Stroke Flashcards
What is a stroke?
- A serious, life-threatening condition that occurs when the blood supply to part of the brain is cut off
- Symptoms and signs persist for more than 24 hours
What are transient ischaemic attacks?
- Have similar clinical features of a stroke but completely resolve within 24 hours
What are the different types of stroke?
- Ischaemic (85%) - thromboembolic
- Haemorrhagic (10%) - intracerebral and subarachnoid
- Other (15%) - dissection, venous sinus thrombosis, hypoxic brain injury
What is a dissection that causes stroke?
- Separation of walls of artery, can occlude branches
What is a venous sinus thrombosis?
- Occlusion of veins causes backpressure and ischaemia due to reduced blood flow
What are the two main principles of stroke management?
- Is the patient within the window for thrombolysis (<4 hours)
- Do a CT head to determine if it is a bleed (if there’s a bleed, cannot proceed with thrombolysis)
What are the different mechanisms of acute imaging of a stroke?
- CT
- MRI
How does stroke appear in a CT head?
- Ischaemic area of brain not visible early on (as infarct becomes more established the ischaemic area will become hypodense)
- A bled will show up as a bright white area, maybe with mass effect
How does stroke appear in an MRI?
- Shows up as a high signal area
What are the classic stroke syndromes?
- Anterior cerebral artery infarct
- Middle cerebral artery infarct
- Posterior cerebral artery infarct
- Cerebellar infarct
- Brainstem strokes
- Basilar artery occlusion
What are the motor symptoms of an anterior cerebral artery infarct?
- Contralateral weakness in lower limb (affected worse than upper limb and face)
What are the sensory symptoms of an anterior cerebral artery infarct?
- Contralateral sensory changes in same pattern as motor deficits
- Lower limb is affected worse than upper limb and face
What are the other symptoms of an anterior cerebral artery infarct?
- Urinary incontinence due to paracentral lobules being affected
- Apraxia
- Dysarthria/aphasia
- Split brain syndrome/alien hand syndrome
What are the paracentral lobules?
- Essentially the most medial part of the motor/sensory cortices
- Supplies perineal area
What is apraxia?
- Inability to complete motor planning e.g. difficulty dressing oneself even when power is normal
- Often caused by damage to left frontal lobe
Is it common to see dysarthria/aphasia in an ACA infarct?
- Very unusual
- Much more common in MCA infarcts
What causes split brain syndrome/alien hand syndrome?
- ## Caused by involvement of corpus callosum which is normally supplied by the ACA
Give an overview of occlusion of the MCA?
- MCA supplies a large area of brain
- Effects are widespread
- 80% mortality if main trunk of MCA is affected due to resulting cerebral oedema
- Haemorrhagic transformation can occur if the vessels in the infarcted area break down
Where can the MCA be occluded?
- Proximal
- Lenticulostriate arteries
- More distal branches
How much of the MCA is affected if the proximal part gets occluded?
- All branches of MCA are affected, including lenticulostriates and distal branches to cortical areas
What are the motor effects of a proximal MCA stroke?
- Contralateral hemiparesis (face, arm and leg affected)
Why does a proximal MCA stroke cause contralateral hemiparesis?
- Internal capsule has been affected, which carries fibres to face, arm and leg
What are the sensory effects of a proximal MCA stroke?
- Contralateral sensory loss in the distribution of the primary sensory cortex supplied by the MCA (face and arm)
- Could involve larger areas if sensory fibres in the internal capsule are affected
What visual field defects are caused by a proximal MCA stroke?
- Contralateral homonymous hemianopia without macula sparing
Why does a proximal MCA stroke cause a contralateral homonymous hemianopia without macula sparing?
- Due to destruction of both superior and inferior optic radiations as they run through the temporal and parietal lobes
- More distal occlusions may affect one radiation alone, causing a quadrantanopia
What are some other features of a proximal MCA stroke?
- Aphasia
- Contralateral neglect
Why does a proximal MCA stroke cause aphasia?
- Global if dominant (usually left) hemisphere is affected
- Cannot understand or articulate words
Why does a proximal MCA stroke cause contralateral neglect?
- Usually due to lesions of right parietal lobe
- Is essentially an issue with not acknowledging that one half of the body and space does not exist
- Visual fields normal
- Can result in tactile extinction, visual extinction and anosognosia on affected side
What is the name given to a stroke caused by occlusion of the lenticulostriate arteries?
- Lacunar stroke
What does lacunar infarct do to the brain?
- Destruction of small areas of internal capsule and basal ganglia
What distinguishes a lacunar infarct from other kinds of stroke?
- These do not cause cortical features e.g. neglect or aphasia
What are the types of lacunar infarct?
- Pure motor
- Pure sensory
- Sensorimotor
What are the features of a pure motor lacunar infarct?
- Face, arm and leg are affected equally
- Caused by damage to motor fibres travelling through the internal capsule
- Due to occlusion of lenticulostriate vessels
What are the features of a pure sensory lacunar infarct?
- Face, arm and leg affected equally, caused by damage to sensory fibres travelling through internal capsule
- Most likely due to occlusion of thalamoperforator arteries
What causes a sensorimotor lacunar infarct?
- Caused by infarct occurring somewhere at boundary between motor and sensory fibres
What are the divisions of the MCA?
- Superior and inferior
What does the superior division of the MCA supply?
- Essentially supplies lateral front lobe
- Including primary motor cortex and Broca’s area
What will occlusion of the superior division of the MCA result in?
- Contralateral face and arm weakness
- Expressive aphasia if left hemisphere is affected
What does the inferior division of the MCA supply?
- Lateral parietal lobe and superior temporal lobe
- Includes primary sensory cortex, Wernicke’s area and both optic radiations
What will occlusion of the inferior division of the MCA result in?
- Contralateral sensory change in face and arm
- Receptive aphasia if left hemisphere
- Contralateral visual field defect without macula sparing (often homonymous hemianopia as both radiations are damaged)
What can occlusion of branches distal to the superior/inferior division of the MCA cause?
- Very specific effects
- E.g. taking out Broca’s areas specifically with no motor deficit
What are the symptoms of PCA occlusion?
- 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
What does Danish stand for in terms of cerebellar signs?
Dysdiadochokinesia
Ataxia (gait and posture)
Nystagmus
Intention tremor
Slurred, staccato speech
Hypotonia/heel-shin test
What are the symptoms of a cerebellar stroke?
- Nausea
- Vomiting
- Headache
- Vertigo/dizziness
- Ipsilateral cerebellar signs
- Possible ipsilateral brainstem signs
- Possible contralateral sensory deficit
- Ipsilateral Horner’s
Why do we get ipsilateral brainstem signs during a cerebellar stroke?
- Cerebellar arteries supply the brainstem as they loop around the cerebellum
What are the symptoms of brainstem strokes?
- A huge number of named syndromes
- Typical feature is contralateral limb weakness seen with ipsilateral cranial nerve signs
Why do brainstem strokes cause contralateral limb weakness and ipsilateral cranial nerve signs?
- This can be explained by damage to corticospinal tracts (above the decussation of the pyramids) and damage to cranial nerve nuclei on same side
What can basilar artery occlusion cause?
- Sudden death because this vessel supplies the brainstem
What does occlusion of the superior basilar artery cause?
- Visual and oculomotor deficits
- Behavioural abnormalities
- Somnolence, hallucinations, and dreamlike behaviour
- Motor dysfunction often absent
Why do superior basilar artery occlusions cause visual and oculomotor deficits?
- Basilar artery sends some branches to the midbrain which contains oculomotor nuclei
- Also, occlusion at this site can prevent blood flowing into the PCAs, affect the occipital lobes
What are the symptoms of proximal basilar artery occlusion?
- Can cause locked in syndrome
- Complete loss of movement of limbs
- Preserved ocular movement
- Preserved consciousness
Why does proximal basilar artery occlusion preserve ocular movement?
- Midbrain is getting supply from PCAs via posterior communicating arteries
What is the Bamford (Oxford) stroke classification?
- Clinical tool used to quickly diagnose strokes
