Stroke Flashcards
What is a stroke?
A neurological deficit attributed to an acute focal injury of the CNS by a vascular cause, including cerebral infarction, intracerebral haemorrhage, & subarachnoid haemorrhage
What is a TIA (transient ischemic attack)?
A transient episode of neurological dysfunction caused by a focal brain, spinal cord or retina ischemia without acute infarction
What are the different types of strokes and their prevelance?
-
Ischemic (85%)
- due to thromboembolism
-
Haemorrhagic (10%)
- Extradural
- Subdural
- Subarachnoid
-
Other (5%)
- Dissection of carotid arteries
- Venous sinus thrombosis
- Hypoxic brain injury
What is the key difference in treatment between haemorrhagic vs ischemic strokes?
You DO NOT give haemorrhagic strokes thrombolytic agents (will increase bleeding)
You do give thrombolytic agents to ischemic
What are some of the causes of stroke in young people?
- Vasculitis
- Thombophilia
- Subarachnoid haemorrhage
- Venous sinus thrombosis
- Carotid artery dissection
What are some of the risk factors for thromboemboli → stroke?
- Hypertension
- Smoking
- Diabetes Mellitus
- Heart disease
- Peripheral arterial disease
- Post TIA
- Carotid artery occusion
- Polycythemia vera
- COCP
- Hyperlipidaemia
- Excess alchol
- Clotting disorders
What is the window for thrombolysis for ischemic strokes? What do you do if missed?
4.5 hours
If missed send patient to stroke ward for physiotherapy etc
How do you distinguish between ischemic vs haemorrhagic strokes on CT scans?
Ischemic: not visible early on → takes time to establish then becomes hypodense (dark)
Haemorrhagic: bright white area with mass effect
What are some of the causes of stroke in the elderly?
- Thrombus in situ
- Athero-thromboembolism (from carotid arteries)
- Heart emboli (AF, infective endocarditis, MI)
- CNS bleed (hypertension, head injury, aneurysm rupture)
- Sudden drop in BP >40 mmHg
- Vasculitis
- Venous sinus thrombosis
Explain what happens to neurones when they become ischemic?
- Grey matter (site of neuronal cell bodies) → infarct leads to permanent damage and death of neurone
- Hypoxia of an axon causes loss of ability to run Na+/ K+ ATPase
- Action potentials therefore inhibited
- Glial supporting cells die → demyelination of action
- Impulse transmission across region is affected
Where does the Anterior cerebral artery supply?
- Medial homunculus of primary motor cortex of frontal lobes
- Medial homonculus of primary sensory cortex of parietal lobes
- Paracentral lobule (cortical input onto M centre for micturition)
- Corpus callosum
What signs and symptoms will you see in an ACA infarction, and why?
-
Contralateral lower limb weakness
- Damage to medial primary motor cortex
-
Contralateral lower limb paraesthesia
- Damage to medial primary sensory cortex
-
Urinary incontinence
- Damage to paracentral lobule input to M centre
-
Alien hand syndrome
- Damage to corpus callosum
- Frontal lobe features
-
Apraxia (decreased motor planning)
- Damage to left frontal lobe
-
Dysarthria
- less common
Where does the middle cerebral artery supply?
- Lateral primary motor cortex of frontal lobe
- Lateral primary sensory cortex of parietal lobe
- Superior temporal lobe
- Superior optic radiations (parietal) and inferior optic radiations (temporal)
- Basal ganglia and internal capsule (via lenticulostriate arteries)
- Part of primary visual cortex that interprets macula vision
What signs and symptoms would you see in a proximal middle cerebral artery infarct?
- Contralateral FULL hemiparesis
-
Contralateral sensory loss of upper limb and face
- Damage of lateral primary sensory cortex in the parietal lobe
-
Contralateral homonymous hemianopia without macula sparing
- Due to destruction of BOTH superior and inferior optic radiations
-
Global aphasia (if left hemisphere)
- Broca’s and Wernicke’s affected
-
Contralateral hemineglect (if right parietal lobe)
- right parietal lobe responsible for awknowledgement of space on the left
Why do you see a contraleteral full hemiparesis in middle cerebral artery infarct and not just weakness of the arm and face as the homonculus would suggest?
As the MCA supplies the internal capsule where all the descending upper motor neurones supplying the contralateral supply of the body will be infarcted
What signs and symptoms do you see if the MCA is occluded at the leniculostriate arteries?
What is the name given to these types of stroke?
Lacunar strokes
Occlusion of the small arteries that supply the basal ganglia and internal capsule
Pure motor:
- Damage to UMN that descend through internal capsule
- Contralateral weakness of Face, arm and leg
Pure sensory:
- Damage of 3rd order sensory neurones that ascend through internal capsule
- Contralateral decreased sensation of face, arm & leg
Sensorimotor:
- If the infarction is at the boundary between sensory and motor fibres of the interna capsule
- Contralateral weakness and decreased sensation of the face arm and leg
What are the distal bifurcations of the MCA, what does each supply?
Superior division:
- supplies the lateral frontal lobe including lateral motor homunculus and Broca’s area (on left hemisphere)
Inferior division:
- supplies lateral parietal lobe including lateral sensory homunculus, superior optic radiation, Wernicke’s area and superior temporal lobe
Why do you get macula sparing if the PCA is occluded?
- Although the PCA supplies the occipital cortex
- If occluded, middle cerebral artery also supplies the macula
- Therefore, macula unaffected
Why can you get brainstem signs if cerebellar arteries are occluded?
Cerebellum arteries supply brainstem nuclei as they pass over the brainstem on their way to the cerebellum
What would you see if the superior basilar artery was occluded (distal to the pontine arteries)
-
Occulomotor defects
- sends branches to midbrain where the occulomotor nuclei are located
-
Visual defects
- Prevention of blood flow to PCA causes ischemia of visual cortex
- Behvaiour abormalities
-
Hallucinations
- Brainstem involved in sleep regulation
- NO MOTOR DYSFUNCYION
What would you see if the basilar artery was occluded involving the pontine arteries?
- Can infarct motor neurones as they descend through brainstem
-
Locked in syndrome
- Complete loss of movement in the limbs
- Preserved occular movement as midbrain (occulomotor nuclei) recieves supply from PCA
- Preserved conciousness
What is rule 1 of the rule of 4 for brain steam strokes?
- 4 CN nuclei located above the pons
- 4 located in the pons
- 4 located in the medula
What is the 2nd rule of the rule of 4s for brainstem strokes?
- 4 CN nuclei below the level of the midbrain are located in the midline
- CN 3,4,6 & 12 (all factors of 12)
- 5 CN nuclei below level of midbrain are located laterally
- CN 5, 7, 9, 10, 11
