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Stroke - Coggle Diagram

- - - - Thrombosis
        
        Result of rupture of atherosclerotic plaque in the intracranial arteries
        
        Activates platelet adhesion and clotting cascade to form occlusive thrombus
      - Embolism
        
        Typically from thrombus in heart of break off from atheroaclerotic plaques in the carotid arteries
      - Hypoperfusion
    - - Within sections to minutes of the loss of glucose + oxygen delivery to neurons, the cellular ischaemic cascade begins and neurons cease to function
        
        Normal electrophysiological function of the cells stops
        
        Neuronal and glial injury produced oedema in the hours post stroke -> further injury to surrounding tissues
    - - Anterior cerebral artery occlusions
        
        Primarily affect frontal lobe function
        
        Disinhibition and speech perseveration
        
        Primitive reflexes (e.g. grasping, sucking)
        
        Altered mental status
        
        Impaired judgement
        
        Contralateral weakness (greater in legs than arms
        
        Contralateral cortical sensory deficits
        
        Gait apraxia
        
        Urinary incontinence
        
        Rarest type of stroke
      - Middle cerebral artery occlusions
        
        Contralateral hemiparesis
        
        Contralateral hyperasethesia
        
        Ipsilateral hemianopia
        
        Gaze preference toward the side of the lesion
        
        Agnosia
        
        Receptive or expressive aphasia
        
        If lesion occurs in dominant hemisphere
        
        Neglect and inattention
        
        Non-dominant hemisphere lesions
        
        Weakness of the arm and face usually worse than lower limb
        
        MCA supplies the upper extremity motor strip
      - Posterior cerebral artery occlusions
        
        Vision and thought affected
        
        Homonymous hemianopia
        
        Cortical blindness
        
        Visual agnosia
        
        Altered mental status
        
        Impaired memory
    - - In acute stroke, ischaemia is more often incomplete, with the injured area of the brain receiving a collateral blood supply from uninjured arterial and leptomeningeal territories
        
        Therefore results in central irreversibly infarcted tissue core surrounded by peripheral region of stunned cells with reduced blood supply (pneumbra)
        
        Evoked potentials in the peripheral region are abnormal and cells have ceased to function, but this region is potentially salvageable with early revascularisation
    - - Main finding is abnormal cortical-subcortical area within a vascular territory
        
        Area is typically darker (hypoattenuation) than normalbrain due to oedema
        
        Extent of hypoattenuating area is crucial
        
        Presence in >1/3 of the MCA territory is a contraindication for revascularisation because of haemorrhagic complications
      - Has relatively low sensitivity in first 24 hours (especially within the limited 3-6 hour time window for thromblytic treatment)
      - Subtle signs include:
        
        Hyperdense vessel sign (high density thrombus occluding middle cerebral artery)
        
        Innability to visualise the left lentiform nucleus due to cytotoxic oedema (may be seen within first 2 hours of symptoms)
      - Faster, readily available, easy to interpret
    - - T1 is best for anatomic delineation
      - T2 shows fluid (e.g. CSF and oedema) as bright white
      - FLAIR (fluid attenuated inversion recovery) - by signal manipulation, free fluid (CSF) is dark whilst oedema may remain bright
      - Gradient echo sequence
        
        Makes blood products very dark
      - The types of pulses can be altered in a multitude of ways in order to detect different pathological findings
      - More specific and sensitive than CT for the detection within first few hours after onset
        
        Has additional benefit of depicting the pathologic entity (stroke and its minics) in multiple planes
      - Typical MRI findings include hyperintense (brighter than normal) signal in white matter on T2-weighted images and fluid-attenuated inversion recovery images, with a resultant loss of gray-matter-white-matter differentiation on T1 weighted imaging analogues
      - Newer MRI sequences e.g. diffusion weighted imaging (MWI) have been proven to be very sensitive to hyperacute strokes
      - Underlying principles
        
        Normal mortion of water molecules in living tissues is random
        
        In stoke, homeostasis is altered (intracellular vs extracellular)
        
        Extracellular water accumulation (cytotoxic oedema) with a decreased rate of extracellular diffusion within the affected tissue
        
        On diffusion-weighted images, ischaemic tissue appears bright in comparison with normal brain tissue
    - - Iodine based fluid injected
        
        Infarcted core shows almost no blood flow however penumbra shows less than normal brain but more than infarcted core