Stroke Flashcards
What is the definition of a stroke?
An acute focal neurological deficit resulting from cerebrovascular disease and lasting more than 24 hours or causing earlier death
What happens during a stroke?
- blockage of blood delivery of oxygen to tissues
- no local cerebral blood flow
- cell death = death of brain tissue
- infarction of tissue
- haemorrhage into brain tissue
What is a TIA?
Transient Ischaemic Attack
- temporary ischaemia
What is the acronym FAST in relation to stroke?
F - facial drooping
A - arm weakness
S - speech difficulty
T - time
What feature of TIAs differs from strokes?
- recovery time
- full recovery after 24 hours
- many experience full recovery in 30 minutes
Why do TIAs only have a temporary effect?
- ischaemia is cleared
How are TIAs thought to occur?
- platelet emboli from neck vessels block blood supply to brain tissues
- ischaemia caused by emboli
- emboli cleared by circulation
- no permanent damage caused
What do TIAs increase the risk of?
- full stroke
- myocardial infarction
What are the risk factors for stroke?
Major:
- hypertension
- smoking
- ischaemic heart disease
Minor:
- alcohol
- atrial fibrillation
- diabetes mellitus
What level of hypertension increases the risk of stroke?
- diastolic >110mmHg
- 15x increase
- borderline hypertension still carries risk
Why does atrial fibrillation increase the risk of stroke?
- associated with emboli from abnormally contracting atria
- emboli pass through ventricle into cerebral circulation
- ischaemia caused
What are the incidences of the different types of strokes?
infarction - 85%
haemorrhage - 10%
subarachnoid haemorrhage - 5%
venous thrombosis - <1%
What is the cause of ischaemia stroke?
- uncertain
- usually narrowing of vessels and plaque formation
What is the cause of haemorrhagic stroke?
- inter cranial bleed
- usually from aneurysm rupture
- weak point in vessel fails
What are the causes of embolic strokes?
- embolism from left side of heart
- atrial fibrillation
- heart valve disease
- recent MI
- atheroma of cerebral vessels (TIA or full)
- carotid bifurcation
- internal carotid artery
- vertebral artery
What type of stroke can be seen on CT scans?
- haemorrhage
- visible as radiopaque mass
What type of stroke can be seen on an MRI?
- infarction
- shows inflammatory change around bleed
What are potential causes of stroke?
- venous thrombosis
- oral contraceptive pill use
- polycythaemia (high Hb)
- thrombophilia (increased clotting)
- borderzone infarction
- poor brain perfusion over period of time
- resulting brain injury
- severe hypotension, cardiac arrest etc.
- vasculitis
- narrowed vessels to brain
- limited oxygen delivery
How can stokes be prevented?
- reduction of risk factors
- quit smoking
- improve diabetic control
- control hypertension
- anti-platelet action
- only as secondary prevention
- aspirin (NSAID)
- dipyridamole (anti-platelet)
- clopidogrel (anti-platelet)
- anticoagulants
- less commonly used
- appropriate for embolic risk (e.g. AF, LVT)
- warfarin
- apixiban
- carotid endarterectomy
- preventative neurosurgery
What is carotid endarterectomy and when is it used?
Used in case of:
- severe stenosis
- previous TIAs
- under 85s
- incision of vessel containing large atherosclerosis
- collateral circulation of head and brain compensate
- atherosclerosis can be removed to increase patency
- 7.5% mortality rate
What are examples of preventative neurosurgery?
- aneurysm clips
- AV malformation correction
How can strokes be investigated and what are the advantages and disadvantages of each method?
- CT scan
- quick and easy
- poor for ischaemic stroke detection
- MRI scan
- cannot be done quickly
- shows haemorrhagic and ischaemic
- good for visualising early damage
- MRA (angiography) is best for brain circulation
- Digital Subtraction Angiography (DSA)
- if MRA not available
- Assessment of risk factors
- carotid ultrasound
- evidence of atherosclerosis
- carotid artery - cardiac ultrasound
- formation of thrombi
- left ventricle - ECG
- arrhythmias
- particularly AF - blood pressure
- hypertension - diabetes screen
- assess control - thrombophilia screen
- younger patients
- increased clot formation
- carotid ultrasound
What are the effects of stroke?
- loss of functional brain tissue
- immediate nerve cell death
- nerve cell ischaemia in penumbra
- nerve cells will die if not protected
- loss dependent on type/volume of damage
- gradual or rapid loss of function
- stroke can evolve over hours or minutes
- inflammation In tissue surrounding infarct/bleed
- penumbra (survivable ischaemia)
- size depends on time before treatment
- inflammation can cause further function loss
- final loss assessed after several days
What are the complications of stroke?
- motor function loss
- cranial nerve or somatic (opposite side)
- autonomic in brainstem lesions
- dysphonia
- changes to speech
- aphagia/dysphagia
- aspiration of food/saliva
- increased risk of pneumonia
- sensory loss
- cranial nerve or somatic (opposite side)
- body perception altered
- neglect (patient does not look after area)
- phantom limbs (less common than neglect)
- cognitive impairment
- appreciation of special sensation
- processing of speech and language
- difficulty understanding information
- memory impairment
- emotional lability and depression
How is the acute phase of stroke managed?
- limit damage
- improve blood flow/oxygenation
- thrombolysis within 3 hours
- maintain perfusion pressure to brain - normoglycemia
- hypo/hyper is harmful
- glucose is sole energy store of brain
- abnormalities may increase damage - preserve penumbra
- calcium channel blockers (nimodipine)
- improve blood flow/oxygenation
- reduce further risk
- manage penumbra to reduce loss of function
- institution of treatment
- 300mg aspirin daily
- anticoagulation if AF or LFT (after 2 weeks)
- removal of haematoma for subarachnoid haemorrhages
How is the chronic phase of stroke managed?
- rehabilitation
- immobility support
- prevention of bed sores
- physiotherapy to prevent contractures - speech and language therapy
- communications
- swallowing and eating - occupational therapy
- immobility support
- reduce further risk
What are the dental considerations of stroke?
- impaired mobility and dexterity
- more challenging to attend appointments
- difficult to maintain adequate oral hygiene
- communication difficulties
- dysphonia (abnormal/hoarse voice)
- dysarthria (difficulty speaking)
- cognitive difficulties
- risk of cardiac emergencies
- MI
- further stroke
- loss of protective reflexes
- aspiration
- saliva management (anticholinergic drugs)
- loss of sensory information
- difficult to adapt to new oral environment
- stroke pain
- CNS generated pain perception
- e.g. pain reported as a result of peripheral stimuli
