Abstract
Our objective was to study the characteristics of patients with subjective tinnitus and normal hearing and to investigate whether the features correlated to different shapes on audiograms. In this retrospective study, 313 patients with subjective tinnitus and clinically normal hearing were enrolled from the tinnitus outpatient department of the Eye and ENT Hospital of Fudan University. The following phenotypic variables were collected: age, dominant tinnitus pitch (TP), tinnitus loudness, tinnitus duration, tinnitus severity, sex, education, hearing thresholds, tinnitus position, and tinnitus condition. The dominant TPs of patients with normal hearing were mostly high-pitched, with a mean of 4866.8 ± 2579.6 Hz; thus, we speculated that the condition is related to high-frequency hearing threshold elevations. We further divided the patients into four subgroups based on the matched TP: (i) TP ≤ 500 Hz (n = 34), (ii) 500 Hz < TP ≤ 3,000 Hz (n = 15), (iii) 3,000 Hz < TP ≤ 8,000 Hz (n = 259), and (iv) TP > 8,000 Hz (n = 5). We studied the phenotypic profiling of different audiograms and found that the group with TP of ≤500 Hz had an average “inverted-U” shaped audiogram, and the group with TP between 500 and 3,000 Hz had a slowly ascending slope audiogram below 2,000 Hz, followed by a drastically descending slope audiogram ranging from 2,000 to 8,000 Hz; further, the high-frequency (3,000–8,000 Hz) and ultra-high-frequency (>8,000 Hz) groups had flat curves below 2,000 Hz and steeper slope audiograms over 2,000 Hz. Our findings confirmed a consistency ratio between the distributions of dominant TPs and the frequencies of maximum hearing thresholds in both ears. The dominant TP was positively correlated with the maximum hearing threshold elevation frequency (left ear: r = 0.277, p < 0.05; right ear: r = 0.367, p < 0.001). Hearing threshold elevations, especially in high frequency, might explain the appearance of dominant high-frequency TP in patients without clinically defined hearing loss. This is consistent with the causal role of high-frequency coding in the generation of tinnitus.
Highlights
Tinnitus is the auditory perception of sound in the absence of a corresponding external acoustic or electric stimulus
Another study performed pure-tone audiometry (125 Hz–16 kHz), speech audiometry, transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), threshold equalizing noise (TEN) test (500 Hz–4 kHz), and electrocochleography (ECochG) for 9 individuals with tinnitus and normal hearing and 13 controls with normal hearing but no tinnitus, and the results showed that the SP/AP ratio in the ECochG test, together with the detection of dead regions in the TEN test, might be valuable in diagnosing hidden hearing loss, while the between-group differences in DPOAE and TEOAE were not significant (Kara et al, 2020)
We focused on phenotypic profile of patients presenting with the primary complaint of subjective tinnitus and clinically normal hearing and confirmed that dominant tinnitus pitch (TP) was positively correlated with the maximum hearing threshold elevation frequency, which indicated that a more sophisticated pure-tone test, including extended high frequency, might be needed in evaluating the audiological features of dominant high-frequency TP in patients without clinically defined hearing loss
Summary
Tinnitus is the auditory perception of sound in the absence of a corresponding external acoustic or electric stimulus. The commonly described sounds of tinnitus are chirping, buzzing, ringing, and hissing. Tinnitus is a tonal-like sensation, but in few cases, it sounds like a noise. Tinnitus affects 5–43% of people worldwide (McCormack et al, 2016). The risk of developing tinnitus increases with age, noise exposure, and hearing loss (Baguley et al, 2013; Langguth et al, 2013). It is widely accepted that the generation of tinnitus is often triggered by peripheral hearing damage and involves a central mechanism (Norena and Eggermont, 2003; Eggermont and Roberts, 2004). Clinical audiometric hearing loss does not occur in all cases of tinnitus. The percentage of tinnitus patients without clinical hearing loss is estimated at 20% (Jastreboff and Jastreboff, 2003)
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