Update on Stroke

Posted By SHL Librarian

Presented by: Greg Albers, MD
Director, Stanford Stroke Center
May 15, 2014

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About 780,000 Americans suffer from a stroke each year—someone every 45 seconds. It’s the fourth leading cause of death in the U.S. but the greatest cause of long-term disability. Most people do not die from a stroke but its effects cause more than half of all neurologic hospitalizations. The direct and indirect costs from lost work and lost productivity are enormous.

Though it can occur at any age, the risk of stroke doubles for each decade after age 55, and the aging Baby Boomer population is expanding the number of the most susceptible people.

“Stroke is incredibly common,” said Greg Albers, MD, director of the Stanford Stroke Center and the Coyote Foundation Professor of Neurology, who spoke at a presentation sponsored by the Stanford Hospital Health Library. “Almost everybody’s lives have been touched by stroke in one way or another.”

Stroke is defined as a brain injury that occurs from an abrupt disruption of blood flow to the brain. Ischemic stroke, the more common of the two types of stroke, is caused by a clot that blocks an artery in the brain. Hemorrhagic stroke occurs when a blood vessel breaks and leaks blood in or around the brain. Strokes can cause paralysis, language disturbances, coordination or balance difficulties, confusion, or vision loss.

Types of Stroke
An ischemic stroke occurs when a blood vessel becomes blocked with cholesterol deposits, a condition known as atherosclerosis. A thrombotic stroke is caused by a clot that forms inside a blocked blood vessel in the brain; an embolic stroke is caused by a clot that forms elsewhere in the body and travels toward the brain until it becomes lodged in a narrow artery. Since there’s no bleeding, ischemic strokes typically doesn’t hurt and many occurs during sleep therefore the exact time of onset is unclear. About 85 percent of strokes are ischemic and 15 percent are caused by hemorrhage.

The less common hemorrhagic stroke usually stems from years of hypertension (high blood pressure) that eventually causes blood vessel walls inside the brain to weaken and rupture.

“A blocked artery and a ruptured artery are two very different problems that require different solutions,” said Dr. Albers.

Vessel Network
Two carotid arteries supply blood to the front of the brain, and two vertebral arteries supply blood to the back of the brain. A loop of arteries at the base of the brain, called the Circle of Willis, helps determine how well the brain can compensate for a blocked vessel. Some people have a genetic advantage in which a complete Circle of Willis can provide a protective back-up system to compensate for a blocked vessel. The system is made less efficient by smoking or unhealthy lifestyle habits.

The junctions where these arteries come together at the Circle of Willis may develop weak spots that can balloon out, creating sacs called aneurysms that can leak or rupture.

About 25 percent of ischemic strokes occur because of atherosclerosis in the large vessels in the neck. About 20 percent are caused by a heart embolism, and another 20 percent stem from small vessel atherosclerosis in the brain. About one third are undetermined, creating a diagnostic and treatment challenge for stroke specialists.

Location, Location, Location
The symptoms of stroke depend on which vessel is blocked. A stroke in the anterior parts of the brain will often cause numbness, weakness, and partial vision loss. In the left hemisphere  it will typically cause language or speech problems; in the right side it can cause a condition called neglect, in which the person is unaware of his or her neurologic deficits. A stroke in the left hemisphere will affect the right side of the body, and vice versa. A stroke in the posterior part of the brain can lead to bilateral weakness, vertigo, double vision, or blindness.

Behavioral risk factors include smoking, alcohol abuse, diet, and inactivity. Contributing physiological factors include high blood pressure, high cholesterol, atrial fibrillation, diabetes, and prior stroke or a TIA.

A transient ischemic attack, or TIA, is a clot in the brain that dissolves before it has done any damage. A TIA does not cause disability, but the risk of a significant stroke within the next 48 hours is about 5 percent and a warning of more potential trouble ahead.

Control Factors
“Controlling high blood pressure is our most powerful tool for controlling stroke,” Dr. Albers said. “In general, the lower, the better”. Controlling blood pressure can reduce the risk of stroke by 30 to 40 percent.”

Multiple studies have shown that statins reduce risk of stroke in patients with coronary artery disease and high cholesterol. Dr. Albers cited the SPARCL study that found that a high dose of a statin medication reduced the risk of stroke and was well tolerated, with side effects (such as muscle aches) comparable to that of the placebo group.

Studies also have shown that quitting smoking can reduce risk by almost 50 percent within one year, and controlling cholesterol levels can decrease risk by about 20 percent. Dr. Albers suggested that for patients with atherosclerosis, LDL cholesterol (the “bad” cholesterol) should be lowered to below 80 to100 mg/dL.

After the cause of a stroke is determined, different medications are prescribed based on the type of stroke. For most patients with an ischemic stroke, regular use of an antiplatelet agent such as aspirin or clopidogrel (Plavix) can help prevent blood clots from forming. If atrial fibrillation is the cause, anticoagulants, such as warfarin (Coumadin), are typically prescribed.

New Options
While the FDA has approved the use of a clot-busting medication called tissue plasminogen activator (tPA) for up to three hours after a stroke, many people do not recognize the symptoms and do not make it to the emergency room in time. Dr. Albers and his Stroke Center associates typically give tPA up to 4.5 hours after the onset of certain kinds of stroke.

“The reality is that not everyone can make it to the emergency room during that ‘golden window,’” he said. “There’s only a small window of opportunity, so if you think you are experiencing a stroke, call 911 and go the emergency room immediately. You need to act quickly because we need to take some images and do some tests before starting treatment, and that takes time.”

About the Stanford Stroke Center
The Stanford Stroke Center was one of the first centers of its kind in the United States and was the first to be designated a comprehensive stroke center by The Joint Commission, a not-for-profit organization that accredits more than 15,000 health care organizations in the U.S.

The Center incorporates a multidisciplinary approach to stroke care. It’s staffed 24 hours a day with neurologists, neurosurgeons, radiologists, and rehabilitation experts, who use the latest technology when patients come in with signs or symptoms of stroke. In addition to utilizing cutting-edge technology for emergency stroke care, the Center is involved in studies to improve existing therapies and to develop new techniques for treating, diagnosing, and preventing stroke.

About the Speaker
Gregory Albers, MD is director of the Stanford Stroke Center and the Coyote Foundation Professor of Neurology and Neurological Sciences. A nationally known stroke expert, his research and clinical work focuses on the treatment and prevention of cerebrovascular disorders and the use of diffusion and perfusion MRI to expand the treatment window for ischemic stroke. Dr. Albers received his MD from University of California, San Diego, School of Medicine and did his internship, residency and stroke fellowship at Stanford. He is Board Certified in Neurology and in Vascular Neurology by the American Board of Psychiatry and Neurology.

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About Dr. Albers

Stanford Stroke Center