• A stroke occurs when part of the brain loses its blood supply and stops working. This causes the part of the body that the injured brain controls to stop working.
• A stroke also is called a cerebrovascular accident, CVA, or "brain attack."
• The types of strokes include:
  • Ischemic stroke (part of the brain loses blood flow)
  • Hemorrhagic stroke (bleeding occurs within the brain)
• Transient ischemic attack, TIA, or ministroke (The stroke symptoms resolve within minutes, but may take up to 24 hours on their own without treatment. This is a warning sign that a stroke may occur in the near future.)
• A stroke is a medical emergency. The affected individual, family, friends, or bystanders need to call 9-1-1 (activate EMS) to access emergency care.
• From onset of symptoms, there is only a 3 to 4 1/2 hour window to use clot-busting drugs (thrombolytics) to try to restore blood supply to the affected part of the brain.
• Remember FAST if you think someone might be having a stroke:
  • Face drooping
  • Arm weakness
  • Speech difficulty
  • Time to call 9-1-1
• Causes of strokes include ischemia (loss of blood supply) or hemorrhage (bleeding) in the brain occurs.
• People at risk for stroke include those who have high blood pressure, high cholesterol, diabetes, and those who smoke. People with heart rhythm disturbances, especially atrial fibrillation are also at risk.
• Stroke is diagnosed by the patient's symptoms, history, and blood and imaging tests.
• You can prevent stroke by quitting smoking, controlling blood pressure, maintaining a healthy weight, eating a healthy diet, and exercising on a regular basis.
• The prognosis and recovery for a person that has suffered a stroke depends upon the location of the injury to the brain.

What is a stroke?

A stroke, also known as a cerebrovascular accident or CVA is when part of the brain loses its blood supply and the part of the body that the blood-deprived brain cells control stops working. This loss of blood supply can be ischemic because of lack of blood flow, or hemorrhagic because of bleeding into brain tissue. A stroke is a medical emergency because strokes can lead to death or permanent disability. There are opportunities to treat ischemic strokes but that treatment needs to be started in the first few hours after the signs of a stroke begin. The patient, family, or bystanders, should call 9-1-1 and activate emergency medical services immediately should a stroke be suspected.
A transient ischemic attack (TIA or mini-stroke) describes an ischemic stroke that is short-lived where the symptoms resolve spontaneously. This situation also requires emergency assessment to try to minimize the risk of a future stroke. By definition, a stroke would be classified as a TIA if all symptoms resolved within 24 hours.

What is the NIH Stroke Scale?

Not all strokes affect the brain equally, and stroke symptoms and signs depend upon the part of the brain affected.

• For example, most people’s speech center is located in the left half of the brain so a stroke affecting the left side of the brain would affect speech and comprehension. It also would be associated with weakness of the right side of the body.
• A right brain stroke would make the left side of the body weak. And depending on where in the brain the injury occurred, the weakness could be the face, arm, leg or a combination of the three.

The NIH Stroke Scale tries to score how severe a stroke might be. It also monitors whether the person's stroke is improving or worsening as times passes as the patient is re-examined.
There are 11 categories that are scored and include whether the patient

• is awake,
• can follow commands,
• can see,
• can move their face, arms and legs,
• has normal body sensations or feelings,
• has speech difficulties, or
• has coordination problems.

What are the risk factors for stroke?

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Overall, the most common risk factors for stroke are:

• high blood pressure,
• high cholesterol,
• smoking,
• diabetes, and
• increasing age.

Heart conditions like atrial fibrillation, patent foramen ovale, and heart valve disease can also be the potential cause of stroke.
When stroke occurs in younger individuals (less than 50 years old), less common risk factors to be considered include illicit drugs, such as cocaine or amphetamines, ruptured aneurysms, and inherited (genetic) predispositions to abnormal blood clotting.
An example of a genetic predisposition to stroke occurs in a rare condition called homocystinuria, in which there are excessive levels of the chemical homocystine in the body. Scientists are trying to determine whether the non-hereditary occurrence of high levels of homocystine at any age can predispose to stroke.
In the aftermath of stroke, brain damage is exacerbated by electrical discharges. Researchers at the German Center for Neurodegenerative Diseases (DZNE) have investigated the mechanisms of these "spreading depolarizations" in mice, and found that brain cells termed astrocytes potentiate the fatal discharges. The study highlights potential counter-measures: a signaling pathway that acts upon the calcium concentration in astrocytes may be a potential starting point for treating stroke in humans. Dr. Cordula Rakers and Prof. Gabor Petzold report on these findings in The Journal of Clinical Investigation.
The brain depends on a constant supply of oxygen. This is why a stroke can have fatal consequences. Whether caused by cerebral hemorrhage or a blocked artery, the oxygen deficit triggers a rapid loss of nerve cells. Stroke is, therefore, one of the most common causes of death, and even if the patient survives, paralysis, speech difficulties or other disabilities may remain depending on which part of the brain was injured.
The damaged area can even expand to some extent. This is due to "spreading depolarizations", which can occur minutes after a stroke and may recur over the following days. They start at the infarct core and engulf the surrounding tissue like an avalanche. These electrical discharges put the cells under severe stress. "The spreading depolarizations radiate into the healthy tissue. Each wave can increase the volume of the brain affected by stroke," says Petzold. "Incidentally, these depolarizations do not occur only in stroke but also in other severe brain injuries. A therapy might therefore be relevant for many neurological diseases."
Favourable opportunities for treatment might arise from the fact that the discharges spread over several days. Petzold notes: "Each wave is potentially harmful. However, the damage occurs gradually as there is a cumulative effect. Treatment could therefore have a positive impact, even if it is given days after the stroke. The time window for treating spreading depolarizations might therefore be larger than in established therapies against stroke."

Harmful interaction between nerve cells and astrocytes

DZNE researchers have now discovered how various events and cell types interact during spreading depolarizations, thereby intensifying the discharge. Cells known as astrocytes play a key role. These cells form a dense network with the brain's nerve cells and are involved in various metabolic processes.
"When nerve cells depolarize, they release large quantities of the neurotransmitter glutamate. Glutamate then diffuses to other cells, in particular to neighboring astrocytes," explains Petzold. "This was known before. However, we have now been able to show what follows this event. The glutamate causes calcium levels in the astrocytes to soar. As a result, the astrocytes release glutamate as well. This in turn can act on nerve cells. A vicious circle emerges that potentiates the spreading depolarizations. This process is amplified by the astrocytes."
The neuroscientists were also able to show that certain drugs can interrupt this chain of events. Ultimately, these drugs reduce the abnormally elevated calcium levels in astrocytes. "At present, there is no established treatment that directly affects spreading depolarizations. Our results show that it is possible to reduce the frequency and severity of these discharges by modulating the astrocytes' calcium metabolism. In theory, this could also be possible in humans. This could lead to a new approach to treating stroke," says Petzold.