CT Imaging Tied to Higher Risk of Missing Stroke in Dizzy Patients

By Anne Harding

NEW YORK (Reuters Health) - Computed tomography (CT) scanning is not recommended for emergency department (ED) patients with vertigo, and new findings from Canada show that using the test actually boosts the risk of missing stroke in these patients.

Dr. Clare Atzema of the University of Toronto and her colleagues found that patients discharged with a diagnosis of peripheral vertigo were more likely to experience a stroke soon afterwards if they underwent a CT scan in the ED.

"It confirms what we already suspected, which is that CT probably misses the stroke and gives us a false sense of reassurance," Dr. Atzema told Reuters Health. "It's an incredibly rare outcome, so we're sort of saved by that."

Most of the time, vertigo is due to problems in the inner ear, but rarely, it can be caused by a stroke, Dr. Atzema and her team write in their report, published online December 1 in Stroke.

"Strokes that cause vertigo usually originate from the cerebellum and brain stem; these stroke types are associated with particularly high morbidity and mortality," they add.

A full history and examination, followed by diffusion-weighted magnetic resonance imaging (MRI) of the posterior fossa if neurological exam results are abnormal, is considered to be the best way to determine if patients with vertigo are indeed having one of these rare but serious strokes.

But MRIs are very difficult to obtain in most EDs, Dr. Atzema noted. "Most doctors default to the CT, because a CT you can get within an hour easily. Well CT is very good for the top part of the brain, but it's not very good for seeing into the cerebellum," she said.

To investigate whether CT imaging influenced the likelihood that stroke would be missed in patients with vertigo, the researchers looked at nearly 42,000 patients discharged from an Ontario ED with a diagnosis of peripheral vertigo between April 2006 and March 2011. Among these patients, 21% underwent CT scans in the ED.

Twenty-five (0.29%) of the patients who had CT scans were hospitalized for stroke within 30 days of being discharged, versus 11 (0.13%) of matched patients who has not been exposed to CT.

Patients who had CT were 2.27 times as likely to have a stroke within 30 days of discharge, and 1.94 times as likely to have one within 90 days. The median time to a stroke was 32 days for the patients who had CT scans, versus 105 days for the controls.

Even though the missed strokes were rare, Dr. Atzema said, "it actually translates into several thousand missed strokes per year."

Using CT in vertigo patients in the ED is even more common in the United States, she noted. The percentage of dizzy ED patients who underwent the test in the U.S. jumped from 9.4% in 1995 to 37.4% in 2009.

Dr. Atzema said she is hoping that the findings will convince clinicians and hospital administrators that MRI testing must be made more easily available in EDs.

"Maybe in 10 or 20 years we'll be able to get an MRI relatively easily," she said. "Right now it means hours of waiting."

SOURCE: https://bit.ly/12R4KNE

Stroke 2014.

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