A central nervous system approach to tinnitus

Abstract

Chronic tinnitus is a phantom auditory perception of meaningless sound. It is a highly prevalent symptom with potential severe morbidity. In this thesis diagnostic and therapeutic aspects of tinnitus are assessed, based on the notion that tinnitus most probably arises from hyperactivity in the central nervous system, in most cases as a result from damage to the peripheral hearing organ. The majority of the studies in this thesis are performed in (a proportion of) the 321 tinnitus patients who were seen at the Tinnitus Care Group of the University Medical Center Utrecht between 2007 and 2012. Patients were evaluated through a structured diagnostic protocol by a multidisciplinary team. Three months after visiting the Tinnitus Care Group, they were generally satisfied with the care they had received and the burden of their tinnitus was slightly, but significantly lower. It seems that a larger significant effect can be obtained by the group counseling offered by the Tinnitus Care Group. In a retrospective cohort study performed in these patients it was shown that a higher percentage of tinnitus awareness during the day, presence of self-reported depression and/or anxiety, a higher educational level, presence of additional somatic complaints, a louder tinnitus (subjectively experienced), and a more variable tinnitus in loudness and/or pitch (subjectively experienced) were all related to tinnitus severity. Awareness during the day turned out to be the most important factor. In a second retrospective cohort study performed in these patients it was shown that a routine MRI scan is of little or no value in tinnitus patients with persistent complaints, both in bilateral as well as in unilateral tinnitus patients. Incidental findings are common on these MRI scans. A vascular loop of the Anterior Inferior Cerebellar Artery was often encountered on the MRI scan, but rarely related to the tinnitus. It should thus be considered an incidental finding unless on clinical signs a possible audiovestibular nerve compression syndrome was suspected beforehand on clinical grounds and the MRI scan was made specifically to confirm or exclude this syndrome. Through a Cochrane review it was shown that there is no evidence from studies performed so far that the anticonvulsants gabapentin, carbamazepine, lamotrigine or flunarizine have a large positive effect in the treatment of tinnitus, but a small effect (of doubtful clinical significance) has been demonstrated. A double-blind randomized controlled trial on the effect of low-frequency repetitive Transcranial Magnetic Stimulation (rTMS) on tinnitus was performed in fifty chronic tinnitus patients who were seen at this Tinnitus Care Group. It was shown that bilateral low-frequency rTMS of the auditory cortex was not effective in treating tinnitus. Lastly a review was performed on Health-Related Quality of Life instruments that are currently used to measure treatment outcomes in tinnitus trials. It was shown that none of the six questionnaires that are used (the Tinnitus Handicap Inventory, the Tinnitus Questionnaire, the Tinnitus Reaction Questionnaire, the Tinnitus Severity Index, the Tinnitus Handicap Questionnaire, and the Tinnitus Severity Questionnaire) is validated to measure the effectiveness of intervention therapies.