Download Why MRI scans CAN make you dizzy: Magnetic fields disrupt fluid in

Why MRI scans CAN make you dizzy:
Magnetic fields disrupt fluid in inner ear
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Strong magnetic fields may disrupt the fluid levels in the
As any patient who has had an MRI scan knows, lying inside the giant
magnetic machine can feel quite claustrophobic.
But those who say it makes them feel dizzy will be relieved to hear it's not all
in their mind.
Scientists have found the powerful magnetic fields and radio waves, used to
create detailed images from within the body, may affect the inner ear.
Researchers from John Hopkins Medical Institutions in the U.S. traced the
problem to the labyrinth - the tube-like structure of the inner ear that controls
balance.
MRI scan: Scientists said the effect of the magnetic fields should be taken into account when
interpreting brain scans
The findings suggest that the strong magnetic field pushes on fluid within the
labyrinth, giving rise to a feeling of unexpected or unsteady movement.
The study involved comparing the experiences of 10 healthy volunteers and
two who lacked functioning labyrinths.
As participants underwent MRI scans, the researchers looked for an effect
called nystagmus, an involuntary eye movement that reflects the brain's
detection of motion.
The effect was seen in all healthy volunteers undergoing scans, but not those
with the inner ear disorder. This was a sure indication that the labyrinth
played a role in MRI-related vertigo.
Further tests showed that higher magnetic field strengths caused faster
nystagmus.
The direction of the eye movements also changed depending on which way
volunteers entered the machines.
The findings were published online today in the journal Current Biology.
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MRI vertigo is caused by interplay between the magnetic field and the salty
fluid that fills labyrinth canals, the scientists believe.
The magnetic field is thought to push on the current of electrically charged
particles circulating within the tubes. This in turn exerts a force on the cells
which use the fluid's flow to detect motion.
The discovery has implications for MRI-based brain research, say the
scientists.
They point out that the scanner could itself be inducing previously unnoticed
brain activity related to movement and balance.
Researcher Dale Roberts, from Johns Hopkins Medical Institutions, said:
'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
the MRI itself is causing some effect.
'These effects must be taken into account in the way we interpret functional
imaging.'
The MRI effect on balance could in future be used to diagnose and treat inner
ear disorders by stimulating the labyrinth, said the researchers.