Scientists in the US think they have solved the riddle of why patients get dizzy inside hospital scanners.
The researchers claim they have traced the problem to the labyrinth - a tube-like structure of the inner ear that controls balance.
Many patients who have had a MRI (magnetic resonance imaging) scan have complained of feelings of vertigo while inside the tube-like machines, which produce very detailed images from inside the body using powerful magnetic fields and radio waves.
The scientists studied a dozen patients to study the effects of the MRI machines on them. Ten of the volunteers were healthy and the other two lacked functioning labyrinths.
The study focussed on involuntary eye movement, called nystagmus, which occurs when the brain senses motion.
Nystagmus was found in all 10 healthy subjects, but was not witnessed in the two volunteers with the inner ear disorder, leading the researchers to deduce that the labyrinth played a part in MRI-related dizziness.
The researchers also discovered that faster nystagmus was evident when the magnetic field strengths were increased and that the way the volunteers entered the machine would change the direction of the eye movements.
The findings have been published online in the journal Current Biology.
- Roberts DC, et al. MRI Magnetic Field Stimulates Rotational Sensors of the Brain. Current Biology 2011; Advance online publication