Session 10 Stroke Flashcards
(19 cards)
Define stoke
Aka ‘cerebrovascular accident’
It 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
How is a TIA different from a stroke?
TIA = transient ischaemic attack or ‘mini stroke’
They have similar clinical features of a stroke but completely resolve within 24 hours
What are the types of stroke and which one is the most common?
- Ischaemic (85%) = most common!
- thromboembolic
- Haemorrhagic (10%)
- intracerebral (rupture of a vessel in brain parenchyma)
- subarachnoid
- Other (15%)
- Dissection = separation of walls of an artery, can occlude branches
- venous sinus thrombosis = occlusion of veins causes back pressure and ischaemia due to reduced blood flow
- hypoxic brain injury e.g. post cardiac arrest
What are the two main principles of emergency management of stroke?
- are they within the window for thrombolysis? = ( <4 hours)
- do a head CT to determine if it is a bleed (if it is they you can’t proceed with thrombolysis!!)
How would stoke show up using CT or MRI ?
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
If someone has a anterior cerebral artery (ACA) infarct - what would some signs and symptoms?
Contralateral weakness in lower limb
(Lower limb would be affected much worse than upper limb and face)
Contralateral sensory changes in same pattern as motor deficits
Urinary incontinence due to paracentral lobules being affected
* paracentral lobules = the most medial part of the motor/sensory cortices and supply the perineal area
Apraxia = inability to complete motor planning
- difficulty undressing 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 callosum which is normally supplied by the ACA
What symptoms and signs would you se with a middle cerebral artery (MCA) infarct?
- MCA supplies a large area of brain so these strokes can have a very widespread effect 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 happens if the MCA is occluded proximally? I.e. the main stem - before the lenticulostriate arteries come off
- in this case - ALL branches of MCA will be affected including the lentoculostriate and distal branches to cortical areas
- contralateral fill hemiparesis (face, arm and leg)
- as internal capsule is affected
- contralateral sensory loss
- in the distribution of primary sensory cortex supplied by MCA
- visual field defects
- usually contralateral homonymous hemianopia with our macular sparing
- due to destruction of both superior and inferior optic radiations as they run through (superior) temporal and parietal lobes
- more distal occlusion may affect one radiation alone causing quadrantanopias
- aphasia
- global if dominant (left) hemisphere affected - cant understand or articulate words
- contralateral neglect
- usually in lesions of RPL
- an issue with not ‘acknowledging’ that the usually left side of space exists
What are the features of contralateral neglect?
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 confabulation to explain disability
What happens if the lenticulostriate artery(ies) is occluded?
What are the types of this stroke?
= lacunar strokes
- cause destruction of small areas of internal capsule and basal ganglia
- essential distinguishing feature from (for example - proximal MCA infarct) is that these ones DO NOT cause cortical features like neglect or aphasia
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 left affected equally, caused by damage to sensory fibres travelling through internal capsule probably due to occlusion of thalamoperforator arteries)
- Sensorimotor (mixed, caused by infarct occurring somewhere at boundary between motor and sensory fibres)
The MCA splits into a superior and inferior division. What do each of these divisions supply and what would happen if they were occluded?
Superior division = lateral frontal lobe (including primary motor cortex and Broca’s area)
Occlusion = contralateral face and arm weakness and expressive aphasia if left hemisphere affected
Inferior division = lateral parietal lobe and superior temporal lobe (including primary sensory cortex, Wernicke’s area and both optic radiations)
Occlusion = contralateral sensory change in face and arm, receptive aphasia if left hemisphere and contralateral visual field defect without macula sparing (often homonymous hemianopia as both radiations damaged)
What would happen if the posterior cerebral artery were to become occluded?
Contralateral homonymous hemianopia (with macular sparing due to collateral supply from MCA)
Contralateral sensory loss due o damage to thalamus
What are the symptoms of cerebellar infarcts?
Nausea
Vomiting
Headache
Vertigo / dizziness
What are the signs of a cerebellar infarct?
Ipsilateral cerebellar signs = DANISH
Possible ipsilateral brainstem signs since cerebellar arteries supply brainstem as they loop round to the cerebellum
Possible contralateral sensory deficit or ipsilateral Horner’s
(Due to brainstem involvement)
What is a typical feature of a brainstem stroke?
Contralateral Limb weakness is seen with ipsilateral cranial nerve signs
This can be explained by damage to corticospinal tracts (above decussation of pyramids) an damage to cranial nerve nuclei on same side
What vessel supplies the brainstem?
Basilar artery - if occluded can cause sudden death
What would happen if you had an occlusion of the 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 the PCAs affecting occipital lobes)
Behavioural abnormalities
Somnolence, hallucinations an 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 PCAs which in tern are being filled by the posterior communication arteries
What would happen if you had a proximal basilar occlusion (at level of pontine branches)
Locked in syndrome
Complete loss of one emend of limbs but 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 Bamford (Oxford) stroke classification?
A clinical tool to quickly diagnose strokes
Based upon all the neuroanatomy we have learned so far
