A , also known as '''cerebrovascular accident''' ('''CVA'''), is an acute neurologic injury whereby the
Blood supply to a part of the
Brain is interrupted, either by a clot in the artery or if the artery bursts. The result is that the part of the brain perfused by that artery no longer can receive oxygen carried by the blood and it dies (becomes
Necrotic ) with cessation of function from that part of the brain. In addition to tissue death, hemorrhages also cause damage from physical impingement of blood on the brain tissue. Stroke is a
Medical Emergency and can cause permanent neurologic damage or even death if not promptly diagnosed and treated. It is the third leading cause of
Death and adult disability in the US and industrialized European nations.
1
Risk factors include advanced age,
Hypertension (high blood pressure),
Diabetes Mellitus ,
High Cholesterol , and
Cigarette Smoking . Cigarette smoking is the most important modifiable risk factor of stroke.
Strokes can be classified into two major categories: ischemic and hemorrhagic.
Ischemia can be due to
Thrombosis ,
Embolism , or systemic hypoperfusion.
Hemorrhage can be due to
Intracerebral Hemorrhage or
Subarachnoid Hemorrhage . ~80% of strokes are due to ischemia.
In ischemic stroke, which occurs in approximately 85-90% of strokes, a
Blood Vessel becomes occluded and the blood supply to part of the brain is totally or partially blocked. Ischemic stroke is commonly divided into thrombotic stroke, embolic stroke, systemic hypoperfusion (Watershed stroke), or venous thrombosis
In thrombotic stroke, a
Thrombus forming process develops in the affected artery and gradually the thrombus—built up clot—narrows the lumen of the artery and impedes blood flow to distal tissue. These clots usually form around
Atherosclerotic plaques. Since occlusion of the artery is gradual, onset of symptomatic thrombotic strokes is slower. A thrombus itself (even if non-occluding) can lead to an embolic stroke (see below) if the thrombus breaks off—at which point it is then called an "embolus." Thrombotic stroke can be divided into two types depending on the type of vessel the thrombus is formed on:
Embolic stroke refers to the blockage of arterial access to a part of the brain by an
Embolus -- a travelling particle or debris in the arterial bloodstream originating from elsewhere. An embolus is most frequently a blood clot, but it can also be a plaque broken off from an
Atherosclerotic blood vessel or a number of other substances including fat, air, and even
Cancer ous cells. Because an embolus arises from elsewhere, local therapy only solves the problem temporarily; source of the embolus must be identified. Because the embolic blockage is sudden in onset, symptoms usually are maximal at start. Also, symptoms may be transient as the embolus lyses and moves to a different location or dissipates altogether.
Embolic stroke can be divided into four categories:
- those with known cardiac source
- those with potential cardiac or aortic source (from Transthoracic or Transesophageal Echocardiogram )
- those with an arterial source
- those with unknown source
High risk cardiac causes include:2
- Atrial Fibrillation and Paroxysmal Atrial Fibrillation
- Rheumatic mitral or aortic valve disease
- Bioprosthetic and mechanical heart valves
- Atrial or ventricular thrombus
- Sick Sinus Syndrome
- Sustained Atrial Flutter
- Recent Myocardial Infarction (within one month)
- Chronic myocardial infarction together with Ejection Fraction <28 percent
- Symptomatic Congestive Heart Failure with ejection fraction <30 percent
- Dilated Cardiomyopathy
- Libman-Sacks Endocarditis
- Antiphospholipid Syndrome
- Marantic Endocarditis from cancer
- Infective Endocarditis
- Papillary Fibroelastoma
- Left Atrial Myxoma
- Coronary Artery Bypass Graft ( CABG ) surgery
Potential cardiac causes include:
- Mitral Annular Calcification
- Patent Foramen Ovale
- Atrial septal Aneurysm
- Atrial septal aneurysm with patent foramen ovale
- Left ventricular aneurysm without thrombus
- Isolated left atrial smoke on echocardiography (no mitral stenosis or atrial fibrillation)
- Complex atheroma in the ascending aorta or proximal arch
Systemic hypoperfusion is the reduction of blood flow to all parts of the body. It is most commonly due to cardiac pump failure from cardiac arrest or arrhythmias, or from reduced Cardiac Output as a result of Myocardial Infarction , Pulmonary Embolism , Pericardial Effusion , or bleeding. Hypoxemia (low blood oxygen content) may precipitate the hypoperfusion. Because the reduction in blood flow is global, all parts of the brain may be affected, especially "watershed" areas --- border zone regions supplied by the major cerebral arteries. Blood flow to these area has not necessary stopped, but instead may have lessened to the point where brain damage occurs.
Veins in the brain function to drain the blood back to the body. When veins are occluded due to thrombosis, the draining of blood is blocked and the blood backs up, causing cerebral edema. This can result in both ischemic and hemorrhagic strokes. This commonly occurs in the rare disease Sinus Vein Thrombosis .
A hemorrhagic stroke, or cerebral hemorrhage, is a form of stroke that occurs when a blood vessel in the brain ruptures or bleeds. Like ischemic strokes, hemorrhagic strokes interrupt the brain's blood supply because the bleeding vessel can no longer carry the blood to its target tissue. In addition, blood irritates brain tissue, disrupting the delicate chemical balance, and, if the bleeding continues, it can cause increased intracranial pressure which physically impinges on brain tissue and restricts blood flow into the brain. In this respect, hemorrhagic strokes are more dangerous than their more common counterpart, ischemic strokes. There are two types of hemorrhagic stroke: intracerebral hemorrhage, and subarachnoid hemorrhage.
See Also: intracerebral hemorrhage
Intracerebral hemorrhage (ICH) is bleeding directly into the brain tissue, forming a gradually enlarging Hematoma (pooling of blood). It generally occurs in small arteries or arterioles and is commonly due to Hypertension , trauma, bleeding disorders, Amyloid Angiopathy , illicit drug use ( Amphetamines and Cocaine ), and vascular malformations. The hematoma enlarges until its surround pressure limits its growth, or until it decompresses by emptying into the ventricular system, CSF or the Pial surface. A third of intracerebral bleed is into the brain's ventricles. ICH has a mortality rate of 44 percent after 30 days, higher than ischemic stroke or even the very deadly subarachnoid hemorrhage.3
See Also: subarachnoid hemorrhage
Subarachnoid hemorrhage (SAH) is bleeding into the Cerebrospinal Fluid (CSF) of the Subarachnoid Space surrounding the brain. The two most common causes of SAH are rupture of Aneurysms from the base of the brain and bleeding from Vascular Malformations near the pial surface. Bleeding into the CSF from a ruptured aneurysm occurs very quickly, causing rapidly increased Intracranial Pressure . The bleeding usually only lasts a few seconds but rebleeding is common. Death or deep coma ensues if the bleeding continues. Hemorrhage from other sources is less abrupt and may continue for a longer period of time. SAH has a 40% mortality over 30 day period.
The symptoms of stroke depends on the type of stroke and the area of the brain affected. Ischemic strokes usually only affect regional areas of the brain perfused by the blocked artery. Hemorrhagic strokes can affect local areas, but often can also cause more global symptoms due to bleeding and increased intracranial pressure.
If the area of the brain affected contains one of the three prominent Central Nervous System Pathways -- the Spinothalamic Tract , Corticospinal Tract , and Dorsal Column ( Medial Lemniscus ), symptoms may include:
- muscle weakness or numbness ( Hemiplegia )
- reduction of pain or temperature sensation
- reduction in sensory or vibratory sensation
In most cases, the symptoms affects one side of the body, from the neck downwards, excluding the face. The defect in the brain is ''usually'' on the opposite side of the body (depending on which part of the brain is affected). However, the presence of any one of these symptoms does not necessarily suggest a stroke, since these pathways also travel in the Spinal Cord and any lesion there can also produce these symptoms.
In addition to the above CNS pathways, the '' Brainstem '' also consists of the 12 Cranial Nerves . A stroke affecting the brainstem therefore can produce symptoms relating to deficits in these cranial nerves:
- altered smell, taste, hearing, or vision (total or partial)
- drooping of eyelid ( Ptosis ) and weakness of ocular muscles
- decreased reflexes: gag, swallow, pupil reactivity to light
- decreased sensation and muscle weakness of the face
- balance problems and Nystagmus
- altered breathing and heart rate
- weakness in Sternocleidomastoid Muscle (SCM) with inability to turn head to one side
- weakness in tongue (inability to protrude and/or move from side to side)
If the '' Cerebral Cortex '' is involved, the CNS pathways can again be affected, but also can produce the following symptoms:
- Aphasia (inability to speak or understand language from involvement of Broca 's or Wernicke 's area)
- Apraxia (altered voluntary movements)
- disorganized thinking, confusion, hypersexual gestures (with involvement of frontal lobe)
- altered vision (involvement of occipital lobe)
- memory deficits (involvement of temporal lobe)
- hemineglect (involvement of parietal lobe)
If the '' Cerebellum '' is involved, the patient may have the following:
- trouble walking
- altered movement coordination
- dizziness
Loss of consciousness, headache, and vomiting usually occurs more often in hemorrhagic stroke than in thrombosis because of the increased intracranial pressure from the leaking blood compressing on the brain.
If symptoms are maximal at onset, the cause is more likely to be a subarachnoid hemorrhage or an embolic stroke.
See Also: subarachnoid hemorrhage
The symptoms of SAH occur abruptly due to the sudden onset of increased intracranial pressure. Often, patients complain of a sudden, extremely severe and widespread headache. The pain may or may not radiate down into neck and legs. Vomiting soon occurs after the onset of headache. Usually the neurologic exam is nonfocal --- meaning no deficits can be identified that attributes to certain areas of the brain --- unless the bleeding also occurs into the brain. The combination of headache and vomiting is uncommon in ischemic stroke.
If the symptoms resolve within an hour, or maximum 24 hours, the diagnosis is Transient Ischemic Attack (TIA), and not a stroke. This syndrome may be a warning sign, and a proportion of patients develop strokes in the future. The chances of suffering an Ischemic Stroke can be reduced by using Aspirin , which inhibits platelets from aggregating and forming obstructive clots; but, for that same reason, aspirin probably increases the likelihood and effects of Hemorrhagic Stroke since it reduces clotting at breaks in artery walls.
Stroke is diagnosed through several techniques: a neurological examination, Blood Test s, CT Scan s (without contrast enhancements) or MRI Scan s, Doppler Ultrasound , and Arteriography .
If a stroke is confirmed on imaging, various other studies may be performed to determine whether there is a peripheral source of Emboli :
It is important to identify a stroke as early as possible because patients who are treated earlier are more likely to survive and have better recoveries.
If a patient is suspected of having a stroke, emergency services should be contacted immediately. The patient should be transported to the nearest hospital that can provide a rapid evaluation and treatment with the latest available therapies targeted to the type of stroke. The faster these therapies are started for hemorrhagic and ischemic stroke, the chances for recovery from each type improves greatly. Quick decisions about medication and the need for surgery have been shown to improve outcome.
Only detailed Physical Examination and Medical Imaging provide information on the presence, type, and extent of stroke.
Studies show that patients treated in hospitals with a dedicated Stroke Team or Stroke Unit and a specialized care program for stroke patients have improved odds of recovery.
As ischemic stroke is due to a Thrombus (blood clot) occluding a cerebral artery, a patient is given Antiplatelet Medication ( Aspirin , Clopidogrel , Dipyridamole ), or Anticoagulant medication ( Warfarin ), dependent on the cause, when this type of stroke has been found. Hemorrhagic stroke must be ruled out with medical imaging, since this therapy would be harmful to patients with that type of stroke.
In increasing numbers of primary stroke centers, Thrombolysis ("clot busting") is used to dissolve the clot and unblock the artery. However, there is a time constraint: the more time that goes by, the more brain that has irreversibly died. There is also a small risk of making the patient worse by causing bleeding. When used within the first 3 hours, thrombolysis improves the outcome in 1 of every 3.1 patients and worsens the outcome in 1 in every 32 patients. The routine use of thrombolysis is not approved beyond 3 hours. As an easily administered therapy that can be given at any hospital with a CAT scanner, thrombolysis is available at most hospitals in the US, but not where no institutional commitment to stroke care has occurred.
Another intervention for acute ischemic stroke is removal of the offending thrombus directly. This is accomplished by inserting a catheter into the femoral artery, directing it up into the cerebral circulation, and deploying a corkscrew-like device to ensnare the clot, which is then withdrawn from the body. In August 2004, the FDA cleared one such device, called the Merci Retriever.4
Whether thrombolysis is performed or not, the following investigations are required:
Other immediate strategies to protect the brain during stroke include ensuring that blood sugar is as normal as possible (such as commencement of an Insulin Sliding Scale in known Diabetics ), and that the stroke patient is receiving adequate Oxygen and Intravenous Fluid s. The patient may be positioned so that his or her head is flat on the stretcher, rather than sitting up, since studies have shown that this increases blood flow to the brain. Additional therapies for ischemic stroke include Aspirin (50 to 325 mg daily), Clopidogrel (75 mg daily), and combined aspirin and Dipyridamole extended release (25/200 mg twice daily).
It is common for the Blood Pressure to be Elevated immediately following a stroke. Studies indicated that while high blood pressure causes stroke, it is actually beneficial in the emergency period to allow better blood flow to the brain.
If studies show Carotid Stenosis , and the patient has residual function in the affected side, Carotid Endarterectomy (surgical removal of the stenosis) may decrease the risk of recurrence.
If the stroke has been the result of Cardiac Arrhythmia (such as Atrial Fibrillation ) with cardiogenic emboli, treatment of the arrhythmia and Anticoagulation with Warfarin or high-dose aspirin may decrease the risk of recurrence.
Patients with bleeding into ( Intracerebral Hemorrhage ) or around the brain ( Subarachnoid Hemorrhage ), require Neurosurgical evaluation to detect and treat the cause of the bleeding. Anticoagulants and antithrombotics, key in treating ischemic stroke, can make bleeding worse and cannot be used in intracerebral hemorrhage. Patients are monitored and their blood pressure, blood sugar, and oxygenation are kept at optimum levels.
Stroke rehabilitation is the process by which patients with disabling strokes undergo treatment to help them return to normal life as much as possible by regaining and relearning the skills of everyday living. It is multidisciplinary because it involves a team with different skills working together to help the patient. These include nursing staff, Physiotherapy , Occupational Therapy , Speech And Language Therapy , and usually a Physician trained in Rehabilitation Medicine . Some teams may also include Psychologists , Social Work ers, and Pharmacist s.
Good nursing care is fundamental in maintaining skin care, feeding, hydration, positioning, and monitoring vital signs such as temperature, pulse, and blood pressure. Stroke rehabilitation begins almost immediately.
For most stroke patients, Physical Therapy is the cornerstone of the rehabilitation process. Often, Assistive Technology such as a Wheelchair and Standing Frame may be beneficial. Another type of therapy involving relearning daily activities is Occupational Therapy (OT). OT involves exercise and training to help the stroke patient relearn everyday activities sometimes called the Activities Of Daily Living (ADLs) such as eating, drinking and swallowing, dressing, bathing, cooking, reading and writing, and toileting. Speech And Language Therapy is appropriate for patients with problems understanding speech or written words, or problems forming speech.
Patients may have particular problems, such as complete or partial inability to swallow, which can cause swallowed material to pass into the lungs and cause Aspiration Pneumonia . The condition may improve with time, but in the interim, a nasogastric tube may be inserted, enabling liquid food to be given directly into the stomach. If swallowing is still unsafe after a week, then a Percutaneous Endoscopic Gastrostomy (PEG) tube is passed and this can remain indefinitely.
Stroke rehabilitation can last anywhere from a few days to several months. Most return of function is seen in the first few days and weeks, and then improvement falls off. Complete recovery is unusual but not impossible. Most patients will improve to some extent.
Disability affects 75% of stroke survivors enough to decrease their employability.5
Stroke can affect patients physically, mentally, emotionally, or a combination of the three. The results of stroke vary widely depending on size and location of the lesion.6
Dysfunctions correspond to areas in the brain that have been damaged.
Some of the physical disabilities that can result from stroke include Paralysis , numbness, Pressure Sore s, Pneumonia , Incontinence , Apraxia (inability to perform learned movements), difficulties carrying out daily activities, appetite loss, vision loss, and Pain . If the stroke is severe enough, Coma or Death can result.
Emotional problems resulting from stroke can result from direct damage to emotional centers in the brain or from frustration and difficulty adapting to new limitations. Post-stroke emotional difficulties include Anxiety , Panic Attack s, Flat Affect (failure to express emotions), Mania , apathy, and Psychosis .
30 to 50% of stroke survivors suffer post stroke Depression , which is characterized by lethargy, irritability, sleep disturbances, lowered self esteem, and withdrawal.7
Depression can reduce motivation and worsen outcome, but can be treated with Antidepressant s.
Emotional Lability , another consequence of stroke, causes the patient to switch quickly between emotional highs and lows and to express emotions inappropriately, for instance with an excess of laughing or crying with little or no provocation. While these expressions of emotion usually correspond to the patient's actual emotions, a more severe form of emotional lability causes patients to laugh and cry pathologically, without regard to context or emotion.
Some patients show the opposite of what they feel, for example crying when they are happy.8
Emotional lability occurs in about 20% of stroke patients.
Cognitive deficits resulting from stroke include perceptual disorders, speech problems, Dementia , and problems with attention and memory. A stroke sufferer may be perpetually unaware of his or her own disabilities or even the fact that he or she has suffered a stroke. In a condition called Agnosia , or neglect, a patient is unable to see anything on the left or right side and is unaware of and unable to conceive of anything on the neglected side.
Up to 10% of all stroke patients develop Seizure s, most commonly in the week subsequent to the event; the severity of the stroke increased the likelihood of a seizureReith J, Jorgensen HS, Nakayama H, Raaschou HO, Olsen TS. Seizures in acute stroke: predictors and prognostic significance. The Copenhagen Stroke Study. ''Stroke'' 1997;28:1585-9. PMID 9259753.Burn J, Dennis M, Bamford J, Sandercock P, Wade D, Warlow C. Epileptic seizures after a first stroke: the Oxfordshire Community Stroke Project. ''BMJ'' 1997;315:1582-7. PMID 9437276..
The most important risk factors for stroke are Hypertension , Heart Disease , Diabetes , and cigarette smoking. Other risks include heavy alcohol consumption, High Blood Cholesterol levels, illicit drug use, and Genetic or congenital conditions. Family members may have a genetic tendency for stroke or share a lifestyle that contributes to stroke. Having had a stroke in the past greatly increases one's risk of future strokes.
One of the most significant stroke risk factors is advanced age. 95% of strokes occur in people age 45 and older, and two-thirds of strokes occur in those over the age of 65.9
A person's risk of dying if he or she does have a stroke also increases with age. However, stroke can occur at any age, including in fetuses.
Sickle Cell Anemia , which can cause blood cells to clump up and block blood vessels, also increases stroke risk. Stroke is the second leading killer of people under 20 who suffer from sickle-cell anemia.
Men are 1.25 times more likely to suffer CVA's than women,
yet 60% of deaths from stroke occur in women.
Since women live longer, they are older on average when they have their strokes and thus more often killed (NIMH 2002).
Some risk factors for stroke apply only to women. Primary among these are pregnancy, childbirth, menopause and the treatment thereof ( HRT ). Stroke seems to run in some families.
Prevention is an important public health concern. Identification of patients with treatable risk factors for stroke is paramount. Treatment of risk factors in patients who have already had strokes (secondary prevention) is also very important as they are at high risk of subsequent events compared with those who have never had a stroke. Medication or drug therapy is the most common method of stroke prevention. Aspirin (usually at a low dose of 75 mg) is recommended for the primary and secondary prevention of stroke, and treating Hypertension is another way to modify a patient's risk factor profile.
Surgery such as Carotid Endarterectomy can be used to remove significant narrowing of the neck (internal) Carotid Artery which supplies blood to the brain. This operation has been shown to be an effective way to prevent stroke in particular groups of patients, but generally only if the obstruction has proven to be symptomatic.
When Neuron s and Glia receive insufficient Oxygen and Nutrient s due to inadequate blood supply, a Biochemical Cascade called the Ischemic Cascade is unleashed. The ischemic cascade, as well as sudden bleeding from ruptured blood vessels into or around the brain, can injure and kill cells. These damaged cells can linger in a compromised state for several hours. With timely treatment, these cells can be saved. Intriguingly, when the brain cells suffer the ischemia, they begin to fill up with free zinc ions which are released from some of their proteins, especially metallothionein, which can release 7 zinc ions per molecule. This released zinc is a major player in the ensuing death of the brain cells. Drugs that buffer the zinc and reduce the level of free zinc are already being tested to reduce brain cell death after stroke.
Lack of oxygen or glucose leads to cell death by excital toxicity: glutamate receptors are activated, which leads to the uncontrolled entry of calcium ions into the neurons.
Over 2,400 years ago, Hippocrates (460 to 370 BC) was first to describe the phenomenon of sudden Paralysis , which we now know is caused by stroke. Apoplexy , from the Greek word meaning "struck down with violence,” first appeared in Hippocratic writings to describe stroke symptoms.1011
In 1658, in his ''Apoplexia'', Johann Jacob Wepfer (1620-1695) identified the cause of Hemorrhagic Stroke when he suggested that people who had died of apoplexy had bleeding in their brains.
Wepfer also identified the main arteries supplying the brain, the Vertebral and Carotid Arteries , and identified the cause of ischemic stroke when he suggested that apoplexy might be caused by a blockage to those vessels.
