neurology Flashcards
TIA: definition
Transient neurological dysfunction caused by focal brain/spinal cord/retinal ischaemia without evidence of acute infarction
previously: transient neurological dysfunction w resolution w/in 24 hrs
up to a third of patients whose symptoms have resolved within 24 hours have evidence of infarction on imaging - definition is now TISSUE based rather than TIME based
TIA: aetiology
Temporary blockage of blood flow → ischaemia
Difference b/w presentation of stroke vs TIA
In TIA symptoms usually resolve within 1 hour (max 24 hours) rather than persisting (as in the case of a stroke)
TIA: possible clinical features
- unilateral weakness/sensory loss
- aphasia/dysarthria
- ataxia/vertigo/loss of balance
- visual problems (sudden transient loss of vision in one eye, diplopia, homonymous hemianopia)
transient vision loss in one eye = amaurosis fugax
dysarthria - affects muscles used in speech production
aphasia - impairment of ability to express/understand speech
Suspected TIA: immediate management
- Aspirin 300mg immediately (unless contraindicated)
- Assessed urgently w/in 24 hrs by stroke specialist clinician
What are some TIA mimics that require exclusion
- hypoglycaemia
- intracranial haemorrhage
all pts on anticoagulants or similar RFs (for haemorrhage) should be admitted for urgent imaging to exclude haemorrhage
What happens if a pt presents > 7 days following TIA
should be seen by stroke specialist clinician ASAP w/in 7 days
TIA: what does assessment by stroke specialist clinician involve
make decision on brain imaging (whether to do or not)
NICE recommend that CT brains should not be done ‘unless there is clinical suspicion of an alternative diagnosis that CT could detect’
an example exception would be when there is a concern about haemorrhage as the patient is taking anticoagulants
TIA: which brain imaging is preferred
- MRI (including diffusion weighted and blood-sensitive sequences)
- to determine territory of ischaemia/ detect presence of haemorrhage/other pathologies
- this should be done on same day as specialist assessment if possible
what specific type of drug is used to manage nausea following chemo/radiotherapy
5 HT3 antagonists e.g. ondansetron, palonosetron- these work at the chemoreceptor trigger zone in the medulla
palonostrone - 2nd gen 5HT3 antagonist advantage as less QT prolongation
CTZ is an area in the brain that can detect chemicals e.g. chemo drugs and contains many 5 HT3 receptors (usually detecting serotonin) - serotonin can be released in the gut in response to chemo drugs/irritants - high levels of serotonin stimulates vagus nerve - signal is sent to brain –> triggers sensation of nausea
potential S/Es of 5HT3 antagonists
e.g. ondansetron, palonosetron
* prolonged QT interval
* constipation is common
serotonin usually promotes gut motility - so blocking this means less stimulation of peristalsis –> slowing down of movement of contents through the intestines
prolonged QT - slightly inhibits K+ channels in the heart, so slows down the repolarisation process leading to increased QT interval
