Stroke

Stroke, also known as cerebrovascular accident (CVA), or brain attack, is when poor blood flow to the brain results in necrosis and cell death. Stroke is the second most frequent cause of death worldwide. South Asians are at particularly high risk for stroke, accounting for 40% of global stroke deaths.

There are two main types of stroke: ischemic and hemorrhagic. Ischemic strokes are caused by interruption of the blood supply to the brain, while hemorrhagic strokes result from the rupture of a blood vessel or an abnormal vascular structure. Most of the strokes are ischemic, the rest being hemorrhagic. Bleeding can develop inside areas of ischemia, a condition known as hemorrhagic transformation.

Brain tissue ceases to function if deprived of oxygen for more than 60 to 90 seconds, and after approximately three hours will suffer irreversible injury possibly leading to death of the tissue or necrosis. Since blood vessels in the brain are now blocked, the brain becomes low in energy, and thus it resorts into using anaerobic metabolism within the region of brain tissue affected by ischemia.

In addition to damaging effects on brain cells, ischemia and infarction can result in loss of structural integrity of brain tissue and blood vessels The loss of vascular structural integrity results in a breakdown of the protective blood brain barrier that contributes to cerebral edema, which can cause secondary progression of the brain injury.

Brain ischemia causes insufficient blood flow to the brain, and can be acute or chronic. Acute ischemic stroke is a neurological emergency that may be reversed if treated rapidly. Chronic ischemia of the brain may result in a form of dementia called vascular dementia. A brief episode of ischemia affecting the brain is called a transient ischemic attack, often erroneously referred to as a “mini-stroke” (1).

(1) “Thrombus”. MedlinePlus. U.S. National Library of Medicine

Stroke types, symptoms and care

Causes of clots

The cause of blood clots (or thrombi) is not always known. The body creates blood clots as a normal response to prevent a leak in a damaged blood vessel. Clots that brake way (called embolism) from the area they protect can   cause brain stroke and heart attack. Another type of clots resulting from irregular pumping of the heart that cause the blood to remain in the heart chamber and form a clots, this clots can then travel to the brain an cause a ischemic brain stroke. Some blood clots may form in a narrowed artery as a result of atherosclerosis, commonly known as hardening of the arteries, in this type, the arterial wall is thicken, harden and narrow over time until blood flow is reduced. As a result, these arteries become vulnerable to injury. If they tear, a blood clot called thrombus may form, blocking the already narrowed artery and shutting off oxygen to part of the heart or brain.

In addition to damaging effects on brain cells, ischemia and infarction can result in loss of structural integrity of brain tissue and blood vessels The loss of vascular structural integrity results in a breakdown of the protective blood brain barrier that contributes to cerebral edema, which can cause secondary progression of the brain injury.

Signs and Symptoms

Symptoms often appear soon after a stroke has occurred, and may include: trouble with speaking and understanding; paralysis, numbness, or loss of sensation of the face, arm, or leg, especially on one side of the body. Symptoms may also include: trouble seeing in one or both eyes, and seeing double; or sudden severe headache, that may be accompanied by vomiting, dizziness, or altered consciousness. Common signs include trouble walking, and loss of balance or coordination. If symptoms last less than one or two hours, it is known as a transient ischemic attack. Some symptoms can be permanent, and long-term complications may include pneumonia or loss of bladder control.

Brain tissue ceases to function if deprived of oxygen for more than 60 to 90 seconds, and after approximately three hours will suffer irreversible injury possibly leading to death of the tissue or necrosis. Since blood vessels in the brain are now blocked, the brain becomes low in energy, and thus it resorts into using anaerobic metabolism within the region of brain tissue affected by ischemia.

Treatment and Limitations

A stroke requires emergency care. During every minute of delayed treatment, brain cells are dying. The treatment process for patients with stroke is to stabilize the patient, and complete initial evaluation and assessment, including imaging (CT) and laboratory studies. This is followed by critical decisions focused on the need for intubation, blood pressure control, and determination of risk/benefit for thrombolytic (anti-clot) medication. An ischemic stroke, if diagnosed within three to four-and-a-half hours after the initial onset, may be treatable.

The currently available treatments for the necrosis of brain cells that result from hypoxia (lack of oxygen) due to stroke are: (i) dissolve the clot to allow red blood cells to supply oxygen; (ii) surgery to remove the clot; (iii) blood thinner to reduce blood viscosity; and (iv) supply oxygen by means of a high-pressure vessel.

Prevention includes decreasing risk factors, as well as administration of prophylactic rtPA (recombinant tissue plasminogen activator) to dissolve clots; aspirin, statins, and surgery to open up the arteries in those with problematic narrowing; and warfarin in those with atrial fibrillation.

Economics of Stroke 

Global Data

In 2010 there were about 33 million stroke survivals. In 2013 approximately 6.9 million people had an ischemic stroke and 3.4 million people had a hemorrhagic stroke. In the same year, stroke was the second most frequent cause of death after coronary artery disease, accounting for 6.5 million deaths (out of 54 million survivals). Close to 3.3 million deaths resulted from ischemic stroke, while 3.2 million deaths resulted from hemorrhagic stroke. About 50% of individuals who suffer a stroke live less than one year. Overall, two-thirds of strokes occurred in those over 65 years old.

Survival

Disability affects 75% of stroke survivors enough to decrease their employability. Stroke can affect people physically, mentally, and emotionally. The results of stroke vary widely, depending on the size and location of the lesion. Dysfunctions correspond to areas in the brain that have been damaged. About 60% of ischemic stroke survivors will regain functional independence following rehabilitation, while 15%-30% will be permanently disabled, and 20% will require institutionalized care.

US Data

There are about 795,000 new or recurrent cases of stroke each year; of these, 610,000 are new cases and 185,000 recurrent cases, after cardiovascular diseases and cancer. Stroke ranks third as cause of death in the US. About 87% of the strokes are ischemic in nature, 10% with intra-cerebral hemorrhage, and 3% sub-arachnoid hemorrhage (bleeding in the area between the brain and the thin tissues that cover the brain). Someone in the US has a stroke every 40 seconds; 15% of those die shortly after the stroke, and 14% of the survivors experience a second stroke in the first year following a stroke (4).

According to the American Heart Association (AHA), costs to treat stroke are projected to more than double, and the number of people having strokes may increase from 4% to nearly one in 25 adults by 2030 (largely due to the ageing US population). This translates to 3.4 million people with stroke by 2030. The cost to treat stroke may increase from $71.5 billion in 2010 to $183 billion in 2030. Annual costs due to lost productivity could rise from $33.65 billion to $56.54 billion.(4)

(4) American Heart Association Policy Statement May 22, 2013