Abstract
Tinnitus is characterized by the perception of sound in the absence of an external auditory stimulus. The network connectivity of auditory and non-auditory brain structures associated with emotion, memory and attention are functionally altered in debilitating tinnitus. Current studies suggest that tinnitus results from neuroplastic changes in the frontal and limbic temporal regions. The objective of this study was to use Single-Photon Emission Computed Tomography (SPECT) to evaluate changes in the cerebral blood flow in tinnitus patients with normal hearing compared with healthy controls. Methods: Twenty tinnitus patients with normal hearing and 17 healthy controls, matched for sex, age and years of education, were subjected to Single Photon Emission Computed Tomography using the radiotracer ethylenedicysteine diethyl ester, labeled with Technetium 99 m (99 mTc-ECD SPECT). The severity of tinnitus was assessed using the “Tinnitus Handicap Inventory” (THI). The images were processed and analyzed using “Statistical Parametric Mapping” (SPM8). Results: A significant increase in cerebral perfusion in the left parahippocampal gyrus (pFWE <0.05) was observed in patients with tinnitus compared with healthy controls. The average total THI score was 50.8+18.24, classified as moderate tinnitus. Conclusion: It was possible to identify significant changes in the limbic system of the brain perfusion in tinnitus patients with normal hearing, suggesting that central mechanisms, not specific to the auditory pathway, are involved in the pathophysiology of symptoms, even in the absence of clinically diagnosed peripheral changes.
Highlights
Tinnitus is an auditory phantom sensation, described as ringing or buzzing in one or both ears, in the absence of an external auditory stimulus
No differences were observed between control individuals and tinnitus patients regarding age (42.95+9.03 years versus 41.41+ 9.98 years, respectively; p = 0.613), gender (6 males and 14 females versus 6 males and 11 females, respectively; p = 0.985), or years of education (11.2+3.87 versus 11.41+3.78, respectively; p = 0.860)
A comparison of the Single-Photon Emission Computed Tomography (SPECT) images revealed a significant increase in the metabolic activation of the left parahippocampal gyrus in patients compared with the controls
Summary
Tinnitus is an auditory phantom sensation, described as ringing or buzzing in one or both ears, in the absence of an external auditory stimulus. The prevalence of chronic tinnitus varies from 5–15%, and 1–3% of these cases severely affect the quality of life, resulting in anxiety and emotional disorders, sleep disturbance and work impairment [1]. Over 20 years, it has been suggested that tinnitus reflects peripheral pathology, primarily cochlear dysfunction or auditory nerve damage [2]. Imaging and electrophysiological methods have suggested the involvement of central mechanisms in generation and perception of tinnitus symptoms. The central origin of tinnitus-related activity has replaced the peripheral hypothesis [3,4,5,6]. Synchrony or reorganized tonotopic maps have been proposed as neural substrates of tinnitus [7]
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