Stroke Flashcards
Hemiparesis
Hemiparesis is weakness or the inability to move on one side of the body
Hemiplegia
Hemiplegia is a condition caused by brain damage or spinal cord injury that leads to paralysis on one side of the body
Ischemic vs. hemorrhagic stroke
No symtom differences but vessel occlusion = ischemic stroke (80-90% of all strokes) and Intracranial bleeding = hemorrhagic stroke (10-20 % of all strokes)
Best therapy for strokes?
Prevention: no smoking, diabetes, low blood pressure etc.
Symptoms of stroke
Hemiparesis and Hemiplegia
Pathophysiology of stroke
Very complex. core components are vascular occlusions, glutamate relates, increase in intercellular Ca2+, free radical production and so on
Current therapies for stroke
Mechanical recanalization up to 24 hours later (destruction/removal or cloth) or Thrombolysis with recombinant t-PA (4.5-6 hours after, disolves cloth)
Limitations of current therapies for stroke
Suitable only for minority of patients
Narrow time window
High intracranial bleeding risk
3R Principle
1) Avoid animal experiments altogether (Replacement)
2) To limit the number of animals (Reduction)
3) their suffering (Refinement) in tests to an absolute minimum.
Craniotomy
A craniotomy is the surgical removal of part of the bone from the skull to expose the brain
Photocoagulation
Photocoagulation takes place by using the laser to create a microscopic burn in the target tissue
Vasogenic edema
Vasogenic edema is defined as extracellular accumulation of fluid resulting from disruption of the blood-brain barrier (BBB) and extravasations of serum proteins
Vasoconstriction
Vasoconstriction is the narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels
Microsphere
A Microsphere is a small spherical microparticle, with diameters typically ranging from 1 μm to 1000 μm (1 mm)
What types of stroke models exists
In-silico, in-vitro, ex-vivo and (most importantly) in-vitro (Genetically engineered/ mutated animals, Invasive methods in animals, Non-invasive methods for investigations of humans)
An ideal stroke models should:
… mimic the clinical situation
… be highly reproducible, controllable and standardized
… be easily to perform
… not produce side-effects within the brain
… allow physiological monitoring
… allow for analysis before (!) symptoms become visible (first minutes)
… allow for fast and direct access to brain tissue
… be cost effective
…and should be of limited ethical concern!
Intraluminal suture MCAO model
Use filament that is inserted in the CCA until it comes to the middle cerebral artery. One can do it in 5-7 min.
By occluding the middle cerebral artery, the have a highly comparable model for stroke. Advantage: fast to perform, easy access to tissue, we can use CCT stain to see the ischemic tissue.
You can see what mechanical recanalizing can do to the tissue, as it would be re-oxygenized
Pros: Mimics human ischemic stroke; penumbra; reproducible; reperfusion controllable; no craniectomy
Cons: Increased hemorrhage; not for thrombolysis studies
Bederson Score
from 0- 5 on global neurological ability. Test for severe motor deficits in the acute phase. Circling and spinning is considered bad (4), but not as bad a no movement (5)
Craniectomy model
Permanent Distal Middle Cerebral Artery Occlusion (including occlusion of both CCAs). Reduces collateral blood flow and thus consolidates the ischemic damage.
Pros: Long-term survival; visual conformation of success
Cons: Highly invasive; surgical skills needed; affects intracranial pressure
Photothrombosis model
Using Photoactive dye to and using the laser to create a microscopic burn in the target tissue.
Pros: Long-term survival; defined location; reproducible; low invasiveness
Cons: Early Vasogenic edema formation; not good for research in neuroprotective agents
Endothelin-1(ET-1) Model
Injecting a Vasoconstrictive peptide to decrease the circumference of the blood vessel. Leads to a dose dependent ischemic lesion and rapid cerebral blood flow reduction. Reperfusion will occur over hours
Pros: Low mortality; low invasiveness; lesions in cortical/subcortical regions
Cons: Duration of ischemia is not controllable; induction of axonal sprouting and astrocytosis, which can lead to biases
Embolic Stroke model
Inserting a microsphere or a thromboembolic clot to mimic a blood-clot. Pros: Mimics human pathogenesis best; appropriate to study thrombolysis
Cons: Spontaneous recanalization; High variability of lesion size
Analysis of experimental stroke
Functional outcome
- Behavior tests
Stroke size in the brain (most important)
- MRI/ Histology
Tissue analysis
- Molecular biology (PCR, qPCR)
- Protein analysis (Western blot, ELISA)
- Histology
- Flow Cytometry (Cells/Cytokines)
- Injection of tracersGrip Test
tests motor function, coordination and movement. Scored from 0-5.
Infarct volume
Infarct volume is a direct measurement of 1 of the final pathologic steps leading to the clinical deficits caused by an ischemic stroke
ischemia-reperfusion injury (IRI)
Reperfusion injury, sometimes called ischemia-reperfusion injury (IRI) or reoxygenation injury, is thetissue damage caused when blood supply returns to tissue (re- + perfusion)after a period of ischemia or lack of oxygen (anoxia or hypoxia)
no-reflow
The no-reflow phenomenon refers to the observation that when an organ is made ischemic by occlusion of a large artery supplying it, restoration of patency in that artery does not restore perfusion to the microvasculature supplying the parenchyma of that organ
Infarct volume
Infarction is tissue death (necrosis) due to inadequate blood supply to the affected area.
Platelets
Platelets, or thrombocytes, are small, colorless cell fragments in our blood that form clots and stop or prevent bleeding. Having them together with T cells can cause increased infarct volume in RAG1 deficient mice
Ladder rung walking task
For photosympotic stroke - shows recognition, coordination and motorfunctioning and is good long term, but takes training, more complex than a 1-5 rating
Only appoved drug againts strokes?
rt-PA (Alteplase), which is a ”clot-blaster” drug
Why don’t we have more drugs for clearing up strokes?
The reproducibility in studies are low
Studies are not comparable (different methods)
The publication bias
Possible solutions to getting more drugs for clearing up strokes approved?
To make the clinical trials in mice match the human conditions better - one proposal to that is the STAIR criteria:
Randomization, defining inclucion/exclusion criteria
Power and sample size calculations
Disclosure relevant conflict of interest
Aged animals, animals with comorbidities should be included
Male and female animals
Interaction studies with other medications
Relevant biomarker endpoints (e.g. diffusion/perfusion MRI)
What causes neuroinflamation in stroke
T-cells , as shown by the RAG1 defficint mouse-model, however, platelets have a modulatory (increasing effect)
Effectiveness in rapid recanalization?
Up to 80%
After how long do we see infarction after an induced Middle Cerebral Artery Occlusion stroke model?
8 hours
Which part of the platelets should be affected if we want to decrease it’s modulatory effect on T-cells leading to infarction?
The proteins associated with the early phases platelet activation (GPIb and maybe GPVI). Affecting later stage proteins which are responsible fo aggregation and thrombus growth might lead to hemorrhagic stages.
Targeting GPIb protects the brain from?
I/R-injury
Function of fingolimod (FTY720)
It inhibits the egress of the lymphocytes from the lymponode into the bloodcirculation and thereby redcuces the lymphocyte counts in the blood –> T cells can’t be damaging if they’re not in the blood. In strok it leads to less lession growth and less behavioral damage. This is also seen if the thrombolysis (clot-blaster) was given later
When a T cells detrimental and beneficial
For the subacute and chronic stroke: T-cell prevention does not make sense later in the process (in the chronic stage we have immunodepression, so it might be downright problematic to block the T-cells)
As the detrimental effects only occur in the hyper acute and the acute phases, where the T cells increase infarction
