Effect of tinnitus on distortion product otoacoustic emissions varies with hearing loss

Comparisons of Audiologic Characteristics in Patients with Continuous and Intermittent Tinnitus

BACKGROUND

No studies to date have compared audiologic characteristics in patients with continuous and intermittent tinnitus. The present study classified tinnitus patients into continuous and intermittent groups based on tinnitus duration and compared their audiologic characteristics.

METHODS

This study enrolled 604 patients with tinnitus from January 2019 to December 2022. Clinical manifestations, PTA results, the frequency and loudness of tinnitus, ABR, DPOAE, and TEOAE tests were compared in patients with continuous and intermittent tinnitus.

RESULTS

Of the 604 patients, 231 (38.2%) had continuous and 373 (61.8%) had intermittent tinnitus. There were no significant between-group differences in otologic symptoms, tinnitus onomatopoeia. PTA showed that hearing thresholds, except at 125 Hz, were significantly higher in patients with continuous rather than intermittent tinnitus. The loudness of tinnitus was significantly greater in patients with continuous rather than intermittent tinnitus. ABR tests showed that the absolute latency of wave V was significantly longer in continuous than in intermittent tinnitus. Signal-to-noise ratios on TEOAE tests were significantly lower in patients with continuous rather than intermittent tinnitus at all frequencies tested (1, 1.5, 2, 3, and 4 kHz). Response rates to sound stimuli at all frequencies, except for 1 kHz, were significantly lower on DPOAE tests in patients with continuous rather than intermittent tinnitus.

CONCLUSIONS

Continuous tinnitus is more common in males, more persistent over time, and is associated with a higher rate of hearing loss. In contrast, intermittent tinnitus is more common in women, appears acutely, and is associated with a relatively lower rate of hearing loss. Based on the findings of the current paper, it seems that audiologic characteristics may differ between patients with continuous and intermittent tinnitus.

Effect of Tinnitus in Distortion Products Otoacoustic Emissions (DPOAEs) in Normal Hearing Patients

Tinnitus is a symptom whose pathophysiology remains still unclear. Its diagnosis and treatment is complicated, due to its subjectivity. The generation of tinnitus is commonly linked with the impaired functioning of the outer hair cells (OHC) inside the cochlea. Distortion product otoacoustic emissions (DPOAEs) are the objective test used to assess their activity. This study investigates the cochlear outer hair cell function in patients with tinnitus and normal hearing using DPOAEs. We performed a prospective study of the cochlear function in normal hearing patients complaining of tinnitus by analysing DPOAEs amplitude and signal/noise (S/N) ratio. We gathered a sample of 21 ears from adults that attended to the ENT Department complaining of tinnitus with normal hearing. We compared their results with a control group of 21 ears, with the same demographic characteristics, presenting normal hearing but without tinnitus in order to exclude the influence of age in DPOAEs results. A decreased mean of S/N levels in DPOAEs was found in tinnitus and normal hearing group comparing with control group, although these differences were not statistically significant (p > 0.05). Based on the results, OHC dysfunction is not necessary to experience tinnitus. The majority of the patients that present OHC dysfunction do not present a tinnitus at the moment. Other mechanisms in auditory pathway may be evaluated in the tinnitus development.

Comparison of otoacoustic emissions in tinnitus and hyperacusis in adults with normal hearing sensitivity

Objective: To investigate the effect of tinnitus and/or hyperacusis on distortion product otoacoustic emission (DPOAE) measures in adults with normal hearing thresholds from 0.25 to 8 kHz, while accounting for extended high-frequency (EHF) thresholds.Design: A behavioural study consisted of comprehensive audiological assessment, validated tinnitus and hyperacusis questionnaires, DPOAE amplitudes and input/output (I/O) functions.Study sample: Data of 56 participants with normal hearing were included for the analysis. Participants were categorised into four groups: (1) without tinnitus or hyperacusis, (2) with tinnitus only, (3) with hyperacusis only, and (4) with both tinnitus and hyperacusis.Results: The groups with tinnitus showed elevated EHF thresholds compared with those without tinnitus. DPOAE amplitudes were not significantly affected by tinnitus and/or hyperacusis status; however, they were significantly affected by EHF thresholds. Further, no appreciable differences in DPOAE I/O functions were found across groups.Conclusions: The reported non-significant differences in DPOAEs in individuals with tinnitus and/or hyperacusis do not support a peripheral mechanism or an interaction between peripheral and central mechanisms underlying tinnitus or hyperacusis. Our findings, however, suggest the need to assess basal cochlear function (e.g. EHF thresholds) for a better understanding of differences in DPOAE measures in tinnitus and/or hyperacusis.

Ultra-High Frequency Distortion Product Otoacoustic Emissions for Detection of Hearing Loss and Tinnitus

Several studies have suggested that distortion product otoacoustic emissions (DPOAEs) may be an early marker not only of hearing loss (HL) but also of tinnitus. The purpose of this study was to investigate whether DPOAEs measured up to 16 kHz are affected by the presence of tinnitus. Pure tone thresholds and DPOAEs were measured in two groups: 55 patients with tinnitus and 63 subjects without tinnitus. The subjects were divided into three groups according to their audiometric results-better than 25 dB HL at all tested frequencies from 0.125 to 16 kHz, better than 25 dB up to 8 kHz, and hearing impaired. Receiver operator characteristics (ROCs) were used to test whether DPOAEs could differentiate between normal hearing, hearing loss, and tinnitus. Comparison of tinnitus subjects with the control group, matched accurately according to thresholds, did not yield any significant difference in DPOAEs. However, in both these groups hearing loss was accompanied by a decrease in DPOAEs, specifically, at 2-6 kHz and 16 kHz. The results suggest that any decrease in DPOAEs seems to be related only to hearing loss and there is no additional effect from tinnitus.

Double tinnitus in a single ear

OBJECTIVE

To search for distinctive clinical features of patients with double tinnitus in a single ear. Design retrospective: Study sample: Six hundred and fourteen tinnitus patients were interviewed using a detailed questionnaire. They underwent thorough audiological evaluation. Records of seven patients reporting double tinnitus in 10 ears were identified and analysed. There were three women and four men in the group (mean age 40, range 29-49 years).

RESULTS

All but two individuals declared sudden onset of the complaints. Three patients had been diagnosed with sudden sensorineural hearing loss. In all the patients, the components of double tinnitus were compared both to a pure tone and to a narrow band noise. The sounds were considered by the patients to be primary (more prominent) or secondary. All but one patient declared hypersensitivity to loud sounds. Vertigo was present in only two of the double tinnitus sufferers. Abnormal DPOAEs frequency values and audiogram notch frequencies were closer to the primary than the secondary tinnitus matches.

CONCLUSIONS

In our study, double tinnitus was rare, mostly perceived by patients with a sudden onset of tinnitus. This is the first report presenting audiological findings in patients with double tinnitus in a single ear. Prospective search of cohorts of tinnitus sufferers for such patients and functional neuroimaging of their auditory pathways for determining underlying mechanisms of the complaints is advocated.