Assessment of middle ear structure and function with optical coherence tomography.

BACKGROUND: Current clinical tests for middle ear (ME) injuries and related conductive hearing loss (CHL) are lengthy and costly, lacking the ability to noninvasively evaluate both structure and function in real time. Optical coherence tomography (OCT) provides both, but its application to the audiological clinic is currently limited. OBJECTIVE: Adapt and use a commercial Spectral-Domain OCT (SD-OCT) to evaluate anatomy and sound-evoked vibrations of the tympanic membrane (TM) and ossicles in the human ME. MATERIALS AND METHODS: SD-OCT was used to capture high-resolution three-dimensional (3D) ME images and measure sound-induced vibrations of the TM and ossicles in fresh human temporal bones. RESULTS: The 3D images provided thickness maps of the TM. The system was, with some software adaptations, also capable of phase-sensitive vibrometry. Measurements revealed several modes of TM vibration that became more complex with frequency. Vibrations were also measured from the incus, through the TM. This quantified ME sound transmission, which is the essential measure to assess CHL. CONCLUSION AND SIGNIFICANCE: We adapted a commercial SD-OCT to visualize the anatomy and function of the human ME. OCT has the potential to revolutionize point-of-care assessment of ME disruptions that lead to CHL which are otherwise indistinguishable via otoscopy.

[Integrated assessment of middle ear dysfunction in cleft palate patients and optimization of therapeutic schedule].

OBJECTIVE: To explore evaluation strategies for middle ear dysfunction in cleft palate patients, to optimize the diagnosis and treatment of this dysfunction, and ultimately to improve the comprehensive treatment of cleft palate. METHODS: The relationship among abnormal tympanic types (B, C, and Anomaly), effusion rate, tympanic pressure, and hearing loss were analyzed. We collected relevant information on 469 ears of cleft palate patients and traced one-year longitudinal changes in the tympana of 124 ears from 62 patients with both cleft lip and cleft palate. RESULTS: The effusion rates of cleft palate patients with type B, type C, and type Anomaly were 50.3% (97/193), 34.8% (8/23), and 20.9% (53/253), respectively. The tympanic pressure of the ears with and without effusion showed no significant difference (P>0.05). The hearing loss in type B cleft palate patients with middle ear effusion was worse than that in patients without effusion (P=0.001). However, the hearing loss in type Anomaly showed no difference (P>0.05). The constituent ratio of each tympanic type remained constant during the period between cheiloplasty and palatoplasty for cleft lip and palate patients (P>0.05). CONCLUSION: Cleft palate patients of all tympanic types may all suffer from middle ear effusion at different rates. Examination by centesis is suggested for ears with abnormal tympanic types. Early aggressive therapy is essential for type B cleft palate patients with middle ear effusion to avoid hearing loss. However, catheterization may be not necessary for type Anomaly patients, and conservative observation should be performed instead. Myringotomy with grommet insertion during palatoplasty does not delay treatment timing for patients with both cleft lip and cleft palateg.

High-fidelity, inexpensive surgical middle ear simulator.

HYPOTHESIS: A high-fidelity, inexpensive middle ear simulator could be created to enhance surgical training that would be rated as having high face validity by experts. BACKGROUND: With rapid prototyping using additive manufacturing technology (AMT), one can create high-resolution 3-dimensional replicas of the middle ear at low cost and high fidelity. Such a simulator could be of great benefit for surgical training, particularly in light of new resident training guidelines. METHODS: AMT was used to create surgical middle ear simulator (SMS) with 2 different materials simulating bone and soft tissue. The simulator is composed of an outer box with dimensions of an average adult external auditory canal without scutum and an inner cartridge based on an otosclerosis model. The simulator was then rated by otology experts in terms of face validity and fidelity as well as their opinion on the usefulness of such a device. RESULTS: Eighteen otologists from 6 tertiary academic centers rated the simulator; 83.3% agreed or highly agreed that SMS has accurate dimensions and 66.6% that it has accurate tactile feedback. When asked if performance of stapedotomy with the SMS improves with practice, 46% agreed. As to whether practicing stapedotomy with the SMS translates to improvement with live surgery, 78% agreed with this statement. Experts' average rating of the components of SMS (of possible 5) was as follows: middle ear dimensions, 3.9; malleus, 3.7; incus, 3.6; stapes, 3.6; chorda tympani, 3.7; tensor tympani, 4.1; stapedius, 3.8; facial nerve, 3.7; and promontory, 3.5. Overall, 83% found SMS to be at least "very useful" in training of novices, particularly for junior and senior residents. CONCLUSION: Most experts found the SMS to be accurate, but there was a large discrepancy in rating of individual components. Most found it to be very useful for training of novice surgeons. With these results, we are encouraged to proceed with further refinements that will strengthen the SMS as a training tool for otologic surgery.

Laser Doppler vibrometric assessment of middle ear motion in Thiel-embalmed heads.

HYPOTHESIS: Thiel-embalmed human whole head specimens represent an alternative model in middle ear research. BACKGROUND: Research into middle ear mechanics and the evaluation of active middle ear implants are generally performed on fresh human temporal bone specimens. A drawback of this method is the limited period during which the specimen can be used before tissue decay begins. Tissue conservation that preserves mechanical properties is desirable. METHODS: Using laser Doppler vibrometry, the movement of the tympanic membrane, stapes, and round window were measured in 23 ears from 15 human whole head specimens embalmed according to Thiel. The ears were acoustically stimulated through the intact external auditory canal. The measurement results were compared with data from the literature. RESULTS: The results were similar to those measured in living subjects and from fresh temporal bones, after excluding measurements with nontypical shapes or low amplitudes, that is, 9% for tympanic membrane, 38% for stapes, and 67% for round window. The best agreement was found for the tympanic membrane (mean difference between 0 and 5.2 dB) and for the stapes measurements (mean difference between 0 and 7.4 dB). Larger differences were found for the round window measurements (mean difference between 3 and 19 dB). For the stimulation levels used, the Thiel specimens behaved linearly in amplitude. The results remained reproducible for more than 20 hours in ambient air, and when the specimen was put back into Thiel solution, the measurements were stable for up to several months between measurements. CONCLUSION: Our results showed that the middle ears of Thiel-embalmed human whole head specimens can be used to study human middle ear mechanics; however, significant differences in some frequencies, particularly at the round window, have to be considered.

Tympanometry assessment of 61 inbred strains of mice.

Otitis media (OM) accounts for more than 20 million clinic visits in the United States every year. Resistance to antibiotics has hampered current management of the disease. Identification of genetic factors underlying susceptibility to OM is greatly needed in order to develop alternative treatment strategies. Genetically defined inbred mouse strains offer a powerful tool for dissecting genetic and environmental factors that may lead to OM in mice. Here, we report a study of middle ear function of 61 genetically diverse inbred strains of mice using tympanometry. Of the 61 inbred strains tested, the 129P1/ReJ, 129P3/J, 129S1/SvImJ, 129X1/SvJ, A/HeJ, BALB/cJ, BUB/BnJ, C57L/J, EL/SuzSeyFrkJ, FVB/NJ, I/LnJ, LP/J, NZB/BlNJ, PL/J and YBR/Ei strains exhibited tympanograms that were statistically different from other healthy strains according to parameters including middle ear pressure, volume and compliance. These differences are most likely the result of genetic factors that, when understood, will facilitate prevention and treatment of otitis media in humans. In addition, a negative correlation between age and compliance of the tympanic membrane was discovered. This is the first report to successfully use tympanometry to measure mouse middle ear function, which has been a challenge for the hearing research field because of the mouse's tiny ear size.

Evaluation of human middle ear function via an acoustic power assessment.

Measurements of middle ear (ME) acoustic power flow (power reflectance, power absorption, and transmittance) and normalized impedance (acoustic resistance, acoustic reactance, and impedance magnitude) were compared for their utility in clinical applications. Transmittance, a measure of the acoustic power absorbed by the ME, was found to have several important advantages over other measures of acoustic power flow. In addition to its simple and audiologically relevant physical interpretation (absorbed power), the normal transmittance curve has a simple shape that is visually similar to the ME transfer function. The acoustic impedance measures (resistance and reactance) provided important additional information about ME status and supplemented transmittance measurements. Together these measurements can help identify unusual conditions such as eardrum perforations. While this article is largely a review of the development of a commercial power reflectance measurement system, previously unpublished experimental results are presented.

Prediction of conductive hearing loss based on acoustic ear-canal response using a multivariate clinical decision theory.

This study evaluated the accuracy of acoustic response tests in predicting conductive hearing loss in 161 ears of subjects from the age of 2 to 10 yr, using as a "gold standard" the air-bone gap to classify ears as normal or impaired. The acoustic tests included tympanometric peak-compensated static admittance magnitude (SA) and tympanometric gradient at 226 Hz, and admittance-reflectance (YR) measurements from 0.5 to 8 kHz. The performance of individual, frequency-specific, YR test variables as predictors was assessed. By applying logistic regression (LR) and discriminant analysis (DA) techniques to the multivariate YR response, two univariate functions were calculated as the linear combinations of YR variables across frequency that best separated normal and impaired ears. The tympanometric and YR tests were also combined in a multivariate manner to test whether predictive efficacy improved when 226-Hz tympanometry was added to the predictor set. Conductive hearing loss was predicted based on air-bone gap thresholds at 0.5 and 2 kHz, and on a maximum air-bone gap at any octave frequency from 0.5 to 4 kHz. Each air-bone gap threshold ranged from 5 to 30 dB in 5-dB steps. Areas under the relative operating characteristic curve for DA and LR were larger than for reflectance at 2 kHz, SA and Gr. For constant hit rates of 80% and 90%, both DA and LR scores had lower false-alarm rates than tympanometric tests-LR achieved a false-alarm rate of 6% for a sensitivity of 90%. In general, LR outperformed DA as the multivariate technique of choice. In predicting an impairment at 0.5 kHz, the reflectance scores at 0.5 kHz were less accurate predictors than reflectance at 2 and 4 kHz. This supports the hypothesis that the 2-4-kHz range is a particularly sensitive indicator of middle-ear status, in agreement with the spectral composition of the output predictor from the multivariate analyses. When tympanometric and YR tests were combined, the resulting predictor performed slightly better or the same as the predictor calculated from the use of the YR test alone. The main conclusion is that these multivariate acoustic tests of the middle ear, which are analyzed using a clinical decision theory, are effective predictors of conductive hearing loss.

Assessment of the gas exchange function of the middle ear using nitrous oxide. A preliminary study.

A method for assessing the gas exchange through the middle ear (ME) mucosa using nitrous oxide is introduced. Increases in the ME pressure was determined by a tympanogram or a micropressure sensor inserted into the mastoid cavity during ear surgery under general anesthesia using 67% nitrous oxide, 33% oxygen, and sevoflurane on 30 normal ears, 12 ears with otitis media with effusion (OME), and 3 postoperative ears with chronic adhesive otitis media or cholesteatoma. All the 30 normal ears except one showed varying pressure increase, and an inverse correlation was observed between pressure increase and area of mastoid on radiographs. Pressure increase was observed in 6 (50%) ears with OME, and this finding correlated well with the presence or absence of air space in the ME on computed tomography images examined preoperatively, on ears which had ear surgery, the presence or absence of pressure increase correlated with the degree of previous surgical intervention on the mastoid. The rationale and possibility of clinical application of this method is discussed.

Round window versus promontory stimulation: assessment for cochlear implant candidacy.

Electrical stimulation of the cochlea is a part of the preliminary evaluation protocol for cochlear implant candidacy at many centers. Typically, a transtympanic needle electrode is placed on the promontory of the ear under consideration and electrical current is presented to measure auditory percepts and psychophysical-electrophysiologic measures. Since 1984, we have used a ball electrode placed directly on the round window (via a tympanotomy) for stimulation, with 27 subjects being so tested to date. Nine additional subjects have had stimulating electrodes placed on both the round window and the promontory. Seven of these subjects yielded complete data. For measurements of threshold, maximum acceptable loudness level, and dynamic range, promontory testing mean values were higher than round window measurements. However, the differences were not significant.

[Significance of tube manometry in the assessment of tube function. A comparison of tube manometry results and continuous direct determination of pressure in the middle ear]. / Die Bedeutung der Tubenmanometrie zur Beurteilung der Tubenfunktion. Ein Vergleich tubenmanometrischer Ergebnisse und kontinuierlicher direkter Mittelohrdruckbestimmungen.

Tube manometry--also known as aspiration-deflation-test--is an often used, practicable clinical test for tube function. By comparing tube manometric results with continual measurements of the middle ear pressure, a close correlation between both test results could be demonstrated. Tube manometric tests thus permit an estimation of the tube function as well as of the probable development of the middle ear pressure. An exact classification in terms of physiologic and pathologic tube function, however, is not possible. It is clear that even a partial equalization of low-pressure values in tube manometry should be interpreted as physiologic.

Hearing assessment in young infants by means of a classical conditioning procedure.

A classical conditioning procedure, in which tones of different intensities and frequencies constituted the conditioned stimuli and an air puff on the corner of the infants' eye represented the unconditioned stimulus, proved to be an effective device for evaluating the hearing ability of young babies. The 45 infants participating in the present study were able to start responding to the presentation of the tones (i.e. complete and prolonged closure of their eye before the onset of the air puff or independent of the puff) in a relatively short period of time. The presence of responding could be regarded as a reliable sign of the infants' hearing functioning across frequencies and intensities.

The occurrence of negative middle ear pressure in children: an analysis of supposed associated factors.

This study analyzed the occurrence of negative middle ear pressure in various groups of children by comparing them with control groups. A screening procedure recording middle ear pressure and screening audiogram was performed several times throughout the year in an unselected group of 352 seven-year-old children. From about 4000 measurements of middle ear pressure an average value for each child was calculated. By applying thresholds of pathology of -160 mm H2( and -240 mm H2O, the occurrence of pathology in the different groups was analyzed. A medical history of each child was obtained by questionnaires answered by parents, giving information concerning allergy, previous adenoidectomy, previous exposure to respiratory tract infections and the social group of the family. A score of dental caries was obtained in each child. Furthermore, the relationship to antibiotic treatment and the child's use of swimming pools was analyzed, based on single measurements. The use of swimming pools seems to be beneficial to children suffering from a negative middle ear pressure. However, the other variables showed no relationship to negative middle ear pressure. It is concluded that other unknown factors must be involved in the development of negative middle ear pressure and chronic OME in children.

An examination of variables involved in tympanometric assessment of eustachian tube function in adults.

Eustachian tube function was assessed tympanometrically in a group of normal adults. A pressure-swallow technique of assessing Eustachian tube ventilatory function was administered with positive and negative induced pressures in the range of +/- 200 mm to +/- 400 mm H2O. This study indicated the relative efficiency of measurement of Eustachian tube function under each of the experimental conditions. Recommendations of procedures for further clinical data collection are presented.

Tympanometric assessment of eustachian tube patency in children.

Eustachian tube patency was assessed tympanometrically in a group of otologically normal children at a pediatric outpatient clinic. A pressure-swallow technique of assessing eustachian tube patency was administered. The results indicated the importance of the examination of both middle ear pressure and function changes in the evaluation of eustachian tube test results.

[Assessment of hearing losses using diagrammatic curves (author's transl)]. / Bewertung von Schwerhörigkeiten mit Hilfe von Kurvendarstellungen

Diagrams are given to facilitate the assessment of hearing losses and make it more flexible. These indicate the degree of deafness derived from the results of various test procedures and the MdE of the degree of deafness of both ears. It is suggested that "degree of deafness" be used instead of the "percentage hearing loss".