Stroke Flashcards
What national screening tool is used to identify stroke Sx?
FAST
Face
Arms
Speech/Smile
Time (is brain)
What are the differential diagnoses for stroke?
- seizures (post-ictal activity)
- Wernicke’s encephalopathy
- Psychiatric disorders: Somatic disorders, conversion disorder)
- Brain tumour
- Trauma
What signs may suggest seizure rather than stroke?
- eye deviation away from lesion (for many types of seizure)
- EEG: seizure activity
- MRI: to rule out strokes or structural abnormalities
What is Wernicke’s encephalopthy?
A type of Beri Beri disease
Caused by thiamine (vit. B1) deficiency
often seen in alcoholics
In acute setting, PABRINEX can be given to resolve the low B1 levels
WERNICKE’S TRIAD:
- confusion
- ophthalmoplegia
- ataxia
How may a brain tumour present?
- picked up by imaging: CT/MRI
- may present with seizure activity
- can increase risk of coagulopathies such as stroke
What are the defining features of a stroke?
Sx must develop over a period of 24hr (officially)
usually Sx are NEGATIVE causing loss of function
e.g. ataxia
however some of the Ddx would present with POSITIVE Sx e.g. migraine with aura
What are the main types of haemorrhagic stroke?
INTRACEREBRAL (66%)
within the brain parenchyma
SUBARACHNOID (10%)
within subarachnoid space
INTRAVENTRICULAR (<5%)
within ventricles
What is a TIA?
= transient ischaemic attack
episodes usually last ~ 10mins (defo less than 24hr unlike full strokes)
cannot visualise TIA on imaging (CT/MRI)
Afro-Caribbean or S. Asian ethnicity carry the biggest risks for TIA
there is a high risk of reoccurrence of TIA
What is the main MODIFIABLE risk factor for strokes?
hypertension
What is the main NON-MODIFIABLE risk factor for strokes?
age
Which drugs (abuse) can elevate risk of strokes?
EtOH abuse
COCP (oestrogen containing)
cocaine
all of these will cause blood to be more thrombophilic or prone to bleeding
What is the MONROE-KELLIE HYPOTHESIS in cerebral perfusion?
Cerebral Perfusion Pressure (CPP) = MAP - ICP
where MAP = mean arterial pressure (i.e. systolic+diastolic/2 pressure)
ICP = intracranial pressure
in order for the brain to be adequately perfused, the systolic BP must always be higher than the ICP
hence, if there is increased ICP due to oedema in the brain, then the relative perfusion of the brain is going to be reduced
(at this level, the MAP < ICP and therefore no auto-regulation of CPP can occur)
What is a ‘cerebral sinus venous thromboembolism’?
when a clot develops in the venous dural sinuses in the brain
What are the biggest risks or causes of EMBOLIC STROKES?
recent MI
Atrial fibrillation
Why do cardiac arrests result in increased stroke risk?
cardiac arrest -> systemic hypoperfusion -> can cause endothelial damage -> stroke (ischaemia)
What is the main component of ANTERIOR CIRCULATION of the brain?
common carotid bifurcates to form internal + external carotids (C4)
internal carotids travel in the carotid sheath towards cranial vault
Once in the cranial vault, the internal carotid joins the circle of Willis structure at base of brain
here, it gives off branches Anterior Cerebral Artery (ACA) and becomes the Middle Cerebral Artery (MCA)
What are the main components of the POSTERIOR CIRCULATION of the brain?
subclavian arteries cross the transverse foramina of C6 and become the vertebral arteries
these travel superiorly towards the cranial vault passing through the C1 transverse foramina and through the foramen magnum
Once within in the cranial vault, they then give off cerebellar branches (PICA), meningeal arteries (PMA, AMA) and spinal arteries (PSA, ASA).
The main vertebral arteries then converge to become the basilar artery (circle of Willis)
What are CEREBELLAR branches of the vertebral arteries?
Posterior inferior cerebellar artery (PICA)
Superior cerebellar artery (SCA)
Anterior inferior cerebellar artery (AICA)
all supply the cerebellum
What do the meningeal branches of the vertebral arteries supply?
Posterior/Anterior meningeal arteries
supply the dura mater
What is the broad function of the CIRCLE OF WILLIS?
provides collateral circulation to the cerebrum and cerebellum
What is a LACUNAR INFARCT?
- most common type of ischaemic stroke
- affects smaller (perforating) arteries that supply the deep brain parenchyma
- also most common type in patients with DM or HTN
- location of infarct entirely dictates the presenting Sx
e. g. can be a purely motor stroke or a purely sensory stroke
common location of a lacunar stroke is the LENTICULOSTRIATE ARTERIES - supply the pons, internal capsule and putamen (basal ganglia structures)
What are the main locations of WATERSHED INFARCTS?
CORTICAL BORDER ZONES
regions between the MCA, ACA and vertebrobasilar arteries
INTERNAL ZONES
superficial-deep areas of the MCA territory
What are the main Sx in watershed infarcts?
SYSTEMIC HYPOPERFUSION
hypotension
tachycardia
pallor etc
CORTICAL BLINDNESS
bilateral vision loss
PROXIMAL LIMB WEAKNESS
e.g. affecting the legs but not the feet
What is a REPERFUSION INJURY in strokes?
occur at 6hr+ after initial ISCHAEMIC stroke
caused by sudden re-introduction of blood flow to the ischaemic/damaged area
can increase risk of haemorrhagic complication
REPEFUSION -> damage to endothelium and vascular structures
- INCREASED ROS
- REDUCED NO
pro-inflammatory environment with immune cell infiltration
What are the main features of an EXTRADURAL HAEMORRHAGE?
often caused by trauma, which ruptures the middle meningeal artery due to fracture of the skull
since the bleeding is limited by cranial sutures, bleed appears BICONVEX on imaging (CT/MRI)
causes initial transient loss of consciousness and then LUCID INTERVAL. Followed by rapid deterioration. “Talk and die” syndrome
if haemorrhage is severe, then may cause MIDLINE SHIFT of brain parenchyma
What are the main features of a SUBDURAL HAEMORRHAGE?
In young people, often caused by RTA or other trauma
In older people, often caused by falls
usually follows BLUNT FORCE TRAUMA causing shaking of the brain
this causes shearing forces on BRIDGING CORTICAL VEINS
Results in a depressed consciousness state + pupillary abnormalities
subdural haemorrhages may occur spontaneously
EtOH abuse: elevated risk of subdural haemorrhage due to brain atrophy (less brain tissue, more space inside cranium), more movement, higher coagulopathy risk due to malnutrition etc
What are the main features of a SUBARACHNOID HAEMORRHAGE?
commonly caused by rupture of BERRY ANEURYSMS
causes spider-like presentation of bleed on imaging
MRI: more sensitive to picking up this type of bleed (higher resolution)
“thunderclap headache” pathognomic almost for this type of haemorrhage
may present with FOCAL NEURO DEFICITS:
e.g. loss of consciousness, elevated ICP, elevated presentation of Cushing’s triad of Sx
What is Cushing’s triad of Sx?
[stimulated by Cushing’s reflex, related to the Monroe-Kellie equation]
- systemic HTN
- bradycardia
- irregular breathing
What are the main features of an INTRAPARENCHYMAL HAEMORRHAGE?
affects brain parenchyma
often caused by congenital or autoimmune disorders (increased risk for this type of bleed)
e.g. sickle cell, Moya Moya disease, arteriovenous malformation etc
less common form of haemorrhagic strokes
What are the main INVESTIGATIONS that should be done in suspected stroke?
** CT HEAD : key, first line Ix
important to distinguish type: Rx will depend on this
used to rule out haemorrhage
ischaemic strokes may present with a normal CT head
MRI: gold standard for DIAGNOSIS of ischaemic strokes since resolution much higher. Can provide info on: - location - damage - severity
Note that for haemorrhagic strokes, CT = MRI (sensitivity)
VASCULAR IMAGING
often used in TIAs
e.g. carotid dopplers (remember will only be able to scope the anterior cerebral circulation)
BLOOD TESTS
Serum glucose: rule out hypoglycaemia
Cardiac enzymes: MI can often occur simultaneously or precipitate embolic strokes
U+Es: some stroke Rx are contra-indicated in renal failure
ECG 24hr MONITORING (telemetry)
may need to monitor for AF (as major risk factor for embolic stroke)
What screening tools are useful for monitoring stroke risk in patients with atrial fibrillation (AF)?
Scores used together to do cost-benefit analysis of starting ANTI-COAGULATION in a given patient with AF
CHAD-VASc SCORE
used to identify patients with AF in whom ANTI-COAGULATION should be started
risk of developing a stroke to be minimised
HAS-BLED
risk of haemorrhage following initiation of anti-coagulation therapy
What are the main features of MANAGEMENT for strokes?
A to E assessment upon admission
e.g. if GCS < 8 then consider intubation
Rule out other causes of Sx, use OBS
e.g. O2 sats and serum Glu
If Sx < 4.5hr and ISCHAEMIC
then give tPA (alteplase)
(but need to be certain that Sx do not exceed 4.5hr)
If Sx < 6.5hr AND tPA not indicated
can do manual thrombectomy or other surgical interventions
If Sx > 4.5hr and ISCHAEMIC
no tPA given
only supportive care
e.g. aspirin
