pupil

32
Q

which type of 3rd nerve lesion causes painless and pupil sparing

A

diabetic infarction. posterior communicating aneurysm causes it to be painful and doesn’t spare the pupil

33
Q

what way does the eye go in 6th nerve palsy

A

inwards (esotropia), cant fully abduct

34
Q

what happens to the eye in trochlear palsy

A

torsional diplopia- 2 objects at an angle when attempting to look down so head tilts away from that side

35
Q

what does the trochlear supply

A

superior oblique

36
Q

what does the abducens supply

A

lateral rectus

37
Q

what is BPPV due to

A

loose otoliths in the semicircular canal

38
Q

signs BPPV

A

precipitated by head movements- position, turning in bed, sitting up. sudden onset seconds-minds. less severe on repeated movement- fatigue

39
Q

what can BPPV sometimes follow

A

vestibular neuritis, head injury, ear infection

40
Q

diagnosis BPPV

A

hallpike manoeuvre. sit up then lie down and support head turn towards affected side. nystagmus with a latent interval

41
Q

how is BPPV treated

A

Epley manoeuvre- shift otoliths

42
Q

DDX BPPV

A

cerebellar mass but there may be nystagmus and vertigo immediately- no latent interval. also doesn’t fatigue

43
Q

vertigo that lasts secs-mins

A

BPPV

44
Q

vertigo that lasts mins-hours

A

menieres

45
Q

vertigo that lasts hours-days

A

labyrinthine or central pathology

46
Q

symptoms with menieres

A

episodic rotatory vertigo 30 mins-hours. sensorineural hearing loss, fullness in affected ear, loss of balance, tinnitus, vomiting

47
Q

what can be used in treatment Menieres

A

betahistine prochlorperazine. vestibular sedatives- cinnazine. chemical labyrinthectomy using ototoxic- gentamicin

48
Q

how long should vestibular sedatives be use for

A

cease within 2 weeks as can cause parkinsonian side effects

49
Q

what is the main sign of vertigo

A

nystagmus

50
Q

what symptoms would be accompanying vertigo in peripheral (vestibular) vertigo

A

tinnitus, deafness

51
Q

what symptoms would be accompanying vertigo in central vertigo

A

diplopia, weakness, cerebellar signs

52
Q

central causes of vertigo

A

brainstem pathology. infarction eg in lateral medullary syndrome; demyelination; posterior fossa ass lesions; migraine; CPA mass lesions; drugs

53
Q

investigations in vertigo

A

examine eye movements, assess heaing, head impulse (thrust) test, Hallpike, caloric testing (labyrinthine function), pure tone audiogram, MRI is central cause suspected

54
Q

what is vestibular neuronitis

A

isolated vertigo with nystagmus. vomiting, days-weeks, self limiting rarely recurs. can be followed by BPPV. deafness absent. vestibular sedatives used

55
Q

if vomiting isn’t a prominent feature is it central or peripheral

A

central

56
Q

what is the head impulse test

A

to check vestibular ocular reflex. high velocity head turns fixating on target look for catch up (overt) saccade. if abnormal the fixation is lost and then catch up

57
Q

what are the 2 phases of nystagmus and what do they mean

A

fast- direction of the beat. slow- eye catching up

58
Q

what does the fast phase nystagmus show in central

A

ipsilateral lesion. shows contralat in perhipheral

59
Q

what direction can central nystagmus be

A

horizontal, vertical or mixed

60
Q

what is the effect of visual fixation in both types nystagmuc

A

no effect on central, suppresses nystamus in peripheral

61
Q

what is the effect of head shaking on central and peripheral nystagmus

A

reverses direction in central, increases intensity but no change in direction in peripheral

62
Q

type of nystagmus in central

A

jerk or pendular (jerk only in peripheral)

63
Q

difference between dysphasia and dysarthria

A

dysphasia- problem with language and speech. dysarthria- problem in speech but language is in tact (disordered articulation, slurred speech)

64
Q

drugs that can cause vertigo

A

gentamicin, metronidazole, diuretics, co trimaxole

65
Q

what is Menieres due to

A

dilatation endolymphatic spaces of membranous labyrinth

66
Q

what is a positive Rombergs

A

balance worse when eyes are shut- impaired JPS or vestibular input

67
Q

what is a positive Unterbergers

A

march up and down on the spot with arms stretched out in front and eyes closed if >45 degree turn in

68
Q

treatment menieres

A

prochlorperazine, betahistine

69
Q

what is acute vestibular failure

A

follows a febrile illness in adults- sudden vertigo, vomiting, exacerbated by head movement. try cyclizine

neuro year 4 (19 decks)

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