trigger week 2

7/27/2019 Trigger Week 2

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Review of Anatomyof Cerebrum & Diencephalon


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THE CEREBRAL HEMISPHERES

The cerebral hemisphere

consists of:-

(1) an outer gray matterthe

cortex and

(2) an inner white matterinwhich are embeddeddeep

nuclear masses called basal

nuclei (ganglia) &

diencephalon.

Coronal section

Horizontal section

cortex

white matter

basal nuclei

thalamus

cortex

basal

nuclei

dien-

cephalon


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THE SUPERO-LATERAL SURFACE

A. THE MAJOR SULCI

It has 3 important sulci: the lateral , central

and parieto-occipital sulci.

(1) The lateral sulcus (lateral fissure of Rolando)is a deep sulcus

which extends from the base of the brain along the lateral surface

to terminate as an upward curve within the inferior parietal lobule.

Parieto-occipitalsulcus


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B. LOBES OF SUPERO-LATERAL SURFACE

1. FRONTAL LOBE

It is the largest lobe consisting 1/3 of the wholehemisphere. It has 3 sulci:

(1)One vertical sulcusthe precentral sulcus

(2)Two horizontal sulcithe superior & inferior frontal sulci


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1.The precentral sulcus

- Runs parallel to the central

sulcus; the gyrus between them is theprecentral gyrus orprimary motor

area orBrodmanns area 4.

This area is responsible for the

voluntary motor activities of the

opposite half of the body.

The homunculus is

upside down with the head region

upright & the lower extremity is on

the medial surface

(the paracentral lobule).

4


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Motor homunculus

The area of cortex controlling a particular movement is

proportional to the skill involved in performing the movement and is

unrelated to the mass of muscle participating in the movement.


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4

6 3

1

28

9

10

114445

4142

2243

40

39

17

18

19

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Functional areas of cerebral cortexon the superolateral surface


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Applied Anatomy

Functional areas on the frontal lobe

Lesion of Primary Motor Area

(Brodmanns Area4)results in paralysis of contralateral side of the body

Lesion of Premotor Area

(Broadmanns Area6)produces difficulty in the performance of skilled movements.

Lesion ofBrocas Motor Speech Area

(Brodmanns area 45 and 44

results in the loss of ability to produce speech, i.e. expressive aphasia.


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Basal Nuclei (Basal Ganglia)

Collection of gray matter masses

within each cerebral hemisphere.

Consists of:caudate nucleus

lentiform nucleus

amygdaloid nucleus

claustrum

Caudate nu.

Lentiform nu

Claustrum

Caudate nucleus

Lentiform nu.

Amygdaloid nucleus

Horizontal section


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Functions of the Basal Nuclei

-Involved with the subconscious control ofskeletal muscle tone and the

coordination of the learned movement patterns.

-Under normal conditions, these nuclei do not initiate particular

movements.

- But once a movement is under way, the basal nuclei provide the

general pattern and rhythm, especially for movements of the trunks and

proximal limb muscles.


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Internal capsule is a compact band of white fibres flanked

between the caudate nucleus and thalamus medially and lentiform

nucleus laterally.

anterior limb

posterior limb

genu

retrolenticular part

sublenticular part

caudate nucleus

thalamus

lentiform nucleus


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Lesions

CVA - Cerebrovascular Accident,

due to thrombosis (or) haemorrhage .

Hemiplegia

Interruption of blood supply to internal capsule will give rise

to paralysis of voluntary movements occuring in the opposite

side of the body called hemiplegia.


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It supplies:

1. all the medial surface of the

cerebrum as far as the parieto-

occipital sulcus2. It supply a strip of cortex about

1 wide on the adjoining lateral

surface

3. Adjacent medial half of theorbital surface of the frontal

lobe

Important functional areas

supplied by ACA :

1. Motor and sensory areas forlower limb and perineum

(paracentral lobule)

2. Cingulate gyrus (limbic lobe)

Medial surface

Superolateral surface


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THE MIDDLE CERERBAL ARTERY

-It is the largest branch of the ICA.

-It enters the lateral sulcus and divides

into cortical branches which supplies:-

1. The entire supero-lateral surface

except

(i) a narrow strip along the superior

border (supplied by ACA)(ii) a narrow strip along the infero-

lateral border (supplied by PCA)

(iii) occipital lobe (supplied by PCA)

2. The lateral of the orbital surface of

the frontal lobe

3. Temporal pole

Medial surface

Superolateral surface


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Important functional areas supplied by MCA:1. Primary motor (Area 4) and sensory areas (Areas 3,1,2)

for the whole body except lower limb and perineum

2. Brocas motor speech area (Areas 45,44)

3. Higher sensory association areas (areas 40, 39)4. Primary & secondary auditory areas (Areas 41, 42 & 22)

5. Taste area - Area 43


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Clinical Importance - Cerebral IschaemiaUnconsciousness occurs in 5 to 10 seconds if the blood flow to the brain is completely cut off.

Neuronal function ceases after about 1 minute and irreversible changes start to occur after

about 4 minutes.

Anterior Cerebral Artery Occlusion

1. Contralateral hemiparesis and hemisensory loss involving mainly the leg and foot

(paracentral lobule of cortex)

2. Inability to identify objects correctly, apathy, and personality changes (frontal and parietal

lobes)

Middle Cerebral Artery Occlusion

1. Contralateral hemiparaesis and hemisensory loss involving mainly the face and arm

(precentral and post central gyri)

2. Aphasia if the left hemisphere is affected (rarely if the right hemisphere is affected)

3. Contralateral homonymous hemianopia (damage to the optic radiation)

Posterior Cerebral Artery Occlusion

1. Contralateral homonymous hemianopia with some degree of macular sparing (damage to

the calcarine cortex, macular sparing due to the occipital pole receiving collateral blood

supply from the middle cerebral artery)


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Physiology of cerebrum &diencephalon


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Functions of Specific Cortical Areas


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Association Areas

Large areas of the cerebral cortex that do not fitinto the rigid categories of primary and secondarymotor and sensory areas are called associationareas

The association areas receive and analyze signalssimultaneously from multiple regions of both themotor and sensory cortices

Important association areas include

theparieto-occipitotemporal association area

theprefrontal association area

the limbic association area

P i t i it t l i ti


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Parieto-occipitotemporal association

area

provides a high level of interpretative meaning for signalsfrom all the surrounding sensory areas.

Analysis of the Spatial Coordinates of the Body

receives visual sensory information from the posterior occipitalcortex and simultaneous somatosensory information from the

anterior parietal cortex.

From all this information, it computes the coordinates of the

visual, auditory, and body surroundings.

Wernickes Area Is Important for Language Comprehension

most important region of the entire brain for higher intellectual

function because almost all such intellectual functions are

language based.


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Angular Gyrus Area Is Needed for Reading

needed to make meaning out of the visually perceived

words.

In its absence, a person can still have excellent language

comprehension through hearing but not through reading.

Area for Naming Objects

names are learned mainly through auditory input, whereas

the physical natures of the objects are learned mainly

through visual input


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Limbic Association Area

Concerned primarily with behavior,

emotions, and motivation

This limbic system provides most of the

emotional drives for activating other areas of

the brain and even provides motivational

drive for the process of learning itself.


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It consists of

Thalamus :-the large oval mass of grey matter Subthalamus:- it lies directly above midbrain

Hypothalamus : lies infront of subthalamus

Metathalamus : formed by lateral & medial

geniculate body

Epithalamus: Formed of pineal body, 2 habenular

nuclei & commissures &posterior commissure.


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Thalamus

Receives and analyses all thesensory information (exceptolfactory) from the body

Having extensive connections withthe basal ganglia and the motorcortices, it plays a pivot role involuntary motor activity.

Connections with the limbicsystem makes it important in the

control of mood, emotional andsexual behavior, and memory

Anterior thalamic nuclei areconcerned with Emotional tone,mechanism of recent memory .


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Pineal body

An endocrine organ

Synthesize melatonin

Controls:

Sleep/awake cycle

Regulation of onset of puberty

Habenular nuclei

Have connections with limbic system Serves autonomic function and emotional drives


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Subthalamus

The main function of the subthalamus is the

regulation of movements produced by skeletal

muscles

3 nuclei

upper end of red nucleus,

upper end of substantia nigra

subthalamic nuclei

bundles of projection fibers


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Pathophysiology of speech

problem


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Blood supply of the brain


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Stroke

A stroke occurs when the blood flow to an area of

the brain is interrupted; either it is due to the

blockage of blood vessel leading to the brain or

rupture of a blood vessels leading to compression ofbrain tissue from an expanding haematoma.


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Middle cerebral artery

It supply most of the lateral cortex of each cerebralhemisphere which are involved in speech, languageand swallowing.

Damage to these cortical areas on either side of the

brain can impair motor speech and swallowingfucntions.

Damage to the left MCA may cause aphasia to occur.

Decrease blood supply to cerebral cortex affect left

frontal-temporal-parietal region affect Brocas area loss in language production aphasia.


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Brocas aphasia


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Brocas aphasia

Motor or non-fluent: Lesion is in Brocas area ofdominant hemisphere and frontal lobe.

Speech output is slow, poorly articulated, speakin short sentences.

Able to understand the speech of others

Limited writing ability

Aware of the language difficulties

May associated with right sidedparalysis/weakness due to the damage of thefrontal lobe.


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Wernickes aphasia


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Wernickes aphasia

Sensory or fluent: lesion in Wernickes area of

dominant hemisphere and temporal lobe.

Speak in long sentences that have no

meaning, use unnecessary words.

Difficulty understanding speech.

Reading and writing are impaired.

Unaware of the mistakes.


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Two common processes that leads stroke

a) hypoxia, ischemia and infarction from

impairment of blood supply and oxygenation

of CNS tissue.

b) hemorrhage resulting from the ruptured of

CNS vessels.


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Types of stroke

1. Ischemia stroke

2. Hemorrhagic stroke.

Brain ischemia can be further subdivided, by

cause, into thrombotic, embolic, and

hypoperfusion. Thrombotic and embolic are

generally focal or multifocal in nature while

hypoperfusion affects the brain globally.


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Ischemia Strokes

two typesa) Global cerebral Ischaemia

b) Focal cerebral Ischaemia

Global Cerebral Ischaemia

occurs when blood flow to the brain is halted or drasticallyreduced. This is commonly caused by cardiac arrest. If sufficientcirculation is restored within a short period of time, symptoms

may be transient. However, if a significant amount of timepasses before restoration, brain damage may be permanent.While reperfusion may be essential to protecting as much braintissue as possible, it may also lead to reperfusion injury.Reperfusion injury is classified as the damage that ensues after

restoration of blood supply to ischemic tissue


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Ischemia stroke can be divided into two forms :


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1. Embolic Ischemia Stroke

- Associated with embolic events.

- Clot is form outside of the brain ussually in heart

or large arteries of upper chest and neck.

- Embolic will later be dissolve and arteries regain itsblood flow but actually the artery is already damage

and cant withstand the normal blood pressure and

this will lead to hemorrhage.

- Emboli can be fat globules, air bubbles and

atherosclerotic plaque.


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Subarachnoid Hemorrhage (SAH) Subarachnoid hemorrhage occurs when bleeding from a damaged


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Subarachnoid hemorrhage occurs when bleeding from a damagedvessel causes blood to accumulate between the brain and theskull, in the subarachnoid space, and press on the surface of thebrain instead of dispersing into the tissue. The leaked blood can

irritate, damage or destroy surrounding brain cells. When blood enters the subarachnoid space, it mixes with the

cerebrospinal fluid (CSF) that cushions the brain and spinal cord.This can block CSF circulation, which leads to fluid buildup andincreased pressure on the brain. The open spaces in the brain

(ventricles) may enlarge, resulting in a condition calledhydrocephalus. This can make a patient lethargic, confused orincontinent. The large accumulation of blood increases thepressure surrounding the brain, interfering with brain function.

Most often, a subarachnoid hemorrhage occurs because a

cerebral aneurysm, an abnormal bulging outward in the wall of anartery, ruptures. SAH also can occur because blood leaks fromabnormal blood vessel connections (AVMs and AVFs) near thesurface of the brain.


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Damage to your arteries Healthy arteries are flexible strong and elastic Their inner


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Healthy arteries are flexible, strong and elastic. Their innerlining is smooth so that blood flows freely, supplying vitalorgans and tissues with adequate nutrients and oxygen. If

you have high blood pressure, the increased pressure ofblood flowing through your arteries gradually can cause avariety of problems, including:

Artery damage and narrowing.

High blood pressure can damage the cells of your arteries'

inner lining. That launches a cascade of events that makeartery walls

Aneurysm. Over time, the constant pressure of bloodmoving through a weakened artery can cause a section of its

wall to enlarge and form aneurysm. An aneurysm (canpotentially rupture and cause life-threatening internalbleeding. Aneurysms can form in any artery throughoutyour body, but they're most common in the aorta, yourbody's largest artery.

How does Smoking cause Stroke?


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How does Smoking cause Stroke? Smoking increases the risk of high blood pressure-the single biggest risk factor forstroke.

The chemicals in cigarettes include carbon monoxide, arsenic, formaldehyde and

cyanide damage the blood vessel walls, this leads to atherosclerosis (narrowing or furring ofthe arteries). This increases the chances of blood clots forming on the arteries to the brainand the heart. These clots can suddenly block an artery completely causing a stroke.

Nicotine is a highly addictive drug. It causes your blood vessels to narrow, increasesyour heart rate and raises your blood pressure. Elevated blood pressure is a majorcontributory factor to stroke.

The carbon monoxide in tobacco smoke is the same type of poisonous gas found in

car exhaust fumes; it deprives the blood vessels of vital oxygen. Carbon monoxide joinsonto the haemoglobin which carries oxygen around the body in red blood cells. In somesmokers, up to half of the blood can be carrying carbon monoxide instead of oxygen.

Smoking increases the stickiness of special blood cells called platelets, furtherincreasing the risk of blood clots forming.

Smoking increases LDL (bad) cholesterol and reduces HDL (good) cholesterol. Highlevels of LDL cholesterol are a risk for cardiovascular disease and stroke.

Smoking increases the risk of stroke in women using the oral contraceptive pill.

Second hand smoke-breathing in someone elses smoke is also hazardous. Recentresearch suggests second hand smokers were nearly twice as likely to have a stroke as thosewho did not live or work in a smoky atmosphere.


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Sign & Symptoms of stroke


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Trouble with seeing in one or both eyes

headache


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Physical examination.-symptom

-medications you take

-whether you have experienced any head injuries

-check blood pressure

-stethoscope to listen to heart

-ophthalmoscope to check for signs of tiny cholesterolcrystals or clots in the blood vessels at the back ofyour eyes.


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Computerized tomography (CT) scan

-determining if you're having a stroke and what type of

stroke you may be experiencing.

-can show a brain hemorrhage, tumors, strokes andother conditions.


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Magnetic resonance imaging (MRI)

-uses powerful radio waves and magnets to create a

detailed view of your brain.

-can detect brain tissue damaged by an ischemic strokeand brain hemorrhages.


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Carotid ultrasound.

-uses sound waves create detailed images of the inside

of the carotid arteries in your neck.

-shows buildup of fatty deposits (plaques) and bloodflow in your carotid arteries.


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Echocardiogram.

-uses sound waves to create detailed images of yourheart.

-can find a source of clots in the heart that may havetraveled from heart to brain and caused stroke.


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Treatment

d


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Medication

Types of medcines to prevent clotting:-Antiplatelet medicines.

Prevents platelets in the blood from sticking together. Egaspirin

-Anticoagulant medicines.prevent blood clots from forming and keep existing bloodclots from getting bigger. Atrial fibrillation is treated withanticoagulant such as warfarin.

-Cholesterol-lowering (Statins) and blood-pressure-lowering medicines are also used to prevent TIAs andstrokes.

S


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Surgery

Surgery for ischemic stroke

If you have significant blockage in the carotid

arteries in your neck, you may need a carotid

endarterectomy . During this surgery, asurgeon removes plaque buildup in the

carotid arteries to reduce the risk of transient

ischaemic attack TIA or stroke.


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Build-up of spinal fluid within the brain(hydrocephalus). Fluid on the brain is more likely tooccur if the stroke was caused by bleeding(haemorrhagic stroke).

Spasms of blood vessels (vasospasm). Vasospasm mayoccur if the stroke was caused by a subarachnoidhaemorrhage from an aneurysm

Blood clot in the legs (deep vein thrombosis) that maytravel to the llungs (pulmonary embolism).

seizures Another stroke.

coma

Surgery for hemorrhagic stroke


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Surgery for hemorrhagic stroke

Surgeries for hemorrhagic stroke include:

Surgery to drain or remove blood in the brain

Endovascular coil embolization : repair a brainaneurysm that is the cause of a hemorrhagicstroke. A small coil is inserted into the aneurysmto block it off and stop or prevent bleeding.

Surgery (craniotomy) : repair the aneurysm thatcaused the hemorrhagic stroke. A small metal clipis placed around the base of the aneurysm toblock it off. This stops the bleeding in the brain.

arteriovenous malformation: Surgery to removeor block off abnormally formed blood vessels thathave caused bleeding in the brain.

Th b l i


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Thrombolysis

Thrombolysis, also known as thrombolytictherapy, is a treatment to dissolve dangerousclots in blood vessels, improve blood flow, andprevent damage to tissues and organs.

Thrombolysis is often used as an emergencytreatment to dissolve blood clots that form inarteries feeding the heart and brain

If blood clot is determined life threatening, it has

to be carried out ideally within one to two hours -- after the onset of symptoms of a heart attack,stroke, or pulmonary embolism


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Forms of thrombolysis includes:

clot-busting drugs

another type of thrombolysis called

mechanical thrombectomy. During this

procedure, a long catheter tipped with a tiny

suction cup, rotating device, high-speed fluid

jet, or ultrasound device is used to physicallybreak up the clot.


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Stroke Rehab Begins Right Away

Stroke rehabilitation begins once your

condition has stabilized -- as soon as 24 to 48

hours after your stroke. While some strokesurvivors recover fully, others will always have

some disability.


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Stretching Exercises Improve Range ofMotion

Stretching exercises promote blood flow and

make it easier to move your arm.


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. Electrical stimulation (ES) therapy is a

safe way to stimulate the nerves thatmake your muscles contract.


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Intrathecal Baclofen Therapy for Spasticity

Another option may be intrathecal baclofen therapy.For this, a small pump is surgically implanted to

administer muscle relaxant medicine to the spinal fluid.It can be useful when someone has severe spasticity orhasn't done well on oral medications. The pump uses asmaller amount of baclofen medication than when it'staken by pill, so it can cut down on some side effects.


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Spasticity Treatment: Oral Medications

Drug therapy for spasticity is often used in

addition to physical exercises and stretching.

Oral muscle relaxant medications help reducelarge areas of spasticity by interfering with the

nerve signals that cause muscles to contract.

However, these medications may cause sideeffects such as drowsiness and weakness.


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Risk factor


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Age

For each successive 10 years after age 55, the

stroke rate more than doubles in both men and

women.Stroke incidence rates are 1.25 times greater in

men, but because women tend to live longer than

men, more women than men die of stroke each

year.


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Race Blacks are more than twice as likely to die of stroke as

whites are. Between the ages of 45 and 55, mortality ratesare four to five times greater for African-Americans thanfor whites; the difference decreases with increasing age.

Asians, specifically Chinese and Japanese, have high strokeincidence rates. Stroke incidence and mortality rates inJapan were very high for most of this century andexceeded those for heart disease. As in the United States,stroke death rates in Japan have fallen dramatically since

World War II. In recent years stroke incidence rates inJapanese men in Hawaii were similar to those of whiteAmericans and between the rates of Japanese men inJapan and in California.


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Hypertension

The prevalence of hypertension is greater in blacks

than in whites.

Cardiac diseaseAtrial fibrillation (AF) is the most powerful and

treatable cardiac precursor of stroke.

The incidence and prevalence of AF increase withage.


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Diabetes

Cigarette smoking

Cigarette smoking increases risk (RR) of ischemic

stroke nearly two times, with a clear dose-response relation.

Alcohol

Increasing alcohol consumption increases risk forbrain haemorrhage.


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Obesity

obesity (weight greater than 30% above average)

was a significant independent contributor to

incidence of brain infarction in men aged 35 to 64and women aged 65 to 94.

obesity was identified as an independent factor

related to stroke incidence


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Physical activityModerate and heavy levels of physical activity have been

associated with reduced CHD incidence.

In recent years evidence supports a protective effect ofmoderate physical activity on stroke incidence in men and

women. In Framingham, physical activity was protective in men;

adjusted relative risk was 0.41.

However, there was no evidence of a protective effect ofphysical activity on risk of stroke in women.

In addition, as has been found in coronary heart disease,there was no evidence that heavy physical activityconferred greater benefit than moderate levels.


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Physical activity exerts a beneficial influence on riskfactors for atherosclerotic disease by

reducing blood pressure,

weight, and pulse

rate; raising HDL cholesterol and

lowering LDL cholesterol;

decreasing platelet aggregability;

increasing insulin sensitivity and

improving glucose tolerance;

promoting a lifestyle conducive to changing diet

promoting cessation of cigarette smoking.


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Prevention


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Avoid fatty foods. Follow healthy diet

Do not drink more than 1 to 2 alcohol drinks

per day

Exercise regularly

Get blood pressure checked every 1 to 2 years

Have cholesterol level checked

Quit smoking


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