Significance of a notch in the otoacoustic emission stimulus spectrum.

Objective: To explain a clinical observation: a notch in the stimulus spectrum during transient evoked otoacoustic emission measurement in ears with secretory otitis media. Methods: The effects of tympanic under-pressure were investigated using a pressure chamber. A model of the ear canal was also studied. Results: Tympanic membrane reflectance increased as a consequence of increased stiffness, causing a notch in the stimulus spectrum. In an adult, the notch could be clearly distinguished at an under-pressure of approximately -185 daPa. The sound frequency of the notch corresponded to a wavelength four times the ear canal length. The ear canal of infants was too short to cause a notch within the displayed frequency range. The notch was demonstrated using both Otodynamics and Madsen equipment. Conclusion: A notch in the otoacoustic emission stimulus spectrum can be caused by increased stiffness of the tympanic membrane, raising suspicion of low middle-ear pressure or secretory otitis media. This finding is not applicable to infants

Long-term measurement of binaural intensity and pitch matches. II. Fluctuating low-frequency hearing loss.

Thirteen subjects made consecutive long-term recordings of binaural intensity and pitch matches in their homes using portable equipment to assess hearing fluctuations. Two groups of subjects were used; one with monaural fluctuating low-frequency hearing loss (FLFHL) without vertigo, and one with monaural Meniere's disease (i.e. FLFHL with vertigo). The subjects measured binaural pitch matches using a 0.25- or 1-kHz reference tone presented at 60 dB SPL to one ear, and a loudness-matched test tone of adjustable frequency presented to the other ear during one to several weeks. Their results were compared to those previously obtained from ten normal-hearing subjects. Both groups of subjects showed fluctuations in binaural intensity and pitch matches not seen in the normal-hearing group. We calculated the average day-to-day difference in matched intensity and frequency for each subject's test period as a measure of disease activity. This measure indicated that the group with Meniere's disease has a higher disease activity than the group with FLFHL without vertigo, and that both these groups of subjects had higher disease activity than normal-hearing subjects

Long-term measurement of binaural intensity matches and pitch matches. I. Normal hearing.

Changes in pitch perception and hearing thresholds over time have been observed in subjects with monaural fluctuating low-frequency hearing loss and Ménière's disease. Long-term suprathreshold audiometry and binaural pitch matches could provide information of these changes. Ten normal subjects were tested for stability of binaural intensity and pitch matches during 9-22 days in their homes with newly developed portable test equipment. Binaural pitch matches were measured using a 0.25- or 1-kHz reference tone presented at 60 dB SPL to one ear, and a loudness-matched test tone of adjustable frequency presented to the other ear. The results showed stable binaural intensity matches (individual inter-quartile ranges, IQRs, 1.2 to 5.7 dB), but binaural pitch matches varied greatly (IQR -0.6 to 5.3% at 0.25 kHz; IQR -1.6 to 7.9% at 1 kHz). Binaural pitch-matching was much better in subjects who could define pitch precisely during monaural pitch matching. It was concluded that in future long-term evaluations of patients with fluctuating inner-ear function, binaural intensity matches could be suitable for all, but binaural pitch matching only for selected patients

Hypobaric pressure exposure effects on cochlear frequency selectivity in fluctuating, low-frequency hearing loss.

Aim:To study the effects of hypobaric pressure chamber exposure on the cochlear frequency selectivity of subjects with monaural, fluctuating, low-frequency hearing loss, such as occurs in Ménière's disease.Methods:We used a hypobaric pressure chamber to create relative underpressure in the ear canal, in order to impose positive pressure gradients on the inner ear. Psychophysical tuning curves, transiently evoked otoacoustic emissions and speech recognition scores in noise were measured in 10 subjects with fluctuating, low-frequency hearing loss, before and after pressure exposure.Results:After the exposure, subjects' overall pure tone averages showed no improvement, but individual results showed improved speech recognition scores in noise (six subjects), increased transiently evoked otoacoustic emission strength (three subjects) and increased psychophysical tuning curve steepness (two subjects). Deteriorations were also seen, mainly in psychophysical tuning curves. No association could be established between the different tests, and the measured parameters could not predict subjective improvement.Conclusion:The results suggest variable effects of hypobaric pressure exposure on inner-ear physiology

Effects on cochlear frequency selectivity after hypobaric pressure exposure.

The effects of hypobaric pressure chamber exposure was measured in noise in ten patients with monaural fluctuating low-frequency hearing loss (FLFHL) such as Meniere's disease using psychophysical tuning curves (PTC), transiently evoked otoacoustic emissions (TEOAE), binaural pitch matches and speech recognition scores (SRS) in noise. In the literature, reversible hearing losses have been observed in about 50 % of the patients, but sometimes improved SRS can be observed in patients without hearing threshold improvement. This indicates possible effects of pressure treatment on cochlear frequency selectivity. The relative overpressure in the middle ear obtained after repeated exposures in hypobaric pressure chamber (total duration 18.5 to 28 minutes) was used to impose pressure gradients to the inner ear. The results indicated that the treatment effects were small, but slightly improved SRS in noise, TEOAEs emission strength and PTCs were observed after treatment. Pure tone hearing thresholds improved only for patients exposed to longer treatment durations. Subjective improvement at follow-up could not be predicted from the results. Although the effects were small, the data suggest that hypobaric pressure treatment may improve cochlear frequency selectivity in the affected ear in patients with monaural FLFHL

Long-term measurements using home audiometry with Békésy’s technique

Objective: To examine the efficacy of fixed-frequency Békésy’s home audiometry to assess hearing fluctuation and treatment outcomes in patients with subjectively fluctuating hearing loss. Design: SMAPH, a software audiometry program for Windows, was installed and calibrated on laptop computers. Békésy’s audiometry was carried out daily in the patients’ homes, using sound-attenuating earphones. Study sample: Seventeen patients with previously or currently subjectively fluctuating hearing loss. Five patients received of treatment for their conditions during the measurement period. Results: Measurement periods ranged from 6 to 60 days. Varying degrees of compliance were seen, some patients measuring less than 50% of the days, others measuring every day. Based on their long-term measurements the patients were classified into three groups: patients with stable recordings, with fluctuating low-frequency hearing loss, or with fluctuating high-frequency hearing loss. In the patients with stable recordings, significant test–retest differences were seen below 10 dB at frequencies 0.125–8 kHz. Conclusions: Home audiometry with Békésy’s technique can be used to evaluate disease activity and to monitor hearing results after therapy