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1.  Diagnostic Utility of Laser-Doppler Vibrometry in Conductive Hearing Loss with Normal Tympanic Membrane 
It was hypothesized that laser-Doppler vibrometry measurements of umbo velocity in aerated middle ears with conductive loss can differentiate ossicular interruptions, stapes fixations, and mallear fixations. More generally, we hypothesize that laser-Doppler vibrometry measurements of umbo velocity can give information about how differences in the impedance that the ossicles work against affect middle-ear function.
Laser-Doppler vibrometry is a well-established research tool for exploring middle-ear function. The authors wished to investigate its potential as a clinical tool for differential diagnosis of the cause of conductive hearing loss.
Laser-Doppler vibrometry was used to investigate the relationship between the sound-induced velocity of the tympanic membrane at the umbo and the cause of conductive hearing loss when the tympanic membrane was normal and the middle ear was aerated. The results of measurements in 17 adult ears before exploratory tympanotomy were compared with the surgically determined cause of the hearing loss. The authors also measured the motion of the umbo in 10 patients who had undergone successful small-fenestra stapedectomy procedures. In all the studied ears, pure-tone audiograms were measured at the time of laser-Doppler vibrometry testing.
There were clear statistical differences between the umbo velocity in normal ears and in ears with different ossicular pathologic conditions. There was also a clear separation of the results between ears with ossicular interruptions and ossicular fixation. The pattern of laser-Doppler vibrometry measurements in poststapedectomy ears approximated the pattern in ears with ossicular interruptions.
Comparison of laser-Doppler vibrometry results and audiometry may be a sensitive and selective indicator of ossicular pathologic conditions as well as a useful tool for investigating middle ear function.
PMCID: PMC1464085  PMID: 12621328
Laser-Doppler vibrometry; Conductive hearing loss; Middle ear function; Audiometry
2.  Middle Ear Cavity Morphology Is Consistent with an Aquatic Origin for Testudines 
PLoS ONE  2013;8(1):e54086.
The position of testudines in vertebrate phylogeny is being re-evaluated. At present, testudine morphological and molecular data conflict when reconstructing phylogenetic relationships. Complicating matters, the ecological niche of stem testudines is ambiguous. To understand how turtles have evolved to hear in different environments, we examined middle ear morphology and scaling in most extant families, as well as some extinct species, using 3-dimensional reconstructions from micro magnetic resonance (MR) and submillimeter computed tomography (CT) scans. All families of testudines exhibited a similar shape of the bony structure of the middle ear cavity, with the tympanic disk located on the rostrolateral edge of the cavity. Sea Turtles have additional soft tissue that fills the middle ear cavity to varying degrees. When the middle ear cavity is modeled as an air-filled sphere of the same volume resonating in an underwater sound field, the calculated resonances for the volumes of the middle ear cavities largely fell within testudine hearing ranges. Although there were some differences in morphology, there were no statistically significant differences in the scaling of the volume of the bony middle ear cavity with head size among groups when categorized by phylogeny and ecology. Because the cavity is predicted to resonate underwater within the testudine hearing range, the data support the hypothesis of an aquatic origin for testudines, and function of the middle ear cavity in underwater sound detection.
PMCID: PMC3544720  PMID: 23342082
3.  Evolution of a sensory novelty: Tympanic ears and the associated neural processing 
Brain Research Bulletin  2007;75(2-4):365-370.
Tympanic hearing is a true evolutionary novelty that appears to have developed independently in at least five major tetrapod groups—the anurans, turtles, lepidosaurs, archosaurs and mammals. The emergence of a tympanic ear would have increased the frequency range and sensitivity of hearing. Furthermore, tympana were acoustically coupled through the mouth cavity and therefore inherently directional in a certain frequency range, acting as pressure difference receivers. In some lizard species, this acoustical coupling generates a 50-fold directional difference, usually at relatively high frequencies (2–4 kHz).
In ancestral atympanate tetrapods, we hypothesize that low-frequency sound may have been processed by non-tympanic mechanisms like those in extant amphibians. The subsequent emergence of tympanic hearing would have led to changes in the central auditory processing of both high-frequency sound and directional hearing. These changes should reflect the independent origin of the tympanic ears in the major tetrapod groups. The processing of low-frequency sound, however, may have been more conserved, since the acoustical coupling of the ancestral tympanate ear probably produced little sensitivity and directionality at low frequencies. Therefore, tetrapod auditory processing may originally have been organized into low- and high-frequency streams, where only the high-frequency processing was mediated by tympanic input.
The closure of the middle ear cavity in mammals and some birds is a derived condition, and may have profoundly changed the operation of the ear by decoupling the tympana, improving the low-frequency response of the tympanum, and leading to a requirement for additional neural computation of directionality in the central nervous system. We propose that these specializations transformed the low- and high-frequency streams into time and intensity pathways, respectively.
PMCID: PMC3269633  PMID: 18331899
Middle ear; Tympanum; Lizard; Frog; Hearing; Auditory; Brain stem
4.  Hearing in the African lungfish (Protopterus annectens): pre-adaptation to pressure hearing in tetrapods? 
Biology Letters  2010;7(1):139-141.
Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes resembles the tetrapod ear more than the ear of ray-finned fishes and is therefore of interest for understanding the evolution of hearing in the early tetrapods. The water-to-land transition resulted in major changes in the tetrapod ear associated with the detection of air-borne sound pressure, as evidenced by the late and independent origins of tympanic ears in all of the major tetrapod groups. To investigate lungfish pressure and vibration detection, we measured the sensitivity and frequency responses of five West African lungfish (Protopterus annectens) using brainstem potentials evoked by calibrated sound and vibration stimuli in air and water. We find that the lungfish ear has good low-frequency vibration sensitivity, like recent amphibians, but poor sensitivity to air-borne sound. The skull shows measurable vibrations above 100 Hz when stimulated by air-borne sound, but the ear is apparently insensitive at these frequencies, suggesting that the lungfish ear is neither adapted nor pre-adapted for aerial hearing. Thus, if the lungfish ear is a model of the ear of early tetrapods, their auditory sensitivity was limited to very low frequencies on land, mostly mediated by substrate-borne vibrations.
PMCID: PMC3030901  PMID: 20826468
lungfish; hearing; vibration; tetrapod; sound; evolution
5.  Investigation of the Mechanics of Type III Stapes Columella Tympanoplasty Using Laser-Doppler Vibrometry 
To investigate the middle ear mechanics of Type III stapes columella tympanoplasty using laser-Doppler vibrometry (LDV) and to determine whether LDV was useful in the identification of structural factors responsible for poor hearing outcomes.
The Type III stapes columella tympanoplasty procedure involves placing a tympanic membrane (TM) graft directly onto the stapes head. Postoperative hearing results vary widely, with air-bone gaps (ABGs) ranging from 10 to 60 dB.
Laser-Doppler vibrometry measurements were performed in 22 patients (23 ears) who underwent Type III stapes columella tympanoplasty. The measurements were made at three locations on the TM graft: over the stapes head, over the round window, and on the anterior TM. The LDV results were correlated with the clinical and audiologic findings.
The 23 ears were divided into three groups: Nonaerated ears (n = 2). The ABGs were 30 to 60 dB. The TM velocities over all three locations were 20 to 40 dB lower than normal umbo velocity (in normally hearing subjects). Fixed stapes with aerated middle ear (n = 2). The ABGs were 40 to 60 dB, and TM velocities were equivalent to normal umbo velocity in one case and lower by 15 to 20 dB in another case. Mobile stapes and aerated middle ear (n = 19). There were two subgroups in this category: 1) small ABGs less than 25 dB (n = 7) and large gaps greater than or equal to 25 dB (n = 12). There were small differences in TM graft velocity at all three measurement locations between these two subgroups. However, these small differences did not explain the large difference in ABG between the two subgroups.
Nonaeration of the middle ear and stapes fixation lead to large residual conductive hearing losses after Type III tympanoplasty. Laser-Doppler vibrometry can aid in the diagnosis of nonaeration of the middle ear but does not readily diagnose stapes fixation. Postoperative results can vary even in cases of a mobile stapes and an aerated middle ear. We hypothesize that these variations may be the result of differences in the coupling between the TM graft and the stapes head. Measurements of TM velocities by means of LDV did not show clear differences between cases with good hearing and cases with poor hearing in ears with a mobile stapes and an aerated ear. Except for diagnosis of nonaeration of the middle ear, LDV seems to have limited clinical usefulness to identify causes of failure after Type III tympanoplasty.
PMCID: PMC2586981  PMID: 17948356
Air-bone gap; Laser-Doppler vibrometry; Middle ear mechanics; Tympanoplasty
6.  Determinants of Hearing Loss in Perforations of the Tympanic Membrane 
Although tympanic membrane perforations are common, there have been few systematic studies of the structural features determining the magnitude of the resulting conductive hearing loss. Our recent experimental and modeling studies predicted that the conductive hearing loss will increase with increasing perforation size, be independent of perforation location (contrary to popular otologic belief), and increase with decreasing size of the middle-ear and mastoid air space (an idea new to otology).
To test our predictions regarding determinants of conductive hearing loss in tympanic membrane perforations against clinical data gathered from patients.
Study Design
Prospective clinical study.
Tertiary referral center.
Inclusion Criteria
Patients with tympanic membrane perforations without other middle-ear disease.
Main Outcome Measures
Size and location of perforation; air-bone gap at 250, 500, 1,000, 2,000, and 4,000 Hz; and tympanometric estimate of volume of the middle-ear air spaces.
Isolated tympanic membrane perforations in 62 ears from 56 patients met inclusion criteria. Air-bone gaps were largest at the lower frequencies and decreased as frequency increased. Air-bone gaps increased with perforation size at each frequency. Ears with small middle-ear volumes, ≤4.3 ml (n = 23), had significantly larger air-bone gaps than ears with large middle-ear volumes, >4.3 ml (n = 39), except at 2,000 Hz. The mean air-bone gaps in ears with small volumes were 10 to 20 dB larger than in ears with large volumes. Perforations in anterior versus posterior quadrants showed no significant differences in air-bone gaps at any frequency, although anterior perforations had, on average, air-bone gaps that were smaller by 1 to 8 dB at lower frequencies.
The conductive hearing loss resulting from a tympanic membrane perforation is frequency-dependent, with the largest losses occurring at the lowest sound frequencies; increases as size of the perforation increases; varies inversely with volume of the middle-ear and mastoid air space (losses are larger in ears with small volumes); and does not vary appreciably with location of the perforation. Effects of location, if any, are small.
PMCID: PMC2918411  PMID: 16436981
Audiometry; Conductive hearing loss; Perforation; Tympanic membrane; Tympanometry
We report the results of anatomical and vibrometric studies of the middle ear of the African clawed frog, Xenopus laevis. The cartilaginous tympanic disk of Xenopus shows pronounced sexual dimorphism, that of male frogs being much larger than that of females, relative to body size. The stapes footplate, however, is not enlarged in males. The cucullaris muscle was found to insert on the stapes in frogs of both sexes. Using laser interferometry to examine the response of middle ear structures to airborne sound, the stapes footplate was found to vibrate close to 180° out-of-phase with the tympanic disk across a range of frequencies, this resembling the relationship between tympanic membrane and footplate movement previously described in ranid frogs. By contrast, whereas there is a pronounced difference in vibration velocity between tympanic membrane and footplate in ranids, the footplate vibration velocity in Xenopus was found to be similar to that of the tympanic disk. This may be interpreted as an adaptation to improve the detection of sound underwater.
PMCID: PMC2953823  PMID: 20953303
8.  Comparison of umbo velocity in air and bone conduction 
Hearing research  2012;290(0):83-90.
This study investigates the ossicular motion produced by bone-conducted (BC) sound in live human ears. Laser Doppler Vibrometry was used to measure air conduction (AC) and BC induced umbo velocity (Vu) in both ears of 10 subjects, 20 ears total. Sound pressure in the ear canal (PEC) was measured simultaneously. For air conduction, Vu at threshold was calculated. For BC, ΔV was defined as the difference between Vu and the tympanic ring velocity (an estimate of the skull velocity measured in the ear canal). ΔV and PEC at BC threshold were calculated and compared to the corresponding air conduction measurements.
ΔV at BC threshold was significantly smaller than Vu at AC threshold between 500 Hz and 2000 Hz. Ear canal pressure at BC threshold tended to be smaller than for AC below 3000 Hz (with significant differences at 1000 Hz and 2000 Hz). Our results are most consistent with inertia of the ossicles and cochlear fluid driving BC hearing below 500 Hz, but with other mechanisms playing a significant role at higher frequencies. Sound radiated into the external ear canal might contribute to BC hearing at 3000 Hz and above.
PMCID: PMC3998651  PMID: 22609771
umbo velocity; bone conduction; middle ear inertia; cochlear inertia; sound radiated in the external ear canal
9.  Middle-Ear Pressure Gain and Cochlear Partition Differential Pressure in Chinchilla 
Hearing research  2009;263(1-2):16-25.
An important step to describe the effects of inner-ear impedance and pathologies on middle- and inner-ear mechanics is to quantify middle- and inner-ear function in the normal ear. We present middle-ear pressure gain GMEP and trans-cochlear-partition differential sound pressure ΔPCP in chinchilla from 100 Hz to 30 kHz derived from measurements of intracochlear sound pressures in scala vestibuli PSV and scala tympani PST and ear-canal sound pressure near the tympanic membrane PTM. These measurements span the chinchilla's auditory range. GMEP had constant magnitude of about 20 dB between 300 Hz and 20 kHz and phase that implies a 40-μs delay, values with some similarities to previous measurements in chinchilla and other species. ΔPCP was similar to GMEP below about 10 kHz and lower in magnitude at higher frequencies, decreasing to 0 dB at 20 kHz. The high-frequency rolloff correlates with the audiogram and supports the idea that middle-ear transmission limits high-frequency hearing, providing a stronger link between inner-ear macromechanics and hearing. We estimate the cochlear partition impedance ZCP from these and previous data. The chinchilla may be a useful animal model for exploring the effects of nonacoustic inner-ear stimulation such as “bone conduction” on cochlear mechanics.
PMCID: PMC2866808  PMID: 19945521
Middle-ear sound transmission; introcochlear sound pressure; middle-ear gain; cochlear impedance; chinchilla
10.  Mouse Middle Ear Ion Homeostasis Channels and Intercellular Junctions 
PLoS ONE  2012;7(6):e39004.
The middle ear contains homeostatic mechanisms that control the movement of ions and fluids similar to those present in the inner ear, and are altered during inflammation.
The normal middle ear cavity is fluid-free and air-filled to allow for effective sound transmission. Within the inner ear, the regulation of fluid and ion movement is essential for normal auditory and vestibular function. The same ion and fluid channels active in the inner ear may have similar roles with fluid regulation in the middle ear.
Middle and inner ears from BALB/c mice were processed for immunohistochemistry of 10 specific ion homeostasis factors to determine if similar transport and barrier mechanisms are present in the tympanic cavity. Examination also was made of BALB/c mice middle ears after transtympanic injection with heat-killed Haemophilus influenza to determine if these channels are impacted by inflammation.
The most prominent ion channels in the middle ear included aquaporins 1, 4 and 5, claudin 3, ENaC and Na+,K+-ATPase. Moderate staining was found for GJB2, KCNJ10 and KCNQ1. The inflamed middle ear epithelium showed increased staining due to expected cellular hypertrophy. Localization of ion channels was preserved within the inflamed middle ear epithelium.
The middle ear epithelium is a dynamic environment with intrinsic mechanisms for the control of ion and water transport to keep the middle ear clear of fluids. Compromise of these processes during middle ear disease may underlie the accumulation of effusions and suggests they may be a therapeutic target for effusion control.
PMCID: PMC3376096  PMID: 22720014
11.  The Auditory Anatomy of the Minke Whale (Balaenoptera acutorostrata): A Potential Fatty Sound Reception Pathway in a Baleen Whale 
Cetaceans possess highly derived auditory systems adapted for underwater hearing. Odontoceti (toothed whales) are thought to receive sound through specialized fat bodies that contact the tympanoperiotic complex, the bones housing the middle and inner ears. However, sound reception pathways remain unknown in Mysticeti (baleen whales), which have very different cranial anatomies compared to odontocetes. Here, we report a potential fatty sound reception pathway in the minke whale (Balaenoptera acutorostrata), a mysticete of the balaenopterid family. The cephalic anatomy of seven minke whales was investigated using computerized tomography and magnetic resonance imaging, verified through dissections. Findings include a large, well-formed fat body lateral, dorsal, and posterior to the mandibular ramus and lateral to the tympanoperiotic complex. This fat body inserts into the tympanoperiotic complex at the lateral aperture between the tympanic and periotic bones and is in contact with the ossicles. There is also a second, smaller body of fat found within the tympanic bone, which contacts the ossicles as well. This is the first analysis of these fatty tissues' association with the auditory structures in a mysticete, providing anatomical evidence that fatty sound reception pathways may not be a unique feature of odontocete cetaceans. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.
PMCID: PMC3488298  PMID: 22488847
cetacea; mysticete; hearing; ear; acoustic fat; imaging
12.  Scleraxis is Required for Differentiation of the Stapedius and Tensor Tympani Tendons of the Middle Ear 
Scleraxis (Scx) is a basic helix-loop-helix transcription factor expressed in tendon and ligament progenitor cells and the differentiated cells within these connective tissues in the axial and appendicular skeleton. Unexpectedly, we found expression of the Scx transgenic reporter mouse, Scx-GFP, in interdental cells, sensory hair cells, and cochlear supporting cells at embryonic day 18.5 (E18.5). We evaluated Scx-null mice to gain insight into the function of Scx in the inner ear. Paradoxical hearing loss was detected in Scx-nulls, with ~50% of the mutants presenting elevated auditory thresholds. However, Scx-null mice have no obvious, gross alterations in cochlear morphology or cellular patterning. Moreover, we show that the elevated auditory thresholds correlate with middle ear infection. Laser interferometric measurement of sound-induced malleal movements in the infected Scx-nulls demonstrates increased impedance of the middle ear that accounts for the hearing loss observed. The vertebrate middle ear transmits vibrations of the tympanic membrane to the cochlea. The tensor tympani and stapedius muscles insert into the malleus and stapes via distinct tendons and mediate the middle ear muscle reflex that in part protects the inner ear from noise-induced damage. Nothing, however, is known about the development and function of these tendons. Scx is expressed in tendon progenitors at E14.5 and differentiated tenocytes of the stapedius and tensor tympani tendons at E16.5–18.5. Scx-nulls have dramatically shorter stapedius and tensor tympani tendons with altered extracellular matrix consistent with abnormal differentiation in which condensed tendon progenitors are inefficiently incorporated into the elongating tendons. Scx-GFP is the first transgenic reporter that identifies middle ear tendon lineages from the time of their formation through complete tendon maturation. Scx-null is the first genetically defined mouse model for abnormal middle ear tendon differentiation. Scx mouse models will facilitate studies of tendon and muscle formation and function in the middle ear.
PMCID: PMC3123444  PMID: 21399989
middle ear muscle reflex; tendon; tenocytes; laser interferometry; otitis media
13.  Combined Effect of Fluid and Pressure on Middle Ear Function 
Hearing research  2007;236(1-2):22-32.
In our previous studies, the effects of effusion and pressure on sound transmission were investigated separately. The aim of this study is to investigate the combined effect of fluid and pressure on middle ear function. An otitis media with effusion model was created by injecting saline solution and air pressure simultaneously into the middle ear of human temporal bones. Tympanic membrane displacement in response to 90 dB SPL sound input was measured by a laser vibrometer and the compliance of the middle ear was measured by a tympanometer. The movement of the tympanic membrane at the umbo was reduced up to 17 dB by the combination of fluid and pressure in the middle ear over the auditory frequency range. The fluid and pressure effects on the umbo movement in the fluid-pressure combination are not additive. The combined effect of fluid and pressure on the umbo movement is different compared with that of only fluid or pressure change in the middle ear. Negative pressure in fluid-pressure combination had more effect on middle ear function than positive pressure. Tympanometry can detect the middle ear pressure of the fluid-pressure combination. This study provides quantitative information for analysis of the combined effect of fluid and pressure on tympanic membrane movement.
PMCID: PMC2346543  PMID: 18162348
laser vibrometer; middle ear mechanics; otitis media; temporal bone; tympanometry
14.  Clinical Investigation and Mechanism of Air-Bone Gaps in LargeVestibular Aqueduct Syndrome 
Patients with large vestibular aqueduct syndrome (LVAS) often demonstrate an air-bone gap at the low frequencies on audiometric testing. The mechanism causing such a gap has not been well elucidated. We investigated middle ear sound transmission in patients with LVAS, and present a hypothesis to explain the air-bone gap.
Observations were made on 8 ears from 5 individuals with LVAS. The diagnosis of LVAS was made by computed tomography in all cases. Investigations included standard audiometry and measurements of umbo velocity by laser Doppler vibrometry (LDV) in all cases, as well as tympanometry, acoustic reflex testing, vestibular evoked myogenic potential (VEMP) testing, distortion product otoacoustic emission (DPOAE) testing, and middle ear exploration in some ears.
One ear with LVAS had anacusis. The other 7 ears demonstrated air-bone gaps at the low frequencies, with mean gaps of 51 dB at 250 Hz, 31 dB at 500 Hz, and 12 dB at 1,000 Hz. In these 7 ears with air-bone gaps, LDV showed the umbo velocity to be normal or high normal in all 7; tympanometry was normal in all 6 ears tested; acoustic reflexes were present in 3 of the 4 ears tested; VEMP responses were present in all 3 ears tested; DPOAEs were present in 1 of the 2 ears tested, and exploratory tympanotomy in 1 case showed a normal middle ear. The above data suggest that an air-bone gap in LVAS is not due to disease in the middle ear. The data are consistent with the hypothesis that a large vestibular aqueduct introduces a third mobile window into the inner ear, which can produce an air-bone gap by 1) shunting air-conducted sound away from the cochlea, thus elevating air conduction thresholds, and 2) increasing the difference in impedance between the scala vestibuli side and the scala tympani side of the cochlear partition during bone conduction testing, thus improving thresholds for bone-conducted sound.
We conclude that LVAS can present with an air-bone gap that can mimic middle ear disease. Diagnostic testing using acoustic reflexes, VEMPs, DPOAEs, and LDV can help to identify a non–middle ear source for such a gap, thereby avoiding negative middle ear exploration. A large vestibular aqueduct may act as a third mobile window in the inner ear, resulting in an air-bone gap at low frequencies.
PMCID: PMC2585521  PMID: 17727085
air-bone gap; audiometry; conductive hearing loss; large vestibular aqueduct syndrome
15.  Factors Affecting Loss of Tympanic Membrane Mobility in Acute Otitis Media Model of Chinchilla 
Hearing research  2014;309:136-146.
Recently we reported that middle ear pressure (MEP), middle ear effusion (MEE), and ossicular changes each contribute to the loss of tympanic membrane (TM) mobility in a guinea pig model of acute otitis media (AOM) induced by S. pneumoniae (Guan and Gan, 2013). However, it is not clear how those factors vary along the course of the disease and whether those effects are reproducible in different species. In this study, a chinchilla AOM model was produced by transbullar injection of Haemophilus influenzae. Mobility of the TM at the umbo was measured by laser vibrometry in two treatment groups: 4 days (4D) and 8 days (8D) post inoculation. These time points represent relatively early and later phases of AOM. In each group, the vibration of the umbo was measured at three experimental stages: unopened, pressure-released, and effusion-removed ears. The effects of MEP and MEE and middle ear structural changes were quantified in each group by comparing the TM mobility at one stage with that of the previous stage. Our findings show that the factors affecting TM mobility do change with the disease time course. The MEP was the dominant contributor to reduction of TM mobility in 4D AOM ears, but showed little effect in 8D ears when MEE filled the tympanic cavity. MEE was the primary factor affecting TM mobility loss in 8D ears, but affected the 4D ears only at high frequencies. After the release of MEP and removal of MEE, residual loss of TM mobility was seen mainly at low frequencies in both 4D and 8D ears, and was associated with middle ear structural changes. Our findings establish that the factors contributing to TM mobility loss in the chinchilla ear were similar to those we reported previously for the guinea pig ears with AOM. Outcomes did not appear to differ between the two major bacterial species causing AOM in these animal models.
PMCID: PMC3963815  PMID: 24406734
acute otitis media; conductive hearing loss; middle ear pressure; middle ear effusion; ossicular adhesion; umbo vibration; laser vibrometry; Haemophilus influenzae
16.  Measurement of Conductive Hearing Loss in Mice 
Hearing research  2009;263(1-2):93-103.
In order to discriminate conductive hearing loss from sensorineural impairment, quantitative measurements were used to evaluate the effect of artificial conductive pathology on distortion product otoacoustic emissions (DPOAEs), auditory brainstem responses (ABRs) and laser Doppler vibrometry (LDV) in mice. The conductive manipulations were created by perforating the pars flaccida of the tympanic membrane, filling or partially filling the middle-ear cavity with saline, fixing the ossicular chain, and interrupting the incudo-stapedial joint. In the saline-filled and ossicular-fixation groups, averaged DPOAE thresholds increased relative to the control state by 20 to 36 dB and 25 to 39 dB respectively with the largest threshold shifts occurring at frequencies less than 20 kHz, while averaged ABR thresholds increased 12 to 19 dB and 12 to 25 dB respectively without the predominant low-frequency effect. Both DPOAE and ABR thresholds were elevated by less than 10 dB in the half-filled saline condition; no significant change was observed after pars flaccida perforation. Conductive pathology generally produced a change in DPOAE threshold in dB that was 1.5 to 2.5 times larger than the ABR threshold change at frequencies less than 30 kHz; the changes in the two thresholds were nearly equal at the highest frequencies. While mild conductive pathology (ABR threshold shifts of < 10 dB) produced parallel shifts in DPOAE growth with level functions, manipulations that produced larger conductive hearing losses (ABR threshold shifts > 10 dB) were associated with significant deceases in DPOAE growth rate. Our LDV measurements are consistent with others and suggest that measurements of umbo velocity are not an accurate indicator of conductive hearing loss produced by ossicular lesions in mice.
PMCID: PMC2866764  PMID: 19835942
Middle ear pathology; Distortion product otoacoustic emissions; Auditory brainstem responses; Umbo velocity; Mouse
17.  Clinical Utility of Laser-Doppler Vibrometer Measurements in Live Normal and Pathologic Human Ears 
Ear and hearing  2008;29(1):3-19.
The laser-Doppler vibrometer (LDV) is a research tool that can be used to quickly measure the sound-induced velocity of the tympanic membrane near the umbo (the inferior tip of the malleus) in live human subjects and patients. In this manuscript we demonstrate the LDV to be a sensitive and selective tool for the diagnosis and differentiation of various ossicular disorders in patients with intact tympanic membranes and aerated middle ears. Patients with partial or total ossicular interruption or malleus fixation are readily separated from normal-hearing subjects with the LDV. The combination of LDV measurements and air-bone gap can distinguish patients with fixed stapes from those with normal ears. LDV measurements can also help differentiate air-bone gaps produced by ossicular pathologies from those associated with pathologies of inner-ear sound conduction such as a superior semicircular canal dehiscence.
PMCID: PMC2572196  PMID: 18091103
18.  Effects of middle-ear disorders on power reflectance measured in cadaveric ear canals 
Ear and hearing  2012;33(2):195-208.
Reflectance measured in the ear canal offers a noninvasive method to monitor the acoustic properties of the middle ear, and few systematic measurements exist on the effects of various middle-ear disorders on the reflectance. This work utilizes a human cadaver-ear preparation and a mathematical middle-ear model to both measure and predict how power reflectance ℛ is affected by the middle-ear disorders of static middle-ear pressures, middle-ear fluid, fixed stapes, disarticulated incudo-stapedial joint, and tympanic-membrane perforations.
ℛ was calculated from ear-canal pressure measurements made on human-cadaver ears in the normal condition and five states: (1) positive and negative pressure in the middle-ear cavity, (2) fluid-filled middle ear, (3) stapes fixed with dental cement, (4) incudo-stapedial joint disarticulated, and (5) tympanic-membrane perforations. The middle-ear model of Kringlebotn (1988) was modified to represent the middle-ear disorders. Model predictions are compared to measurements.
For a given disorder, the general trends of the measurements and model were similar. The changes from normal in ℛ, induced by the simulated disorder, generally depend on frequency and the extent of the disorder (except for the disarticulation). Systematic changes in middle-ear static pressure (up to ± 300 daPa) resulted in systematic increases in ℛ. These affects were most pronounced for frequencies up to 1000 to 2000 Hz. Above about 2000 Hz there were some asymmetries in behavior between negative and positive pressures. Results with fluid in the middle-ear air space were highly dependent on the percentage of the air space that was filled. Changes in ℛ were minimal when a smaller fraction of the air space was filled with fluid, and as the air space was filled with more saline, ℛ increased at most frequencies. Fixation of the stapes generally resulted in a relatively small low-frequency increase in ℛ. Disarticulation of the incus with the stapes led to a consistent low-frequency decreases in ℛ with a distinctive minimum below 1000 Hz. Perforations of the tympanic membrane resulted in a decrease in ℛ for frequencies up to about 2000 Hz; at these lower frequencies, smaller perforations led to larger changes from normal as compared to larger perforations.
These preliminary measurements help assess the utility of power reflectance as a diagnostic tool for middle-ear disorders. In particular, the measurements document (1) the frequency ranges for which the changes are largest and (2) the extent of the changes from normal for a spectrum of middle-ear disorders.
PMCID: PMC3718455  PMID: 22037477
middle ear; reflectance; cadaver measurements; transmittance
19.  Effect of Middle Ear Fluid on Sound Transmission and Auditory Brainstem Response in Guinea Pigs 
Hearing research  2011;277(1-2):96-106.
Combined measurements of middle ear transfer function and auditory brainstem response (ABR) in live guinea pigs with middle ear effusion (MEE) are reported in this paper. The MEE model was created by injecting saline into the middle ear cavity. Vibrations of the tympanic membrane (TM), the tip of the incus, and the round window membrane (RWM) were measured with a laser vibrometer at frequencies of 0.2-40 kHz when the middle ear fluid increased from 0 to 0.2 ml (i.e., full fill of the cavity). The click and pure tone ABRs were recorded as the middle ear fluid increased. Fluid introduction reduced mobility of the TM, incus and RWM mainly at high frequencies (f > 1 kHz). The magnitude of this reduction was related to the volume of fluid. The displacement transmission ratio of the TM to incus varied with frequency and fluid level. The volume displacement ratio of the oval window to round window was approximately 1.0 over most frequencies. Elevation of ABR thresholds and prolongation of ABR latencies were observed as fluid level increased. Reduction of TM displacement correlated well with elevation of ABR threshold at 0.5-8 kHz. Alterations in the ratio of ossicular displacements before and after fluid induction are consistent with fluid-induced changes in complex ossicular motions.
PMCID: PMC3137689  PMID: 21414396
middle ear effusion; middle ear transfer function; laser vibrometer; auditory brainstem response
20.  Comparison of Eardrum Mobility in Acute Otitis Media and Otitis Media with Effusion Models 
To investigate the eardrum mobility difference between acute otitis media (AOM) and experimental otitis media with effusion (OME).
Animal models
Thirty-three Hartley guinea pigs were included in this study. The AOM and OME were created by transbullar injection of Streptococcus pneumoniae and lipopolysaccharide into the middle ear, respectively.
Main Outcome Measures
Three days post inoculation, the morphological changes of the middle ear were assessed with otoscopy and histological sections. Vibrations of the tympanic membrane (TM) at umbo in response to pure tone sound were measured using laser Doppler vibrometry.
The purulent effusion, ossicular adhesion, and thickened TM and middle ear mucosa were observed in the AOM ears, and the OME ears had serous effusion and less thickened TM and mucosa in the middle ear. The displacement of TM in AOM was lower than that in OME ears, especially at 0.2–4 kHz.
The TM mobility difference between the AOM and OME ears were mainly caused by the middle ear ossicular structure changes during the bacterial infection in AOM.
PMCID: PMC3744608  PMID: 23921936
acute otitis media; otitis media with effusion; middle ear; eardrum mobility
21.  Sound transmission along the ossicular chain in common wild-type laboratory mice 
Hearing research  2012;301:27-34.
The use of genetically modified mice can accelerate progress in auditory research. However, the fundamental profile of mouse hearing has not been thoroughly documented. In the current study, we explored mouse middle ear transmission by measuring sound-evoked vibrations at several key points along the ossicular chain using a laser-Doppler vibrometer. Observations were made through an opening in pars flaccida. Simultaneously, the pressure at the tympanic membrane close to the umbo was monitored using a micro-pressure-sensor. Measurements were performed in C57BL mice, which are widely used in hearing research. Our results show that the ossicular local transfer function, defined as the ratio of velocity to the pressure at the tympanic membrane, was like a high-pass filter, almost flat at frequencies above ~15 kHz, decreasing rapidly at lower frequencies. There was little phase accumulation along the ossicles. Our results suggested that the mouse ossicles moved almost as a rigid body. Based on these 1-dimensional measurements, the malleus–incus-complex primarily rotated around the anatomical axis passing through the gonial termination of the anterior malleus and the short process of the incus, but secondary motions were also present.
PMCID: PMC3669248  PMID: 23183032
22.  Ear-Canal Reflectance, Umbo Velocity and Tympanometry in Normal Hearing Adults 
Ear and hearing  2012;33(1):19-34.
This study compares measurements of ear-canal reflectance (ECR) to other objective measurements of middle-ear function including, audiometry, umbo velocity (VU), and tympanometry in a population of strictly defined normal hearing ears.
Data were prospectively gathered from 58 ears of 29 normal hearing subjects, 16 female and 13 male, aged 22–64 years. Subjects met all of the following criteria to be considered as having normal hearing. (1) No history of significant middle-ear disease. (2) No history of otologic surgery. (3) Normal tympanic membrane (TM) on otoscopy. (4) Pure-tone audiometric thresholds of 20 dB HL or better for 0.25 – 8 kHz. (5) Air-bone gaps no greater than 15 dB at 0.25 kHz and 10 dB for 0.5 – 4 kHz. (6) Normal, type-A peaked tympanograms. (7) All subjects had two “normal” ears (as defined by these criteria). Measurements included pure-tone audiometry for 0.25 – 8 kHz, standard 226 Hz tympanometry, Ear canal reflectance(ECR) for 0.2 – 6 kHz at 60 dB SPL using the Mimosa Acoustics HearID system, and Umbo Velocity (VU ) for 0.3 – 6 kHz at 70–90 dB SPL using the HLV-1000 laser Doppler vibrometer (Polytec Inc).
Mean power reflectance (|ECR|2) was near 1.0 at 0.2– 0.3 kHz, decreased to a broad minimum of 0.3 to 0.4 between 1 and 4 kHz, and then sharply increased to almost 0.8 by 6 kHz. The mean pressure reflectance phase angle (∠ECR) plotted on a linear frequency scale showed a group delay of approximately 0.1 ms for 0.2 – 6 kHz. Small significant differences were observed in |ECR|2 at the lowest frequencies between right and left ears, and between males and females at 4 kHz. |ECR|2 decreased with age, but reached significance only at 1 kHz. Our ECR measurements were generally similar to previous published reports. Highly significant negative correlations were found between |ECR|2 and VU for frequencies below 1 kHz. Significant correlations were also found between the tympanometrically determined peak total compliance and |ECR|2 and The results suggest that middle-ear compliance VU at frequencies below 1 kHz. contributes significantly to the measured power reflectance and umbo velocity at frequencies below 1 kHz, but not at higher frequencies.
This study has established a database of objective measurements of middle ear function (ear-canal reflectance, umbo velocity, tympanometry) in a population of strictly defined normal hearing ears. The data will promote our understanding of normal middle ear function, and will serve as a control for comparison to similar measurements made in pathological ears.
PMCID: PMC3223546  PMID: 21857517
23.  Experimental measurement of tympanic membrane response for finite element model validation of a human middle ear 
SpringerPlus  2013;2:527.
The middle ear consists of a tympanic membrane, ligaments, tendons, and three ossicles. An important function of the tympanic membrane is to deliver exterior sound stimulus to the ossicles and inner ear. In this study, the responses of the tympanic membrane in a human ear were measured and compared with those of a finite element model of the middle ear. A laser Doppler vibrometer (LDV) was used to measure the dynamic responses of the tympanic membrane, which had the measurement point on the cone of light of the tympanic membrane. The measured subjects were five Korean male adults and a cadaver. The tympanic membranes were stimulated using pure-tone sine waves at 18 center frequencies of one-third octave band over a frequency range of 200 Hz ~10 kHz with 60 and 80 dB sound pressure levels. The measured responses were converted into the umbo displacement transfer function (UDTF) with a linearity assumption. The measured UDTFs were compared with the calculated UDTFs using a finite element model for the Korean human middle ear. The finite element model of the middle ear consists of three ossicles, a tympanic membrane, ligaments, and tendons. In the finite element model, the umbo displacements were calculated under a unit sound pressure on the tympanic membrane. The UDTF of the finite element model exhibited good agreement with that of the experimental one in low frequency range, whereas in higher frequency band, the two response functions deviated from each other, which demonstrates that the finite element model should be updated with more accurate material properties and/or a frequency dependent material model.
PMCID: PMC3806984  PMID: 24171153
Laser doppler vibrometer (LDV); Tympanic membrane; Middle ear; Umbo displacement transfer function (UDTF); Finite element model
24.  Investigation of a Novel Completely-In-The-Canal Direct-Drive Hearing Device: A Temporal Bone Study 
Whether a prototype direct-drive hearing device (DHD) is effective in driving the tympanic membrane (TM) in a temporal bone specimen to enable it to potentially treat moderate to severe hearing loss.
Patient satisfaction with air conduction hearing aids has been low due to sound distortion, occlusion effect, and feedback issues. Implantable hearing aids provide a higher quality sound, but require surgery for placement. The DHD was designed to combine the ability of driving the ossicular chain with placement in the external auditory canal.
DHD is a 3.5 mm wide device that could fit entirely into the bony ear canal and directly drive the TM rather than use a speaker. A cadaveric temporal bone was prepared. The device developed in our laboratory was coupled to the external surface of the TM and against the malleus. Frequency sweeps between 300 Hz to 12 kHz were performed in two different coupling methods at 104 and 120 dB, and the DHD was driven with various levels of current. Displacements of the posterior crus of the stapes were measured using a Laser Doppler Vibrometer.
The DHD showed a linear frequency response from 300Hz to 12kHz. Placement against the malleus showed higher amplitudes and lower power requirements than when the device was placed on the TM.
DHD is a small completely-in-the-canal device that mechanically drives the TM. This novel device has a frequency output wider than most air conduction devices. Findings of the current study demonstrated that the DHD had the potential of being incorporated into a hearing aid in the future.
PMCID: PMC3530668  PMID: 23202151
25.  Analysis of chick (Gallus gallus) middle ear columella formation 
The chick middle ear bone, the columella, provides an accessible model in which to study the tissue and molecular interactions necessary for induction and patterning of the columella, as well as associated multiple aspects of endochondral ossification. These include mesenchymal condensation, chondrogenesis, ossification of the medial footplate and shaft, and joint formation between the persistent cartilage of the extracolumella and ossified columella. Middle and external ear defects are responsible for approximately 10% of congenital hearing defects. Thus, understanding the morphogenesis and the molecular mechanisms of the formation of the middle ear is important to understanding normal and abnormal development of this essential component of the hearing apparatus.
The columella, which arises from proximal ectomesenchyme of the second pharyngeal arch, is induced and patterned in a dynamic multi-step process. From the footplate, which inserts into the inner ear oval window, the shaft spans the pneumatic middle ear cavity, and the extracolumella inserts into the tympanic membrane. Through marker gene and immunolabeling analysis, we have determined the onset of each stage in the columella's development, from condensation to ossification. Significantly, a single condensation with the putative shaft and extracolumella arms already distinguishable is observed shortly before initiation of five separate chondrogenic centers within these structures. Ossification begins later, with periosteum formation in the shaft and, unexpectedly, a separate periosteum in the footplate.
The data presented in this study document the spatiotemporal events leading to morphogenesis of the columella and middle ear structures and provide the first gene expression data for this region. These data identify candidate genes and facilitate future functional studies and elucidation of the molecular mechanisms of columella formation.
PMCID: PMC2834582  PMID: 20158901

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