Jan Grenner

Continuous 24-hour Measurement of Middle Ear Pressure

A new method was developed for continuous measurement of the middle ear pressure during a 24-h period. The equipment consisted of a piezo-electric pressure device and a digital memory. To allow continuous pressure recordings during normal every-day activities the equipment was made light and portable. The measurement accuracy of the equipment as well as the base-line and temperature stability were tested and found to meet to our requirements satisfactorily. In 4 volunteers with different middle ear conditions, a small perforation was made through the tympanic membrane. A rubber stopper containing a small polyethylene tube was fitted into the external ear canal. Tubal function tests were made to establish the equipments ability to monitor fast pressure changes. The tests were well in accordance with other methods of direct pressure measurements. The equipment was carried by the volunteers for 24 h to monitor any slow or rapid dynamic pressure changes in the middle ear. Four continuous 24-h measurements are presented. The method was found to be suitable for valid measurements of dynamic pressure changes in the middle ear during normal every-day activities. It may become a useful instrument in the search for a better understanding of the development of chronic middle ear disease.

Long term hearing degeneration after platinum-based chemotherapy in childhood.

Abstract The aim of this study was to investigate long-term development of hearing in subjects who had received platinum-based chemotherapy in childhood or adolescence. Another aim was to assess the self-reported hearing loss handicap and compare it to audiometric measurements. Medical records from individuals diagnosed with childhood cancer and treated with platinum-based chemotherapy between 1985 and 2000 at the University Hospital in Lund Sweden were reviewed retrospectively. Fifteen subjects, who fulfilled the eligibility criteria set for the study, underwent a thorough audiometric evaluation. The results show that the hearing loss, in subjects with ototoxicity had increased after the end of treatment, to include also the lower frequencies. The largest deterioration in hearing thresholds, up to 55 dB HL, was found at frequencies above 2 kHz. The findings also reveal that the subjects have a considerably greater hearing loss handicap and disability than would be expected from the results of the audiometric evaluations. The conclusion of this study is that children and adolescence treated with platinum-based chemotherapy should have regular audiometric follow-up examinations, also many years after the end of treatment. Furthermore, assessments of self-reported hearing disability should be made during and after chemotherapy. Sumario El objetivo de este estudio fue investigar el desarrollo de la audición a largo plazo en sujetos que recibieron quimioterapia de platino en la niñez o en la adolescencia. Otro objetivo fue evaluar los auto-reportes de discapacidad por la pérdida auditiva y compararlos con las mediciones audiométricas. Se revisaron retrospectivamente los expedientes médicos de individuos diagnosticados con cáncer en la niñez y tratados con quimioterapia con platino entre 1985 y 2000, en el Hospital Universitario de Lund, Suecia. Quince sujetos que cubrieron los criterios de elegibilidad para el estudio, se sometieron a una evaluación audiométrica minuciosa. Los resultados mostraron que la pérdida auditiva en sujetos con ototoxicidad aumentó después de terminar el tratamiento, incluyendo también las frecuencias graves. La mayor pérdida en los umbrales auditivos, hasta de 55 dB HL, se encontró en las frecuencias superiores a 2 kHz. Los hallazgos revelan también que los sujetos presentan una discapacidad y una desventaja auditiva considerablemente mayor que lo que podría esperarse a partir de los resultados de las evaluaciones audiométricas. La conclusión de este estudio es que los niños y adolescentes tratados con quimioterapia con platino deben ser sometidos a un seguimiento en las evaluaciones audiométricas, incluso muchos años después de terminar el tratamiento. Más aún, las evaluaciones de los auto-reportes sobre discapacidad auditiva, deben practicarse durante y después de la quimioterapia.

Clinical application of long-term intensity and pitch matches in fluctuating low-frequency hearing loss

The purpose of this study was to measure changes in intensity and pitch matches to better assess disease activity in fluctuating hearing loss. Long-term suprathreshold audiometry was carried out at home on a subject with a unilateral fluctuating low-frequency hearing loss during a period when the subject demonstrated no symptoms and a period when the subject reported hearing loss, aural pressure, and tinnitus. Daily measurements of binaural intensity and pitch matches were made. Day-to-day fluctuations were clearly accentuated during the period when the subject experienced symptoms. Specifically, deviations from the reference tone were only observed for binaural pitch matches at 1 kHz during the period without symptoms; however, highly fluctuating binaural intensity and pitch matches were observed at 0.25 kHz during the period with symptoms. These fluctuations were not observed in a normal-hearing group. The results suggest that long-term measurements of binaural intensity and pitch matches can be used to monitor disease activity in fluctuating low-frequency hearing loss.

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 Ménières 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 subjects test period as a measure of disease activity. This measure indicated that the group with Ménières 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 Ménières 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.

Action potential threshold elevation in the guinea-pig as a function of impact noise exposure energy

Eighteen groups of guinea pigs were exposed to a simulated impact noise for periods of 1.5-24 h. The peak level was kept constant at 131.5 dB and the repetition rate was varied to give seven different equivalent levels (Leq) between 96 and 117 dB. The auditory thresholds were assessed by electrocochleography after 1 month and compared with those of a control group. Significant damage occurred even at the lowest exposure energy used. When the total exposure energy was expressed on a decibel scale, the threshold elevation (1-10 kHz) increased 1.07 dB for each decibel increase in the exposure energy, regardless of the combination of Leq and exposure time. The results of the study thus support the equal-energy hypothesis under these conditions.

AP threshold elevation in the guinea pig following exposure to a broadband noise

Sixty guinea pigs were exposed to a steady-state broadband noise with a falling frequency spectrum. The sound-pressure level was varied between 96 and 117 dB SPL, and the duration of the exposure was varied from 3 to 12 h. After 4-5 weeks, the auditory thresholds were determined by electrocochleography at 14 frequencies, and the results were compared with a control group. With increasing sound-pressure level, the thresholds became elevated at all frequencies. The maximum threshold elevation also exhibited a slight shift toward higher frequencies. With increasing exposure time, the threshold elevations increased and shifted into the high-frequency region, whereas the low-frequency region was less affected. Linear regression analysis showed that the average threshold elevation between 1 and 20 kHz did not deviate from that predicted by the equal-energy hypothesis. However, the high-frequency loss at 5-20 kHz was very dependent on the exposure time, whereas the 1- to 4-kHz loss was not. There was no sign of any critical intensity with sudden increments in threshold elevation.

Experimental Studies of Impulse Noise

Based on empirical data from continuous noise exposures, the equal energy hypothesis (EEH) seems to provide a useful approximation of a trading relation between the noise level and the exposure time when the risk for hearing damage is evaluated. The basis for the EEH is discussed by Henderson et al. [1] in this volume. From the EEH, damage risk criteria (DRC) have been derived that relate the risk of hearing loss to noise exposure.

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.

Impulse noise of different durations

This paper describes a comparison between auditory threshold elevations and morphological cochlear changes evaluated with scanning electron microscopy in order to identify cochlear defects in guinea pigs exposed to impulse noise of varying durations. There was a significant difference in the auditory threshold shifts between animals exposed for 3 and 12 hours. Hair cell loss is generally used as a morphological correlate to noise-induced hearing loss. Minor stereocilia changes, quantified with non-standard statistical methods have been used as a complement. Morphologically, it was not possible to separate cochleas exposed to impulse noise for 3 and 12 hours when only lost hair cells were evaluated. Quantitative evaluation of subtle morphological changes are valuable in the correlation of noise-induced hearing loss with morphologic changes.