MRI More Sensitive than CT for Diagnosis of Acute Stroke

National Institutes of Health's (NIH) National Institute of Neurological Disorders and Stroke (NINDS; Bethesda, MD, USA) discovered that the sensitivity of MRI for diagnosing acute strokes was 83%, compared with just 26% for CT performed on the same patients.

The investigators also found that MRI was also superior to CT at diagnosing acute hemorrhagic stroke and chronic stroke, and was comparable at detecting intracranial hemorrhage, reported the researchers. "These NIH research findings on acute stroke imaging are directly applicable to real-world clinical practice,” said NIH director Elias A. Zerhouni, M.D.

The study's findings revealed immediate non-contrast MRI is approximately five times more sensitive than and twice as accurate as immediate non-contrast CT for diagnosing ischemic stroke. Non-contrast CT and MRI were equally effective in the diagnosis of acute intracranial hemorrhage. Non-contrast CT has been the standard in emergency stroke treatment, primarily to exclude hemorrhagic stroke, which cannot be treated with clot-busting therapies.

The study's investigators hope that because of its increased diagnostic accuracy, MRI may lead to better patient outcomes and eventually decrease the cost of stroke care, through increased use of acute treatments and earlier initiation of secondary prevention.

Stroke specialists conducted emergency clinical evaluations with all patients, including the NIH Stroke Scale, which is used to measure stroke severity. MRI was performed prior to CT in 304 patients. Scans were initiated within two hours of each other, with a median difference of 34 minutes. Patients were excluded from the study if either CT or MRI was not done. The images were sorted randomly and independently by two neuroradiologists and two stroke neurologists.

Results of the study, published in the January 27, 2007 issue of the journal The Lancet, demonstrated that conventional MRI is superior to standard CT in detecting acute stroke and particularly acute ischemic stroke. The four readers were unanimous in their agreement on the presence or absence of acute stroke in 80% of patients utilizing MRI compared to 58% using non-contrast CT. No significant difference using the two technologies was seen in the diagnosis of acute intracranial hemorrhage, which is consistent with earlier findings.




Related Links:
National Institute of Neurological Disorders and Stroke