PhD ceremony Ms. L.I. Geven: Clinical observations on tinnitus

PhD ceremony: Ms. L.I. Geven

Dissertation: Clinical observations on tinnitus

Promotor(s): prof. P. van Dijk, prof. B.F.A.M. van der Laan

Faculty: Medical Sciences

Tinnitus is generally known as “ringing in the ears”. Tinnitus is the perception of a meaningless sound without an external source, and cannot be heard by others. Transient tinnitus is experienced by almost all adults at some point in their life, but in 8-20% of the general population it is permanent. Up to 1-3% of people with tinnitus are severely affected by it and seek medical attention.

The pathophysiology of tinnitus is unknown. According to current theory it is a central phenomenon in the brain including auditory areas. Some form of cochlear or hearing damage probably initiates the neuroplastic changes in the brain, that leads to tinnitus.

This thesis deals with the pathophysiology of tinnitus, with special emphasis on the efferent part of the central auditory system. The efferent auditory system runs from the auditory cortex to the cochlea, connecting all auditory regions along its path. Unfortunately, we did not discover the cause of tinnitus. We did find that the previously reported asymmetries in metabolism of auditory brain areas are also present in healthy people and they are therefore not associated with tinnitus. We tested the efferent auditory system at the level of the brain stem and did not find abnormalities in its functioning. To explore the complex system of the entire efferent auditory system we suggest several strategies for future research to investigate the role of the efferent auditory system in the pathophysiology of tinnitus.