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CME / ABIM MOC / CE

Is Computed Tomography Alone Versus Computed Tomography Plus Magnetic Resonance Imaging Enough for the Diagnosis of Strokes?

  • Authors: News Author: Marlene Busko; CME Author: Charles P. Vega, MD
  • CME / ABIM MOC / CE Released: 10/7/2022
  • Valid for credit through: 10/7/2023
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  • Credits Available

    Physicians - maximum of 0.25 AMA PRA Category 1 Credit(s)™

    ABIM Diplomates - maximum of 0.25 ABIM MOC points

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Target Audience and Goal Statement

This activity is intended for primary care physicians, neurologists, emergency medicine specialists, cardiologists, internal medicine physicians, nurses, nurse practitioners, physician assistants, and other clinicians who care for patients with acute ischemic stroke.

The goal of this activity is for learners to be better able to evaluate the value of magnetic resonance imaging in addition to computed tomography among cases of acute ischemic stroke.

Upon completion of this activity, participants will:

  • Distinguish imaging modalities associated with improved outcomes in acute ischemic stroke
  • Evaluate outcomes of adding magnetic resonance imaging to computed tomography imaging of the brain among patients with acute ischemic stroke
  • Outline implications for the healthcare team


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News Author

  • Marlene Busko

    Freelance writer, Medscape

    Disclosures

    Marlene Busko has no relevant financial relationships.

CME Author

  • Charles P. Vega, MD

    Health Sciences Clinical Professor of Family Medicine
    University of California, Irvine School of Medicine

    Disclosures

    Charles P. Vega, MD, has the following relevant financial relationships:
    Consultant or advisor for: GlaxoSmithKline; Johnson & Johnson Pharmaceutical Research & Development, L.L.C.

Editor/Compliance Reviewer

  • Yaisanet Oyola, MD

    Associate Director, Accreditation and Compliance, Medscape, LLC

    Disclosures

    Yaisanet Oyola, MD, has no relevant financial relationships.

Compliance Reviewer

  • Lisa Simani, APRN, MS, ACNP

    Associate Director, Accreditation and Compliance, Medscape, LLC

    Disclosures

    Lisa Simani, APRN, MS, ACNP, has no relevant financial relationships.

Peer Reviewer

This activity has been peer reviewed and the reviewer has no relevant financial relationships.


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CME / ABIM MOC / CE

Is Computed Tomography Alone Versus Computed Tomography Plus Magnetic Resonance Imaging Enough for the Diagnosis of Strokes?

Authors: News Author: Marlene Busko; CME Author: Charles P. Vega, MDFaculty and Disclosures

CME / ABIM MOC / CE Released: 10/7/2022

Valid for credit through: 10/7/2023

processing....

Clinical Context

An increasing number of patients with acute ischemic stroke in the United States are receiving brain imaging studies of computed tomography (CT) followed by magnetic resonance imaging (MRI), but a previous study by Hefzy and colleagues questions the value of this practice. The results of this research involving 727 patients were published in the May 17, 2013, issue of Open Neurology Journal.[1]

Researchers evaluated outcomes 1 year after hospitalization in a single stroke center for stroke or transient ischemic attack. The main study variable was the application of different imaging modalities during their hospital stay.

Older age and more severe stroke severity negatively affected the combined outcome of death, myocardial infarction, or recurrent stroke. However, adding MRI to CT brain imaging did not improve this outcome, nor did the application of echocardiography or transcranial Doppler studies. CT angiography of the brain was associated with a significant improvement in the composite outcome at 1 year.

The current study reevaluates whether adding MRI to CT imaging of the brain improves mortality outcomes in cases of AIS.

Study Synopsis and Perspective

Among patients with acute ischemic stroke, diagnostic imaging with CT alone was noninferior to initial CT plus MRI for discharge and 1-year clinical outcomes in a new study

The rates of death or dependence at hospital discharge, and of recurrent stroke or death at 1 year, were not worse in the patients who only had a cranial CT scan.

Therefore, "the value of MRI added to CT in patients such as these should not be presumed," Heitor Cabral Frade, MD, from the University of Texas, Galveston, and colleagues write in their study, published July 21 in JAMA Network Open.[2]

The addition of MRI to CT has greatly increased, but it is not clear whether the added MRI, which is more expensive, improves outcomes, senior author William J. Powers, MD, from the University of North Carolina, Chapel Hill, explained to theheart.org | Medscape Cardiology.

From 1999 to 2008, the use of MRI to evaluate patients with ischemic stroke in the United States increased from 28% to 66%, and more than 90% of patients who had a brain MRI first had a CT scan, the researchers note. Unnecessary medical imaging is a major cause of preventable waste in the American healthcare system.

"Many clinicians believe that more data lead to better patient outcomes, but that's not always true," said Dr Powers. With MRI, "you see more stuff and you make decisions based on that, but does that mean people do better? That's the implicit assumption, but that's not always true."

When you come up with a new diagnostic test, he continued, unlike with a new drug, you do not have to show the US Food and Drug Administration that using it improves patient outcomes.

"Maybe [this study] will get clinicians to think that we really do need more data and more research to determine which patients hospitalized with acute ischemic stroke benefit from MRI in addition to initial CT," he said.

"Pause and Reconsider"

"Given the pervasiveness of routine MRI in addition to CT in clinical stroke practice, the implications" of this study are "substantial," Michael Teitcher, MD, and Jose Billar, MD, from Loyola University, Chicago, write in an accompanying editorial.[3]

"As stewards of health care resources, clinicians should be asking whether the additional information provided by diagnostic tests meaningfully affects patient outcomes," they advise, and "the answer. . .should be data-driven rather than anecdotal."

There are circumstances in which additional MRI is still justified, Dr Teitcher and Dr Billar acknowledge. "But at a minimum, these results should give the health care practitioners reason to pause and reconsider routine use of CT plus MRI."

"Hopefully, the present study paves the way for future prospective studies that would provide additional data on this common clinical question," the editorialists write, echoing Dr Powers.

Current American Heart Association/American Stroke Association guidelines state that it is reasonable to obtain additional MRI after initial head imaging in cases where initial imaging did not demonstrate infarction.[4]

Some researchers and practitioners recommend that all hospitalized patients with acute ischemic stroke undergo brain imaging with MRI, Dr Billar told theheart.org | Medscape Cardiology  this "may help in differentiating ischemic stroke subtypes (for example, large artery extracranial and intracranial atherosclerotic disease, cardioembolic disease, lacunar, and small vessel disease) within the continuum of ischemic cerebrovascular syndromes."

However, whether this imaging paradigm is associated with improved patient outcomes, he continued, remains unsubstantiated by either consensus or evidence review.

The routine use of brain MRI in addition to CT among hospitalized patients with acute ischemic stroke "requires verification in properly designed clinical trials," Dr Biller said, adding, "let the data speak for itself!"

"In the meantime," he said, "it would be timely and sensible to rethink when to order brain MRIs for hospitalized patients with acute ischemic stroke."

Propensity-Matched Patients

For the propensity-score-matched study, 246 patients with acute ischemic stroke were admitted to University of North Carolina Hospitals Comprehensive Stroke Center between January 2015 and December 2017 and were imaged with either initial CT alone or CT plus MRI.

Patients were classed as having dependence at hospital discharge if they had a modified Rankin Scale score of from 3 to 6 (where 3 indicates needing some help but able to walk unassisted and 5 indicates need for constant nursing care and attention and being bedridden and incontinent; a score of 6 means death). Median age of the study participants was 68 years, and 53% were men.

Among the 123 patients with additional MRI, 42.3% of the tests were ordered under the supervision of attending neurologists, 33.3% under the supervision of attending emergency physicians, and 24.4% by nurse practitioners or neurocritical care attending physicians.

Of the 6 attending neurologists caring for people with stroke during the study period, one never requested an MRI, another always requested one, and the others were in between.

For 111 of the 123 MRIs, there was no specified indication other than stroke or neurologic symptoms.

Death or dependence at hospital discharge occurred more often in patients who had MRI added to CT than in patients who had CT alone (48.0% vs 42.3%), which met the −7.5% margin for noninferiority.

Similarly, stroke or death in the year after discharge occurred more often in patients who had both types of imaging than in patients who had CT alone (19.5% vs 12.5%), meeting the 0.725 margin for noninferiority.

"Consider What Value It Will Add"

Bruce C.V. Campbell, PhD, from Royal Melbourne Hospital, Australia, told theheart.org | Medscape Cardiology that at his center, "we order MRI selectively, in perhaps 20% to 30% of patients."

"We also often do diffusion-only MRI to characterize the infarct," said Dr Campbell, who authored a second editorial that accompanies the article.[5]

"We routinely do CT, CT-perfusion, and aortic arch to cerebral vertex CT-angiography, so we have a lot of vascular information already," he continued.

"The diffusion MRI," he explained, "confirms the diagnosis, indicates infarct volume (which is useful when considering timing of anticoagulation), provides hints to mechanism [such as] small vessel disease, cardioembolism if multiterritory infarcts, watershed patterns, and confirms whether a carotid stenosis is likely to be symptomatic."

"Like any investigation, it's good practice to consider what value it will add to [patient] management decision-making," Dr Campbell summarized. "There are many situations where MRI is valuable after stroke, but it's not needed for everyone."

The authors and editorialists report having no relevant financial relationships.

Study Highlights

  • Study data were drawn retrospectively from 1 academic stroke center in the United States. The study cohort included patients admitted with acute ischemic stroke between 2015 and 2017.
  • All patients were at least 18 years of age and had at least an initial CT of the brain on admission.
  • The main study outcome was either death or modified Rankin Scale score of 3 to 6 at hospital discharge, indicating severe disability with inability to ambulate independently and need for assistance with important daily functioning. Researchers also assessed records for evidence of repeat stroke or death within the 12 months after acute ischemic stroke.
  • The main study variable was the addition of MRI to CT imaging of the brain. A total of 123 patients who did and did not have an additional MRI were matched on the basis of baseline characteristics and compared for this outcome.
  • The study was designed to demonstrate noninferiority of CT alone vs CT plus MRI, with a difference of less than 7.5% between cohorts in the main outcome.
  • The median age of the 246 study patients was 68 years, and 53% were men. Approximately one quarter of patients had a previous stroke.
  • Ischemic changes in the brain were noted on CT in 19.5% of patients who underwent MRI and 31.2% of patients who did not undergo MRI.
  • 42.3% of MRI were ordered by attending vascular neurologists, whereas 33.3% and 24.4% were ordered by attending emergency physicians or the neuroscience intensive care team.
  • 111 of the 123 MRIs included no indication other than stroke or neurological symptoms.
  • At hospital discharge, the rates of death or severe disability in the MRI and no-MRI groups were 48.0% and 42.3%, respectively. This result met the definition of noninferiority, and the difference between the 2 groups was not significant.
  • Mortality rates during hospitalization specifically were 3.3% and 5.7% in the CT alone and CT plus MRI groups, respectively. Again, this difference was not significant.
  • 96% of patients discharged alive had outcomes available at 1 year. Stroke or death occurred in 19.5% of the CT plus MRI cohort and 12.5% of the CT-only group. This difference satisfied the noninferiority standard.

Clinical Implications

  • In a previous study, CT angiography improved the combined outcome of death, myocardial infarction, or recurrent stroke at 1 year after stroke or TIA. However, adding MRI to CT brain imaging did not improve this outcome, nor did the application of echocardiography or transcranial Doppler studies.
  • In the current study, adding MRI to CT brain imaging among patients with acute ischemic stroke did not improve a combined outcome of death and stroke disability at hospital discharge, nor did CT plus MRI improve rates of death or recurrent stroke at 12 months.
  • Implications for the healthcare team: The healthcare team cannot assume that adding MRI of the brain to CT imaging improves mortality or short-term disability outcomes. Members of the healthcare team should consider what value it will add to the patient management decision-making according to each specific case scenario, there are many situations where MRI is valuable after stroke, but it's not needed for everyone and clinical judgment must be taken into consideration.

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