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Understanding StrokeBrain Anatomy and

Cerebral Circulation

Revised June 2007

Cathy Corrigan-LauzonHRSRH Enhanced District Stroke

Program

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What is a Stroke?

“Stroke” is a term used to describe neurological changes lasting more than 24 hours caused by an interruption in the blood supply to a part of the brain. If the blood flow ceases for an extended period of time, the cerebral tissues involved die causing permanent neurological deficits.

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Cerebral Circulation Review

Brain derives its arterial supply from carotid and vertebral arteries

Carotid and vertebral arteries begin extracranially Internal carotid arteries and branches supply

anterior 2/3 of cerebral hemispheres Vertebral and basilar arteries supply posterior

and medial regions of hemispheres, brainstem, cerebellum and cervical spinal cord

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Cerebral Blood Supply

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Cerebral Blood Supply – side view

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Middle Cerebral Artery

http://www.strokecenter.org/education/ais_vessels/ais049b.html

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Posterior Cerebral Circulation

http://www.strokecenter.org/education/ais_vessels/ais049c.html

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Circle of Willis Sits at the base of

the brain Joins the anterior

and posterior circulation

Important route of secondary or collateral circulation

Most common site for congenital aneurysm

http://www.strokecenter.org/education/ais_vessels/ais048.html

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Location

http://www.nlm.nih.gov/medlineplus/ency/imagepages/18009.htm

10http://www.meddean.luc.edu/lumen/meded/Neuro/neurovasc/navigation/cow.htm

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The Brain

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Frontal Lobe Blood supply - ACA and MCA Major functions:

personality, behaviour motor function judgement/problem solving micturation expressive speech - Broca’s

word formation, articulation andspeech production

concentration, reasoning

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Parietal Lobe

Blood supply – ACA, MCAand PCA

Major functions: sensory function body part awareness visual spatial information

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Temporal Lobe

Blood supply - MCA and PCA Major Functions:

understanding speech -Wernickes visual, olfactory and auditory

perception learning, memory, emotional affect

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Occipital Lobe

Blood supply - MCA,PCA Major Functions:

primary visual area some visual reflexes involuntary smooth eye

movements recognition & identification of

objects

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Cerebellum

Blood supply -Vertebrobasilar

Major Functions: control of fine motor

movement coordinates muscle

groups maintains balance,

equilibrium

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Brain Stem

Blood supply - PCA & Vertebrobasilar

Major divisions - midbrain, pons, medulla

Houses CN III-XII Serves as a pathway Reticular Activating System

Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003

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Motor & Sensory Function

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Common Effects by Hemisphere

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COMMON EFFECTS OF A RIGHT

HEMISPERIC STROKE Left visual field loss (homonymous hemianopsia) DysphagiaUsually retain language ability but may have difficulty producing speech (dysarthria) Left-sided weakness (hemiparesis) or paralysis (hemiplegia) Sensory impairment Denial of paralysis, “forget” or “ignore” objects or people on their left side (neglect)Impaired ability to judge spatial relationships (misjudge distances and depth leading to falls, unable to guide hands to button a shirt, problems with directions such as up / down, no concept of time)Impaired ability to locate and identify body parts Short-term memory impairments (difficulty remembering new information) and apraxia (inability to carry out learned movement in the absence of weakness or paralysis) Behavioral changes such as impaired judgement or insight into limitations, overestimate physical ability, impulsivity, inappropriateness and difficulty comprehending and expressing emotions

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COMMON EFFECTS OF A LEFT HEMISPERIC STROKE

Right visual field loss (homonymous hemianopsia) DysphagiaMay develop aphasia (loss of language including spoken, written, reading and comprehension) but may also have dysarthria Right-sided weakness (hemiparesis) or paralysis (hemiplegia) Sensory impairment Usually have normal perception Usually judgement is intact with good insight into limitationsShort-term memory impairments (difficulty remembering new information) and apraxia (inability to carry out learned movement in the absence of weakness or paralysis) Often develop a slow and cautious behavioral style. They need frequent instructions and feedback to complete tasks Better able to comprehend and express emotions

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Types of Stroke Ischemic 80 - 84% Caused by blockage of

the artery resulting in reduction of blood flow and cell death

Include thrombotic, lacunar, embolic cryptogenic

CT scan negative until a few days post stroke then hypodense area - indicates infarction

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Thrombotic Stroke

Atherosclerosis in cerebral arteries Similar to CAD – leading to MI Atherogenesis – decades long process In thrombotic stroke lumen of artery narrows

to point of obstruction

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Lacunar stroke Thrombosis of small,

deep penetrating arteries causing a small lake or cavity

Seen with chronic hypertension

Only minor deficits seen

Necrotic brain cells reabsorbed with time, leaving a very small cavity or lacune

http://www.nlm.nih.gov/medlineplus/ency/imagepages/18009.htm

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A clot travels from source outside of brain Encounters vessel with lumen narrow enough

to block its passage Clot lodges there, blocking blood flow Most common source - heart Common conditions - atrial fibrillation,

valvular disease, ventricular thrombi, atherosclerosis of the proximal aorta

Embolic Stroke

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Ischemic Stroke – CT scan

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Types of Stroke Hemorrhagic 10 - 20% May be classified as

subarachnoid due to ruptured aneurysm or trauma or intracerebral due to hypertension

CT will show hyperdense area indicating bleeding into the damaged tissue

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Hemorrhagic Stroke White box - site of the

hemorrhage Orange region - brain

areas damaged by the stroke

Cells normally nourished by the hemorrhaging blood vessel, deprived of oxygen and other nutrients, perish very quickly leading to disability

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Hemorrhagic Stroke CT scan

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Comparison of Stroke Types

Hemorrhagic Can be fatal at time of

onset Client more likely to be

semi-conscious or unconscious

Client appears more ill and deteriorates rapidly

Ischemic Rarely leads to death in

the first hour Client may be drowsy

but unlikely unconscious unless the infarct is large

Client may deteriorate inthe first 24-48 hours

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Determinant Factors

Location of damage Severity of damage How well the body responds to the

cerebral assault and repairs the blood supply to the brain

How quickly other areas of brain tissue take over the work of the damaged cells

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What about TIA’s? Transient occlusion or reduction in cerebral

blood flow Classic definition of TIA - symptoms lasting up

to 24 hours Most “true” TIA’s last 2 to 20 minutes with

complete symptom resolution - symptoms lasting more than 1 hour is most likely as a result of permanent damage from stroke

Serious warning sign of an increased risk for stroke -5% occur within 48 hoursof a TIA

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Stroke Recognition and Treatment

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Initiating Acute Stroke Care - 3 Golden Hours

In the community Call 9-1-1 immediately Stroke Code initiated by Paramedics en route - goal to identify a

possible stroke and get the patient to the ED as quickly as possible

In-Patient Time of onset of the patient’s witnessed stroke symptoms is 3 hours

or less

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Time is Brain!

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What is rt-PA?

Tissue Plasminogen Recombinant Activator

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Ischemic Penumbra Area around infarct Infarcted brain tissue dies

quickly - brain cells within the penumbra remain viable for several hours after stroke

Penumbra cells supplied with blood by collateral arteries

Reperfusion important as circulation becomes inadequate with time

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Cerebral Reperfusion in Acute Ischemic Stroke

Goal - To limit irreversible ischemic damage during an acute ischemic stroke caused by an arterial occlusion. Thrombolysis will promote reperfusion of viable tissue

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Emergency Management Strategies Neurological vital signs Blood pressure Glycemic control Control of body

temperature Oxygenation Hydration

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Hemorrhagic Stroke Treatment based on the underlying cause

of the bleed and the extent of brain damage

Treatment includes medication and surgical intervention

Management of ICP with antihypertensives or surgical evacuation of hematoma

In patients with ruptured aneurysm - clip or embolization

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Same as stroke - sudden onset with loss of function

Immediate recognition essential - don’t self diagnose or wait for symptom resolution

Treat as a medical emergency - urgent medical assessment to rule out stroke and initiate interventions to prevent stroke

TIA Symptoms

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Strategies to prevent a stroke Maintain a healthy weight - eat a reduced-fat diet Reduce alcohol intake to 1-2 drinks / day Exercise - 30 minutes 3-4 times / week Become smoke free and drug free Management of hypertension (ACE inhibitors) Management of heart disease (anticoagulants),

diabetes and hyperlipidemia (statins) Carotid endarterectomy may be indicated with

stenosis Antiplatelets for plaque / clot formation

Transient Ischemic Attack (TIA)

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Stroke Recovery The most rapid recovery occurs during the

first 3 to 4 months - may continue over many months or years

Mild (6 wks); Moderate (13 wks); Severe (17 wks)

Recovery process is affected by the:• Survivor's age and general health• Survivor's personality• Survivor's coping abilities and emotional state• Support of family and loved ones

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Stroke Risk

A person who has had a stroke has a higher risk of having another one

Risk highest in the first year - 15 times the risk among the general population

Risk remains high for the first five years 30% of people with previous stroke will

have another one

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Black J, Hakanson Hawks J, Keene A. Medical-SurgicalNursing Clinical Management for Positive Outcomes. 2001Habel M, Management of the Patient with Stroke HRSRH Neurosciences Critical Care 10-Module Program, Module 8: Seizures / Stroke (CVA)Neuroanatomy and Cerebral Circulation Review, West GTA Stroke Network, 2003 Heart and Stroke Foundation of Ontario, Tips and Tools for Everyday Living: A Guide for Stroke Caregivers, 2002 Heart and Stroke Foundation Get Stroke Smart, 1999Martin Memorial Health Systems, Health Library A-Z, 2004 (www.mhs.com)Medical Imaging of Cerebrovascular Disease, Unit 2: Anatomy of the Cerebrovascular System, klmccor, 1999 Google Image Search

References