Vertigo
Examples of humans reporting dizziness, vertigo, or nausea in high magnetic fields:
Schenck et al. 1992 PMID 1518472
A survey of technicians at GE who had worked around 1.5 T and 4 T MRI machines over ther previous year.
"A mild level of sensory experiences, apparently associated with motion within the field of the magnet, was reported by some of the volunteers during some of their exposures. A questionnaire regarding sensory effects associated with magnetic resonance scanners and possibly caused by the static magnetic field of these instruments, was given to nine respondents who had experience within both 1.5-T scanners and this 4-T scanner and to another group of 24 respondents who had experience only within 1.5-T scanners. For the sensations of vertigo, nausea, and metallic taste there was statistically significant (p less than 0.05) evidence for a field-dependent effect that was greater at 4 T. In addition, there was evidence for motion-induced magnetophosphenes caused by motion of the eyes within the static field."
Kangarlu et al. 1999 PMID 10609989
In a study on cognitive and cardiac effects of an 8T MRI machine:
"During exposure, subjects were encouraged to verbalize any unusual sensations. The responses to these communications were later recorded on each subject file. According to our subjects, entrance into the magnet and passage through the high gradient region was the dominant characteristic sensations they experienced inside the magnetic field of 8 Tesla. They reported vertigo and metallic taste in the mouth, and slight tingling effects. Most of these reports (except occasional metallic taste) were rare once the subject was positioned at the isocenter. While subjects were being transferred through the region of maximum field gradient, six individuals felt that they needed to lower their insertion rate into the magnet to avoid the unusual sensations. Note, however, that these initial studies were conducted without a patient table."
Chakeres et al. 2003 PMID 12938130
Tests of neuropsychological function in an 8T MRI machine (same machine as Kangarula 1999):
"A few of the subjects commented on mild dizziness or vertigo while entering or exiting the magnet, but there were no significant complaints related to exposure."
de Vocht et al 2003 PMID 14523950
Subjects performed neurobehavioral tests while inside the bore of a 1.5T MRI machine; for controls, subjects were tested in the same MRI machine but with the magnet OFF. Deficits in hand eye coordination and visual contrast were found. No effect was found of movement or gradient fields.
"After adjustment for the learning effect, speed and precision (Pursuit Aiming II) and near visual contrast sensitivity (Vistech 6000TM; 1.5 and 3.0 cycles per degree) were negatively influenced (– 4% (P<0.05), and –16% and –15% (P<0.10), respectively) when subjects were exposed to static and gradient fields generated by the 1.5 Tesla MRI magnet...
They also checked on perception of the magnetic field (but they don't say what "effects" were experienced that might lead to a perception):
"all volunteers were interviewed immediately following the test. One of the questions asked was, “Was the magnetic field, in your opinion, on or off?” With the magnet turned on, 61% of the volunteers did not experience any effects, and thought the magnet was off. With additional movements in the gradient field, 35% of the subjects still did not experience any effects of exposure. [I assume this means that 35% reported the field off when moving in the gradient field].
de Vocht et al 2006 PMID 16374876
Survey of complaints among MRI manufacturing workers at Philips Medical Systems. Nice features: videotaped workers moving around 1.0 T and 1.5 T magnets, so got estimate of movement speed and magnetic field exposure; used X-ray assembly workers as a control group.
"Dizziness, concentration problems, metallic taste, and suggestions of head ringing were significantly more reported by exposed workers, with the latter two only being reported near 1.5-T MRI systems....Our results show that employees from an MRI manufacturing department who moved more rapidly in the RF cage and consequently generated a stronger dynamic field, indeed reported more complaints than individuals who moved at a slower pace through the SMFs. Furthermore, moving speed and intensity was found to be to a large extent a personal characteristic, with a large between-subject and a small within-subject variance."
de Vocht et al 2006 PMID 16463303
Subjects seated right outside a 1.5 T and 3.0 T MRI machine to assess effects of stray field on neurobehavioral tests. Found deficits in hand-eye coordination, visual tracking, and processing of auditory and visual information.
"This study confirms that eye– hand coordination and the visual domain are affected by exposure to SMFs. In addition, our results suggest that processing of visual and auditive information is also affected, and that an exposure–response relation exists for visual and audi-tive working memory, eye– hand coordination speed, and visual-tracking tasks. However, since the stray fields to which the volunteers were exposed were very inhomogeneous, it was difficult to assess the actual exposure in a given time interval. Therefore, it remains unclear whether the speed of motion in combination with the gradient or the SMF strength is the more imporant factor in causing the neurobehavioral effects."
de Vocht et al 2007 PMID 17290435
Subjects seated right outside a 7T MRI machine to assess effects of stray field on neurobehavioral tests; highest exposure was 1.6 - 2.0 T (but a very high gradient). Deficits in visual tracking were found after head movements in the stray field, which might be secondary to vestibular effects (although no vertigo is reported in this paper).
"As shown, only visual tracking performance … differed significantly (P <.01) between different levels of static magnetic field exposure, and the magnitude of the effect also depended on the magnitude of the exposure (P <.01). Performance of the Pursuit Aiming II-test (P =.09) and the time to complete the line bisection-test (P =.06) showed a trend towards dependence on the magnitude of exposure, with borderline statistical significance. There was also a trend for the average deviance in the line bisection-test to improve with increased exposure (P =.08)....Since this and previous studies suggest that cognitive effects occur particularly in the visual sensory domain, a possible mechanism might be that the widely recognized "vertigo’’ effect of moving in a magnetic field, might interfere with the vestibulo-ocular reflex."
Yang et al 2006 PMID 16611792
Examined vital signs (e.g. heartrate, blood pressure, oxygen saturation) on subjects (18 normal, 72 with cerebral pathologies) undergoing MR imaging in an 8T magnet. Two subjects had nausea and vomiting.
After imaging, however, some subjects still reported transient nausea vertigo, and unusual metallic taste in the mouth, especially upon the entering and/or exiting of the magnet. These phenomena have been reported since the introduction of first 4 T system, as well as previous normal subject studies on 8T, and have been found to disappear rapidly after subjects leave the magnet.The mechanisms of these phenomena are based on the influence of induced magnetohydrodynamic (MHD) forces on the inner ear and electric currents introduced on the surface of the tongue. In general, these phenomena should be regarded as unavoidable, though they can be minimized, and patients should be given detailed explanation before imaging to alleviate any anxiety associated with these sensations. Two subjects [out of 92 subjects] vomited immediately after scanning. Had vomiting occurred during scanning, aspiration would have occurred. If a subject is found to be experiencing significant nau-sea while in the scanner, the imaging procedure may need to be terminated immediately and the subject carefully removed from the magnet to avoid such a circumstance.
Glover et al 2007 PMID 17427890
Nice discussion of mechanisms and effect of magnetic fields on otoconia. Thorough psychophysics of both changing magnetic fields around a static subject, and of head movements inside a 7 T magnet. Subjects moved at 0.1 m/s into 7T MRI machine. WHen at center, asked to slowly nod or rotate heads axially (30 s per movement, with 1 min rest period). Head movements while in the field induced mild to severe vertigo.
2 subjects reported subjective movement into magnet, so were inserted into magent from opposite direction -- apparent motion was reversed. (Consistent with reversal of current flow).
Patel et al 2008 PMID 18469627
Evaluated nystagmus with EOG, postural testing, caloric function at 30 min or 3 month after working for 30 min in room with 9.4 T MRI machine (i.e., not clear if exposed to 9.4T for entire 30 minutes). Workers around 9.4 T MRI machine consistently reported "illusions of movement", but other vestibular tests were normal. No apparent correlation with time since last exposure to 9.4T, and no control group.
Theysohn et al. 2008 PMID 18064501
Survey of 102 subjects 7T MRI of head, extremities or breast. In 43 of subjects, also compared to 1.5T scan. Subjects introduced to scanner either head-first or feet first. patient table was moved slowly by hand. Over 25 % reported vertigo while moving into the MRI machine, with very few sensations reported when motionless in the center of the scanner. Vertigo much more common when subjects were moved head-first into the MRI machine (the head only advances to 2-3T field). Also 48/100 subjectes experienced "vertigo, tottering, or sleepiness" when leaving the 7T scanner room.