Presented by: Jeremy Heit, MD, PhD
Fellow, Neuro-interventional Radiology
Stanford University Medical Center
April 30, 2015
About 800,000 Americans suffer from a stroke each year—someone every 45 seconds. Stroke is 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 estimated to run about $73 billion each year. May is National Stroke Prevention Month.
A stroke occurs when a blood vessel carrying oxygen to the brain suddenly bursts or becomes blocked and can cause paralysis, language loss, coordination or balance difficulties, and confusion. Ischemic stroke, the most common type of stroke, is caused by blockage from a clot in the carotid arteries of the neck or in the brain, similar to what occurs during a heart attack.
“When blood flow is interrupted, the effect is almost immediate,” said Jeremy Heit, MD, PhD, a fellow in Stanford’s Neuro-interventional radiology program, who spoke at a presentation sponsored by the Stanford Health Library.
In an ischemic stroke, the area immediately affected by the blood loss—the core infarction—suffers irreversible damage. However cells in the surrounding area—the penumbra—may remain viable for several hours and have a good chance of being salvaged if blood flow to this region can be restored. Every second the brain survives without blood flow, damage is done. The faster blood flow can be restored, the more cells can be saved, causing less neurological damage and better patient outcomes.
“If the penumbra is not saved quickly, there is likely to be more damage,” he said. “As the number of damaged brain cells grows, the complications increase. Restoring blood flow rapidly is the best chance for a good outcome. Our goal is to get the vessel open as quickly as possible.”
There are several options for reperfusion, or restoring blood flow through blocked arteries. A clot-busting medication called tissue plasminogen activator (tPA), which was introduced 20 years ago, has been shown to open up vessels if introduced within four hours on stroke onset. People who receive treatment within four hours are more likely to recover.
But the window of opportunity after a stroke is small—and many people don’t even realize they are having a stroke or don’t make it to the emergency room in time. As a comprehensive stroke center, Stanford has been instrumental in developing new treatments for stroke patients who are not able to receive tPA.
A more recent option is known as a mechanical thrombectomy in which the clot is manually removed using endovascular (minimally invasive) surgical techniques. A catheter is introduced at the femoral artery at the groin, and neuro-interventionalist uses X-rays to navigate the catheter up to the brain. An retrievable stent or suction device is then used to physically pull out the clot. These promising mechanical technologies can be done in less than 20 minutes and show benefit up to eight hours after the onset of a stroke.
“The technology is improving rapidly,” said Dr. Heit, “but we need to know what’s going on in the brain before we act so we can identify the patients who are most likely to have a good outcome with this therapy.”
Dr. Heit, who will join the Stanford faculty next year, is an expert in different imaging tools for assessing where the core of the stroke is located and the areas at risk in the penumbra. Using advanced magnetic resonance imaging (MRI), for example, he can identify the areas at risk and pinpoint the exact location of the clot. Using another imaging system called computed tomography, he can conduct a brain CT scan to show bleeding in the brain or damage to the brain cells. Often he will combine MRI with CT to create the most accurate picture of the brain that neuro-interventionalists can use as a map to deliver therapy. The same systems can show response to treatment in just minutes.
“Our challenge is to know who will most benefit from this treatment,” he said. “There are specific questions we have to ask: Where is the clot? How big is the existing stroke? A good candidate will have a small core, have a large amount of tissue at risk, and have a clot that can be reached. Outcomes are better if the patient is selected based on this criteria.”
Recent studies have shown improved outcomes using an endovascular approach over medical treatment with tPA. And now neurologists and neuro-interventionalists are using the two methods in conjunction with excellent results. At Stanford, blood clot removal techniques can be used in 80-85 percent of patients, which maximizes the odds of a good outcome after a stroke, he said.
Dr. Heit emphasized that as a neuro-interventional radiologist, he uses advanced imaging and guidance techniques for both diagnosis and treatment. He is part of a multidisciplinary team made up of neurologists, neurosurgeons, neuroradiologists, intensive care physicians, nurses, and rehabilitation experts who use the latest technology when patients come in with signs or symptoms of stroke.
Stroke Warning Signs
- Sudden numbness or weakness of the face, arm, or leg, especially on one side
- Confusion, trouble speaking or understanding
- Partial loss of vision in one or both eyes
- Difficulty in walking, dizziness, loss of balance or coordination
- Sudden, severe headache
What To Do In Case of Stroke
If you spot the signs of stroke, think FAST:
- Face drooping: Ask the person to smile. Is the smile uneven?
- Arm Weakness: Is one arm weak or numb?
- Speech Difficulty: Is speech slurred? Is the person unable to speak or hard to understand?
- Time to call 9-1-1: Get the person to the hospital immediately. Check the time so you’ll know when the first symptoms appeared.
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