stroke 2 Flashcards
Define stroke
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
Define TIA
Transient ischaemic attacks (TIAs), sometimes colloquially called ‘mini strokes’, have similar clinical features of a stroke but completely resolve within 24 hours
What are types of stroke
Types of strokeoIschaemic (85%)
-Thromboembolico
Haemorrhagic (10%)
- Intracerebral (rupture of a vessel in brain parenchyma)
- Subarachnoid
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
What are the 2 main principles of emergency management of stroke
Two main principle
s 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)
How would CT/MRI appear in ischaemia and haemorrhage
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
What are the symptoms of ACE infarct
Contralateral lower limb weakness and sensory changes Urinary incontnence Apraxia Dysartrhria/Aphasia Split brain syndrome
What are the sensory changes in ACA
oAnterior cerebral artery (ACA) infarct
Contralateral weakness in lower limb
Lower limb affected much worse than upper limb and face
Contralateral sensory changes in same pattern as motor deficits (sensory homunculus in similar arrangement as motor homunculus)
Why do you get urinary incontinence in ACE infarct
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
What is apraxia and why does it occur in ace infarct
Inability to complete motor planning (e.g. difficulty dressing oneself even when power is normal)•Often caused by damage to left frontal lobe
What is dysarthria/aphasia and why doe it occur in aca infarct
A very unusual sign in ACA infarcts compared with MCA infarcts•May be related to frontal lobe damage
Why does split brain/alien hand syndrom occur
Split brain syndrome / alien hand syndrome (both rare)•Caused by involvement of corpus callosum which is normally supplied by the ACA
Give an overview of MCA infarct
oMiddle 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
MCA can be occluded at three main points
What are 3 points at which the mca can become occluded
Proximan main stem before lenticulostriate arteries come off
Lenticulostriate
More Distal branches
What are teh effects seen in a proximal MCA infarct
oIn this case, all branches of MCA will be affected including lenticulostriates and distal branches to cortical areas
- Contralateral full hemiparesis (face, arm and leg affected)
- Contralateral sensory loss
- Visual field degefects
- Aphasia
- Contralateral neglect
Why do you get contralateral full hemiparesis in MCA infarct (ie why is leg not spared)
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
Why do you get contralateral sensory loss in MCA infarct
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
What are the visual field defects seen in MCA infarct and why
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
Decribe aphasia in MCA infarct
oAphasia
Global if dominant (usually left) hemisphere affected)
•Therefore, cannot understand or articulate words
Why can neglect occur in MCA infarct and what are the typical features
oContralateral neglect
Usually in lesions of right parietal lobe (can be caused by occlusions of more distalbranches as well)
Essentially an issue with not ‘acknowledging’ that the usually left side of space or even your own body exists. Visual fields normal
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)
What are lacunar strokes?
•Lenticulostriate artery(ies) occluded
oAKA lacunar strokes
oCause destruction of small areas of internal capsule and basal ganglia
oEssential distinguishing feature from, say, a proximal MCA infarct is that they do not cause cortical features (e.g. neglect or aphasia
What are the types of lacunar stroke
oTypes
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)
Many other syndromes have been recognised which you need to know less abou
What ahppenes if the superior branch of MCA is occluded
oMCA splits into a superior and inferior division
Superior division essentially supplies lateralfrontal lobe
•Including primary motor cortex and Broca’s area
•Occlusion will cause contralateralface and arm weakness and expressive aphasia if left hemisphere affected
What happenes if the inferior division of MAC is occluded
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 contralateralsensory change in face and arm, receptive aphasia if left hemisphere and contralateral visual field defectwithout macular sparing (often homonymous hemianopia as both radiations damaged)
What happens in coclusion even more distal to sup/inf brances of MCA
oOcclusion of branches distal to superior/inferior division may produce even more specific effects,
e.g. taking out Broca’s areas specifically with no motor defici
Describe PCA infacrt
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
Describe cerebellar infarcts
oCerebellar 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
What are the cerebellar signs
Dysdiadochokinesia Ataxia Nystagmus Intention tremor Slurred speech Hypotonia
Desribe brain stem strokes
Brainstem strokes
A huge number of named syndromes (not important to know specifics)
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
Gibve an overview of basilar artery occlusion
oBasilar artery occlusion
As this vessel supplies the brainstem (which contains many vital centres), occlusion can sometimes cause sudden death
What happens in distal basilar occlusion
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)
Describ eproximal basilar occlusion
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)
What is the bramford/Oxford stroke classification
•Bamford (Oxford) stroke classification
oThis is a clinical tool to quickly diagnose strokes
oIt is based upon all the neuroanatomy you have learnt so far
oIt will be an informative exercise for you to go through the classificationand try to unpick the rationale for the different types
