Objective Evidence of Tinnitus in Auditory Evoked Magnetic Fields

Abstract

Tinnitus, or ringing in the ear, often is a very distressing symptom which can be associated with various diseases of the middle and inner ear (e.g. M. Menière, acoustic trauma, sudden hearing loss) or general diseases (e.g. arteriosclerosis). Its incidence is very high (∼ 15%), and in 0.5–1%, tinnitus has a severe effect on the ability to lead a normal life. Apart from a minority of cases in which a real (internal) sound source exists (“objective tinnitus”), “subjective” tinnitus consists in purely subjective auditory sensations which could be evaluated so far only by psychoacoustic methods. All attempts to detect the pathophysiological processes underlying tinnitus in auditory evoked potentials (AEP) or in the electroencephalogram (EEG) have failed so far, which does, however, not rule out that certain components contributing to the AEP or EEG are affected by tinnitus. In view of the great number of individuals who are unable to lead a normal life and the ineffectiveness of current tinnitus therapy it is highly desirable that some method be devised to objectively assess the existence of tinnitus and to determine its representation in the central nervous system. Hence it was natural to study whether the magnetic signals of the brain reveal an interference with tinnitus, owing to the high spatial resolution offered by neuromagnetic measurements.