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MRIs Make You Dizzy? Here's Why

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If you've ever gone for an MRI and been left feeling woozy, new research says you're not just being a wuss: there's an actual physical culprit behind that dizziness.

According to researchers at John's Hopkins University, the magnet in MRI machines can stimulate the inner ear's balance center, causing some patients to feel vertigo while they are inside the machine and in the minute or two after they've left it.

"For a long time, people have felt, 'I'm just nervous' or 'I'm claustrophobic,'" said Dale C. Roberts, M.S., one of the study's co-authors, who likened the sensation to being on a slow merry-go-round.

"Now we know that there's a real physical stimulation of the balance centers that cause you to feel vertigo," he added, explaining that the "why" behind said dizziness has been a mystery since stronger magnets were introduced in machines some 20 years ago. (MRIs rely on a computer, a magnet and radiofrequencies to produce images of the body's internal structures.)

To solve the MRI vertigo puzzle, Roberts and his fellow researchers in the lab of John's Hopkin's neurologist Dr. David Zee put 12 volunteers -- 10 with healthy inner ear balance centers and 2 without -- in MRI scanners, tracking what they reported feeling and simultaneously monitoring any involuntary eye movements that indicate the brain is registering motion.

According to Roberts, the biggest consequence of their discovery that magnetic fields put pressure on the fluids in the inner ear could come in the research world. Machines with stronger magnets, such as those often used in experiments to track metabolic changes in the brain, caused faster eye movements, meaning the machines could be causing brain activity and thus could potentially be skewing results.

Roberts said magnets' effects are a minimal issue in the clinical settings in which MRI machines with lower-strength magnets are typically used, though his colleague Zee added that in certain procedures, doctors rely on functional imaging to make sure they're not working in parts of the brain critical for speech or movement. In those cases, the MRI's impact on the brain's balance organ is something to be aware of.

But even more broadly?

Roberts said the new discovery could help with a minor, but not uncommon, safety concern: Some people jump off the machine too quickly and can be caught off-balance.

"Now when a patient complains, we know why this is happening," he said. "A doctor can explain why, and can tell them what to be aware of."

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