10.1.1 MCA Stroke Flashcards
What is a stroke?
Cerebral vascular incident, serious life threatening condition that occurs when blood supply to the brain is cut off
What are TIAs?
Mini-strokes, completely resolve within 24 hours
What are the different types of stroke?
Ischaemia (85%)
Haemorrhagic (10%)
Other (5%)
What is an ischaemic stroke?
Thromboembolic
What is a haemorrhagic stroke?
Intracerebral rupture of a vessel in the brain parenchyma
Subarachnoid
What happens in other types of stroke?
Dissection- separation of walls of artery, can occlude branches
Venous sinus thrombosis- occlusion of veins causes back pressure and ischaemia due to reduced blood flow
Hypoxia brain injury- post cardiac arrest
What is the emergency management of stroke?
Thrombolysis (if under 4 hours)
CT head to determine a bleed
What acute imaging is used for strokes?
CT
- Ischaemic area of brain not visible early- as infarct becomes established will become hypodense
MRI
- Sometimes used
- Ischaemia shows up as a high signal area
What are the classic stroke syndromes of an anterior cerebral artery infarct?
- Contralateral weakness in lower limb
- Lower limb affected more than upper limb
- Contralateral sensory changes in same pattern as motor deficits
- Urinary incontinence- paracentral lobules affected
- Apraxia- inability to complete motor planning (e.g. cannot dress even when power is normal)
- Dysarthria
- Alien hand syndrome
Why do MCA strokes have such large effects?
MCA supplies large area of the brain
What is the chance of mortality if the main trunk of the MCA is affected?
80%
What are the 3 points the MCA can be occluded?
Proximally, before the lenticulostriates branch off
Lenticulostriate arteries
Distal branches
If the proximal MCA is affected what happens?
All branches of the MCA will be affected leading to:
- Contralateral full hemiparesis
- Contralateral sensory loss
- Visual field defects
- Aphasia
- Contralateral neglect
What causes contralateral full hemiparesis?
Internal capsule is affected which carries fibres to the face, arm and leg
About the internal capsule not the PMC
What causes contralateral sensory loss?
Involvement of the primary sensory cortex
What type of visual defects occur in MCA occlusions?
Contralateral homonymous hemianopia without macular sparing
Due to destruction of both superior and inferior optic radiations as they run through temporal and parietal lobes
More distal occlusions may affect one raidation alone, causing quadrantanopias
What happens in aphasia in MCA occlusions/strokes?
Global aphasia if dominant hemisphere (usually left)
Unable to understand or articulate words
What causes contralateral neglect?
Lesions of right parietal lobe
What is contralateral neglect?
Issue with not ‘acknowledging’ that the usually left side of space or even your own body exists
Normal visual fields
What are some other features of contralateral neglect?
Tactile extinction (if you touch each side simultaneously, won’t feel affected side)
Visual extinction (as with the clock)
Anosognosia (will not acknowledge they had a stroke, will confabulate to explain disabilities)
What happens in lectiulostriate artery occlusion?
Destruction of small areas of internal capsule and basal ganglia
Does not cause cortical features- neglect or aphasia
What are the different types of lenticulostriate strokes?
Pure motor
- Face, arm and leg affected equally
- Damage to motor fibres travelling through internal capsule
Pure sensory
- Face, arm and leg affected equally
- Damage to sensory fibres travelling through internal capsule- due to occlusion of thalamoperforator arteries, maybe lenticulostriates
Sensorimotor
- Mixed, caused by infarct occurring at boundary between motor and sensory fibres
What does the superior division of the MCA supply?
Superior divison supplies lateral frontal lobe, primary motor cortex and Broca’s area
What will happen in a superior division occlusion of the MCA?
Face and arm weakness and expressive aphasia if left hemisphere affected
What does the inferior divison of the MCA supply?
Lateral parietal lobe and superior temporal lobe, primary sensory cortex, Wernicke’s area and both optic radiations
What does an occlusion of the inferior divison of the MCA lead to?
Contralateral sensory change in face and arm
Receptive aphasia if left hemisphere
Contralateral visual defect without macular sparing- often homonymous hemianopia as both radiations damaged
