MRI unlikely to catch speedy CT for initial stroke imaging

Brain MRI may provide more clinical information on some patients with acute stroke, particularly in the detection of acute ischemia and the identification of some stroke-mimicking pathologies. However, every second counts in stroke care—and brain CT has such faster door-to-needle times and better feasibility that it likely will remain the first-line stroke-imaging exam for the foreseeable future. 

That’s the gist of a European study lead-authored by Christine Krarup Hansen, MD, PhD, of the University of Copenhagen and published online May 10 in Clinical Neurology and Neurosurgery.

The researchers looked at the cases of 444 consecutive patients who presented in an established stroke unit with symptoms of acute stroke within four and a half hours from onset of symptoms.

The team quasi-randomized 225 patients for CT and 219 for MRI.

They found that MRI was not feasible in almost a quarter of the MRI-allocated patients due to MRI contraindications, while another 14 percent had clinical conditions incompatible with safe MRI scanning of diagnostic quality.

In total, nearly half the MRI-allocated patients ended up getting imaging with CT instead.

On the other hand, MRI proved the preferred modality for almost 10 percent of the CT-allocated patients, mainly to either avoid irradiation in pregnant or younger patients or to  establish the correct diagnosis prior to potential administration of the gold standard, intravenous-tissue plasminogen activator (iv-tPA).

The most crucial finding was the door-to-needle times were eight minutes shorter for the CT-allocated patients compared to the MRI-allocated patients.

Using simulated prediction, the authors found those eight minutes translated to a 1 percent decreased chance of independent living at three months in 16.9 percent of the iv-tPA-treated MRI-allocated patients.

In their discussion the authors state theirs is the first randomized trial comparing thrombolytic treatment delay for CT- versus MRI-examined acute stroke patients.

“The study shows that MRI is a potential option in the acute stroke-setting—though significantly slower and less often feasible than CT,” they write, acknowledging that their study design does not allow for ascertaining all clinically useful information MRI can supply in stroke care.

As so many of the patients were not able to undergo MRI, use of MRI as the first line of brain imaging during acute stroke “is not uncomplicated,” they write. “It is essential to have access to acute CT in case of patients with contraindications or patients unfit for MRI.”

Further, confirming conclusions from previous studies, Hansen et al. note the low number of iv-tPA treated patients they found to have stroke-mimicking discharge diagnosis in both their CT- and MRI-allocated groups, “proving that fast and efficient assessment is attainable without compromising a high number of noneligible patients.”