Magnetic‐field‐induced vertigo: A theoretical and experimental investigation

Abstract

Vertigo-like sensations or apparent perception of movement are reported by some subjects and operators in and around high field whole body magnetic resonance body scanners. Induced currents (which modulate the firing rate of the vestibular hair cell), magneto-hydrodynamics (MDH), and tissue magnetic susceptibility differences have all been proposed as possible mechanisms for this effect. In this article, we examine the theory underlying each of these mechanisms and explore resulting predictions. Experimental evidence is summarised in the following findings: 30% of subjects display a postural sway response at a field-gradient product of 1 T(2)m(-1); a determining factor for experience of vertigo is the total unipolar integrated field change over a period greater than 1 s; the perception of dizziness is not necessarily related to a high value of the rate of change of magnetic field; eight of ten subjects reported sensations ranging from mild to severe when exposed to a magnetic field change of the order of 4.7 T in 1.9 s; no subjects reported any response when exposed to 50 ms pulses of dB/dt of 2 Ts(-1) amplitude. The experimental evidence supports the hypothesis that magnetic-field related vertigo results from both magnetic susceptibility differences between vestibular organs and surrounding fluid, and induced currents acting on the vestibular hair cells. Both mechanisms are consistent with theoretical predictions.

Pooled analyses of effects on visual and visuomotor performance from exposure to magnetic stray fields from MRI scanners: Application of the Bayesian framework

“…A recent study (37) assessed possible underlying mechanisms of induced vertigo-like sensations under well controlled exposure conditions, but in relatively small populations (N ϭ 12, 10, and 10). The researchers concluded that, in agreement with theoretical predictions, induced vertigo results from magnetic susceptibility differences between vestibular tissue and fluids, as well as induced currents, which present the brain with confusing information.…”

Assessment of Sensations Experienced by Subjects during MR Imaging Examination at 7T

“…To our knowledge, there are no similar descriptions in previous studies, although right head tilt was reported in rats at 14.1 T, 20 and a sensation of falling forward or backward was reported in humans at 7T. 11 The mechanisms of this phenomenon are unknown, but it can be caused by stimulation of the vestibulocochlear nerve or inner ear organs during gradual changes in magnetic field strength at a slow table speed.…”

Magnetic Field-Induced Vertigo in the MRI Environment

“…This can be measured by monitoring their postural sway whilst they fix their gaze on a spot whilst opening and closing their eyes. Subjects report a sudden onset of the effect near the magnet as would be expected with an effect related to the square of the magnetic field [9].…”

“…In the light of the physics of magnetic field interactions, it is now possible to discuss four likely candidates for the sensation of MFIV which have their origins in the vestibular system: forces due to the susceptibility of vestibular structures; current flow due to a net rate of change of magnetic flux; MHD due to head movement [8,9] and fluid pressure due to Lorentz forces [10].…”

“…The otoliths which make up the utricle and saccule maculae have a susceptibility and density close to that of the aragonite form of calcium carbonate. For these structures, a magnetic field gradient product of 46 T 2 m -1 produces a perceived acceleration of 0.1 m s -2 [9]. This mechanism would imply that a subject could sense (but not necessarily perceive) an effective acceleration in areas where such a field-gradient product existseven if the subject is not moving at all.…”