-- Mary Elizabeth Dallas
FRIDAY, Sept. 23 (HealthDay News) -- Many people who undergo MRI
scans describe feeling dizzy while inside the machine or when they
come out, and a new study may explain why.
Researchers believe that the strong magnet used during an MRI
pushes on fluid circulating in the inner ear, impacting balance and
often leading to a feeling of vertigo or free-falling.
In the study, published online Sept. 22 in
Current Biology, researchers assigned 10 volunteers with healthy labyrinths (tube-like structures in the inner ears that control balance) and two volunteers who lacked labyrinthine function to undergo MRI scans of different strengths and for various lengths of time.
The investigators asked the volunteers about feelings of
vertigo, and monitored the participants' nystagmus, an involuntary
eye movement that happens when the brain is detecting motion.
The study authors found that the healthy people had nystagmus
while in the MRI machine, and those without functioning labyrinths
did not. As a result, the researchers concluded that this balance
center of the inner ear is linked to MRI-induced vertigo.
The study also found that higher MRI strengths caused
considerably faster nystagmus among the participants, regardless of
how long the scans lasted.
After taking into consideration known facts about the inner ear,
the researchers concluded that MRI-related vertigo is probably the
result of force exerted on the electrically charged fluid of the
inner ear by the magnetic fields of MRIs.
The finding could challenge the results of previous functional
MRI studies designed to detect brain activity, the study authors
noted, because the scanner itself could be causing brain activity
related to movement and balance, skewing results.
"We've shown that even when you think there's nothing happening in the brain while volunteers are in the scanner, there's actually a lot happening because MRI itself is causing some effect," explained Dale Roberts, senior research systems engineer in the department of neurology at Johns Hopkins University School of Medicine, in a university news release. "These effects must be taken into account in the way we interpret functional imaging."
The researchers noted that MRI's strong magnetic field could
eventually be used to diagnose and treat inner ear and balance
disorders in a more comfortable and noninvasive way than is
The U.S. National Institute on Deafness and Other Communication
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