2- Stroke: Anatomy and Stroke syndrome (3) Flashcards
cerebral circulation is made up of
anterior circulation
posterior circulation
anterior circulation
Internal carotids ascend up carotid canal and become the middle cerebral arteries
Other branches of internal carotids:
- Anterior cerebral arteries
- Anterior communicating arteries connect both ACAs
- Posterior communicating arteries (connect anterior and posterior circulation)
posterior circulation
- Vertebral artery join together to form basilar artery
- Branches of VA
- Posterior inferior cerebellar arteries (PICA)
- Anterior spinal artery
- Branches come off each VA to converge and form the ASA (runs down surface of the spinal cord)
- Anterior inferior cerebellar arteria (AICA)
- Branches of VA
- Basilar artery- one of the few midline arteries in the body (use as main landmark)
- Branches of BA
- Many small branches going into the pons- Pontine arteries (supplying corticospinal fibres running down through the pons)
- Superior cerebellar artery
- 2 posterior cerebral arteries
- Branches of BA
Anterior cerebral artery supplies which area of the brain
- Doesn’t actually supply many anterior structures
- Supplies structures near to the midline
- Arises as one of the branches of the internal carotid (as well as MCA)
- Grey matter distribution: ACA loops back all over the superior surface of the corpus callosum and sends multiple branches to the medial aspect of the cerebral hemisphere (mostly frontal and parietal lobes)
- White matter distribution: as the ACA loops around the CC it will send lots of branches into the white matter of the CC
if ACA occluded e.g. ischaemic stroke
-
Medial areas of the sensory and motor homunculus affected
- Contralateral lower limb more affected
-
Paracentral lobules containing M centre- found in the medial portion of the frontal lobe
- Incontinence
-
Corpus callosum
- Split brain syndrome- Both hemispheres cant communicate meaning limbs wont work together
-
Frontal lobe
- Personality changes
- Apraxia changes- coordinating motor plans e.g. doing laces up
Subfalcine herniation
Can cause ACA stroke due to compression of artery
Most common form of intracranial herniation and occurs when calcarine sulcus is pushed under the falx cerebri compressing the ACA leading to stroke syndrome
Middle cerebral artery
- Supply very large area of the brain
- Arises as a continuation from the internal carotids
- Run laterally and go over the insular cortex and emerges through sylvian (lateral fissure) fissure onto the surface of the cerebral hemisphere
- Branches of the MCA= the lenticular striate arteries which supplies the basal ganglia
- Branches of the MCA emerge superiorly and inferiorly from the sylvian fissure (look at third photo) supplying the lateral aspect of the cerebral hemisphere supplying some
- Frontal
- Parietal
- Temporal lobes
- Also supplies some deeper structures
If MCA occluded e.g. stroke
- Primary motor cortex could be affected
- Lenticular striate arteries some of the most common arteries to be blocked
- Fibres in optic radiation can be affected
The lenticulostriate (lateral striate) arteries
The lenticulostriate (lateral striate) arteries
- Most commonly occluded arteries in stroke
- Can lead to lacunar stroke/infarct (very diverse clinical effects)
- Numerous very small branches
- Lenticulostriate arteries branch of the MCA as it runs laterally and into the lentiform nucleus and into the internal capsule and sometimes into the thalamus
lacunar infarcts can be found in the
- Basal ganglia
- Parkinsonian disorder
- Internal capsule
- If lacunar occurs here- pure motor stroke since internal capsule mostly contains cortical spinal projections
- Near the thalamus
- If lacunar found here- pure sensory stroke (sensory relay station)
summary of cerebral perfusion territories
proximal MCA occlusion will affect
Will affect everything downstream too e.g.
- lenticulate striate arteries
- inferior and superior arteries of the MCA
Common → internal carotid directly supplies the MCA
presentation of a proximal MCA occlusion
Contralateral:
- hemiparesis
- Sensory deficit (often soley face and arms- think lateral area of homunculus)
- homonymous hemianopia
if left sided: aphasia
if right sided (more common): left sided hemispatial neglect
why are proximal occlusion strokes more common on the right side
left parietal region has dual bilateral blood supply
proximal MCA occlusion: contralateral hemiparesis
Contralateral upper limb and face motor problems due to the lateral motor homunculus being affected
why is complete hemiparesis usually seen in proximal MCA occlusion if its the lateral homunculus thats affected
- Actually clinically we usually see a complete hemiparesis → flaccid → spastic hemiparesis
- Why? Because the MCA also supplies the internal capsule (lenticulate striate arteries) which carries fibres from the face, arm and leg
presentation of proximal MCA occlusion: contralateral sensory deficit
-
Problems with the lateral sensory homunculus
- Upper limbs and face sensory problems
- Like likely to be full body sensory problems
- Because the posterior parts of the internal capsule are supplies by the PCA- therefore mismatch between sensory and motor deficits
presentation of proximal MCA occlusion: problems with vision
- Contralateral homonomous hemianopia
- Destruction of both superior and inferior optic radiations as they run through the temporal and parietal lobes
presentation of proximal MCA: aphasia
-
Broca’s aphasia (frontal)
- Reduction in speech fluidity
-
Wernicke’s aphasia (temporal/parietal)
- Problems with understanding language
- If proximal occlusion= both Broca’s and Wernicke’s
presentation of proximal MCA: neglext like symptoms
- Lesions which affect the right parietal lobe
- Pt has issue with acknowledging what is going on, on the LHS
- E.g. may only eat half of the meal
lenticulostriate artery occlusion
- Due to small emboli coming up from the internal carotid
- Lacunar stroke cause destruction of small areas in the internal capsule and basal ganglia
if lacunar infarct in thalamus
sensory deficit
if lacunar infarct in the internal capsule
- E.g. could occur on the posterior arm of the internal capsule and cause motor problems with the leg, trunk or arm
- E.g. At the genu= face motor problems
- If in both thalamus and internal capsule= mixed sensory and motor deficits
distal MCA occlusion
affect either the superior or inferior division of the MCA
distal MCA occlusion: superior division problems
- Supplies the lateral frontal lobe e.g. primary motor cortex and the Broca’s area
- Examples of superior division problems
- Contralateral face and arm weakness
- Broca’s (Expressive) aphasia
- Only if occurs on the LHS
distal MCA occlusion: inferior division problems
- Supplies the lateral parietal lobe and the superior temporal
- Examples of inferior division problems e.g. primary sensory cortex and Wernicke’s area
- Contralateral face and arm loss of sensation
- Wernicke’s aphasia
- Homonomous hemianopia if both optic radiations are damaged or a quadrantanopia if just one radiation is affect
- Without macula sparing
describe the vertebra-basilar system
- Left vertebral artery forms basilary artery (running over surface of the pons)
- Basilar artery bifurcates into the Posterior Cerebral Artery and just proximally the superior cerebellar artery à both supplying the midbrain as they reach their ultimate targets
- Pontine branches on the basilar artery supply the pons
- Important to ensure the cortical spinal tract is perfused
- If occluded and not perfused- locked in syndrome (can only move eyes)
- Cortical spinal tract death à no movement
- Midbrain still supplied so can move eyes
- If occluded and not perfused- locked in syndrome (can only move eyes)
- Anterior inferior cerebellar arteries supply the inferior surface if the cerebellum. Pons also receives branches from the AICA
- Posterior inferior cerebellar artery (PICA) supplies the posterior inferior surface of the cerebellum. Medulla oblongata also receives branches from the PICA
- If blockage distal- cerebellar stroke
- If blockage proximal – brainstem stroke
- Anterior medulla is supplied by branches coming off the vertebral arteries itself
arterial supply to the cord
-
Major vessels
- Anterior spinal artery (runs in the anterior sulcus of spinal cord)
- Arises as the confluence of 2 branches of VA
- Supplies anterior 2/3 of spinal cord
- Paired posterior spinal artery (dorsal aspects)
- Supplies posterior1/3 of spinal cord
- Anterior spinal artery (runs in the anterior sulcus of spinal cord)
- These major arteries are supplied mostly by segmental a. coming off the aorta
- Another important artery to think about: Adamkiewicz arteriesà major tributary to the lower part of the spinal cord
- Particularly vulnerable in AA aneurysm repairs à spinal cord syndromes
Anterior spinal artery supplies
the anterior 2/3 of the spinal cord
Bilateral symptoms
* Grey matter of ventral horn * Corticospinal tract * Spinothalamic tract
Posterior spinal arteries supply the
posterior 1/3 of the spinal cord
- More frequently unilateral (paired arteries)
- Ipsilateral loss of Dorsal column modality below level of blockage
presentation of PCA occlusion: HH with macula sparing
- Contralateral Homonomous hemianopia with macula sparing
- If MCA damaged- everything will be destroyed (doesn’t matter if we have a contralateral supply by the PCA to the macula)- the damage is done
- If PCA occlusion causes damage to the optic radiations, you still have contralateral supply to macula from the MCA therefore macula sparing
presentation of cerebellar artery occlusion: ipsi horners syndrome
Superior and inferior cerebellar arteries wrap around the brainstem
- Can also affect sympathetic running laterally
basilar artery occlusion
can lead to sudden death- supplies brainstem
basilar artery occlusion: occlusion affecting superior aspect of brainstem
visual and oculomotor defects
basilar artery occlusion: occlusion which spans both side of the basilar artery (inc pontine arteries)
- Circle of Willis is a circular therefore can supply most of the cerebral area and the vertebral arteries can supply the some of the brainstem and cerebellar
- Therefore will be a small lesion but can have a large clinical effect e.g. Locked in syndrome
- Complete bilateral motor response
- Can only do oculomotor movements because occurs below the oculomotor nuclei
- Preserved consciousness
how are stroke syndrome classfiied
oxford/ bamford stroke classification system
