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publicado em 23/09/2011 às 20h20:00
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Researchers identify the cause of vertigo during the MRI

The magnetic field of the MRI machine pushes the fluid from the organ of balance in the inner ear

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A team of researchers said they discovered the reason why so many people undergoing MRI, especially on machines with newer high-strength, become lightheaded, dizzy or free-fall while they are in or out of the machine similar to a tunnel .

In a new study, a team of researchers led by scientists at Johns Hopkins University suggested that the strong MRI magnet pushes the fluid that circulates in the balance center of the inner ear, leading to a sense of sudden movement or unstable. The discovery could also call into question the results of functional MRI studies, designed to detect the brain and mind are doing under different circumstances.

To determine the mechanism behind the vertigo induced by the resonance, the researchers put 10 healthy volunteers with mazes and labyrinths whose two volunteers did not work in MRI machines. They not only vertigo followed by reports of the participants, but also to observe the nystagmus, a kind of involuntary eye movement that reflects that the brain is detecting motion. Because visual cues can help suppress the nystagmus, the researchers conducted their experiments in the dark.

The images of night vision cameras showed that all healthy volunteers had nystagmus during scanning, but those whose labyrinths did not work, did not have a clear sign that the labyrinth plays an essential role in the vertigo related to MRI.

To find out how the magnetic field acts in the maze of resonance, the researchers tested the volunteers in the resonances of different strengths, for various periods of time. They also accompanied the nystagmus of the volunteers while they were in and out of resonance machines.

The researchers found that stronger magnetic fields caused nystagmus faster. These eye movements persisted for as long as the volunteers were on the machine, no matter how the experiments lasted. In addition, the direction of eye movements changed depending on how they entered the tunnels of machines (the entrance or behind), suggesting that the effect on the maze was directionally sensitive.

Combining search results with what is known about the inner ear, the researchers determined that the dizziness caused by magnetic resonance imaging is related, more likely, the interaction between the electric currents flowing through the fluid channels of the labyrinth in the salty and the magnetic field resonance.

Through an effect well known to physicists called the Lorentz force, the magnetic field pushes the seemingly stream of charged particles in the fluid of the inner ear. This exerts a force on the cells using the fluid flow as a way to feel the movement.

The new findings suggest that the MRI system itself could be causing brain activity have not noticed about movement and balance, possibly affecting the results. These effects should be taken into account when interpreting functional imaging, said systems engineer Dale C. Roberts.

The researchers add that the strong magnetic field of magnetic resonance imaging could be used as a method for stimulating the maze to diagnose and treat their disorders are a non-invasive and more comfortable than the conventional one.

   Palavras-chave:   MRI    Vertigo    Dizziness    Magnet    Fluid center of balance    Inner ear    Nystagmus    Eye movement   
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MRI    vertigo    dizziness    magnet    fluid center of balance    inner ear    nystagmus    eye movement   
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