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Acute vertigo in an anesthesia provider during exposure to a 3T MRI scanner.

Gorlin A, Hoxworth JM, Pavlicek W, Thunberg CA, Seamans D - Med Devices (Auckl) (2015)

Bottom Line: Vertigo induced by exposure to the magnetic field of a magnetic resonance imaging (MRI) scanner is a well-known phenomenon within the radiology community but is not widely appreciated by other clinical specialists.After discussing previous reports, and the evidence surrounding MRI-induced vertigo, we review potential etiologies that include the effects of both static and time-varying magnetic fields on the vestibular apparatus.We conclude our review by discussing the occupational standards that exist for MRI exposure and methods to minimize the risks of MRI-induced vertigo for clinicians working in the MRI environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Mayo Clinic Arizona, Phoenix, AZ, USA.

ABSTRACT
Vertigo induced by exposure to the magnetic field of a magnetic resonance imaging (MRI) scanner is a well-known phenomenon within the radiology community but is not widely appreciated by other clinical specialists. Here, we describe a case of an anesthetist experiencing acute vertigo while providing sedation to a patient undergoing a 3 Tesla MRI scan. After discussing previous reports, and the evidence surrounding MRI-induced vertigo, we review potential etiologies that include the effects of both static and time-varying magnetic fields on the vestibular apparatus. We conclude our review by discussing the occupational standards that exist for MRI exposure and methods to minimize the risks of MRI-induced vertigo for clinicians working in the MRI environment.

No MeSH data available.


Related in: MedlinePlus

The Lorentz force.Notes: Adapted from Current Biology; 21(19); Straumann D, Bockisch C; Neurophysiology: vertigo in MRI machines; R806–R807; Copyright © 2011, with permission from Elsevier.9 The Lorentz force arises in response to current flow that is induced by the magnetic field. Depending on the orientation of the subject’s head, the Lorentz force can cause deflection of the hair cells in the cupula, which can cause a sense of movement, when in fact the subject is stationary. This is experienced as vertigo (illustration adapted from Straumann and Bockisch,9 with permission of the author and publisher).
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f3-mder-8-161: The Lorentz force.Notes: Adapted from Current Biology; 21(19); Straumann D, Bockisch C; Neurophysiology: vertigo in MRI machines; R806–R807; Copyright © 2011, with permission from Elsevier.9 The Lorentz force arises in response to current flow that is induced by the magnetic field. Depending on the orientation of the subject’s head, the Lorentz force can cause deflection of the hair cells in the cupula, which can cause a sense of movement, when in fact the subject is stationary. This is experienced as vertigo (illustration adapted from Straumann and Bockisch,9 with permission of the author and publisher).

Mentions: The vestibular system in the inner ear is the peripheral organ that is primarily responsible for the sensation of balance as well as movement in one’s environment. It is composed of the six (three on each side) semicircular canals that detect angular acceleration, in addition to the connected structures known as the utricle and the saccule that detect linear acceleration (Figure 1). These structures are filled with fluid known as endolymph that moves or flows when the head moves in space. This fluid movement causes deflections of tiny stereocilia attached to specialized neural structures within the vestibular apparatus, known as hair cells, which respond to these movements by firing neural impulses to the brain that in turn are ultimately interpreted as the perception of movement (Figure 2). As a result, the vestibular system can become activated through hydrodynamic pressure changes in the endolymph, direct deflection of stereocilia, or neurostimulation via electrical currents. However, the precise mechanism through which magnetic vestibular stimulation occurs is unclear, with some proposed mechanisms including electromagnetic induction (ie, voltage induced by a changing magnetic field) and magnetic susceptibility differences between vestibular organs and surrounding fluid.5 In 2011, Roberts et al6 published compelling evidence that the static magnetic field produced by the MRI scanner is the primary cause of vertigo caused by interaction with the vestibular system in the inner ear. The authors contend that the magnetic field induces an electrical perturbation in the potassium-rich endolymph within the semicircular canals, which stimulates the hair cells in the vestibular system, thereby causing an abnormal sensation of movement. This work was later refined by providing more-detailed calculations of the Lorentz forces and resulting pressures within the vestibular system in strong static magnetic fields (Figure 3).7 More recently, stationary exposures to a static 7T MRI field were found to be associated with the presence of vertigo and nystagmus, and the reversal of symptoms following withdrawal from the field was taken as evidence for adaptation to continuous vestibular input caused by the static magnetic field.8 A separate body of work further confirms that these effects should be more pronounced with stronger magnetic fields that are encountered with higher-field-strength MRI scanners and in closer proximity to the epicenter of the MRI scanner bore (ie, on the patient undergoing the MRI). De Vocht et al2 reported an increase in the incidence of symptoms with higher-strength magnets (1.0T and higher) and increased exposure time (>20 minutes). Wilen and de Vocht3 reported that the majority of symptoms in the study subjects were observed after exposure to higher-strength magnets (1.5T and 3.0T).3 There is evidence that the measured velocity of nystagmus in MRI-exposed volunteers increases in proportion to the strength of the magnetic field,9 and Schaap et al4 have found a positive correlation between scanner strength and reported symptoms in health care and research workers using 1.5T, 3T, and 7T systems. Given that the fringe magnetic field declines exponentially with distance from the MRI scanner, the anesthetist in the current case would have experienced the largest static magnetic field when peering into the end of the bore to evaluate the sedated patient, which corresponded to symptom onset (Figure 4). Although variable depending on the exact position of the anesthetist’s head relative to the magnetic flux isolines of the 3T scanner, it is likely that the anesthetist’s head was experiencing a magnetic field on the order of 2T.


Acute vertigo in an anesthesia provider during exposure to a 3T MRI scanner.

Gorlin A, Hoxworth JM, Pavlicek W, Thunberg CA, Seamans D - Med Devices (Auckl) (2015)

The Lorentz force.Notes: Adapted from Current Biology; 21(19); Straumann D, Bockisch C; Neurophysiology: vertigo in MRI machines; R806–R807; Copyright © 2011, with permission from Elsevier.9 The Lorentz force arises in response to current flow that is induced by the magnetic field. Depending on the orientation of the subject’s head, the Lorentz force can cause deflection of the hair cells in the cupula, which can cause a sense of movement, when in fact the subject is stationary. This is experienced as vertigo (illustration adapted from Straumann and Bockisch,9 with permission of the author and publisher).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4362897&req=5

f3-mder-8-161: The Lorentz force.Notes: Adapted from Current Biology; 21(19); Straumann D, Bockisch C; Neurophysiology: vertigo in MRI machines; R806–R807; Copyright © 2011, with permission from Elsevier.9 The Lorentz force arises in response to current flow that is induced by the magnetic field. Depending on the orientation of the subject’s head, the Lorentz force can cause deflection of the hair cells in the cupula, which can cause a sense of movement, when in fact the subject is stationary. This is experienced as vertigo (illustration adapted from Straumann and Bockisch,9 with permission of the author and publisher).
Mentions: The vestibular system in the inner ear is the peripheral organ that is primarily responsible for the sensation of balance as well as movement in one’s environment. It is composed of the six (three on each side) semicircular canals that detect angular acceleration, in addition to the connected structures known as the utricle and the saccule that detect linear acceleration (Figure 1). These structures are filled with fluid known as endolymph that moves or flows when the head moves in space. This fluid movement causes deflections of tiny stereocilia attached to specialized neural structures within the vestibular apparatus, known as hair cells, which respond to these movements by firing neural impulses to the brain that in turn are ultimately interpreted as the perception of movement (Figure 2). As a result, the vestibular system can become activated through hydrodynamic pressure changes in the endolymph, direct deflection of stereocilia, or neurostimulation via electrical currents. However, the precise mechanism through which magnetic vestibular stimulation occurs is unclear, with some proposed mechanisms including electromagnetic induction (ie, voltage induced by a changing magnetic field) and magnetic susceptibility differences between vestibular organs and surrounding fluid.5 In 2011, Roberts et al6 published compelling evidence that the static magnetic field produced by the MRI scanner is the primary cause of vertigo caused by interaction with the vestibular system in the inner ear. The authors contend that the magnetic field induces an electrical perturbation in the potassium-rich endolymph within the semicircular canals, which stimulates the hair cells in the vestibular system, thereby causing an abnormal sensation of movement. This work was later refined by providing more-detailed calculations of the Lorentz forces and resulting pressures within the vestibular system in strong static magnetic fields (Figure 3).7 More recently, stationary exposures to a static 7T MRI field were found to be associated with the presence of vertigo and nystagmus, and the reversal of symptoms following withdrawal from the field was taken as evidence for adaptation to continuous vestibular input caused by the static magnetic field.8 A separate body of work further confirms that these effects should be more pronounced with stronger magnetic fields that are encountered with higher-field-strength MRI scanners and in closer proximity to the epicenter of the MRI scanner bore (ie, on the patient undergoing the MRI). De Vocht et al2 reported an increase in the incidence of symptoms with higher-strength magnets (1.0T and higher) and increased exposure time (>20 minutes). Wilen and de Vocht3 reported that the majority of symptoms in the study subjects were observed after exposure to higher-strength magnets (1.5T and 3.0T).3 There is evidence that the measured velocity of nystagmus in MRI-exposed volunteers increases in proportion to the strength of the magnetic field,9 and Schaap et al4 have found a positive correlation between scanner strength and reported symptoms in health care and research workers using 1.5T, 3T, and 7T systems. Given that the fringe magnetic field declines exponentially with distance from the MRI scanner, the anesthetist in the current case would have experienced the largest static magnetic field when peering into the end of the bore to evaluate the sedated patient, which corresponded to symptom onset (Figure 4). Although variable depending on the exact position of the anesthetist’s head relative to the magnetic flux isolines of the 3T scanner, it is likely that the anesthetist’s head was experiencing a magnetic field on the order of 2T.

Bottom Line: Vertigo induced by exposure to the magnetic field of a magnetic resonance imaging (MRI) scanner is a well-known phenomenon within the radiology community but is not widely appreciated by other clinical specialists.After discussing previous reports, and the evidence surrounding MRI-induced vertigo, we review potential etiologies that include the effects of both static and time-varying magnetic fields on the vestibular apparatus.We conclude our review by discussing the occupational standards that exist for MRI exposure and methods to minimize the risks of MRI-induced vertigo for clinicians working in the MRI environment.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, Mayo Clinic Arizona, Phoenix, AZ, USA.

ABSTRACT
Vertigo induced by exposure to the magnetic field of a magnetic resonance imaging (MRI) scanner is a well-known phenomenon within the radiology community but is not widely appreciated by other clinical specialists. Here, we describe a case of an anesthetist experiencing acute vertigo while providing sedation to a patient undergoing a 3 Tesla MRI scan. After discussing previous reports, and the evidence surrounding MRI-induced vertigo, we review potential etiologies that include the effects of both static and time-varying magnetic fields on the vestibular apparatus. We conclude our review by discussing the occupational standards that exist for MRI exposure and methods to minimize the risks of MRI-induced vertigo for clinicians working in the MRI environment.

No MeSH data available.


Related in: MedlinePlus