Reducing Vertigo Associated With MRI Machines

Overview

Vertigo, dizziness, and imbalance are commonly reported by patients and technologists when near high-field strength magnets (\>4 Tesla, T) used for magnetic resonance imaging (MRI) (1-5) Prior research from the investigators has established that the mechanism is likely a Lorentz force occurring in the inner ear, as a result of interactions with normal electrical currents in the inner ear and the strong static magnetic field of the MRI machine. The investigators have recently developed preliminary data to suggest that slower rates of entry into the magnetic field can greatly attenuate the sensations of vertigo. The explanation for this is that the rates of vestibular adaptation exceed that of the stimulus, allowed a reduction or elimination of the symptoms of vertigo. The aim of this study is to recruit individuals who are already getting an MRI scan as part of other research studies to randomize the rate of entry into and exit from the static magnetic field (i.e., before and after imaging is performed). The usual rate of entry is 20 seconds. This will be increased to one, two or three minutes. The investigators will record subjective sensations of dizziness and vertigo associated with the entry into the MRI.

Vertigo and nystagmus are commonly reported in 7 Tesla MRI machines, in upwards of 2/3 of individuals. Magnetic vestibular stimulation (MVS) of the inner ear explains these symptoms. In the normal state, the inner ear has constant electric current flowing from the dark cells to the hair cells of the utricular macula through the potassium enriched endolymph. This electric current drives the utricle's exquisitely sensitive response to linear accelerations. Near the utricular macula are the cupulae of the lateral and superior semicircular canals (SCCs), which are exquisitely sensitive to angular accelerations. Inside an MRI scanner, the electric current entering the utricular macula in each ear interacts with the MRI static magnetic field to create a Lorentz (magneto-hydrodynamic (MHD) force in the endolymph that pushes on the cupulae of the nearby lateral and superior semicircular canals. The force scales linearly with magnetic field strength. Thus, when a human with an intact vestibular system lies in a 7 T MRI magnet, the Lorenz force causes the endolymph to push on the cupulae, changing activity of the angular vestibulo-ocular reflex (VOR) pathway, generating both a transient sensation of motion and a sustained beating of the eyes (nystagmus), with alternating slow phases from the VOR and quick phases that reset the position of the eye. Adult individuals that are undergoing a 7 Tesla MRI as part of other research protocols at Kennedy-Krieger Kirby Institute, will be recruited. The usual entry into the magnetic field is a button that is pressed, that enters the magnetic field over 20 seconds, and exits the magnetic field over 20 seconds. Each participant will be randomized to one of four groups: 1) entering/exiting at the usual 20 seconds, 2) entering/exiting over 1 minute, 3) entering/exiting over 2 minutes, or 4) entering/exiting over 3 minutes. Participants will be asked to close the eyes during entry and exit. The onset of vertigo and description of the sensation will be recorded. At 15 second intervals, the participants will be asked to rate vertigo on a scale from 0 (no vertigo) to 3 (severe vertigo). The end time of vertigo sensations will also be recorded. The same procedure will be completed when exiting the MRI scan.