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