2.3: 18. Ischemic Stroke

Front 1

What is ischemic stroke?

Back 1

Sudden neurological dysfunction due to vascular cause

Front 2

What is the epidemiology of ischemic stroke?

Back 2

Ischemic stroke accounts for 90% of all strokes
Fourth leading cause of death in US

Front 3

What is the mortality rate of ischemic stroke?

Back 3

20-30% mortality rate at 3 months when there is vessel occlusion

Front 4

What are the causes of ischemic stroke and what are the relative frequencies of each?

Back 4

Each accounts for 25% of all cases:

1) Cardioembolic stroke = source of clot came from heart
- Includes: atrial fibrillation (especially in elderly, atria are prone to irregular heartbeat), Valvular Heart Disease
2) Small vessel disease = occlusion of vessels 0.05 - 0.5mm in diameter (arterioles)
- Often due to: hypertension, diabetes
3) Large vessel disease = occlusion of vessels 1-4mm in diameter eg. carotid artery, middle cerebral artery (MCA)
- Often due to: high cholesterol
4) Unknown cause
- e.g. Stroke due to arterial dissection (tear - leads to clot), blood coagulation abnormality

Front 5

What is the basic distribution of blood vessels in the brain?

Back 5

Rostral brain:
- Internal carotid → bifurcates: ACA (medial) & MCA (lateral)
MCA → bifurcates: M2 segments (superior and inferior branches - designated for therapeutic purposes)

Caudal brain:
- 2 Vertebral arteries (1 is usually larger than the other)
- Vertebral join together → basilar
-- Branch off of vertebral → PICA
-- Branch off of basilar → AICA, SCA, PCA

Front 6

What are the symptoms of an MCA stroke?

Back 6

- Contralateral:
-- hemiparesis (weakness) - Face, Arm > Leg
-- hemianesthesia (sensory loss)
-- homonymous hemianopia
- Eyes deviate to side of lesion
- Left MCA stroke = Aphasia (difficulty communicating or understanding speech)
- Right MCA stroke = Left visual field Neglect (i.e: Asomatognosia - do not recognize own limbs)
-- 1/3 to 1/2 patients do recover from neglect

Front 7

What are the symptoms of a lacunar stroke?

Back 7

- Hemiparesis w/ out aphasia or neglect
- Brainstem Lacunes → crossed findings
- Examples:
-- Midbrain lesions:
--- Weber = CN3 Palsy + contralateral hemiplegia
--- Benedikt = CN3 Palsy + contralateral dysmetria
-- Pons lesion:
--- Millard- Gubler = stroke in pons = CN6 + CN7 Palsy + contralateral hemiparesis = crossed signs, ipsilateral face weakness, contralateral body weakness
-- MLF lesion (midline of the brain stem)
--- Internuclear Ophthalmoplegia (occurs ipsilateral to MLF lesion) = upon lateral gaze, the eye ipsilateral to the MLF lesion is unable to adduct and the opposite eye shows nystagmus = skewing of eyes. Convergence is still possible (because it is NOT a CN 3 palsy). [this was the a small group case]

* Lacunar Artery = single deep penetrating artery that arises directly from the constituents of the Circle of Willis, cerebellar arteries, and basilar artery

Front 8

What are the symptoms of a spinal cord infarction?

Back 8

Affects anterior portion of spinal cord
Occurs typically in setting of AAA (abdominal aortic aneursym) rupture or repair with hypoperfusion
Can be associated renal failure
Impaired motor (i.e: paralysis of legs) and pain/temp loss
Preserved position/vibration sense (which are found in dorsal column)

Front 9

What is NNT?

Back 9

Number Needed to Treat
Represents the number of people that need to be treated (with a drug, typically) for there to be a guaranteed effect in one individual. So, NNT 1 means every person that is treated is guaranteed to have an effect, while NNT 100 means that out of 100 patients treated, only 1 is guaranteed to have an effect

Front 10

What are proven treatments of acute stroke?

Back 10

- tPA - potent blood thinner/clot remover that clears obstructed vessels
-- The sooner it's used, the better - 90m -> NNT 3, 180m -> NNT 8, 270m -> NNT 23
-- Screening:
--- < 4.5 hours of stroke (need to know "time last known well")
--- No hemorrhage on CT
--- BP < 185/110
--- Glucose 50-400
--- Platelets > 100
--- INR < 1.7 (not on warfarin or other blood thinners)
--- No recent procedures
- Aspirin
-- NNT 100
-- Used for tPA non-eligibles
-- Needs be < 48 hours of stroke
- Stroke Units (area in hospital dedicated to stroke patient care)
-- NNT 20-30

Front 11

What are unproven treatments of acute stroke?

Back 11

Heparin and Heparinoids (not even in atrial fibrillation or large vessel atherosclerosis such as carotid stenosis)
Oxygen
Intravenous fluids = raises blood pressure and improves perfusion to brain
Laying head of bed flat = improve perfusion to brain
Modify BP = BP too high or too low is bad
Intra-arterial therapy = catheter to loosen clot in vessel (controversial)
- Recent trials show that this is not a beneficial treatment, maybe unless it’s done at hour 1 (not hour 5 or 6)

Front 12

What are the main components of stroke prevention?

Back 12

ABCDE
A: Antiplatelets - non-atrial fibrillation stroke, Anticoagulants - atrial fibrillation stroke
- Antiplatelets include aspirin and clopidogrel -> should not be combined > 12 months due to increased bleeding risk with no benefit
- Anticoagulants include warfarin, apixaban, rivaroxaban, dibagatran, all reducing intracranial hemorrhage risk, but increasing GI bleeding risk
B: Blood pressure control
- No ideal target, generally 140/90, lacunar <130/80
- With pharmacological (ACE inhibitors, ARB diuretics, Ca2+ channel blockers, B-blockers, A-blockers), non-pharmacology ( ↓ salt diet, DASH diet)
C: Carotid artery repair - surgery (carotid endarterectomy) or stent, cholesterol lowering, smoking cessation
- carotid artery narrowing happens and it is bad, bad cholesterol is bad, smoking is bad
D: Diet
- Low fat, high fruit/veggie
E: Exercise
30 mins/day, encourage exercise in post-stroke patients due to tendency to reduce physical activity