Cerebrovascular Stroke

8/3/2019 Cerebrovascular Stroke

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NEUROANATOMY


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BLOOD SUPPLY OF THE BRAIN


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Definition

A stroke is the death of brain tissue that occurs when the brain

does not get enough blood and oxygen.

Types of stroke

Ischemic stroke: About 80 percent of strokes are ischemic

strokes. They occur when blood clots or other particles block

arteries to the brain and cause severely reduced blood flow

(ischemia). This deprives the brain cells of oxygen and nutrients,

and cells may begin to die within minutes. The most commonischemic strokes are:

Thrombotic stroke.This type of stroke occurs when a bloodclot (thrombus) forms in one of the arteries that supply blood

to your brain. A clot usually forms in areas damaged by

atherosclerosisa disease in which the arteries are clogged

by an accumulation of cholesterol-containing fatty deposits

(plaques). This process can occur within one of the twocarotid arteries of the neck that carry blood to the brain, as

well as in other arteries. An ischemic stroke may also be

caused by plaques that completely clog or markedly narrow

an artery. This narrowing is called stenosis.

Embolic stroke.An embolic stroke occurs when a blood clotor other particle forms in a blood vessel away from the brain

commonly in the heart and is swept through the

bloodstream to lodge in narrower brain arteries. This type ofblood clot is called an embolus. It's often caused by irregular

beating in the heart's two upper chambers (atrial fibrillation).

This abnormal heart rhythm can lead to poor blood flow and the formation ofa blood clot.


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Hemorrhagic stroke

"Hemorrhage" is the medical word for bleeding. Hemorrhagicstroke occurs when a blood vessel in the brain leaks or ruptures.

Hemorrhages can result from a number of conditions that affect the

blood vessels, including uncontrolled high blood pressure

(hypertension) and weak spots in the blood vessel walls

(aneurysms). A less common cause of hemorrhage is the rupture of

an arteriovenous malformation (AVM) a malformed tangle of

thin-walled blood vessels, present at birth. There are two types of

hemorrhagic stroke:

Intracerebral hemorrhage.In this type of stroke, a blood vesselin the brain bursts and spills into the surrounding brain tissue,

damaging cells. Brain cells beyond the leak are deprived of

blood and are also damaged. High blood pressure is the most

common cause of this type of hemorrhagic stroke. High

blood pressure can cause small arteries inside your brain tobecome brittle and susceptible to cracking and rupture.

Subarachnoid hemorrhage.In this type of stroke, bleedingstarts in a large artery on or near the membrane surrounding

the brain and spills into the space between the surface of your

brain and your skull. A subarachnoid hemorrhage is often

signaled by a sudden, severe "thunderclap" headache. This

type of stroke is commonly caused by the rupture of an

aneurysm, which can develop with age or result from agenetic predisposition. After a subarachnoid hemorrhage,

vessels may go into vasospasm, a condition in which arteries

near the hemorrhage constrict erratically, causing brain cell

damage by further restricting or blocking blood flow to

portions of the brain.


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Clinical Features

Transient ischemic attacks (TIAs): Sudden vascular-related focal

neurologic deficit that resolves completely and lasts < 24 hr,

generally < 1 hr.

Acute ischemic stroke:

Anterior cerebral artery (ACA):contralateral legweakness

Middle cerebral artery (MCA):contralateralhemiparesis and hemisensory deficit (face + arm > leg);

aphasia (dominant hemisphere) or neglect

(nondominant hemisphere); contralateral visual-field

defect; deviation of gaze; dysarthria; and other cortical

symptoms

Posterior cerebral artery (PCA):occipital infarctionand contralateral visual-field loss; contralateral

hemiparesis; behavioral changes

Vertebral arteries or basilar artery: crossed facialsensory and body motor signs; diplopia; facial

numbness and weakness; vertigo; nausea and vomiting;tinnitus; hearing loss; ataxia; gait abnormality;

hemiparesis; dysphagia; and dysarthria.

Penetrating vessels: pure motor hemiparesis, puresensory stroke, clumsy handdysarthria syndrome, or

ataxic hemiparesis.

Hemorrhagic stroke

Subarachnoid(5%): Severe headache

Rapid onset Photophobia Stiff neck


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Decreased level of consciousness Focal neurologic signs

Intracerebral(intraparenchymal) (15%)

Severe headache Focal neurologic signs (resembles ischemic stroke)

Risk Factors

Risk factors for stroke are classified into 3 categories: non-

modifiable, well-documented modifiable, and less well-documented or potentially modifiable.

Non-modifiable factors

Increasing age. A person's risk of stroke doubles each yearafter age 55.

Race. Strokes occur approximately twice as often in blacksand Hispanics as they do in whites.

Gender. Men have a 50% higher chance of stroke thanwomen do.

Family history of stroke or transient ischemic attack(TIA). ATIA is a short, reversible form of stroke that may serve as an

early warning sign of stroke

Modifiable risk factors

High blood pressure Smoking Diabetes
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Sickle cell anemia, a blood disorder that forms abnormal redblood cells

High cholesterol levels in the blood, including totalcholesterol and LDL or "bad cholesterol." Low levels of

HDL or "good cholesterol" are also cause for concern Atrial fibrillation, an abnormal heart rhythm

Potentially modifiable risk factors

ObesitySedentary lifestyleAlcohol abuseHigh blood levels of homocysteine, a blood component

sometimes associated with a higher risk of stroke

Drug abuseBlood disorders, such as blood that clots easily or

deficiencies of various blood components

Hormone replacement therapy (HRT). The AHA currentlystates that the risk of stroke associated with HRT appears low

but needs further study.

Use of birth control pills, or oral contraceptives

Investigations

Non-contrast CT to distinguish ischemic stroke fromhemorrhagic stroke

Brain MRI & MRA

CT-angiography (CT-A)Carotid duplex ultrasoundTranscranial Doppler ultrasoundElectrocardiogramTransthoracic echocardiogram (TTE) or trans-

oesophageal echocardiogram (TEE)
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Iintracerebral hemorrhage-Ventricular hemorrhage


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Investigations (cont.)

Laboratory tests:

Fasting lipids within 48 hours of symptom onsetComplete blood countPT & PTTChemistry panel (KFT, LFT, FBS, 2hrsPP)

Management of acute ischemic stroke

Intravenous recombinant tissue plasminogen activator (rt-PA) assoon as possible after onset of symptoms

Indications:

Firm clinical diagnosis of potentially disabling stroke Onset of symptoms or last time seen normal < 3 hr ago

Absolute contraindications

Onset > 3 hr ago or patient not seen normal within previous 3hr

Intracranial mass lesion or hemorrhage on non-contrast headCT

Previous stroke or serious head trauma within previous 3 moAny history of intracranial hemorrhageCurrent use of anticoagulants with PT > 15 sec or use of

heparin within the past 48 hrPlatelets < 100,000/mm3Presenting symptoms suggestive of subarachnoid hemorrhage

(worst headache of patient's life)


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Blood pressure > 185/110 mm Hg unless minimal doses of asmooth-acting I.V. agent such as labetalol were sufficient to

lower below this range

Previously known cerebral aneurysm or arteriovenousmalformation

Relative contraindications:

Glucose < 50 or > 400 mg/dlSeizure at stroke onsetMajor surgery within 14 daysArterial puncture at a non-compressible site or lumbar

puncture within 1 wk

Rapidly improving symptoms suggestive of TIAGI or GU hemorrhage within 21 daysDose: 0.9 mg/kg (maximum dose, 90 mg) infused over 1

hour, with 10% of the total dose infused over the first minute;

if treatment with rt-PA is suspected of inducing intracranial

hemorrhage, the infusion should be suspended

Aspirin (160 to 325 mg daily) administered within 48 hr of

stroke onset; aspirin should be withheld for at least 24 hr afteradministration of thrombolytics

Reduction of risk factors

Management of cardioembolismControl hypertension Tobacco use Hyperlipidemia DiabetesEncourage exercise


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Stroke prevention

Aspirin (160325 mg/day)Clopidogrel (75 mg)Dipyridamole (extended-release) + aspirin

Management ofIntracerebral Hemorrhage

Surgical evacuation of hematomaVentricular drainage for hydrocephalusOsmotic diuretics before hematoma evacuationMannitol load, 0.51.0 g/kg I.V.; maintenance dose, 0.251.0

g q. 6 hr; titrate to keep serum osmolality 300310 mOsm/kg

H2O

Further supportive care as for ischemic strokeManagement ofSubarachnoid Hemorrhage

Emergency CT scanAnticonvulsants at first sign of seizureBlood pressure should be gently, not drastically, controlled

Begin Nimodipine on the first day and continue for 21 daysPatients should be well hydrated, and blood pressure should

be slightly high

Surgical clipping or endovascular coiling within 72 hr ofonset

After clipping, daily Transcranial Dopplerexaminations tomonitor vasospasm


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Cerebrovascular Stroke

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