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PubMed2006

Otoscopic, cytological, and microbiological examination of the equine external ear canal.

Otoscopic examination and cytology of the equine ear would be beneficial in diseases such as head trauma, headshaking, otitis externa secondary to otitis media, vestibular disease, aural neoplasia and aural pruritus secondary to parasites. In practice, otic examinations of horses are rarely done due to the perceived difficulty in visualizing the equine external ear canal and tympanic membrane, as well as the need for chemical restraint. In this study, the proximal external ear canal was examined in live horses using a handheld otoscope and in cadaver heads using video otoscopy. Visualization of the proximal ear canal of the sedated horse could be done with a handheld otoscope, but more sedation or general anaesthesia and a video otoscope would be required to adequately visualize the tympanic membrane in the live horse. The proximal ear canals of 18 horses were examined cytologically and cultured aerobically. In three horses, both ears were sampled. No cells or organisms were seen on cytological examination of 11/21 ears. Nine of the 21 ears were sterile when cultured. Ten of the 21 ears had mixed growth with low numbers of organisms (Corynebacterium sp. being most common). Two of the 21 ears had heavy growth of a single organism (Corynebacterium sp. and Staphylococcus intermedius, respectively). Equine cadaver heads were examined in cross-section by computed tomography (CT) imaging and histopathology in order to further understand the anatomy of the equine external ear canal. Equine practitioners should be aware that otic examination is possible and may provide important diagnostic information.

Animals↗
PubMed1982

The behavior of acoustic distortion products in the ear canals of chinchillas with normal or damaged ears.

Acoustic intermodulation distortion products were measured in 15 ear canals of chinchillas with normal or damaged ears. Pretreatment results showed that when two primary tones at frequencies f1 and f2, f1 less than f2, were presented at levels from 30 to 90 dB SPL, acoustic distortion products at 2f1-f2 and 2f2-f1 were 30 to 50 dB below primary-tone levels. Noise exposures that caused temporary or permanent hearing loss produced corresponding temporary or permanent reductions in distortion-product levels. Mechanical damage to the cochlea or middle ear reduced the distortion-product levels to below the noise floor of the measurement system. Comparisons of distortion-product level with behaviorally measured threshold shift and cochlear histopathology suggest that, in the absence of conductive impairment, the level of 2f1-f2 or 2f2-f1 can be used as a sensitive indicator of hearing sensitivity and the condition of the cochlea.

Animals↗
PubMed1989

Directional sensitivity of sound-pressure levels in the human ear canal.

Changes in sound pressures measured in the ear canal are reported for broadband sound sources positioned at various locations about the subject. These location-dependent pressures are one source of acoustical cues for sound localization by human listeners. Sound source locations were tested with horizontal and vertical resolution of 10 degrees. Sound levels were measured with miniature microphones placed inside the two ear canals. Although the measured amplitude spectra varied with the position of the microphone in the ear canal, it is shown that the directional sensitivity at any particular frequency of the broadband stimulus is independent of microphone position anywhere within the ear canal. At any given frequency, the distribution of sound pressures as a function of sound source location formed a characteristic spatial pattern comprising one or two discrete areas from which sound sources produced maximum levels in the ear canal. The locations of these discrete areas varied in horizontal and vertical location according to sound frequency. For example, around 8 kHz, two areas of maximum sensitivity typically were found that were located laterally and were separated from each other vertically, whereas, around 12 kHz, two such areas were found located on the horizontal plane and separated horizontally. The spatial patterns of sound levels were remarkably similar among different subjects, although some frequency scaling was required to accommodate for differences in the subjects' physical sizes. Interaural differences in sound-pressure level (ILDs) at frequencies below about 8 kHz tended to increase monotonically with increasing distance of the sound source from the frontal midline and tended to be relatively constant as a function of vertical source location. At higher frequencies, however, ILDs varied both with the horizontal and with the vertical location of the sound source. At some frequencies, asymmetries between the left and right ears in a given subject resulted in substantial ILDs even for midline sound sources. These results indicate the types of horizontal and vertical spatial information that are available from sound level cues over various ranges of frequency and, within a small subject population, indicate the nature of intersubject variability.

Acoustic Stimulation↗
PubMedDate not supplied

[Surgical treatment of congenital atresia of the ear canal].

Diagnostics and original operative technique of ear canal abnormalities as well as results in the treatment of 23 patients have been presented. In 5 patients with congenital ear canal stenosis conventional surgical ear canal dilatation was satisfactory and out of 18 patients with atresia in 16 of them described operation was successful. Obliteration reoccurred in 2 cases.

Child, Preschool↗
PubMed1993

Multiple frequency tympanometry: effects of ear canal volume compensation on static acoustic admittance and estimates of middle ear resonance.

Three methods for compensating multiple frequency acoustic admittance measurements for ear canal volume were studied in 26 men with normal middle ear transmission systems. Peak compensated static acoustic admittance (magnitude of y) and phase angle (phi) were calculated from sweep frequency tympanograms (226-1243 Hz in 113 Hz increments). Of the procedures used to compensate for volume in rectangular form, the ear canal pressure used to estimate volume had the largest effect on the estimate of middle ear resonance. Median resonance was 800 Hz for admittance measurements compensated at 200 daPa versus 1100 Hz for measurements compensated at -350 daPa. The remaining two methods, compensation of susceptance only versus both susceptance and conductance and compensation using the minimum volume versus separate volumes at each frequency, did not affect estimates of middle ear resonance. Estimates of middle ear resonance from compensated phase angle measurements also were compared with estimates of resonance from admittance and phase difference curves. Although resonance could not be estimated from the phase difference curve, resonance estimated from the admittance difference curve agreed with the estimate from compensated phase angle.

Acoustic Impedance Tests↗
PubMedDate not supplied

Canalographic evaluation of the external ear canal in dogs.

Canalography was performed to measure the diameter of the horizontal ear canal and to assess the clinical relevance of the measurements in identifying abnormalities of the ear canal. The diameter of the proximal and distal end of the annular cartilage in the horizontal ear canal was measured using canalography in 222 ears. The tympanic membrane could not be visualized with otoscopic examination in 70 ears even after ear cleansing. These canals were classified as being stenotic. The diameter of the proximal annular cartilage in the stenotic canals ranged from 0.8 to 3.1 mm (mean = 2.6 +/- 0.8 mm). The proximal annular cartilage was consistently smaller in diameter than the distal annular cartilage. The ratio between the diameter of the proximal and distal annular cartilage varied between dogs. In stenotic ear canals (70 ears) the ratio was less than 0.65. Total ear canal ablations and histopathological analysis were performed in 70 ear canals classified as stenotic after canalography. Hyperplasia of the epidermal layer was found in 56 stenotic canals. Stenosis of the canal due to otitis externa was found in the other 14 canals. Three canals with severe otitis externa were also diagnosed with canalography as having a ruptured tympanic membrane. The results suggest that canalography can be used to measure the diameter of the horizontal ear canal and to assess whether or not the tympanic membrane is ruptured prior to conservative or surgical therapy.

Animals↗
PubMed1988

Ear canal acoustic distortion at 2f1-f2 from human ears: relation to other emissions and perceived combination tones.

Two aspects of the intermodulation distortion product at 2f1-f2 generated by normal human ears and measured acoustically in the ear canal were studied: (1) its relation to tone-evoked and spontaneous otoacoustic emissions, and (2) its relation to the perceived combination tone at the same frequency. With regard to (1), substantial differences among ears in the detectability of emissions were observed; ears tended to exhibit all or none of the emission types that were sought. Within ears possessing emissions, the magnitudes of tone-evoked emissions and acoustic distortion showed a similar dependence on frequency. With regard to (2), a three-primary-tone stimulus was employed to ask whether the ear canal acoustic distortion tone is canceled under the same stimulus conditions that produce perceptual cancellation. Simultaneous cancellation of perceptual and acoustic distortion was produced rarely. Results are interpreted qualitatively with a model in which primary tones produce distortion at their interaction region within the cochlea; this distortion propagates to the distortion-frequency place where it mediates perception. This same distortion wave produces emission components at additional locations, including the primary-tone interaction region, which sum vectorially to mediate the emitted acoustic distortion product.

Acoustic Stimulation↗
PubMed1990

Cholesteatoma of the external ear canal.

Cholesteatoma arising in the external ear canal is uncommon. A variety of etiologic factors have been attributed to the development of cholesteatoma in the external ear canal. The various disease processes that cause excessive desquamation and cholesteatoma formation are reviewed and their management is presented.

Cholesteatoma↗
PubMed1982

Correlation of postoperative ear canal volumes with obliteration material and with volume of operation cavity.

In this study the preoperative and early and late postoperative volumes of ear canals of 131 operated chronic ears were measured by filling the ear canals with saline solution. The ears were operated on using the Palva method of obliteration of the operative cavity and reconstruction of the ear canal after removing the posterior, bony canal wall at operation. The average preoperative ear canal volume (V0) was 0.8 ml, the early postoperative volume (V1) was 1.0 ml, and the late postoperative volume (V2) was 1.2 ml. There was significantly more widening of the volume of the ear canals in the ears with a larger (greater than 7 ml) operation cavity as compared to ears with smaller (3-7 ml) operation cavity (p less than 0.05). Widening of the ear canals was smaller in the 12 ears with obliteration of the surgical cavity with musculoperiosteal flap and anorganic bone (Ossar) as compared to the 119 ears obliterated with musculoperiosteal flap only, but the difference was not statistically significant (p greater than 0.05).

Bone Transplantation↗
PubMed2000

Acoustic characteristics of reconstructed ear canal after atresia surgery.

The acoustic properties of the reconstructed ear canals of 13 patients after atresia surgery were investigated by comparing them with those of contralateral healthy ear canals. In the third post-operative month, resonant frequency, amplitude and bandwith of the ear canals with Q-factor were measured. Probe microphone measurements showed a significant shift in resonant frequency in the direction of the higher frequencies, and a non-significant change in bandwith in the atresia surgery group. The suggested reason may be a change in ear canal curvature, altered vibration pattern and sound-absorption characteristics of the skin graft lining the reconstructed ear canal.

Acoustics↗
PubMed1989

Sound propagation in the ear canal and coupling to the eardrum, with measurements on model systems.

A theoretical model of sound propagation in the ear canal is described, which takes into account both the complicated geometry of real ear canals and the distributed acoustical load presented by the eardrum. The geometry of the ear canal enters the theory in the form of a cross-sectional area function relative to a curved axis that follows the center of the ear canal. The tympanic membrane forms part of the ear canal wall and absorbs acoustical energy over its surface. Its motion leads to a driving term that must be added to the horn equation describing the pressure distribution in the ear canal. The sound field within the canal is assumed to be effectively one dimensional, depending only on longitudinal position along the canal. Experiments using model ear canals of uniform cross section were performed to test the ability of the theory to handle distributed loads. Sound-pressure distributions within each model canal were measured using a probe microphone. The behavior of the eardrum was simulated using either a distributed, locally reacting impedance or a mechanically driven piston. The agreement between theory and experiment is good up to a nominal upper frequency limit at which the ratio of canal width to wavelength is 0.25. It is estimated that the theory is applicable in ear canals of cats for frequencies at least as high as 25 kHz and in human ear canals to at least 15 kHz.

Acoustic Stimulation↗
PubMed2000

Middle ear pathology can affect the ear-canal sound pressure generated by audiologic earphones.

OBJECTIVE: To determine how the ear-canal sound pressures generated by earphones differ between normal and pathologic middle ears. DESIGN: Measurements of ear-canal sound pressures generated by the Etymtic Research ER-3A insert earphone in normal ears (N = 12) were compared with the pressures generated in abnormal ears with mastoidectomy bowls (N = 15), tympanostomy tubes (N = 5), and tympanic-membrane perforations (N = 5). Similar measurements were made with the Telephonics TDH-49 supra-aural earphone in normal ears (N = 10) and abnormal ears with mastoidectomy bowls (N = 10), tympanostomy tubes (N = 4), and tympanic-membrane perforations (N = 5). RESULTS: With the insert earphone, the sound pressures generated in the mastoid-bowl ears were all smaller than the pressures generated in normal ears; from 250 to 1000 Hz the difference in pressure level was nearly frequency independent and ranged from -3 to -15 dB; from 1000 to 4000 Hz the reduction in level increased with frequency and ranged from -5 dB to -35 dB. In the ears with tympanostomy tubes and perforations the sound pressures were always smaller than in normal ears at frequencies below 1000 Hz; the largest differences occurred below 500 Hz and ranged from -5 to -25 dB. With the supra-aural earphone, the sound pressures in ears with the three pathologic conditions were more variable than those with the insert earphone. Generally, sound pressures in the ears with mastoid bowls were lower than those in normal ears for frequencies below about 500 Hz; above about 500 Hz the pressures showed sharp minima and maxima that were not seen in the normal ears. The ears with tympanostomy tubes and tympanic-membrane perforations also showed reduced ear-canal pressures at the lower frequencies, but at higher frequencies these ear-canal pressures were generally similar to the pressures measured in the normal ears. CONCLUSIONS: When the middle ear is not normal, ear-canal sound pressures can differ by up to 35 dB from the normal-ear value. Because the pressure level generally is decreased in the pathologic conditions that were studied, the measured hearing loss would exaggerate substantially the actual loss in ear sensitivity. The variations depend on the earphone, the middle ear pathology, and frequency. Uncontrolled variations in ear-canal pressure, whether caused by a poor earphone-to-ear connection or by abnormal middle ear impedance, could be corrected with audiometers that measure sound pressures during hearing tests.

Acoustic Impedance Tests↗
PubMed1985

Management of the ear canal in head and neck surgery.

The management of the ear canal in the treatment of tumors occurring in the area of the head and neck is a highly specialized problem. The material for this report is a derivative of the treatment of tumors involving the auricle, tragus, the skin of the cheek, temple, mastoid, parotid gland, ear canal, and middle ear. The extensive variety of histopathologic conditions and positions of the various tumors creates special problems in preserving and reconstructing the ear canal, saving the tympanic membrane, and rehabilitating the area of the ear canal when these structures have had to be resected. Six basic techniques have been used in rehabilitating this unique area, by using regional skin, free skin grafts, regional flaps, cervical flaps, combinations of these techniques, and large cutaneous and myocutaneous chest and back flaps for the larger ablations.

Ear Canal↗
PubMed1993

Ear-canal impedance and reflection coefficient in human infants and adults.

The ear-canal impedance and reflection coefficient were measured in an adult group and in groups of infants of age 1, 3, 6, 12, and 24 months over frequency range 125-10,700 Hz. The development of the external ear canal and middle ear strongly affect input impedance and reflection coefficient responses, and this development is not yet complete at age 24 months. Contributing factors include growth of the area and length of the ear canal, a resonance in the ear-canal walls of younger infants, and a probable influence of growth of the middle-ear cavities. The middle-ear compliance is lower in infants than adults, and the middle-ear resistance is higher. The power transfer into the middle ear of the infant is much less than into that of the adult. Such differences in power transfer directly influence both behavioral and physiological measurements of hearing. The difficulties of interpretation of neonatal tympanograms are shown to be a consequence of ear-canal wall vibration. Impedance and reflectance measurements in the 2-4-kHz range are recommended as a potentially useful clinical tool for circumventing these difficulties.

Acoustic Impedance Tests↗
PubMed1982

Late changes in ear canal volumes after mastoid obliteration.

In this study, preoperative and postoperative ear canal volumes of ears subjected to obliterative radical mastoidectomy were assessed. The measurements were performed using sterile saline solution both at the preoperative stage (V0) and at the early (one year, V1) and the late (five to 13 years, V2) postopertive stages. The mean V0 was 0.8 mL (SD, 0.2 mL; V1, 1.0 mL (SD, 0.3 mL); and V2, 1.2 mL (SD, 0.4 mL). The differences were highly significant. Clinically, the widening of the ear canals was mainly slight and appeared evenly in the epitympanic area and in the posterior ear canal wall.

Chronic Disease↗
PubMed2005

Comparison of an analytic horn equation approach and a boundary element method for the calculation of sound fields in the human ear canal.

The sound field inside a model human ear canal has been computed, to show both longitudinal variations along the canal length and transverse variations through cross-sectional slices. Two methods of computation were used. A modified horn equation approach parametrizes the sound field with a single coordinate, the position along a curved center axis-this approach can accommodate the curvature and varying cross-sectional area of the ear canal but cannot compute transverse variations of the sound field. A boundary element method (BEM) was also implemented to compute the full three-dimensional sound field. Over 2000 triangular mesh elements were used to represent the ear canal geometry. For a plane piston source at the entrance plane, the pressure along the curved center axis predicted by the two methods is in good agreement, for frequencies up to 15 kHz, for four different ear canals. The BEM approach, though, reveals spatial variations of sound pressure within each canal cross section. These variations are small below 4 kHz, but increase with frequency, reaching 1.5 dB at 8 kHz and 4.5 dB at 15 kHz. For source configurations that are more realistic than a simple piston, large transverse variations in sound pressure are anticipated in the vicinity of the source.

Acoustic Stimulation↗
PubMed1987

Ear canal volume and variability in the patterns of temporary threshold shifts.

Ear canal resonance is thought to be responsible for the prominent loss of hearing in the 3.0 to 6.0 kHz region caused by over-exposure to noise. Relationships were identified between frequency-of-maximum temporary threshold shift (TTS) and physical measurements of the ear canal in 56 subjects. TTSs were produced by two separate exposures to broadband noise of either 2 hr or 20 minute duration. Ear canal volume was estimated from admittance tympanograms, diameter of the canal opening was measured, and canal length was calculated. Thirty subjects suffered the greatest TTS at 4.0 kHz, while 17 and 9 subjects had the greatest shift at 3.0 and 6.0 kHz, respectively. With subjects grouped according to frequency-of-maximum TTS, mean ear canal volume was found to be significantly different. Subjects with larger volumes were more likely to suffer the greatest loss at 3.0 kHz. Accordingly, subjects with smaller ear canal volumes suffered peak hearing loss at 6.0 kHz. Significant correlations were identified between ear canal volume and calculated length (resonance). Also, modest correlations were noted between frequency-of-maximum TTS and volume as well as TTS and length.

Acoustic Stimulation↗