Hearing loss from the acoustic artifact of the coil used in extracranial magnetic stimulation

Abstract

The stimulating coil used in extracranial magnetic field stimulation (EMFS) emits a high intensity impulse sound artifact that causes permanent threshold shifts in the unprotected ears of experimental animals. At magnetic stimulation levels of 50 to 100%, the magnetic coil acoustic artifact (MCAA) ranged from 145 to 157 dB peak sound pressure level at the eardrum. The magnetic field alone did not appear to cause hearing impairment since no threshold shifts were observed in ears that were plugged with ear protectors during exposure to the MCAA. These findings suggest that the acoustic artifact produced by EMFS in the clinic may pose some risk for hearing loss in patients and clinicians when held in close proximity to the unprotected ear. We recommend the use of ear protectors for the patient and clinician during EMFS as a precautionary measure to prevent hearing loss.