FRIDAY, Sept. 23 (HealthDay News) -- Individuals with intact labyrinthine function experience nystagmus in magnetic resonance imaging (MRI) machines, according to a study published online Sept. 22 in Current Biology.
Dale C. Roberts, from the Johns Hopkins University School of Medicine in Baltimore, and colleagues investigated MRI-induced nystagmus and possible vertigo by placing 10 healthy individuals and two controls (lacking labyrinthine function) in the static magnetic field of three and seven tesla strength MRI scanners for various durations, with no actual scan performed. Participants were moved into the MRI bore using various speeds and directions, and eye movements were measured in darkness by infrared video camera.
The investigators found that all healthy individuals, but not the controls, developed a robust nystagmus in the presence of the static magnetic field. Based on the eye movement patterns, the vestibular stimulation was static (did not require change in head movement or dynamic magnetic field strength, was continuous, and proportional to static magnetic field strength), and directional (sensitive to head orientation and magnetic field polarity).
"We found that the pattern of eye movements under different conditions argues against previously proposed mechanisms that depend upon movement in the field or on magnetic susceptibility. Rather, our data imply a static, polarity sensitive mechanism. We propose that Lorentz forces (which are polarity sensitive and do not require subject movement or a changing magnetic field) are the best explanation," the authors write.
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