April 20, 2005, New Orleans: Interventional neuroradiologists at West Virginia University School of Medicine and Hospitals today presented the largest study to date on the utility of computed tomography (CT) perfusion imaging of the brain in determining and predicting stroke outcomes. Results will help better identify patients who are suitable candidates for treatment utilizing either clot busting medicines or clot retrieval devices. The research was presented to leading neurosurgeons at the 73rd annual meeting of the American Association of Neurological Surgeons.
The research, which examined 372 stroke patients, is significant because it allows doctors to customize stroke treatments based on the degree of brain death, instead of relying solely on how soon or late a patient comes to the hospital after having stroke symptoms.
Under NIH stroke guidelines, hospitals typically administer tPA (a clot-busting drug) to patients within a three-hour window of stroke onset. After six hours, it's generally considered too risky to administer even interarterial clot busting medicines, due to the risk of a potentially deadly hemorrhage.
But research presented by interventional neuroradiologists Jeff Carpenter, M.D., and Ansaar Rai, M.D., Assistant Professors at The Department of Neurological Surgery of West Virginia University School of Medicine, suggests more lives might be saved and debilitating side effects minimized if treatment of stroke patients was based on qualitative and quantitative imaging such as CT perfusion and CT angiography and not on generalized application of arbitrary time windows of three to six hours.
Those windows can exclude some patients who may benefit from treatment and include others who may suffer from serious complications of the treatment. Application of this research could increase the time window of treatment for stroke patients to greater than seven hours. This is significant because patients often don't present to hospitals until after the three-hour window has closed because they don't recognize the symptoms of stroke, can't summon help quickly, or reside in rural areas. Additionally, those that do present in time can receive treatment that results in hemorrhage. A 2003 study published in Stroke which analyzed 15 published reports of tPA use in more than 2600 acute stroke patients found the intracerebral hemorrhage rate was 5.2 percent.
The WVU study shows that CT perfusion, which measures blood flow, is very accurate at determining which patients would best benefit from treatment and which should not receive clot-busting drugs. In the study, less than one percent of patients suffered a hemorrhage after receiving tPA, compared with the average of 5.2 percent of patients cited by the Stroke study.
CT perfusion allows radiologists to determine which portions of a stroke patient's brain are dead, and which portions are dying but capable of being salvaged. Once a ratio of dead to dying brain is calculated, doctors can determine the best course of treatment. Only those patients whose brains are damaged but still alive will benefit from that treatment of acute revascularization of a blocked blood vessel.
To determine accuracy of CT perfusion, patients received both CT perfusion and an MRI. Results of the study presented shows that CT perfusion results correspond exceedingly well to MRI studies on several parameters including measuring cerebral blood volume, which indicates the severity of a blockage. About 60 percent of patients deemed candidates for intervention following CT perfusion were able to have their clots removed successfully by interarterial administration of tPA and the MERCI (corkscrew) procedure. In MERCI, the blood clot causing the stroke is removed by threading a corkscrew-like device through a catheter fed through the groin.
While MRIs are considered the gold standard for post stroke analysis, they are rarely performed and generally impractical because: they take 30 minutes to perform, require a stroke patient to be still to capture clean images (the patient may be moving or thrashing), require doctors to check for metal in the patients body (which may be impossible if no family members are present) and the MRI units themselves are often not adequately staffed or not located near the emergency room.
CT perfusion offers distinct advantages because most hospital emergency rooms use them frequently for other purposes, they take one to two minutes to scan (versus 30 minutes for MRI), and provide clear images even if a patient cannot lie perfectly still. Most hospitals need only to buy software (at a relatively inexpensive cost) to upgrade their systems and institute training programs.
In the coming months, Drs. Carpenter and Rai are expecting to publish their study in a nationally recognized journal.
If you are interested in speaking to the researchers of this study and patients successfully treated following CT perfusion, please contact Paul Moniz using the above contact information.