Report On Stroke

A stroke
often appears suddenly, without warning, and its effects on the body are immediate.
The common symptoms of a stroke, which appear afterwards, include:

·
Sudden
numbness, weakness, clumsiness, or paralysis on one side of the body. An
example of this symptom can be a dropping arm or leg, eyelid, or dribbling
mouth. This is one of the most common and recognizable stroke symptoms. This
symptom affects only one side of the body and causes difficulties in
controlling the arm or leg. In the worst cases, the weakness or paralysis is
accompanied by muscle and joint stiffness.

·
Sudden
confusion, slurred speech, trouble speaking, or understanding speech. This is
another common symptom in patients that had a stroke. This symptom also
includes difficulties reading and writing.

·
Sudden
blurred vision or loss of sight in one or both eyes. The stroke can damage that
part of the brain that receives, processes, and interprets the information sent
by the eyes to the brain. This can lead to a variety of problems such as double
vision, or losing half of the vision field.

·
Sudden
trouble walking, dizziness, loss of balance, or loss of coordination.

·
·
Loss
of balance or unsteadiness. This can be the result of damage in the part of the
brain responsible with the body’s balance, or as a result of paralysis when the
muscles become weak.

·
Dysphasia
or difficulties swallowing is another common symptom in patients with stroke.
About 50 percent of those that have a stroke have swallowing problems.

·
Perception
and interpretation difficulties. People that suffered a stroke have
difficulties recognizing familiar objects or knowing how to use them.

·
Mental
processes impairment. After a stroke, the person can have problems thinking,
learning, remembering, concentrating, making decisions, reasoning, and
planning.

·
·
Mood
swings. People that suffer a stroke experience emotional ups and downs. They
can become depressed, sad, angry, anxious, experience low self-esteem and low
confidence.

1.7  
Associated symptoms

·
Loss of
consciousness,

·
·
·
If
symptoms are maximal at onset, the cause is more likely to be a subarachnoid
hemorrhage or an embolic stroke.

 
Causes of stroke

There are many different causes of stroke, but whenever a
stroke occurs, there has been an interruption of the normal blood supply to
brain cells that has gone on long enough to cause death to at least some of
them. If the loss is so brief that the brain tissue can quickly recover, and
does not die, then a Transient
Ischemic Attack (TIA)
has occurred, rather than a stroke. The symptoms and signs of a stroke are
highly dependent upon the number of cells that are affected, and exactly where
these cells are located in the brain. Accordingly, strokes can have many
different clinical presentations – ranging from deep coma with the loss of the
ability to breathe; to very limited deficits in the ability to move a part of
the body, or changes in sensory perception like partial blindness from a
restriction in visual field, without any associated problems with movement.

Ordinarily, at least some brain tissue is injured by a stroke
– yet not killed. The injury to these cells is reversible. That’s one reason
why the amount of recovery during the initial time period after a stroke is
difficult to predict, and also why treatment at that time can influence the
course of recovery. If the stroke patient survives the stroke, some brain cells
may actually recover in time if the injury was not too great.

Ten causes of stroke identified by researchers. Scientists
have found ten key health problems that cause almost all strokes.

·
High
blood pressure,

·
Smoking,

·
A
fat stomach,

·
Poor
diet,

·
Lack
of physical activity,

·
High
levels of bad cholesterol,

·
Diabetes,

·
Drinking
too much,

·
Stress
and depression and

·
Heart
disorders accounted for 90 per cent of strokes.

The research conducted by a team at McMaster University on
Ontario, Canada, is one of the most comprehensive looking into the causes of
stroke. The factor with the strongest link was high blood pressure which more
than doubled the risk of a stroke, they said. Around 150,000 people in Britain
each year suffer a stroke and there are 67,000 deaths. It is a leading cause of
disability. The study published in The Lancet and presented at The World
Congress of Cardiology in Beijing looked at 3,000 people who had a stroke and
3,000 similar people who had not suffered a stroke.

They were questioned
about:

·
·
·
Who
much exercise they did and

·
Their
diets given a score according to how healthy they were and tests and
measurements were carried out by professionals.

Alcohol intake was categorized as never or former drinker,
moderate drinker of between one and 30 drinks a month, more than 30 drinks a
month and binge drinker who had more than five drinks in one day in the last
month. They were classed as physically active if they were involved in walking,
cycling, gardening, jogging, football or vigorous swimming for four hours a
week or more. The findings showed that current smokers doubled their risk of
stroke, poor diet increased the risk by 35 per cent, 30 or more drinks a month
or binge drinking increased the risk by half, stress raised the risk by 30
percent and depression by 35 per cent. Being active reduced the risk by about
30 per cent. Martin O’Donnell, lead author said: “Our findings suggest
that ten simple risk factors are associated with 90% of the risk of ischemic
and intracerebral hemorrhagic stroke worldwide.”Targeted interventions that
reduce blood pressure and smoking, and promote physical activity and a healthy
diet, could substantially reduce the global burden of stroke.”Andrea Lane,
Spokesperson for The Stroke Association said: “Over the years there have
been a number of research studies into the causes of stroke, which have
identified a number of major risk factors.”This is an extensive and in-depth
study and so it’s great to see that the findings support previous research and
reflect the preventative advice provided by The Stroke Association.”

1.9  
Effects of Strokes

The most common problems in daily life are likely to be
caused by:

·
Weakness
or lack of movement (paralysis) in legs and/or arms

·
Shoulder
pain.

·
Trouble
swallowing

·
Changes
to way things are seen or felt (perceptual problems)

·
Changes
to the way things are felt when touched (sensory problems)

·
Problems
thinking or remembering (cognitive problems)

·
Trouble
speaking, reading or writing,

·
Incontinence,

·
Feeling
depressed,

·
Problems
controlling feelings,

·
Tiredness

The specific abilities that will be lost or affected by
stroke depend on the extent of the brain damage and, most importantly, where,
in the brain, the stroke occurred: the right hemisphere (or half), the left
hemisphere, the cerebellum or the brain stem. Each stroke is different and each
person that experiences a stroke is affected differently. Some stroke survivors
experience mild symptoms, while other faces severe and lasting damage. Once the
stroke occurs, the brain immediately undergoes changes. Without the blood
supply which provides the brain with nutrients and oxygen, the brain cells are
damaged and can die. Once dead, the cells cannot return to life, but the surrounding
areas can recover and take over or substitute some of the lost functions.
Usually, the recovery process happens in the first few months that follows the
stoke, but in some cases can continue for several years.

The
disability level differs from patient to patient, and depends on the type of
stroke suffered, the area affected, the location of the affected area, and the
extent of the damage. A stroke can occur in any part of the brain causing
damages according to those functions controlled by that area. Each part of the
brain is involved in different essential functions for the body. Usually, the
stroke symptoms and signs occur on the opposite side of the body to the stroke
side of the brain.

The human brain is divided in four main parts: (1) the right hemisphere,
(2) the left hemisphere, (3) the cerebellum, and (4) the brain stem. In most
people, the right hemisphere is responsible for perceptual and spatial skills,
the left hemisphere is responsible for language, the cerebellum controls
balance and coordination, while the brain stem controls those body functions
that do not require conscious control (such as breathing rate, blood pressure,
heart rate, eye movement, hearing, speech, and swallowing).

The effects of a stroke can be divided into two main categories:

(1) Body functions.

(2) Cognitive functions.

Effects of Right Hemisphere Strokes

The right hemisphere of the brain controls the movement of
the left side of the body so stroke in the right hemisphere often causes
paralysis in the left side of the body. This is known as left hemiplegic.
Survivors of right-hemisphere strokes may also have problems with their spatial
and perceptual abilities. This may cause them to misjudge distances (leading to
a fall) or be unable to guide their hands to pick up an object, button a shirt
or tie their shoes. They may even be unable to tell right side up from
upside-down when trying to read. Along with these physical effects, survivors
of right-hemisphere strokes often have judgment difficulties that show up in
their behaviour. They often act impulsively, unaware of their impairments and
certain of their ability to perform the same tasks as before the stroke. This
can be extremely dangerous. It may lead them to try to walk without aid or to
try to drive a car. Survivors of right-hemisphere strokes may also experience
left-sided neglect. This is a result of visual difficulties that cause them to
“forget” or “ignore” objects or people on their left side.
Some survivors of right-hemisphere strokes will experience problems with
short-term memory. Although they may be able to recall a visit to the seashore
that took place 30 years ago, they may be unable to remember what they ate for
breakfast that morning.

Effects of Left Hemisphere Strokes

The left hemisphere of the brain controls the movement of the
right side of the body. It also controls speech and language abilities for most
people. A left-hemisphere stroke often causes paralysis of the right side of
the body. This is known as right hemiplegic. Someone who has had a
left-hemisphere stroke may also develop aphasia. Aphasia is a catch all term
used to describe a wide range of speech and language problems. These problems
can be highly specific, affecting only one part of the patient’s ability to communicate,
such as the ability to move their speech-related muscles to talk properly. The
same patient may be completely unimpaired when it comes to writing, reading or
understanding speech. In contrast to survivors of right-hemisphere stroke,
patients who have had a left-hemisphere stroke often develop a slow and
cautious behaviour. They may need frequent instruction and feedback to finish
tasks. Patients with left-hemisphere stroke may develop memory problems similar
to those of right-hemisphere stroke survivors. These problems can include
shortened retention spans, difficulty in learning new information and problems
in conceptualizing and generalizing.

Effects of Brain Stem Strokes

Strokes that occur in the brain stem are especially
devastating. The brain stem is the area of the brain that controls all of our
involuntary functions, such as breathing rate, blood pressure and heart beat.
The brain stem also controls abilities such as eye movements, hearing, speech
and swallowing. Since impulses generated in the brain’s hemispheres must travel
through the brain stem on their way to the arms and legs, patients with a brain
stem stroke may also develop paralysis in one or both sides of the body.

Effects of Cerebellum Strokes

The cerebellum controls many of
our reflexes and much of our balance and coordination. A stroke that takes
place in the cerebellum can cause abnormal reflexes of the head and torso,
coordination and balance problems, dizziness, nausea and vomiting.

Effect of stroke on
vision

Visual problems are more common in people who have suffered a
stroke affecting the right side of their brain. The damage the stroke does in
the brain impacts the visual pathways of the eye which can result in visual
field loss, blurry vision, double vision and moving images. When stroke affects
the areas of the brain that processes the information we see, it can cause
‘visual neglect’ (lack of awareness to one half of the body or space) as well
as difficulties with judging depth and movement. In a few cases, visual
problems caused by stroke can improve on their own with time.

Some of the vision problems that occur as a result of a
stroke include loss of part of vision or loss of visual field. Visual field is
the term used to describe the whole of our vision, from the centre to the
periphery. It refers to everything we can see in the periphery (around the
edges of our vision) as well as what we are directly looking at (central
vision). Strokes can cause whole sections of the visual field to be missing.
Other visual problems that may occur as a result of stroke include eye muscle
and nerve problems which can result in double vision and moving images as well
as other effects such as sensitivity to light.

Other Effects of Stroke

Depression is very common amongst people who have had a
stroke. It can be quite severe, affecting both the survivor and his/her family.
A depressed person may refuse or neglect to take medications, may not be
motivated to take part in physical rehabilitation or may be irritable with
others. This in turn makes it difficult for those who wish to help, and tends
to deprive the survivor of valuable social contacts that could help dispel the
depression. In time the depression may lift gradually, but counseling and
appropriate medication may be necessary. In the past, researchers speculated
that some of the older anti-depressant drugs might interfere with a person’s
mental performance but recent studies suggest that anything that can
effectively treat post-stroke depression, whether an old or new treatment, may
also improve mental ability and enhance rehabilitation.

Sudden laughing or crying for no apparent reason and
difficulty controlling emotional responses also affects many stroke survivors.
There may be little happiness or sadness involved, and the excessive emotional
display will end as quickly as it started. Apparent changes in personality
following a stroke may be very disturbing to the survivor’s family. Stroke
affected people may not seem the same person as before. The way in which they
think, feel and react may be altered. Problems and activities once tackled
easily may be difficult or impossible, while other tasks are unaffected.

The way in which the person affected by stroke reacts to
these changes will affect their personality, and may cause changes in control
of emotions and behaviour.  People affected by stroke may become confused,
self-centered, uncooperative and irritable, and may have rapid changes in mood.
They may not be able to adjust easily to anything new and may become anxious,
annoyed or tearful over seemingly small matters.

1.10
Complications after Stroke

Common complications of
a stroke:

• Edema –
  brain swelling

·
Seizu
Breathing food into the airway (aspiration)

·
Dementia

·
Falls

·
Loss
of mobility

·
Loss
of movement or feeling in one or more parts of the body

• Muscle spasticityres – abnormal electrical
  activity in the brain, which causes convulsions
• Clinical
  depression – a treatable illness that causes uncontrollable emotional and
  physical reactions to changes and losses
• Bedsores –
  ulcers that result from a decreased ability to move
• Limb
  contractures – shortened muscles in arms or legs that are caused by a
  reduced range of motion or lack of exercise
• Shoulder
  pain – a consequence of lack of support or exercise of the arm
• Blood
  vessel problems – formation of blood clots in the veins
• Urinary
  tract infection and bladder control – urgency and incontinence
• Pneumonia –
  results in breathing problems.

·
Poor
nutrition

·
Pressure sores

·
Problems
speaking and understanding

·
Problems thinking
or focusing.

Chapter – 2

Risk
factors for stroke

Stroke risk factors are medical conditions or behaviors or
traits that make you more likely to develop a stroke. Having one or more risk
factors does not mean that you definitely will have a stroke, only that you are
more likely to do so. More than 750 thousand people suffer from stroke in the
U.S. each year, but up to 50% of strokes could be prevented. In the case of stroke,
many of the risk factors can be treated, modified or controlled. However, some
risk factors for stroke cannot be changed. Knowing ones risk factors is the
first step in preventing stroke. One can change or treat some risk factors, but
others can’t. By having regular medical checkups and knowing the risk, one can
focus on what can change and lower risk
of stroke.

2.1
Risk factors of stroke that can’t control

·
Age: The risk of stroke increases
with advancing age.

·
Ethnicity: People of First Nations,
African, Hispanic, and South Asian descent have greater rates of high blood
pressure and diabetes. These conditions increase the risk of stroke.

·
Family
history: The
risk of stroke may be higher if a parent or sibling has had a stroke before the
age of 65.

·
Gender: 
In most age groups, more men than women have stroke, but more women die
from stroke. Men have a higher risk of stroke than women who have not reached
menopause.

·
Heredity
and race: People
whose close blood relations have had a stroke have a higher risk of
stroke.  African Americans have a higher
risk of death and disability from stroke than whites, because they have high
blood pressure more often. Hispanic Americans are also at higher risk of
stroke.

·
Prior
stroke or transient ischemic attack (TIA): Someone who has had a stroke is at higher risk of
having another one. Up to one-third of people who survive a first stroke or TIA
will have another stroke within 5 years.

2.2
Risk factors of stroke that can control

·
Hypertension
(High blood pressure).

·
 Atrial fibrillation( an abnormal heart rhythm)

·
Cigarette
smoking.

·
Excessive
alcohol intake

·
 Obesity,
unhealthy diet

·
High
cholesterol

·
Diabetes.

·
Physical
inactivity.

·
Stress.

Hypertension (High Blood
Pressure)

High
blood pressure is the most important
modifiable risk factor for stroke. The risk
of stroke increases 4 to 6 times when the person has high blood pressure. The
blood pressure measures the force of blood pushing against the walls of the
arteries. When the blood pressure is high, the heart has to pump harder to move
the blood through the body, which leads to weak blood vessels and damage to
major organs in the body. Normal blood pressure is 120/80 or below, whiles a
blood pressure reading of 140/90 and above is considered high blood pressure
(or hypertension).

Atrial
fibrillation (an abnormal heart rhythm)

Atrial
Fibrillation (AF) is a medical condition where the heart beats irregularly
because the two upper chambers of the heart beat rapidly and unpredictably.
Atrial fibrillation increases the risk of stroke up to 6 times because the
heart does not fully pump the blood out, which pools in the heart. When the
blood pools in the heart, the risk of blood clots forming is high. Once formed,
these blood clots will travel through the bloodstream into the brain
obstructing a blood vessel.

Cigarette
Smoking

Tobacco use damages blood
vessels. Don’t smoke and avoid second-hand smoke. This can contribute to atherosclerosis and can also cause the blood vessels to constrict, which leads to
restrictions in blood flow. Smoking increases
the heart rate and blood pressure. The associated risk increases with the
number of cigarettes smoked per day, and passive smoking also increases this
risk.

 Excessive alcohol intake

It is thought that excessive alcohol intake may also increase
the risk of ischemic stroke by bringing about a rise in blood pressure. However, although drinking too much
alcohol is known to inflate the risk, people who consume moderate amounts (less
than 3 units per day) actually have a lower risk than those who do not drink at
all. This may be because moderate alcohol intake can improve blood lipid
levels, and so protect against vascular diseases such as stroke.

Being
obese or overweight increases the risk of high blood pressure, high
cholesterol, diabetes, heart disease, which all increase the risk for stroke.
Unhealthy diet (including a low fruit and vegetable intake and a high salt
intake).

 High cholesterol

Cholesterol is a waxy, fat-like substance
produced by the liver and is used in different functions essential for the
body. If present in high amounts, cholesterol builds up in the veins and clogs
them (a condition called atherosclerosis). The build-up of plaque
inside the artery causes the walls to lose their elasticity and become weak and
hard.

Figure 5: Image of High Cholesterol

Diabetes

Diabetes is a medical condition where the body
either does not produce enough insulin, or the insulin is not properly used.
This disease is another major cause of stroke because the body can’t properly
process sugar (the basic fuel of the body’s cells) and fats. Diabetes also
leads to other medical complications such as high blood pressure, high
cholesterol, atherosclerosis, and obesity or excessive weight. Diabetes
interferes with the body’s ability to break down blood clots, which leads to an
increased risk of ischemic strokes. In general, those that suffer from diabetes
have a 2 to 4 times the risk of stroke than the non-diabetic population.

Physical Inactivity

In epidemiological studies comparing highly active to
sedentary individuals, physical activities are observed to reduce the risk of
both ischemic and hemorrhagic strokes. The 2008 Physical Activity Guidelines
for Americans concur in recommending regular physical activity to reduce
adverse health outcomes. In this guideline, most health benefits occur with at
least 150 minutes a week of moderate intensity, or 75 minutes a week of
vigorous intensity of aerobic physical activity. When adults with disabilities
are not able to meet these guidelines, they should engage in regular physical
activity according to their abilities, and they should avoid inactivity.
Exercise reduces blood pressure, decreases body weight, and improves other risk
factors, including metabolic syndrome the role of the health provider is
important and the physician’s advice regarding physical activity to patients
can significantly modify exercise and diet style, including those with a prior
stroke. One recent observation of note is associated with the onset of stroke
with physical activity. There might be an increased risk of stroke occurrence
within 1 hour of moderate or vigorous physical activity.

Drug abuse (certain kinds)

Intravenous
drug abuse carries a high risk of stroke from cerebral embolisms (blood clots).
Cocaine use has been closely related to strokes, heart attacks, and a variety
of other cardiovascular complications. Some of them, even among first-time cocaine
users, have been fatal.

 Cardiac structural abnormalities

Damaged
heart valves can cause chronic heart damage, which can ultimately increase the
risk of developing stroke. This is known as valvular heart disease. New
evidence shows that heart structure abnormalities including patent foramen
ovale and atrial septal defect may possibly increase risk for embolic stroke.

2.3 Risk factors for Ischemic
stroke

In general, the risk factors for having an ischemic stroke – a stroke that is caused by a blockage in
an artery supplying the brain – may be
divided into those that can be modified (improved upon), and those that cannot,
as discussed below.Although some risk factors cannot be changed – for example,
a person’s gender or age – it is still important to be aware of them. This is
because people who have a number of unmodifiable risk factors may benefit from
making a greater effort to improve those risk factors that can be modified.In
addition to these risk factors, which are often classed as ‘traditional’, we
are also starting to learn about more recently identified risk factors.

Modifiable risk factors for Ischemic stroke

Fortunately, we do have control over many of the risk factors
for ischemic strokes. These include the following:

• High blood pressure – the most important modifiable
  risk factor for stroke
• Smoking –
  this can contribute to atherosclerosis
  and can also cause the blood vessels to
  constrict, which leads to restrictions in blood
  flow. The associated risk increases with the number of cigarettes smoked
  per day, and passive smoking also increases this risk
• Excessive
  alcohol intake
• Obesity,
  unhealthy diet (including a low fruit and vegetable intake and a high salt
  intake)
• Physical
  inactivity
• Abnormal lipid levels (dyslipidaemia)
• Diabetes mellitus (associated with
  stroke and other forms of vascular disease at a younger than average age)
  and metabolic syndrome
• Carotid artery disease
• Atrial
  fibrillation, an abnormal heart rhythm
• Patent foramen oval (otherwise known as a ‘hole in
  heart’) – present in around 25 per cent of the general population, compared
  with 40 per cent of people who have had a stroke where no other cause is
  found
• Heart
  failure, endocarditis and other forms of
  heart disease
• Oral
  contraceptives – thought to increase the likelihood of the blood to clot

• Polycythaemia,
  a condition in which the red blood cell count is increased
• Sleep
  apnoea, which causes interruptions in breathing while a person sleeps and
  appears to be associated with a higher risk of stroke and other
  cardiovascular diseases
• Sickle cell disease, an inherited condition that
  results in the formation of abnormal, sickle-shaped red blood cells that can block small blood vessels, increasing the risk of an ischemic
  stroke. There is insufficient evidence to support the suggestion that sickle cell trait – a milder version of the disease
  – might also increase the risk.

It is thought that excessive alcohol intake may also increase
the risk of ischemic stroke by bringing about a rise in blood pressure. However, although drinking too much
alcohol is known to inflate the risk, people who consume moderate amounts (less
than 3 units per day) actually have a lower risk than those who do not drink at
all. This may be because moderate alcohol intake can improve blood lipid
levels, and so protect against vascular diseases such as stroke.

Non-modifiable risk factors for Ischemic stroke

Risk factors for stroke that cannot be modified include the
following:

• Male gender
• Older age
• Family
  history
• Past heart attack or stroke
• Ethnicity.

It has also been suggested that migraine may increase the
risk of an ischemic stroke, particularly in women under the age of 35. Migraine
with aura (in other words, migraine accompanied by additional symptoms such as
visual disturbance and numbness or tingling) is associated with reduced blood flow to the brain and inflammation.

Transient ischemic attack, or TIA,
is often referred to as a ‘mini-stroke’. Like a stroke, it is a disturbance in
the function of the nervous system that is caused by a problem with the blood supply to the brain. However, unlike stroke,
the symptoms of TIA settle down within 24
hours.

People who have had a TIA
are known to have a higher risk of a stroke in the future. The chance of
someone who’s had a TIA having a stroke
within 3 months has been estimated to be between 15 and 20 per cent.

Recently identified risk markers

Additional markers (indicators) associated with an increased
risk of ischemic stroke include elevated levels in the blood of:

• Homocysteine
  (a marker that is associated with early-onset atherosclerosis)
• Lipoprotein(a)
  (a type of lipid in the bloodstream that
  is similar to LDL-cholesterol)
• High-sensitivity
  C-reactive protein (CRP; a protein in the blood that suggests inflammation)
• High blood levels of fibrinogen
  (a protein that helps the blood to clot)
• Apolipoprotein
  B (APOB; the protein part of low-density lipoprotein
  (LDL).

2.4 Risk factors for
Hemorrhagic stroke

Some of the risk factors for a hemorrhagic stroke – a stroke caused by a bleed – differ from
those of an ischemic stroke and so are looked at separately.

Modifiable risk factors
for Hemorrhagic stroke

Those risk factors for hemorrhagic stroke that we can improve
upon include:

• High blood pressure – one of the most important
  modifiable risk factors for stroke
• Impaired
  ability of the blood to clot due to
  medication (‘anti-clotting’ drugs, anticoagulants; or ‘clot-busting’
  drugs, thrombolytic)
• Smoking,
  excess alcohol intake and substance misuse (for example, amphetamines and cocaine)
• Lipid
  levels. Unlike ischemic strokes, it seems that reducing cholesterol levels actually increases the risk
  of hemorrhagic strokes
• Vascular
  malformations. These may include arteriovenous malformations, cavernous
  haemangiomas and aneurysms (an aneurysm
  is an abnormal dilation, or bulge, in the wall of an artery.) Vascular malformations are prone to
  rupture. Fortunately, they can sometimes be treated with surgery to reduce
  the risk.
• Conditions
  that interfere with blood clotting, for example,
  blood dyscrasia (an abnormality in the
  balance of the different components of the blood).
  Treatment may lower the risk.

Non-modifiable risk
factors for Hemorrhagic stroke

The risk factors for hemorrhagic stroke that cannot be
modified include the following:

• Increasing
  age. This may be partly because older age is associated with small blood vessel disease, which can increase the
  risk of blood vessel rupture. Increasing
  age also increases the likelihood of the condition amyloid angiopathy,
  which leads to protein build-up in the arteries of the brain, increasing
  the risk of bleeding.
• Ethnicity.

Symptoms similar to a stroke can also sometimes arise as a
result of damage to blood vessels in the
brain following a head injury.

2.5
Other risk factors that can lead to a stroke

·
Other
factors such as oral contraceptive use

·
Hormone
replacement therapy or

·
 Pregnancy and childbirth in women with
pre-existing medical conditions may increase the risk of stroke in specific
cases.

·
Other
medical conditions such as amyloid angiopathy and antiphospholipid antibody
syndrome

·
Use
of illicit drugs such as cocaine or LSD.

·
Some
medications, such as tamoxifen, phenylpropanolamine, and thrombolytic.

In general, the risk factors for having an ischaemic stroke – a stroke that is caused by a blockage in
an artery supplying the brain – may be
divided into those that can be modified (improved upon), and those that cannot,
as discussed below. Although some risk factors cannot be changed – for example,
a person’s gender or age – it is still important to be aware of them. This is
because people who have a number of unmodifiable risk factors may benefit from
making a greater effort to improve those risk factors that can be modified.In
addition to these risk factors, which are often classed as ‘traditional’, we
are also starting to learn about more recently identified risk factors. Some of
the risk factors for a hemorrhagic stroke – a
stroke caused by a bleed – differ from those of an ischemic stroke and so are
looked at separately.

2.6
Self Assessment Chart of Stroke Risk

This is just a guide, but it demonstrates measures that can
take to decrease your risk of stroke.

Chapter
– 3

3.1
Mechanisms of Stroke

3.1.1
Biophysical Mechanisms of Stroke

Although the consequences of both
ischemic and hemorrhagic stroke are similar in that a vessel obstruction and
the resultant reduced blood flow to the brain may lead to neurological deficits
and possibly death, the biophysical and hemodynamic mechanisms behind the
obstruction of blood flow are different. Biophysical mechanisms for the
development of obstructions that ultimately lead to stroke can arise by six
distinct processes: atherosclerosis, embolus, thrombus, reduced systemic
pressure, hemorrhage, and vasospasm.

Atherosclerosis

Atherosclerosis, commonly referred to as “hardening of the
arteries,” is a pathological process in which calcified lipid or fatty deposits
from the flowing blood accumulate circumferentially along the innermost intimal
layer of the vessel wall (Fig 1?). Atherosclerotic plaques are found almost
exclusively at the outer wall (hip) of one or both daughter vessels at major
bifurcations, including the carotid. Atherosclerosis and the development of
arterial plaques are the product of a host of independent biochemical processes
including the oxidation of low-density lipoproteins, formation of fatty
streaks, and the proliferation of smooth muscle cells. As the plaques form, the
walls become thick, fibrotic, and calcified, and the lumen narrows, reducing
the flow of blood to the tissues the artery supplies.

Figure
6:  Schematic diagram of the distribution of
atherosclerotic plaque along the inner wall of the carotid artery bifurcation.

Atherosclerotic deposits promote the development of blood
clots or the process of thrombosis due in part to flow obstruction and to high
shear stresses exerted on the vessel wall by the blood. High wall shear stress
might mechanically damage the inner wall of the artery, initiating a lesion. On
the other hand, low wall shear stress might encourage the deposition of
particles on the artery wall, promoting the accumulation of plaque. Turbulence
has also been implicated in atherosclerotic disease both because it can
increase the kinetic energy deposited in the vessel walls and because it can
lead to areas of stasis, or stagnant blood flow, that promote clotting. In
addition, the presence of atherosclerotic lesions introduces an irregular
vessel surface that, as a result of turbulent blood flow, can cause the
dislodgment of plaques of varying size into the bloodstream until the plaque
lodges into a vessel of smaller size, preventing further passage of blood flow.
Atherosclerotic thrombosis accounts for 33% of all stroke cases.

Embolus

An embolus represents gaseous or particulate (eg, atheromata)
matter that acts as traveling “clots.” A common example of emboli is a platelet
aggregate dislodged from an atherosclerotic lesion. The dislodged platelet
aggregate is transported by the bloodstream through the cerebrovasculature
until it reaches vessels too small for further propagation. The clot has
nowhere to go and remains there, clogging the vessel and preventing blood flow
from entering the distal vasculature. Although our discussion at the present is
focused primarily on the carotid arteries and associated cerebrovasculature,
emboli can originate from distant sources such as the heart, lungs, and
peripheral circulation, which could eventually travel within the cerebral blood
vessels, obstructing flow and causing stroke. Other sources of emboli include
atrial fibrillation and valvular disease. The severity of stroke depends on the
size of the embolus and the location of the obstruction. The bigger the embolus
and the larger the vessel obstruction, the larger the territory of brain at
risk. Approximately 31% of all stroke cases are attributed to emboli.

Thrombus

Thrombosis is an internal physiological mechanism responsible
for the clotting of blood. A thrombus is a blood clot, an aggregation of
platelets and fibrin formed in response either to an atherosclerotic lesion or
to vessel injury. In response to vessel or tissue injury, the blood coagulation
system is activated, which initiates the following cascade of processes
transforming prothrombin and resulting in a fibrin clot:  

????Fibrin Clot

Although a host of mechanisms and causes are responsible for
vessel injury, vessel injury can occur as a result of forces (shear stresses)⁷ coupled with the excess energy created
by the turbulent flow⁸910 exerted against the inner (intimal)
lining of the vessel wall, particularly an atherosclerotic vessel wall.
Approximately 33% of all stroke cases are attributed to thrombi.

Reduced Systemic Pressure

The previously described mechanisms of blood flow obstruction
leading to stroke occur along localized regions of the cerebral arteries. It is
assumed in this instance that the heart is functioning normally under proper
systemic pressure. Cardiovascular diseases such as atrial fibrillation and
myocardial infarction weaken the cardiac wall and introduce abnormalities in
the physiological function of the heartbeat, which ultimately result in reduced
systemic pressure and conditions of ischemia.

Hemorrhage

Blood vessels are typically structurally adept to withstand
the dynamic quantities required to maintain circulatory function. For reasons
that are not entirely understood, the vessel wall can become fatigued and
abnormally weak and possibly rupture. With vessel rupture, hemorrhage occurs
with blood seeping into the surrounding brain tissue. As the blood accumulates
within the brain, the displaced volume causes the blood, now thrombosed, to
ultimately compress the surrounding vessels. The compression of vessels
translates into a reduced vessel diameter and a corresponding reduction in flow
to surrounding tissue, thereby enlarging the insult. Among the vascular lesions
that can lead to hemorrhagic strokes are aneurysms and arteriovenous malformations
(AVMs).

Brain Aneurysms

?,
is a form of cerebrovascular disease that manifests itself as a pouching or
ballooning of the vessel wall. The vascular dilatation develops at a diseased
site along the arterial wall into a distended sac of stressed and thinned
arterial tissue. The fully developed cerebral aneurysm typically ranges in size
from a few millimeters to 15 mm but can attain sizes greater than 2.5 cm. If
left untreated; the aneurysm may continue to expand until it ruptures, causing
hemorrhage, severe neurological complications and deficits, and possibly death.
In the United States, approximately 28 000 aneurysms rupture each year;
approximately 50% of these patients die or become permanently disabled as a
result of the initial hemorrhage, and another 25% to 35% die of a future
hemorrhage.

Blood flow in most aneurysms is regular and predictable
primarily according to the geometric relationship between the aneurysm and its
parent artery. As blood flows within the parent artery with an aneurysm,
divergence of blood flow, as occurs at the inlet of the aneurysm, leads to
dynamic disturbances with a Bernoulli Effect, producing increased lateral
pressure and retrograde vortices that are easily converted to turbulence.¹³ Blood flow proceeds from the parent
vessel into the aneurysm at the distal or downstream extent of the aneurysm
neck, circulates around the periphery along the aneurysm wall from the neck to
the top of the fundus (downstream to upstream), returning in a type of
“isotropic shower” along the aneurysm wall toward the neck region, and exits
the proximal or closest extent of the aneurysm neck into the parent vessel.

As flow persists, areas of stagnation or vortices develop
within a central zone of the aneurysm. These rotating vortices, formed at the
entrance to the aneurysm at each systole and then circulated around the
aneurysm, are caused by the slipstreams or regions of recirculating flow
rolling upon themselves when they enter the aneurysm at its downstream wall
during systole. The stagnant vortex zone occurs in the center and at the fundus
or upper portion of the aneurysm and becomes more pronounced in larger
aneurysms. It is this stagnant zone that is believed to promote the formation of
thrombi or blood clots, particularly in giant aneurysms.

Brain Arteriovenous Malformations

The normal human circulation originates from the heart and
consists of a branching arrangement of arteries of continually decreasing size
until they feed into a capillary bed before exiting the bed through small veins
that increase in size before returning to the heart. The capillary bed serves
an important purpose in that its vascular resistance slows the flow of blood
considerably to allow perfusion of oxygen and nutrients to surrounding tissue
and removal of cellular waste. In one form of cerebrovascular disease, AVMs,
the vessels constituting the capillary bed of the brain become malformed during
embryonic development and prohibit the opportunity for blood to properly
perfuse into the surrounding tissue.

?,
are congenital vascular lesions that occur as a result of capillary
maldevelopment between the arterial and venous systems. Approximately 0.14% of
the United States population has an intracranial AVM that poses a significant
risk and represents a major life threat, particularly to persons under the age
of 50 years. The vessels constituting the AVM are weak and enlarged and serve
as direct shunts for blood flow between the high-pressure arterial system and
the low-pressure venous system, corresponding to a large pressure gradient and
small vascular resistance. The abnormal low-resistance, high-flow shunting of
blood within the brain AVM without an intervening capillary bed causes the
fragile dilated vessels in the nidus to become structurally abnormal and
fatigued, to further enlarge, and possibly to rupture.

Figure
7:  A, MR angiogram of a human arteriovenous
malformation. B, Schematic diagram of a brain arteriovenous malformation,
depicting the structural and angioarchitectural components.

The abnormal microvessels of an AVM serve as passive conduits
for blood flow from the arterial circulation directly to the venous
circulation, bypassing their normal physiological function of brain tissue
perfusion. The hemodynamic consequences of an AVM occur as a result of two
interdependent circulatory mechanisms involved in the shunting of blood between
artery and vein.

In the normal cerebral circulation, blood flows under a high
cerebrovascular resistance and high cerebral perfusion pressure. However, the
presence of a brain AVM in the normal circulation introduces a second abnormal
circuit of cerebral blood flow where the blood flow is continuously shunted
under a high perfusion pressure through the AVM, possessing a low
cerebrovascular resistance and low venous pressure. The clinical consequence of
the abnormal shunt is a significant increase in blood returning to the heart
(?4 to 5 times the original amount, depending on the diameter and size of the
shunt), resulting in a dangerous overload of the heart and possible cardiac
failure. Volumetric blood flow through an AVM ranges from 200 mL/min to 800
mL/min and increases according to nidus size.

The abnormal shunting of blood flow by brain AVMs rapidly
removes or “steals” blood from the normal cerebral circulation and
substantially reduces the volume of blood reaching the surrounding normal brain
tissue. This phenomenon, known as cerebrovascular steal, depends on the size of
the AVM and is the most plausible explanation for the development of
progressive neurological deficits. Cerebrovascular steal could translate into
additional neurological complications developed as a result of cerebral
ischemia or stroke in neuronal territories adjacent to an AVM.

Vasospasm
When bleeding
occurs in the subarachnoid space, the arteries in the subarachnoid space can
become spastic with a muscular contraction, known as cerebral vasospasm. The
contraction from vasospasm can produce a focal constriction of sufficient
severity to cause total occlusion. The length of time that the vessel is
contracted during vasospasm varies from hours to days. However, regardless of
the duration of vessel constriction during vasospasm, reduction of blood flow
induces cerebral ischemia, thought to be reversible within the first 6 hours
and irreversible thereafter. It has been shown that vasospasm is maximal
between 5 and 10 days after subarachnoid hemorrhage and can occur up to 2 weeks
after subarachnoid hemorrhage. The resultant damage to brain tissue can be
minimized with the administration of pharmacological agents such as the
vasodilator papaverine.

3.1.2 Inflammatory Mechanisms of Stroke

Basic and clinical research provides evidence that
inflammatory mechanisms play a central role in the pathogenesis and progression
of atherosclerosis, plaque rupture, thrombosis, and stroke. Inflammatory
biomarkers such as high-sensitivity C-reactive protein have been identified as
predictors of first stroke and prognosis after stroke. The value of
high-sensitivity C-reactive protein and other markers may depend on the
characteristics of the study population; their utility may be less among
populations with high vascular risk. A recent randomized, clinical trial
suggests that the use of rosuvastatin therapy in otherwise healthy patients
with high-sensitivity C-reactive protein >2 mg/dL can reduce the risk of a
first stroke by 50%. The prognostic role of high-sensitivity C-reactive protein
among patients after stroke, however, is less clear, and other biomarkers,
including lipoprotein-associated phospholipase A₂, may provide
complementary information about the risk of stroke recurrence. Infections,
moreover, may contribute to inflammation and stroke risk. Although no single
infectious organism is likely to be identified as the direct cause of
atherosclerosis, summary measures of multiple chronic infectious exposures, or
“infectious burden,” have been associated with the risk of stroke and
atherosclerosis affecting the carotid arteries. Acute infections have also been
found to serve as stroke triggers in epidemiologic studies. Recommendations to
vaccinate patients with cardiovascular disease against influenza represent the
first specific anti-infective strategy to be used in vascular prophylaxis.
Further studies are needed to determine the role of treatment of inflammation
and infection in stroke prevention.

3.1.3 Mechanisms of cardio
embolic stroke

Cardiac embolism is often
involved as a mechanism for embolic stroke, and may be implicated in many
strokes that have traditionally been considered of unknown origin (cryptogenic
strokes). In recent years, significant advancements have been made in understanding
and reducing the risk of stroke from long-known cardio embolic sources (atrial
fibrillation, intracardiac thrombus or tumor, infective endocarditic). Also,
improved cardiac imaging, especially transesophageal echocardiography, has
allowed the identification of newer embolic sources of stroke (aortic
atheromas, patent foramen ovale, atrial septal aneurysm). This article reviews
the current understanding of cardiac embolism as a mechanism for stroke, and
the preventive options that are currently adopted to decrease the stroke risk.

3.1.4 Mechanism of stroke complicating
cardiopulmonary bypass surgery

Stroke is a devastating complication of cardiopulmonary
bypass (CPB) surgery which occurs in 1 to 5% of cases. Strategies to reduce its
incidence require knowledge of the underlying pathology and etiology. To
determine the incidence, pathology and etiology of stroke complicating CPB.
Prospective review of clinical, operative and cranial CT scan findings in all
cases of stroke complicating CPB procedures in our institution over an 18 month
period. Twenty-one (1.6%, 95% CI 0.9-2.3%) cases of stroke were identified from
1336 CPB procedures. Cranial CT scan, performed in all but one patient, was
normal in three patients or consistent with ischemic stroke in 17 patients.
There were no cases of hemorrhagic infarction or intracerebral haemorrhage. It
was difficult to differentiate embolic and borderzone infarcts in two cases.
After considering the clinical, operative and CT scan features together, 12
(57%, 95% CI 36-78%) of the cases were felt to be embolic in origin and nine
(43%, 95% CI 22-64%) due to hypoperfusion in a borderzone. This study
demonstrates that stroke remains an important complication of CPB procedures
with an incidence in our series of 1.6%. The pathologic type of stroke is
predominantly ischaemic in nature due to either cerebral embolism or borderzone
infarction. Strategies for stroke prevention in patients undergoing CPB should
be targeted primarily at these two mechanisms.

3.2 Prevention of Stroke

Strokes are usually the result of a combination of factors
that have been present or developing for a long period of time. If someone has
two or more of the risk factors below, stroke risk is dramatically increased.
Anyone who is high risk should see their doctor who will usually assess each
risk factor for stroke (and heart disease) before deciding on necessary
treatments.

Here are some
simple rules to reduce stroke risk:

Get blood
pressure checked

Because it is one of the greatest stroke risk factors,
failure to detect and control high blood pressure is the number one cause of
avoidable strokes. A person with high blood pressure is up to seven times more
likely to have a stroke than someone with normal or low blood pressure. High
blood pressure puts too much pressure and stress on the walls of blood vessels
and increases the risk of both hemorrhages’ and blood clots.

Stop smoking

Smoking quadruples stroke risk. Chemicals and gases in
tobacco smoke speed up the process of atherosclerosis (hardening of the
arteries) and make blood vessels throughout the body tighten, reducing blood
flow. Smoking also makes the blood more likely to clot, especially inside
damaged blood vessels.

Note: If one smoke and have high blood pressure you are 18
times more likely to have a stroke than someone the same age that doesn’t smoke
and has normal blood pressure.