Computed tomography (CT)

What is a CT scanner?

A CT (computerised tomography) scanner is a special kind of X-ray machine. Instead of sending out a single X-ray through your body as with ordinary X-rays, several beams are sent simultaneously from different angles.

How does a CT scanner work?

The X-rays from the beams are detected after they have passed through the body and their strength is measured.

Beams that have passed through less dense tissue such as the lungs will be stronger, whereas beams that have passed through denser tissue such as bone will be weaker.

A computer can use this information to work out the relative density of the tissues examined. Each set of measurements made by the scanner is, in effect, a cross-section through the body.

The computer processes the results, displaying them as a two-dimensional picture shown on a monitor. The technique of CT scanning was developed by the British inventor Sir Godfrey Hounsfield, who was awarded the Nobel Prize for his work.

What are CT scans used for?

CT scans are far more detailed than ordinary X-rays. The information from the two-dimensional computer images can be reconstructed to produce three-dimensional images by some modern CT scanners. They can be used to produce virtual images that show what a surgeon would see during an operation.

CT scans have already allowed doctors to inspect the inside of the body without having to operate or perform unpleasant examinations. CT scanning has also proven invaluable in pinpointing tumours and planning treatment with radiotherapy.

What is the CT scanner used for?

The CT scanner was originally designed to take pictures of the brain. Now it is much more advanced and is used for taking pictures of virtually any part of the body.

The scanner is particularly good at testing for bleeding in the brain, for aneurysms (when the wall of an artery swells up), brain tumours and brain damage. It can also find tumours and abscesses throughout the body and is used to assess types of lung disease.

In addition, the CT scanner is used to look at internal injuries such as a torn kidney, spleen or liver; or bony injury, particularly in the spine. CT scanning can also be used to guide biopsies and therapeutic pain procedures.

How is a CT scan prepared for?

If the patient is receiving an abdomen scan, for example, they will be asked not to eat for six hours before the test. They will be given a drink containing gastrografin, an aniseed flavoured X-ray dye, 45 minutes before the procedure. This makes the intestines easier to see on the pictures.

Sometimes a liquid X-ray dye is injected into the veins during the test. This also makes it easier to see the organs, blood vessels or, for example, a tumour. The injection might be a little uncomfortable, and some people also experience a feeling of warmth in their arm.

How is a CT scan carried out?

The scanner looks like a large doughnut. During the scan the patient lies on a bed, with the body part under examination placed in the round tunnel or opening of the scanner. The bed then moves slowly backwards and forwards to allow the scanner to take pictures of the body, although it does not touch the patient. The length of the test depends on the number of pictures and the different angles taken.

How is a CT scan carried out?

The examination does not hurt but some people find it uncomfortable to lie in the tunnel. As there is little room inside the tunnel, people who suffer from severe claustrophobia sometimes have problems with CT scans.

Let the doctors and radiographers know if this might be a problem. Other people get slightly nervous because of the whirring noise the machine makes while working.

Is a CT scan dangerous?

Far more X-rays are involved in a CT scan than in ordinary X-rays, so doctors do not recommend CT scans without a good medical reason. Some patients may experience side effects due to allergic reactions to the liquid dye injected into the veins.

In very rare cases, this dye has been known to damage already weakened kidneys. It is important to let the X-ray doctors or technicians know if you have any allergies, asthma or kidney trouble , prior to having the X-ray dye injected.

How is a CT scan read?

A CT scan can give the doctor a much clearer picture of the inside of the body than an ordinary X-ray. For example, different types of tissue such as bone, muscle and fatty tissue are easy to see on a CT scan. When looking at the abdomen, the scan shows various organs such as the pancreas, spleen and liver.

When it is necessary to look at the brain, the areas containing liquid - the ventricles - are also clearly defined. Very small shadows on the lungs can also be detected using CT and there are now studies looking into using it as a screening test for lung cancer.

How to Avoid Another Stroke

Secondary prevention to reduce your risk

Secondary prevention is a very serious matter

40% of stroke survivors have a second stroke within five years with the highest risk being in the first few months after the stroke or TIA.

A repeat stroke is frequently more devastating than the first.

Lifestyle adjustments often need to be made- these seem simple but require commitment and permanence.

Secondary prevention measures include:

• Regular checks by your doctor for:
  Blood pressure
  Cholesterol
  High blood pressure and high cholesterol usually respond well to medication taken as prescribed
  Diabetes
  Control diabetes by following medical advice carefully
  Heart beat
• Don’t smokeStopping smoking is not easy for the dedicated smoker – but it is vital - it is possible to give up cigarettes. Assistance is available.
• Reduce your stress levels
• Limit your alcohol intake
• Manage your weight
• Exercise regularlyMany forms of exercise are available to suit individual tastes. Walking is easy –no special equipment, can be done at any time, in most weather –exercise that also provides fun, pleasure and companionship is very valuable.
• Eat a balanced diet, avoid food high in salt and fat
• Enjoy work and play
• Follow medical advice faithfully
  

Life After Stroke

Patients are generally encouraged to return to their normal lives - depending on the effects persisting from stroke

Some aspects of life after stroke include:

• Resuming work How soon this is possible depends partly on remaining disability, the type of work involved, and the feelings about returning to work. Some people feel quite tired after a stroke, and have difficulty carrying out any kind of physical activity for any length of time. Part-time work at least in the early stages may be a good idea. Unless the stroke has reduced awareness of impairment, it is probable that the person who had the stroke is the best judge of when to return to work.
• Driving Even someone who appears to have made a full recovery after stroke should not drive a car for at least a month as the risk of another stroke is greatest at this time. To drive again involves being cleared by the doctor (who will be aware of relevant government regulations) as the stroke may have left subtle impairments, not always apparent, such as poor co-ordination, lack of awareness on one side, difficulties in judging distance, changes in vision, difficulties in concentration and confusion between left and right.
• Sexual activity Resumption of sexual activity after stroke is encouraged. Most couples experience some difficulty in their sex life after stroke, but this is usually due to psychological factors rather than any disability caused by stroke. A doctor can advise on any difficulty such as erectile problems in men.
• Sport and Exercise Resumption of physical activity and hobbies is an important part of rehabilitation- normal activity should be resumed as soon as physically possible.
• Drinking Alcohol The intake of excessive amounts of alcohol should be avoided after stroke as it may interact adversely with medication, raise blood pressure, and affect judgement resulting in injury. Moderate consumption (two standard drinks per day) should not cause any problem.

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital
Date created: 26 September 2003

Treatment of Stroke

Regular medical supervision, medication and lifestyle changes

Medical advice will be given on continuing care for stroke survivors and may include:

• Regular medical supervision
  Regular checks of blood pressure, and cholesterol levels leading to appropriate medication
  Carotid surgery -one in ten stroke patients have a very narrow artery in the front of the neck on one side (the carotid artery) that restricts the flow of blood to the brain. Surgery to open and clear the artery or to place a small cylinder (stent) in it will increase the flow.
• Medication – two kinds of tablets are prescribed: “clot-busters” and blood-thinners
  Anti-clotting (antiplatelet) medication, such as aspirin, probably in combination with another drug such as clopidogrel or dipyridamole (for those patients who have had an ischaemic stroke caused by a clot forming on an area of hardening of the arteries).
  Anti-coagulant medication (such as warfarin) where an ischaemic stroke has been caused by a blood clot forming in the heart, breaking off and lodging in the brain. These drugs are very powerful, may have significant side effects and must be carefully supervised by the doctor.
• Changes to lifestyle
  Attention to diet, which should be varied, but low in saturated fat, alcohol, and salt, and high in fibre, fruit and vegetables.
  Avoidance of smoking - this is absolutely essential.
  Stress management - stress in life is unavoidable but can be reduced by various strategies including exercise, changing attitudes to work, meditation and relaxation.
  Regular exercise – which will help to regulate weight and improve circulation.

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital
Date created: 26 September 2003

Effects of Stroke

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.

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 hemiplegia.

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 hemiplegia.

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 conceptualising and generalising.

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.

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.

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 counselling 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 theexcessive 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-centred, 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.

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital

Date created: 26 September 2003

Symptoms of Stroke

The symptoms of stroke usually come on suddenly. The suddenness of onset distinguishes stroke from other conditions such as migraine or brain tumour. Every patient is affected differently and the most common symptoms are:

• Sudden numbness or weakness of face, arm or leg, often one side of the body.

A lack of muscle strength in any group of muscles, most commonly those on the face, hand, arm and leg on one side (called hemiparesis). At least half of patients suffer some form of hemiparesis, some with a mild form that involves difficulty in controlling movement, rather than weakness.

A loss of sensation or feeling in any part of the body. Numbness of the skin of the face, hand, arm, and leg on one side (hemiananaesthia) is most common.

• Sudden confusion, trouble speaking or understanding.

Difficulty in speech - slurring of speech (from weakening of face, mouth, throat muscles) may be accompanied by swallowing difficulty. There may be difficulty understanding others’ speech, finding the right words, understanding written words or in writing (aphasia).

• Sudden trouble seeing in one or both eyes.

Difficulty with vision - may take the form of total loss of vision in one eye, or loss of vision in half the visual field of each eye, or double vision.

• Sudden trouble walking, dizziness loss of balance or co-ordination.

Dizziness - injury to inner ear nerves may cause loss of balance, a spinning feeling, of the world moving (vertigo). May cause nausea, unsteadiness on the feet, a tendency to veer to one side or the other, or an unexplained fall.

• Sudden severe headache with no known cause.

Headache - stroke and TIA do not usually cause headache, but headache may result from stretching or irritation of the membrane covering the brain (meninges) or the blood vessels in the brain.

Subarachnoid haemorrhage may be preceded by the sudden (within seconds) onset of an extremely severe ‘thunderclap’ headache (the most intense the patient has ever felt), together with neck stiffness. Irritation from light may also be a problem. After minutes to hours the headache spreads to the back of the head, neck and back as blood tracks down the spinal subarachnoid space. Subarachnoid hemorrhage may be associated with drowsiness or loss of consciousness and with other stroke symptoms.

• Less common symptoms include:

Nausea and vomiting- can be associated with vertigo or involvement of the ‘vomiting centre’ (the medulla) of the brain; common at the outset of subarachnoid haemorrhage.

Drowsiness or unconsciousness - also not common, but may occur, often briefly, depending on the location of the injury in the brain.

Epileptic seizures (10% of patients with subarachnoid haemorrhage).

Symptoms of Transient Ischaemic Attack (TIA)

The symptoms of TIA are not easily distinguished from those of stroke, except that they do not last as long. They may include:

• Short term blindness, blurred vision, double vision, other visual disturbances
• Speech disturbance – often an inability to put thoughts into words, or the substitution of a similar word for another of different meaning (‘I bent on the ball’ for ‘I leant on the wall’), or slurring of speech
• Vertigo – a spinning sensation – usually in conjunction with other symptoms
• Facial numbness or weakness
• Swallowing difficulty
• Arm or leg weakness or paralysis
• Loss of balance
• Nausea and vomiting

A TIA is significant and must not be ignored. Advice must be sought immediately.

A TIA may be the start of a stroke that can follow the TIA within hours.

A TIA can warn of a future stroke and rapid investigation and treatment can reduce the risk of having a stroke.

If the symptoms disappear quickly, a TIA may be diagnosed and the patient discharged with appropriate instructions for medical follow-up, investigation and treatment to minimise the risk of recurrence.

If the symptoms persist, tests to determine the nature, precise location and extent of the injury to the brain will be started. These are likely to include Brain scans (Computer Tomography) and MRIs (Magnetic Resonance Imaging).

Treatment to may be started to rescue damaged brain tissue, to prevent complications such as difficulty swallowing, and to minimise the chance of further strokes.

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital, Australia

Date created: 26 September 2003

How to Reduce the Risk of Stroke?

Regular checks by your doctor and lifestyle changes

Visit your doctor for regular checks

• Blood pressure - Your doctor will if necessary prescribe appropriate medication – most hypertension drugs are now virtually side-effect free and very effective.
• Cholesterol - can often be controlled by diet, but if necessary cholesterol-lowering medication can be prescribed.
• Diabetes - iIf you have diabetes follow your doctor’s instructions regarding diet and medication carefully.
• Heart beat - a form of irregular heart beat called atrial fibrillation is associated with an increased risk of stroke.

A recent study recommends that GPs screen patients as young as 30 for risk factors for stroke. This recommendation follows a large audit in Australia, which found that 70% of patients had one or more risk factors for stroke and 24% had two or more. Hypertension was the most common risk factor (44%).

Be especially vigilant if you have a family history of heart disease or stroke.

Don’t smoke

Reduce your stress levels

Limit your alcohol intake

Manage your weight

Exercise regularly

A brisk 30 minute walk daily or other regular exercise (cycling, tennis, swimming, aerobics) will assist weight control and improve your health in many ways.

Eat a balanced diet, avoid food high in salt and fat

A diet that includes plenty of fruit and vegetables, bread and cereals, and is low in fat and salt will help in both weight and cholesterol control.

Enjoy work and play

Balance work and leisure time

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital

Date created: 26 September 2003

What is a Stroke?

What is a Stroke?

Two major types of stroke ischaemic and haemorrhagic

A stroke occurs when a blood clot blocks a blood vessel or artery, or when a blood vessel breaks and interrupts blood flow to an and bleeding occurs into an area of the brain.

Every stroke is different. The symptoms and effects vary according to the type of stroke, the part of the brain affected and the size of the damaged area. For some people the effects are severe, for some mild. Usually the symptoms come on suddenly but they may come on during sleep. Usually injury to one side of the brain affects the opposite side of the body.

There are two major types of stroke:

• An Ischaemic Stroke occurs when an artery carrying blood to part of the brain is blocked. The brain needs the constant supply of oxygen and glucose that the blood brings. If this blood supply is blocked for more than a few minutes then that part of the brain stops working properly and brain tissue at the centre of the area affected begins to die. If the blockage is not cleared within a few hours then that all the part of the brain supplied by the blocked vessel may die; that is, it permanently ceases to work properly. This is called brain infarction. Ischaemic strokes are the most common type of stroke, occurring more than five times as often as haemorrhagic stroke cerebral haemorrhages.
• A Haemorrhagic Stroke Cerebral Haemorrhage occurs when a blood vessel ruptures within the brain (called an intracerebral haemorrhage) or into the space surrounding the brain (called a subarachnoid haemorrhage). Blood in the artery is under pressure and so, as it spurts out, it tears some of the soft brain tissue and forms a large clot (or haematoma) that squashes the surrounding brain. Brain tissue on the rim of thein and around the clot may therefore die.

A mini stroke is called a Transient Ischaemic Attack (TIA).

• About 30% of patients who subsequently have an ischaemic stroke have a small warning episode termed a transient ischaemic attack.
• A TIA is like an ischaemic stroke in that it is results in the sudden loss of function of a particular part of the body because of a sudden lack of blood flow to a part of the brain.
• The difference between a TIA and an ischaemic stroke is that in a TIA the symptoms disappear completely within 24 hours. In 75% of cases the symptoms clear within one hour, often within only a few minutes, because the blockage in the artery clears itself very quickly before the affected brain tissue has died. 30% of people have damage evident on sensitive brain imaging techniques such as MRI after a TIA.
• A TIA is a very important warning that the person is at increased risk of a future stroke. It is essential that proper medical treatment is sought so that this risk can be significantly reduced.

Reviewed by Professor Alastair Corbett, Consultant Neurologist, Concord Hospital, Australia

Date created: 26 September 2003

MULTI - INFARCT

What is Multi-Infarct Dementia?

Multi-infarct dementia (MID) is a common cause of memory loss in the elderly. MID is caused by multiple strokes (disruption of blood flow to the brain). Disruption of blood flow leads to damaged brain tissue. Some of these strokes may occur without noticeable clinical symptoms. Doctors refer to these as “silent strokes.” An individual having a silent stroke may not even know it is happening, but over time, as more areas of the brain are damaged and more small blood vessels are blocked, the symptoms of MID begin to appear. MID can be diagnosed by an MRI or CT of the brain, along with a neurological examination. Symptoms include confusion or problems with short-term memory; wandering, or getting lost in familiar places; walking with rapid, shuffling steps; losing bladder or bowel control; laughing or crying inappropriately; having difficulty following instructions; and having problems counting money and making monetary transactions. MID, which typically begins between the ages of 60 and 75, affects men more often than women. Because the symptoms of MID are so similar to Alzheimer’s disease, it can be difficult for a doctor to make a firm diagnosis. Since the diseases often occur together, making a single diagnosis of one or the other is even more problematic.

Is there any treatment?

There is no treatment available to reverse brain damage that has been caused by a stroke. Treatment focuses on preventing future strokes by controlling or avoiding the diseases and medical conditions that put people at high risk for stroke: high blood pressure, diabetes, high cholesterol, and cardiovascular disease. The best treatment for MID is prevention early in life – eating a healthy diet, exercising, not smoking, moderately using alcohol, and maintaining a healthy weight.

What is the prognosis?

The prognosis for individuals with MID is generally poor. The symptoms of the disorder may begin suddenly, often in a step-wise pattern after each small stroke. Some people with MID may even appear to improve for short periods of time, then decline after having more silent strokes. The disorder generally takes a downward course with intermittent periods of rapid deterioration. Death may occur from stroke, heart disease, pneumonia, or other infection.

CT BRAIN INFARCT

Stroke

What causes a stroke?

Stroke is a disease that affects the blood vessels that supply blood to the brain.

A stroke occurs when a blood vessel that brings oxygen and nutrients to the brain bursts or is clogged by a blood clot or some other mass. Because of this rupture or blockage, part of the brain doesn't get the blood and oxygen it needs. Deprived of oxygen, nerve cells in the affected area of the brain can't work and die within minutes. And when nerve cells can't work, the part of the body they control can't work either. The devastating effects of a severe stroke are often permanent because dead brain cells aren't replaced.

There are two main types of stroke. One (ischemic stroke) is caused by blockage of a blood vessel; the other (hemorrhagic stroke) is caused by bleeding. Bleeding strokes have a much higher fatality rate than strokes caused by clots.

What is ischemic stroke?

Ischemic stroke is the most common type. It accounts for about 88 percent of all strokes. It occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain. Blood clots usually form in arteries damaged by fatty buildups, called atherosclerosis.

When the blood clot forms within an artery of the brain, it's called cerebral thrombotic stroke. These often occur at night or first thing in the morning. Another distinguishing feature is that very often they're preceded by a transient ischemic attack. This is also called a TIA or "warning stroke."

What is a cerebral embolism?

A wandering clot (an embolus) or some other particle that forms away from the brain, usually in the heart, may also cause an ischemic stroke. This is called cerebral embolism. The clot is carried by the bloodstream until it lodges in an artery leading to or in the brain, blocking the flow of blood.

The most common cause of these emboli is blood clots that form during atrial fibrillation (AF). AF is a disorder found in about 2.2 million Americans. It's responsible for 15–20 percent of all strokes. In AF, the heart's two small upper chambers (the atria) quiver instead of beating effectively. Some blood isn't pumped completely out of them when the heart beats, so it pools and clots. When a blood clot enters the circulation and lodges in a narrowed artery of the brain, a stroke occurs.

What is hemorrhagic stroke?

A subarachnoid hemorrhage occurs when a blood vessel on the brain's surface ruptures and bleeds into the space between the brain and the skull (but not into the brain itself).

A cerebral hemorrhage occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood.

Hemorrhage (or bleeding) from an artery in the brain can be caused by a head injury or a burst aneurysm. Aneurysms are blood-filled pouches that balloon out from weak spots in the artery wall. They're often caused or made worse by high blood pressure. Aneurysms aren't always dangerous, but if one bursts in the brain, they cause a hemorrhagic stroke.

When a cerebral or subarachnoid hemorrhage occurs, the loss of a constant blood supply means some brain cells no longer can work. Accumulated blood from the burst artery also may put pressure on surrounding brain tissue and interfere with how the brain works. Severe or mild symptoms can result, depending on the amount of pressure.

The amount of bleeding determines the severity of cerebral hemorrhages. In many cases, people with cerebral hemorrhages die of increased pressure on their brains. But those who live tend to recover much more than people who've had strokes caused by a clot. That's because when a blood vessel is blocked, part of the brain dies — and the brain doesn't regenerate. But when a blood vessel in the brain bursts, pressure from the blood compresses part of the brain. If the person survives, gradually the pressure goes away. Then the brain may regain some of its former function.

ANATOMY BRAIN

In order to understand how stroke occurs and the damage it can cause, it is useful to understand the basic anatomy of the brain. The signs and symptoms of a stroke depend on which region of the brain is affected and how severely.

The brain has three primary components. Each is responsible for different functions:

The Cerebrum: The cerebrum is the largest and most developmentally advanced portion of the brain. It controls a number of higher functions, including speech, emotion, the integration of sensory stimuli, initiation of the final common pathways for movement, and fine control of movement.

It is divided into a left and a right hemisphere. The left hemisphere controls the majority of functions on the right side of the body, while the right hemisphere controls most of functions on the left side of the body. Thus, injury to the left cerebral hemisphere produces sensory and motor deficits on the right side, and vice versa.

The cerebrum is composed of the frontal, parietal, temporal, and occipital lobes:

• The frontal lobe is involved in planning, organizing, problem solving and selective attention. The portion known as the prefrontal cortex controls personality and various higher cognitive functions such as behavior and emotions. The back of the frontal lobe consists of the pre-motor and motor areas, which produce and modify movement.
• The left and right parietal lobes contain the primary sensory cortex, which controls sensation (touch and pressure), and a large association area that controls fine sensation (judgment of texture, weight, size, and shape). Damage to the right parietal lobe can cause visuo-spacial deficits, making it hard for the patient to find his/her way around new or even familiar places. Damage to the left parietal lobe may disrupt a patient’s ability to understand spoken and/or written language.
• The left and right temporal lobes, located around ear level, allow a person to differentiate smells and sounds. They also help in sorting new information and are believed to be responsible for short-term memory. The right lobe is primarily involved in visual memory (i.e., memory for faces and pictures). The left lobe is primarily involved in verbal memory (i.e., memory for words and names).
• The occipital lobe processes visual information. It is mainly responsible for visual reception and contains association areas that help in the visual recognition of shapes and colors. Damage to this lobe can cause visual deficits.

The Cerebellum: The cerebellum is the second largest area of the brain. It controls reflexes, balance and certain aspects of movement and coordination.

The Brain Stem: The brain stem is responsible for a variety of automatic functions that are critical to life, such as breathing, digestion and heart beat – as well as alertness and arousal (the state of being awake).

Symptoms Point to Stroke Location

A stroke can occur anywhere in the brain or just outside it. The symptoms that a stroke victim experiences depend on which area(s) of the brain are involved.

When a stroke occurs in the right hemisphere of the cerebrum, the result may be paralysis on the left side of the body, difficulty reasoning or thinking out solutions to even the simplest problem. A stroke in the left hemisphere can result in paralysis of the right side of the body and may disrupt the ability to speak.

A stroke involving the cerebellum may result in a lack of coordination (ataxia), clumsiness and balance problems, shaking, or other muscular difficulties. This can interfere with a person’s ability to walk, talk, eat and perform other self-care tasks.

Brain stem strokes are the most devastating and life threatening because they can disrupt the involuntary functions essential to life. People who survive may remain in a vegetative state or be left with severe impairments.

Blood Flow to the Brain

The heart pumps oxygen- and nutrient-laden blood to the brain, face, and scalp via two major sets of vessels: the carotid arteries and the vertebral arteries. The jugular and other veins bring blood out of the brain.

The carotid arteries run along the front of the neck – one on the left and one on the right. They are what you feel when you take your pulse just under your jaw. The carotid arteries split into external and internal arteries near the top of the neck.

The external carotid arteries supply blood to the face and scalp. The internal carotid arteries supply blood to the front (anterior) three-fifths of cerebrum, except for parts of the temporal and occipital lobes.

The vertebral arteries travel along the spinal column and cannot be felt from the outside. They join to form a single basilar artery (hence the name vertebrobasilar arteries) near the brain stem at the base of the skull. The arteries supply blood to the posterior two-fifths of the cerebrum, part of the cerebellum, and the brain stem.

Because the brain relies on only two sets of major arteries for its blood supply, it is very important that these arteries are healthy. Often when an ischemic stroke occurs, the carotid or vertebral artery system is blocked with a fatty buildup called plaque, allowing little or no blood to flow to the brain. During a hemorrhagic stroke, an artery in or on the surface of the brain has ruptured or is leaking, causing bleeding and damage in or around the brain.

These arteries that conduct blood to the brain — the internal-carotid and vertebral arteries — connect through the Circle of Willis, which loops around the brainstem at the base of the brain. From this circle, other arteries — the anterior cerebral artery (ACA), the middle cerebral artery (MCA), and the posterior cerebral artery (PCA) — arise and travel to all parts of the brain.

Because the carotid and vertebrobasilar arteries form a circle, if one of the main arteries is blocked, the smaller arteries that the circle supplies can receive blood from the other arteries. This phenomenon is called collateral circulation.

Collateral circulation is a process in which small (normally closed) arteries open up and connect two larger arteries or different parts of the same artery. They can serve as alternate routes of blood supply. Sometimes when an artery in the brain is blocked due to ischemic stroke or transient ischemic attack (TIA), open “collateral” vessels can allow blood to "detour" around the blockage, restoring blood flow to the affected part of the brain. Everyone has collateral vessels, at least in microscopic form. These vessels normally aren't open. However, they grow and enlarge in some people with coronary heart disease or other blood vessel disease. While everyone has collateral vessels, they don't open in all people.

The Circle of Willis has a downside, however. Cerebral aneurysms tend to occur at the junctions between the arteries that make up the Circle.

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brain ct stroke

CT BRAIN with or without Contrast

Indications

A CT brain is ordered to look at the structures of the brain and evaluate for the presence of pathology, such as mass/tumor, fluid collection (such as an abcess), ischemic processes (such as a stroke). It is particularly good for hemorrhage, trauma or fracture to the skull and for hydrocephalus.

• Bone abnormalities


• Brain mass/tumor


• Fluid collection, such as an abcess


• Hemorrhage


• Hydrocephalus


• Ischemic process, such as a stroke


• Trauma or fracture of the skull

Contrast

CT of the brain can be done with or without contrast, but it is often not needed.

In general, it is preferred that the choice of contrast or no contrast be left up to the discretion of the imaging physician.

preparation

Without Contrast:No preparation is required

With Contrast:

• Only one CT contrast study should be scheduled within a 48 hour period


• BUN & Creatinine must be done within 72 hours of the scan.


• Nothing but clear liquid after midnight before the scan.


• NPO 4 hours prior to exam (no food or drink )