S10 - Stroke Flashcards
what is the general definition of a stroke and a TIA
Stroke, AKA a ‘cerebrovascular accident’, is a ‘serious life threatening condition that occurs when the blood supply to part of the brain is cut off’. The symptoms and signs persist for more than 24 hours - causes an acute neurological deficit due to vascular injury - can be a cerebral infarciton, intracerebral hemmorage or a subarachnoid hemmoraghe
Transient ischaemic attacks (TIAs), sometimes colloquially called ‘mini strokes’, have similar clinical features of a stroke but completely resolve within
24 hours
6 types of stroke are …
o Ischaemic (85%) Thromboembolic
o Haemorrhagic (10%)
Intracerebral (rupture of a vessel in brain parenchyma)
Subarachnoid
o Other (15%)
Dissection (separation of walls of artery, can occlude branches)
Venous sinus thrombosis (occlusion of veins causes
backpressure and ischaemia due to reduced blood flow)
Hypoxic brain injury (e.g. post cardiac arrest)
2 principles of treating a stroke are ?
Two main principles
Are they within the window for thrombolysis (<4 hours)?
Do a CT head to determine if it is a bleed (if bleed cannot proceed with thrombolysis)
o Acute imaging of stroke
CT
• Ischaemic area of brain not visible early on (as infarct
becomes more established the ischaemic area will
become hypodense)
• A bleed will show up as a bright white area, maybe with mass effect
MRI
• Sometimes performed
• Ischaemia shows up as a high signal area
symptoms of a ACA stroke are….
Anterior cerebral artery (ACA) infarct
Contralateral weakness in lower limb
Lower limb affected much worse than upper limb and face (as ACA does medial brain)
Contralateral sensory changes in same pattern as motor deficits
(sensory homunculus in similar arrangement as motor
homunculus)
Urinary incontinence due to paracentral lobules being affected
• Paracentral lobules are essentially the most medial part
of the motor/sensory cortices and supply the perineal
area
Apraxia
• Inability to complete motor planning (e.g. difficulty
dressing oneself even when power is normal)
• Often caused by damage to left frontal lobe
Dysarthria / aphasia
• A very unusual sign in ACA infarcts compared with MCA infarcts
• May be related to frontal lobe damage
Split brain syndrome / alien hand syndrome (both rare)
• Caused by involvement of corpus collosum damage (ACA supplies
3 types of a MCA stroke are…..
Proximal (pre - lenticulorstrates)
Lacunar (the lenticulostriates)
Distal (post Lenticulostriates)
o Middle cerebral artery (MCA) infarct
As MCA supplies a large area of brain these stroke can have very widespread effects and are associated with an 80% mortality if the main trunk of the MCA is affected due to resulting cerebral oedema
Haemorrhagic transformation can occur if the vessels in the infarcted area break down
symptoms of a MCA Proximal (pre - lenticulorstrates) stroke are
all branches of MCA will be affected including lenticulostriates and distal branches to cortical areas
o Contralateral full hemiparesis (face, arm and leg
affected)
- Because the internal capsule has been affected which carries fibres to face, arm and leg so even though the MCA supplies the face and arm area of the motor homunculus, this is irrelevant
o Contralateral sensory loss
Probably in the distribution of primary sensory cortex supplied by MCA (i.e. face and arm), but could involve larger areas if sensory fibres in internal capsule affected
o Visual field defects
Usually contralateral homonymous hemianopia without macular sparing
• Due to destruction of both superior and inferior optic radiations as they run through (superior) temporal and
parietal lobes
• More distal occlusions may affect one radiation alone causing quadrantanopias
o Aphasia
Global if dominant (usually left) hemisphere affected)
• Therefore, cannot understand or articulate words
o Contralateral neglect
Usually in lesions of right parietal lobe (can be caused by occlusions of more distal branches as well)
Other features
• Tactile extinction (if touch each side
simultaneously doesn’t feel the affected side)
• Visual extinction (as with half clock face etc.)
• Anosognosia (literally does not
acknowledge that they have had a stroke, so will confabulate to explain disability)
symptoms of a MCA Lacunar (the lenticulostriates) stroke are
Lenticulostriate artery(ies) occluded - lacunar strokes
o Cause destruction of small areas of internal capsule and basal ganglia
o Essential distinguishing feature from, say, a proximal MCA infarct is that they do not cause cortical features (e.g. neglect or aphasia)
o Types
- Pure motor (face, arm and leg affected equally, caused by damage to motor fibres travelling through internal capsule due to occlusion of lenticulostriate arteries)
- Pure sensory (face, arm and leg affected equally, caused by damage to sensory fibres travelling through internal capsule probably due to occlusion of thalamoperforator arteries and maybe also lenticulostriate)
- Sensorimotor (mixed, caused by infarct occurring somewhere at boundary between motor and sensory fibres)
symptoms of a MCA Distal (post Lenticulostriates) sroke are
MCA splits into a superior and inferior division
-Superior division essentially supplies lateral
frontal lobe
• Including primary motor cortex and Broca’s area
• Occlusion will cause contralateral face and arm weakness and expressive aphasia if left hemisphere affected
- Inferior division essentially supplies lateral parietal lobe and superior temporal lobe
- Including primary sensory cortex, Wernicke’s area and both optic radiations
- Occlusion will cause contralateral sensory change in face and arm, receptive aphasia if left hemisphere and contralateral visual field defect without macular sparing (often homonymous hemianopia as both radiations damaged)
o Occlusion of branches distal to superior/inferior
division may produce even more specific effects,
e.g. taking out Broca’s areas specifically with no
motor deficit
Symptoms of a PCA stroke …
Posterior cerebral artery (PCA)
Somatosensory and visual dysfunction typical
• Contralateral homonymous hemianopia (with macular
sparing due to collateral supply from MCA)
• Contralateral sensory loss due to damage to thalamus
Symptoms of a Cerebellar stroke
Cerebellar infarcts -Symptoms • Nausea • Vomiting • Headache • Vertigo / dizziness
Ipsilateral cerebellar signs (remember DANISH)
- Possible ipsilateral brainstem signs since cerebellar arteries supply brainstem as they loop round to the cerebellum
- Possible contralateral sensory deficit / ipsilateral Horner’s (once again due to brainstem involvement)
Symptoms of brainstem strokes
A huge number of named syndromes - not key
A typical feature is that contralateral limb weakness is seen with ipsilateral cranial nerve signs
• This can be explained by damage to corticospinal tracts (above decussation of pyramids) and damage to cranial nerve nuclei on same side
symptoms of a basillar artery occulsion…
As this vessel supplies the brainstem (which contains many vital centres), occlusion can sometimes cause sudden death
- Occlusion of distal (superior) basilar artery
• Visual and oculomotor deficits (as basilar sends some
branches to midbrain which contains oculomotor nuclei.
Also, occlusion at this site can prevent blood flowing into
PCAs affecting occipital lobes) - Behavioural abnormalities
- Somnolence, hallucinations and dreamlike behaviour (as brainstem contains important centres for sleep regulation – reticular activating system etc.)
• Motor dysfunction often absent (if the cerebral peduncles can get blood from the PCAs which in turn are being filled by the posterior communicating arteries)
- Proximal basilar occlusion (at level of pontine branches.
Embolus in basilar artery can occlude pontine branches on each side)
• Can cause locked in syndrome
• Complete loss of movement of limbs however preserved ocular movement. Eyes still move because midbrain is getting supply from PCAs via posterior communicating arteries
• Preserved consciousness (maybe because midbrain
reticular formation is still intact)
