Introduction: Tinnitus is often associated with hearing loss, but it may occur in patients with normal hearing. However, normal hearing thresholds do not exclude cochlear damage.Tinnitus may be initiated by abnormal activity from the peripheral auditory system, but its progress and maintenance is due to the central nervous system involvement. For that reason, Auditory Brainstem Response (ABR) may contribute to clarify the origin of tinnitus.
Aim: The aim of this study is to evaluate the ABR waveform amplitude and latencies in tinnitus patients with normal hearing to explore the origin of tinnitus.
Results: Auditory brainstem response, recorded using ipsilateral rarefaction click stimuli at 80 dBnHL in 10 normal hearing tinnitus adult patients and 10 matching controls, showed that Wave I amplitude was significantly reduced in the study group when compared to control group. The V/I amplitude ratio was significantly higher in the study group compared to control group. The absolute latency of wave I was significantly increased in the study group compared to control group. Interpeak I-V latency was significantly decreased in the study group compared to control group.
Conclusion: Tinnitus sufferers with normal audiometric thresholds might show ABR amplitude changes indicative of cochlear synaptopathy (reduced wave I amplitude) and compensated central responses (no reduction in wave V amplitude). The increased responsiveness of central regions might lead to tinnitus generation secondry to increased spontaneous activity.