Anatomy and Physiology of Stroke Flashcards
What is a transiet ischaemic attack?
A stroke that resolves within 24 hours from the onset of symptoms
What are the two main types of stroke?
(name one additional cause)
Ischaemic (85%)
Haemorrhagic (10%)
venous sinus thrombosis / dissection
What are two common causes of emboli that can cause stroke?
Carotid Artery Atherosclerosis
Atrial Fibrillation
- Valvular Disease*
- Septic Emboli (endocarditis)*
Which two cerebral arteries comprise the anterior circulation of the brain?
Anterior Cerebral Artery
Middle Cerebral Artery
Which major artery of the head and neck supplies the anterior circulation of the brain?
Internal Carotid
Which arteries comprise the posterior circulation of the brain?
Posterior Cerebral Arteries
Cerebellar Arteries
Arteries Supplying Brainstem
Which area of the brain would be affected by an anterior artery occlusion?
medial aspect of frontal and parietal lobe
anterior part of corpus callosum
Which homuncular area corresponds to the medial aspect of frontal and parietal lobe?
motor and sensory innervation to
lower limb and genitals
How may a patient present with following stroke due to an anterior cerebral artery occlusion?
Motor
contralateral weakness of lower limb
Sensory
contralateral loss of all sensory modalities
What is the role of the paracentral lobule, where are they located and a stroke involving which vessel may lead to altered function?
controls micturation and defecation
located on medial aspect of hemisphere as a continuation of pre- and post-central gyri
anterior cerebral artery occlusion can lead to incontinence
Which area of the brain is supplied by the middle cerebral artery?
majority of the lateral hemisphere
(frontal, parietal and temporal lobe)
basal ganglia, internal capsule and macular cortex
Which homuncular area corresponds to the majority of the lateral aspect of the frontal and parietal lobes?
motor and sensory cortex
supplying the face, arms and trunk
Outline the conditon ‘malignant MCA’
occlusion of the middle cerebral artery
death of large amount of brain tissue
significant cerebral oedema > causing raised ICP
resulting in coma ± death
(decompressive hemicraniectomy illustrated)
Why do some patients with a stroke cause by MCA occulsion present with face, arm, trunk and leg weakness, whereas some may only present with face, arm and trunk weakness?
proximal occlusion of the MCA interrupts blood supply to the lenticulostriate arteries supplying the internal capsule
distal occlusion of the MCA spares the lenticulostriate arteries, results in motor weakness of the areas innervated from the lateral homunculus
(internal capsule contains ALL descening pathways from motor cortex)
As the middle cerebral artery has many branches, what visual defects may occur if the parietal and/or the temporal lobes are affected?
proximal occlusion of MCA
contralateral homonymous hemianopia
distal occlusion of MCA
contratateral homonymous superior or inferior quadrantinopiua (rare)
superior - parietal lobe affected / inferior - temporal lobe affected
Which hemisphere of the brain is most likely to be affected if a patinet presents with speech difficulties following a stroke?
How would a patinet present with a stroke affecting:
Broca’s Area
Wernicke’s Area
Both Broca’s and Wernicke’s Area
Left Hemisphere
- Broca’s Area
- expressive aphasia - struggle to find words
- Wernicke’s Area
- receptive aphasia - speaks fluently but nonsece
- Both Broca’s and Wernicke’s Area
- aphasic - does not understand or communicate
Which area of the brain is supplied by the posterior cerebral artery?
inferior temporal lobe
occipital lobe
cerebellum
brainstem
When a patinet suffers an occlusion of the posterior cerebral artery, which artery provides the collateral circulation to afford macular sparing with a homonymous hemianonia?
middle cerebral artery
What symptoms may a patient present with following a cerebellar stroke, caused by occlusion of the cerebellar artery?
think ‘DANISH’
- D - dysdiadochokinesia
- A - ataxis
- N - nystagmus
- I - intention tremor
- S - slurred speech
- H - hypotonia
What is a ‘cross deficit’ in the context of a brainstem stroke?
damage to long tracts (ascending and descending pathways) on contralateral side of body
damage to cranial nerves or their nuclei gives ipsilateral side
(e.g. CN III palsy)
Occlusion of which cerebral artery can be associated with ‘locked in’ syndrome if the lesion is very proximal, and why?
Basilar Artery
Why?
the pons contains corticospinal tracts (motor pathways), therefore occlusion will lead to quadraplegia, as well as loss of all cranial nerves except CN I, II, III, IV
Which area of the brain is supplied by the lenticulostriate arteries and from which major artery do they arise?
Supply Internal Capsule
Branch of Middle Cerebral Artery
The internal capsule can be divided into an anterior limb, posterior limb and genu; what function is provided by the posterior limb and genu?
Posterior Limb
carries descending motor fibres for entire body
Genu
contains the motor fibres for the face
Lesions of which structure will produce pure motor hemiparesis?
Internal Capsule
What will be the effect of a stroke affecting the left thalamoperforator artery (a branch of the posterior cerebral artery)?
pure sensory stroke
(as lesion affects thalamus)
asending inputs are not able to reach the post-central gyrus, therefore the patient will present with right sided sensory loss of ALL modalities
Although MRI is better at highlighting strokes in the hyperacture phase, why are CT scans often performed more frequently in the early stages?
identify haemorragic stroke
(patients not eligable for thrombolysis)
CT is quicker and cheaper to allow thrombolysis treatment to be started as soon as possible
