Reducing Vertigo Associated With MRI Machines

Description

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.