Newswise — CLEVELAND – Results from the DAWN stroke trial presented at the European Stroke Organization Conference (ESOC) provide compelling evidence that selected patients suffering a major ischemic stroke recovered significantly better with mechanical retrieval of the blood clot with medical therapy compared with medical therapy alone when initiated past the current guidelines of within 6 hours and up to 24 hours of the stroke.

University Hospitals Cleveland Medical Center was one of the top seven recruiting sites in the multi-site study that enrolled a total of 206 patients in the nation. The results showed that patients treated with the retrieval system, known as mechanical thrombectomy, had significantly decreased post-stroke disability and improved functional independence at 90 days compared to medical management alone.

“This is incredible,” said Cathy Sila, MD, Director of UH’s Comprehensive Stroke Center, and principal investigator of the study at the UH site. “Almost half of the patients (48.6 percent) receiving the thrombectomy therapy had a good outcome at 90 days after treatment—defined as the patients being independent in activities of daily living—as opposed to only 13.1 percent of the patients treated medically or with clot-busting drugs alone. This 35 percent difference may be higher than any level of benefit from any stroke trial.” 

“Not only did the patients treated with mechanical thrombectomy  dramatically improve during hospitalization, sometimes being able to walk and be discharged to home, but there was also a much lower risk of subsequent neurological worsening because of the poor blood flow to the brain,” said Dr. Sila.

“The number of patients needed to treat to achieve a good outcome was 2.8. This is a much greater chance of response than what was seen in trials that did not routinely use advanced brain imaging to guide treatment,” she said.  “We have long believed in the usefulness of MRI scans to define appropriateness of treatment.  UH had been using a similar MRI  protocol since 2010, five years before the DAWN trial began in 2015.”

Anthony Furlan, MD, Chairman of the Department of Neurology at UH and Case Western Reserve University School of Medicine, was on the DAWN study’s steering committee and helped write the study protocol.

“These results provide physicians who treat stroke with evidence of the benefits of thrombectomy even when administered out as far as 24 hours, and should help to make decisions clearer as to which patients to treat,” said Dr. Furlan. “These positive outcomes of the DAWN trial represent a major change in patient selection for endovascular therapy for stroke,” he said.

In the study, researchers used neuroimaging to determine which patients would likely benefit from the procedure. According to Dr. Sila, they would examine how much brain tissue had suffered irreversible damage and how much might be able to be saved.  If the amount of damaged tissue were no bigger than the size of a small apricot, researchers believed the patient could benefit from the therapy.

Neuro-interventionists would then use a mechanical stent retriever called the Trevo Retriever to remove the blood clot, followed by treatment with the clot-busting medication.

The study had been stopped earlier this year after an FDA-approved planned interim review by the independent Data Safety Monitoring Board (DSMB) of data from the first 200 patients enrolled nationally because there was such a dramatic difference between the two arms of the study. The study had been designed to enroll up to a maximum of 500 patients.

Dr. Sila said that in Northeast Ohio, we have about 18,000 strokes per year.  Stroke survivors commonly experience devastating disabilities and loss of independence due to impaired movement, paralysis, loss of speech and memory. Randomized clinical data has proven the benefit of mechanical thrombectomy with stent retrievers in helping patients with large vessel occlusion strokes, but these devices have only been indicated to reduce disability if used within six hours of stroke onset.

“For patients presenting with stroke symptoms beyond six hours, the benefit of clot retrieval using a stent retriever was unknown,” said Dr. Furlan. “Now we have evidence that for patients who present to the hospital outside of the six hour time window could have a better chance for an independent life with improved clinical outcomes. Although this is great news, earlier treatment is always better because with stroke ‘time is brain.’”

The study was supported by Stryker, which produces the Trevo Retriever, a tiny stent-shaped medical device that is attached to a thin wire.  The retriever is designed to ensnare the blood clot to remove it from a blood vessel.

UH is working with Case Western Reserve University to develop the Cleveland Brain Health Initiative, linking this kind of leading edge neuroscience work from CWRU, UH, Cleveland Clinic, MetroHealth Medical Center and the Louis Stokes Cleveland VA Medical Center to advance progress therapy and treatment of devastating neurological diseases.


A video of a UH patient who was in the DAWN trial at:


About the DAWN Trial

The DAWN trial is an international, multi-center, blinded endpoint assessment, randomized study. The purpose of the study is to demonstrate superior clinical outcomes at 90 days with Stryker’s Trevo Retriever plus medical management compared to medical management alone in appropriately selected patients treated six to 24 hours after last seen well. The Trevo Retriever indication within the DAWN Trial is currently approved for investigational use only by the U.S. Food and Drug Administration in the United States under an Investigational Device Exemption (IDE) study approval.

About University Hospitals / Cleveland, Ohio

Founded in 1866, University Hospitals serves the needs of patients through an integrated network of 18 hospitals, more than 40 outpatient health centers and 200 physician offices in 15 counties throughout northern Ohio. The system’s flagship academic medical center, University Hospitals Cleveland Medical Center, located on a 35-acre campus in Cleveland’s University Circle, is affiliated with Case Western Reserve University School of Medicine. The main campus also includes University Hospitals Rainbow Babies & Children's Hospital, ranked among the top children’s hospitals in the nation; University Hospitals MacDonald Women's Hospital, Ohio's only hospital for women; and University Hospitals Seidman Cancer Center, part of the NCI-designated Case Comprehensive Cancer Center. UH is home to some of the most prestigious clinical and research programs in the nation, including cancer, pediatrics, women's health, orthopedics, radiology, neuroscience, cardiology and cardiovascular surgery, digestive health, transplantation and urology. UH Cleveland Medical Center is perennially among the highest performers in national ranking surveys, including “America’s Best Hospitals” from U.S. News & World Report. UH is also home to Harrington Discovery Institute at University Hospitals – part of The Harrington Project for Discovery & Development. UH is the second largest employer in northern Ohio with 26,000 employees. For more information, go to

About the Trevo Retriever

The Trevo Retriever is a tiny stent-shaped medical device that is attached to a thin wire. In a minimally invasive procedure that utilizes X-ray, the physician navigates the retriever from the femoral artery (located in the upper leg) to the blocked blood artery in the brain. The retriever is designed to ensnare the blood clot and remove it from the body. Originally cleared by the FDA in 2012 for the revascularization of patients experiencing ischemic stroke, the Trevo Retriever has been used in thousands of patients worldwide. Stryker’s Trevo Retriever was the only mechanical thrombectomy device used in this trial.

An animation of Stryker’s Trevo Retriever is available here:

About ischemic stroke

An ischemic stroke occurs when an artery in the brain becomes blocked by a blood clot or other substance such as plaque, a fatty material. Blood vessels carry blood, oxygen and nutrients throughout the body and to the brain. When the brain is deprived of blood and oxygen, it fails to work properly. Depending on the severity of the stroke and the area of the brain affected, loss of brain function or death may occur. According to the World Heart Federation, ischemic stroke contributes to nearly six million deaths around the globe.


About Stryker

Stryker is one of the world's leading medical technology companies and, together with our customers, we are driven to make healthcare better. The Company offers a diverse array of innovative products and services in Orthopedics, Medical and Surgical, and Neurotechnology and Spine that help improve patient and hospital outcomes. Stryker is active in over 100 countries around the world. Please contact us for more information at