Stroke #1

Stroke: Risk Factors (Non-Modifiable)

male, advancing age, African-American, family history. 3rd most common cause of death in U.S., behind cancer and heart disease. 5.4 million Americans live with disabilities from stroke. 160,000 die annually from stroke in the U.S.

Hemorrhagic Stroke: Intracerebral Hemorrhage (ICH)

occurs when a small, deep-penetrating blood vessel ruptures and bleeds into brain tissue common sites: cerebral lobes, basal ganglia, thalamus, pons, and cerebellum

Hemorrhagic Stroke: Subarachnoid Hemorrhage (Manifestations- neck stiffness, Kernig sign, Brudzinski sign)

(nuchal rigidity), fever, irritability, restlessness knee is straightened and then flexed- produces pain in back and neck passive flexion of neck-neck pain and ↑d rigidity

Cerebral Autoregulation: What is compliance?

Ability of the brain to adapt

Classification of aneurysms: Dissecting

occurs when the intima of the vessel is torn and blood escapes the lumen through the tear Expanding mass occludes the vessel— 1/3 of patients die from initial hemorrhage May cause clots in the subarachnoid space, which can obstruct CSF flow leading to hydrocephalus and ↑d ICP

Classification of aneurysms: fusiform

spindle-shaped dilation of an artery, with tapering at either end Usually do not rupture, but develop from atherosclerotic changes that impair vascular elasticity Cause symptoms of cranial nerve compression, cerebral ischemia, or impaired CSF circulation

Collateral Circulation

the development of an alternative vascular channel in order to stabilize cerebral blood flow when the principal channel is occluded. Occurs when there is a gradual ↓ in CBF from the build-up of atherosclerosis.

Cerebral Autoregulation: Monro-Kellie Hypothesis

when one of the 3 components expands, the other 2 must compensate by ↓ing in volume

Cerebral Blood Flow Supplied by What Arteries

2 internal carotid arteries (anterior circulation) 2 vertebral arteries (posterior circulation)

How Strokes Occur

A blood vessel or artery is clogged or obstructed, which interrupts blood flow to a certain area of the brain OR A vessel or artery hemorrhages, with the blood itself interrupting blood flow to a certain area of the brain. Both deprive areas in the brain of O2. Cells deprived of O2 for a period of time begin to die; this area of dead tissue is called an infarction

Cerebral Autoregulation

Adequate cerebral blood flow (CBF) must be maintained at all times in order to ensure the constant delivery of sufficient O2 and glucose to the brain Cerebral Autoregulation: a compensatory mechanism that adjusts the diameter of cerebral blood vessels in response to changes in systemic arterial pressure or changes in arterial CO2 or O2 levels....purpose is to keep blood flow to the brain at a constant

Ischemic Stroke: Thromboembolism (Causes-amphetamine, cocaine)

Amphetamine users are 5 times more likely to suffer a hemorrhagic stroke, and cocaine is associated with a greater than two-fold ↑d risk of both hemorrhagic and thromboembolic stroke than nonusers Both drugs ↑ BP, vasoconstrict, damage vessel walls, and cause vasospasms

Cerebral Autoregulation: Chemoreceptors

Are also located in the aorta and carotid arteries. Initiate changes in response to chemical stimulation. Blood vessels alter the volume of blood flow through the brain by dilating or constricting EX: Blood flow to the brain ↑s when PaCO2 rises or the level of PaO2 drops

Ischemic Stroke: Embolic Stroke (Other Causes)

Artificial cardiac valve replacement is associated with emboli due to the rough surface vs. normal endocardium. Risk of emboli after MI is greatest in the first 2 to 4 weeks Bacterial vegetations from infectious endocarditis break off and cause emboli

What is the major cause of strokes

Atherosclerosis is a major cause of stroke. It causes thrombosis formation and contributes to emboli Ischemic strokes account for 85% of all strokes. Hemorrhagic strokes account for 15%

Hemorrhagic Stroke: Subarachnoid Hemorrhage (SAH)

Bleeding into the CSF-filled space between the arachnoid and pia mater. Usually caused by ruptured cerebral aneurysm which may be the result of a congenital defect or due to HTN Majority occur in the circle of willis Causes: trauma, AVM, illicit drug use

Thrombotic Stroke: Lacunar Stroke

Called small artery occlusive disease or "penetrating artery stroke." Patho: a small artery is occluded and a small cavity remains in brain tissue after dead tissue from the infarcted area has sloughed away Occurs primarily in deep areas of the brain, such as basal ganglia or thalamus... therefore, significant deficits often occur. HTN is the principal risk factor.

Cerebral Autoregulation: Baroreceptors

Change in pressure is sensed by baroreceptors located in the aorta and carotid arteries Either the SNS or PNS will be stimulated with an ↓ BP, stimulation of baroreceptors sends information to the brainstem inhibits the PNS and enhances the SNS causing ↑ in HR and vasoconstriction, which ↑s BP and maintains cerebral blood flow at a constant

Cerebral Blood Flow (CBF)

Changes in blood viscosity causes a change in CBF—anemia ↑s blood flow, polycythemia ↓s it Metabolic factors—high PaCO2 results in cerebral vessel dilation, with restoration of CBF Condition of blood vessels supplying the brain effects CBF—congenital anomalies (malformations, coiling, kinking of vessels), or atherosclerosis

Hemorrhagic Stroke: Intracerebral Hemorrhage (Causes)

Common cause: hypertension. *large hemorrhages usually originate from arteries. *small hemorrhages—veins and capillaries Other causes: tumors, trauma, thrombolytic drugs, ruptured congenital aneurysms, AV malformations (cluster of abnormal formed blood vessels; any one of these vessels can rupture causing bleeding in the brain), coagulation disorders, cocaine use

Thrombotic Stroke: Information

Common site is bifurcation of common carotid into the internal and external carotid arteries. *Most common stroke in diabetic patients. *Signs and symptoms progress slowly— SLOW ONSET *Tends to develop during sleep or within 1 hour after rising.

Ischemic Stroke: Thromboembolism (Causes-Hematological disorders)

Conditions that cause hypercoagulability and ↑d blood viscosity may lead to both thrombosis and embolism formation, as well as reduced CBF Disorders include: polycythemia (occurs with COPD); thrombocytosis (too many platelets, seen in certain types of cancer, can be genetic); oral contraceptive use; sickle cell disease

Thrombotic Stroke

Damage to the lining of an arterial wall and the formation of a blood clot. Clots narrows lumen of vessel-leads to eventual occlusion

Cerebral Autoregulation: ICP

ICP is the pressure exerted in the cranium by the contents of the vault (consists of 80% brain, 10% CSF, 10% blood)

Hemorrhagic Stroke Types

Intracerebral hemorrhage: causes blood to leak into the brain itself Subarachnoid hemorrhage: occurs when blood spill into the space surrounding the brain

Types of Strokes:

Ischemic: Thrombotic, Hemorrhagic

Hemorrhagic Stroke: Subarachnoid Hemorrhage (Manifestations)

May experience forewarning signs if aneurysm applies pressure to surrounding brain tissue Headaches are common and associated with leakage of aneurysm....occurs before major rupture Expanding hematoma impairs CSF reabsorption and CSF circulation, and it compresses and displaces brain tissue Other: decerebrate or decorticate posturing, pupil dilation and impaired gaze Vasospasm: causes ↓d CBF (ischemia) and can produce infarction

Ischemic Stroke: Thromboembolism (Causes- Illicit drug use)

Mechanism of infarction is multifactorial, including embolism from endocarditis, injection of foreign matter, an immune-mediated response altering cerebral blood vessels, or direct effect on the aorta or carotid arteries causing dissection and thrombus formation

Thrombotic Stroke: TIA's

Most caused by microemboli coming from atherosclerotic areas of the carotid or vertebral arteries. May be due to thrombus formation from ↓d blood flow through atherosclerotic arteries within the brain Starts suddenly and typically last between 2 - 60 minutes. Reversible without residual effects—blockage either breaks up quickly or nearby blood vessels compensate

Classification of aneurysms: saccular or "berry"

Most common and usually develops in the Circle of Willis Due to: -a congenital defect in the artery -a degenerative change in the internal wall elasticity that gradually weakens the arterial wall

Cerebral Autoregulation: Cerebral Blood Flow

Must be maintained— If interrupted, such as with cardiac arrest or stroke, neurologic.... *metabolism is altered in 30 seconds, *metabolism stops in 2 minutes, *cellular death occurs in 5 minutes If MAP falls below 70 or rises above 160 mmHg, CBF is altered Cardiac output must be reduced by ⅓ before CBF is reduced

Stroke: Risk Factors (Modifiable)

Obesity Hypercholesterolemia Prior TIAs DM—risk for stroke is 4 - 5 times higher HTN CAD Atrial fibrillation—responsible for 20% of all strokes LV hypertrophy Alcohol—heavy drinking Smoking—doubles the risk Oral contraceptives Emotional stress Migraines Polycythemia Sickle cell anemia Drug abuse

Hemorrhagic Stroke: Intracerebral Hemorrhage (Other)

Occurs during periods of activity Sudden onset of symptoms with progression over minutes to hours Mass of blood is formed as bleeding continues into brain tissue— adjacent brain tissue is displaced and compressed, producing ischemia and edema-->↓d CBF and ↑d ICP

Ischemic Stroke: Embolic Stroke

Occurs when an embolus lodges in and occludes a cerebral artery—results in infarction and edema of the area supplied by the involved vessel Most commonly affected artery—middle cerebral. Common embolus is plaque originating in the heart—breaks off from endocardium and enters circulation

Hemorrhagic Stroke

Results when a weakened blood vessel ruptures or leaks directly into brain tissue or in the space surrounding the brain Most common cause is chronic hypertension which causes degenerative changes in the walls of arteries Chronic HTN leads to cerebral aneurysm

Hemorrhagic Stroke: Intracerebral Hemorrhage (Manifestations)

Severe headache w/ N/V (d/t blood irritating brain tissues) ↓ LOC occurs in about 50% of patients, with neurological deficits such as weakness on one side, slurred speech, deviation of eyes.....progressing to hemiplegia, fixed and dilated pupils = herniation, nuchal rigidity, posturing, rapid progression into coma

Ischemic Stroke: Thromboembolism

Sometimes it is difficult to determine clinically whether a cerebral infarct results from emboli, thombus, or combination of the two. Thrombus of a vessel can lead to embolism of distal arteries

Ischemic Stroke: Embolic Stroke (Onset)

Sudden onset, rapid occurrence of severe clinical manifestations—occurs within 10 to 30 seconds— no time for development of collateral circulation No TIA's or forewarning signs; may or may not be related to activity No headache or slight headache develops on the side where embolus is lodged Patient has severe neurological deficits, sometimes followed by improvement, if clot breaks up and allows partial blood flow.

Thrombotic Stroke: TIA Manifestations

When carotid and middle cerebral arteries involved: Hemiparesis Aphasia Paresthesias—involving one side of the body Visual disturbances— temporary loss of vision in one eye When vertebral and basilar arteries involved: Dizziness Tinnitus Diplopia/Blurred vision Headaches Dysphagia/ Dysphasia Unilateral/Bilateral weakness

Hemorrhagic Stroke: Subarachnoid Hemorrhage (Manifestations-Rupture of aneurysm)

With onset: "explosive headache" with associated visual disturbances (photophobia and blurred vision), n/v, motor deficits, confusion, loss of consciousness— r/t dramatic rise in ICP

Thrombotic Stroke: Warning Signs

about 50% are preceded by a series of transient ischemic attacks (TIA) Risk for stroke is greatest within the first 48 hours after a TIA Temporary loss of normal neurological function caused by a transient (brief) interruption of blood flow to the brain

Hemorrhagic Stroke: Intracerebral Hemorrhage (Brain Herniation)

causes death in more than 50% of patients within first 2 days after ICH. No forewarning signs/symptoms

Cerebral Autoregulation: Cerebral Perfusion Pressure (CPP)

is the amount of blood flow from the systemic circulation that is required to provide adequate O2 and glucose for brain metabolism CPP= MAP-ICP Normal CPP is 70 - 100 mmHg. CPP must be at least 70 for adequate brain perfusion. CPP less 50 mmHg = cerebral ischemia and brain cell death. CPP less than 30 mmHg is incompatible with life. ICP = MAP no brain perfusion.

Ischemic Stroke: Embolic Stroke (Causes- Atrial Fibrillation)

most common cause—blood pools and thrombi forms in the atria as result of ineffective contraction embolized clot enters the circulation and passes to the brain—Risk of stroke ↑s 5-fold with AF and risk is even higher if patient has structural heart disease, HTN, and over the age of 65