Signal and morphological changes in the endolymph of patients with vestibular schwannoma on non-contrast 3D FLAIR at 3 Tesla.

BACKGROUND: Non-contrast FLAIR revealed increased signal within the inner ear in patients with vestibular schwannoma, which is generally assumed to occur in the perilymph; however, the majority of previous studies did not differentiate between the endolymph and perilymph. Therefore, endolymph signal changes have not yet been investigated in detail. The purpose of the present study was three-fold: (1) to assess perilymph signal changes in patients with vestibular schwannoma on heavily T2-weighted (T2W) 3D FLAIR, also termed positive perilymphatic images (PPI), (2) to evaluate signal and morphological changes in the endolymph on PPI, and (3) to establish whether vertigo correlates with the signal intensity ratios (SIR) of the vestibular perilymph or vestibular endolymphatic hydrops. METHODS: Forty-two patients with unilateral vestibular schwannoma were retrospectively recruited. We semi-quantitatively and qualitatively evaluated the perilymph signal intensity on the affected and unaffected sides. We also quantitatively examined the signal intensity of the vestibular perilymph and assessed the relationship between vertigo and the SIR of the vestibular perilymph on the affected side. We semi-quantitatively or qualitatively evaluated the endolymph, and investigated whether vestibular hydrops correlated with vertigo. RESULTS: The perilymph on the affected side showed abnormal signal more frequently (signal intensity grade: overall mean 1.45 vs. 0.02; comparison of signal intensity: overall mean 36 vs. 0 cases) and in more parts (the entire inner ear vs. the basal turn of the cochlea and vestibule) than that on the unaffected side. No significant difference was observed in the SIR of the vestibular perilymph with and without vertigo (5.54 vs. 5.51, p = 0.18). The endolymph of the vestibule and semicircular canals showed the following characteristic features: no visualization (n = 4), signal change (n = 1), or vestibular hydrops (n = 10). A correlation was not observed between vestibular hydrops and vertigo (p = 1.000). CONCLUSIONS: PPI may provide useful information on signal and morphological changes in the endolymph of patients with vestibular schwannoma. Further research is warranted to clarify the relationship between vertigo and the MR features of the inner ear.

Evaluation of the blood-perilymph barrier in ears with endolymphatic hydrops.

BACKGROUND: Otological diseases including Meniere's disease (MD) involve endolymphatic hydrops (EH), which can be visualized by magnetic resonance imaging (MRI) with gadolinium contrast agents, but the temporal changes of contrast in the inner ear have not been evaluated. OBJECTIVES: We investigated the permeability of the blood-perilymph barrier (BPB) in ears with EH to evaluate the severity of the inner ear disturbances. MATERIALS AND METHODS: The study included 32 ears from 16 patients with EH or related diseases who underwent MRI. The permeability of the BPB was assessed by the signal-intensity ratio (SIR) at four-time points: before and at 10 min, 4 h, and 24 h after administration of gadolinium for assessing EH. RESULTS: Cochlear EH was found in 25 of the 32 ears, and vestibular EH in 11. The rate of EH was significantly higher in symptomatic ears; however, the existence of EH was not related to SIR values. Nevertheless, SIR values in the basal turn were significantly higher 4 and 24 h after injection of gadolinium in patients aged ≥50 years. CONCLUSION AND SIGNIFICANCE: Higher SIR values observed in older patients with EH indicate severe disturbances of the BPB in the cochlea, which may account for intractable inner ear disturbances in older patients.

Chaotic Dynamics Enhance the Sensitivity of Inner Ear Hair Cells.

Hair cells of the auditory and vestibular systems are capable of detecting sounds that induce sub-nanometer vibrations of the hair bundle, below the stochastic noise levels of the surrounding fluid. Furthermore, the auditory system exhibits a highly rapid response time, in the sub-millisecond regime. We propose that chaotic dynamics enhance the sensitivity and temporal resolution of the hair bundle response, and we provide experimental and theoretical evidence for this effect. We use the Kolmogorov entropy to measure the degree of chaos in the system and the transfer entropy to quantify the amount of stimulus information captured by the detector. By varying the viscosity and ionic composition of the surrounding fluid, we are able to experimentally modulate the degree of chaos observed in the hair bundle dynamics in vitro. We consistently find that the hair bundle is most sensitive to a stimulus of small amplitude when it is poised in the weakly chaotic regime. Further, we show that the response time to a force step decreases with increasing levels of chaos. These results agree well with our numerical simulations of a chaotic Hopf oscillator and suggest that chaos may be responsible for the high sensitivity and rapid temporal response of hair cells.

The role of monocytes and macrophages in the dynamic permeability of the blood-perilymph barrier.

The blood-perilymph barrier serves a critical role by separating the components of blood from inner ear fluids, limiting traffic of cells, proteins and other solutes into the labyrinth, and allowing gas (O2-CO2) exchange. Inflammation produces changes in the blood-perilymph barrier resulting in increased vascular permeability. It is commonly thought that compromise of the blood-inner ear barrier would lead to hearing impairment through loss of the endocochlear potential (EP). In fact, the effect of increasing cochlear vascular permeability on hearing function and EP is poorly understood. We used a novel method to measure the integrity of the blood-perilymph barrier and demonstrated the effects of barrier compromise on ABR threshold and EP. We also investigated the contribution of CX3CR1 cochlear macrophages and CCR2 inflammatory monocytes to barrier function after systemic exposure to lipopolysaccharide (LPS). We found that systemic LPS induced a profound change in vascular permeability, which correlated with minimal change in ABR threshold and EP. Macrophage depletion using CX3CR1-DTR mice did not alter the baseline permeability of cochlear vessels and resulted in preservation of barrier function in LPS-treated animals. We conclude that cochlear macrophages are not required to maintain the barrier in normal mice and activated macrophages are a critical factor in breakdown of the barrier after LPS. CCR2 null mice demonstrated that LPS induction of barrier leakiness occurs in the absence of CCR2 expression. Thus, enhanced aminoglycoside ototoxicity after LPS can be linked to the expression of CCR2 in inflammatory monocytes, and not to preservation of the blood-perilymph barrier in CCR2 knockout mice.

Development and performance of a biomimetic artificial perilymph for in vitro testing of medical devices.

OBJECTIVE: Cochlear implants interface with the fluid in the cochlea called perilymph. The volume of this fluid present in human and animal model cochlea is prohibitively low for isolation for in vitro studies. Thus, there is a need for an artificial perilymph that reflects the complexity of this fluid in terms of competitive protein adsorption. APPROACH: This study established a biomimetic artificial perilymph (BAP) comprising serum albumin, immunoglobulin G, transferrin, inter-alpha-trypsin inhibitor, apolipoprotein A1 and complement C3 to represent the major components of human perilymph. Adsorption of the BAP components to platinum was analysed. MAIN RESULTS: It was established that this six component BAP provided competitive and complex adsorption behaviours consistent with biologically derived complex fluids. Additionally, adsorption of the BAP components to platinum cochlear electrodes resulted in a change in polarisation impedance consistent with that observed for the cochlear device in vivo. SIGNIFICANCE: This study established a BAP fluid suitable for furthering the understanding of the implant environment for electroactive devices that interface with the biological environment.

Cochlear potential difference between endolymph fluid and the hair cell's interior: a retold interpretation based on the Goldman equation.

Reported cochlear potential values of near 150 mV are often attributed to endolymph itself, although membrane potentials result from ion fluxes across the adjacent semipermeable membranes due to concentration gradients. Since any two fluids separated by a semipermeable membrane develop potential due to differences in solute concentrations, a proposed interpretation here is that positive potential emanates from the Reissner membrane due to small influx of sodium from perilymph to endolymph. Basolateral hair cell membranes leak potassium into the interstitial fluid and this negative potential inside hair cells further augments the electric gradient of cochlear potential. Taken together as a sum, these two potentials are near the reported values of cochlear potential. This is based on reported data for cochlear fluids used for the calculation of Nernst and Goldman potentials. The reported positive potential of Reissner membrane can be explained almost entirely by the traffic of Na+ that enters endolymph through this membrane. At the apical membrane of hair cells, acoustic stimulation modulates stereocillia permeability to potassium. Potassium concentration gradients on the apical membrane are low (the calculated Nernst value is <+3 mV), suggesting that the potassium current is not caused by the local potassium concentration gradient, but an electric field between the positive sodium generated potential on the Reissner membrane and negative inside hair cells. Potassium is forced by this overall electric field to enter hair cells when stereocilia are permeable due to mechanical bending.

Human cochlear hydrodynamics: A high-resolution µCT-based finite element study.

Measurements of perilymph hydrodynamics in the human cochlea are scarce, being mostly limited to the fluid pressure at the basal or apical turn of the scalae vestibuli and tympani. Indeed, measurements of fluid pressure or volumetric flow rate have only been reported in animal models. In this study we imaged the human ear at 6.7 and 3-µm resolution using µCT scanning to produce highly accurate 3D models of the entire ear and particularly the cochlea scalae. We used a contrast agent to better distinguish soft from hard tissues, including the auditory canal, tympanic membrane, malleus, incus, stapes, ligaments, oval and round window, scalae vestibule and tympani. Using a Computational Fluid Dynamics (CFD) approach and this anatomically correct 3D model of the human cochlea, we examined the pressure and perilymph flow velocity as a function of location, time and frequency within the auditory range. Perimeter, surface, hydraulic diameter, Womersley and Reynolds numbers were computed every 45° of rotation around the central axis of the cochlear spiral. CFD results showed both spatial and temporal pressure gradients along the cochlea. Small Reynolds number and large Womersley values indicate that the perilymph fluid flow at auditory frequencies is laminar and its velocity profile is plug-like. The pressure was found 102-106° out of phase with the fluid flow velocity at the scalae vestibule and tympani, respectively. The average flow velocity was found in the sub-µm/s to nm/s range at 20-100Hz, and below the nm/s range at 1-20kHz.

Cochlear perfusion with a viscous fluid.

The flow of viscous fluid in the cochlea induces shear forces, which could provide benefit in clinical practice, for example to guide cochlear implant insertion or produce static pressure to the cochlear partition or wall. From a research standpoint, studying the effects of a viscous fluid in the cochlea provides data for better understanding cochlear fluid mechanics. However, cochlear perfusion with a viscous fluid may damage the cochlea. In this work we studied the physiological and anatomical effects of perfusing the cochlea with a viscous fluid. Gerbil cochleae were perfused at a rate of 2.4 µL/min with artificial perilymph (AP) and sodium hyaluronate (Healon, HA) in four different concentrations (0.0625%, 0.125%, 0.25%, 0.5%). The different HA concentrations were applied either sequentially in the same cochlea or individually in different cochleae. The perfusion fluid entered from the round window and was withdrawn from basal scala vestibuli, in order to perfuse the entire perilymphatic space. Compound action potentials (CAP) were measured after each perfusion. After perfusion with increasing concentrations of HA in the order of increasing viscosity, the CAP thresholds generally increased. The threshold elevation after AP and 0.0625% HA perfusion was small or almost zero, and the 0.125% HA was a borderline case, while the higher concentrations significantly elevated CAP thresholds. Histology of the cochleae perfused with the 0.0625% HA showed an intact Reissner's membrane (RM), while in cochleae perfused with 0.125% and 0.25% HA RM was torn. Thus, the CAP threshold elevation was likely due to the broken RM, likely caused by the shear stress produced by the flow of the viscous fluid. Our results and analysis indicate that the cochlea can sustain, without a significant CAP threshold shift, up to a 1.5 Pa shear stress. Beside these finding, in the 0.125% and 0.25% HA perfusion cases, a temporary CAP threshold shift was observed, perhaps due to the presence and then clearance of viscous fluid within the cochlea, or to a temporary position shift of the Organ of Corti. After 0.5% HA perfusion, a short latency positive peak (P0) appeared in the CAP waveform. This P0 might be due to a change in the cochlea's traveling-wave pattern, or distortion in the cochlear microphonic.

Endolymphatic hydrops in superior canal dehiscence and large vestibular aqueduct syndromes.

OBJECTIVES/HYPOTHESIS: Pathologic third window lesions, such as superior semicircular canal dehiscence syndrome (SCDS) or large vestibular aqueduct syndrome (LVAS), cause several auditory and vestibular symptoms, which might affect perilymphatic pressure and induce endolymphatic hydrops (EH). In this study, the existence of EH in subjects with SCDS or LVAS was investigated using contrast-enhanced magnetic resonance imaging (MRI). STUDY DESIGN: Case series at university hospital. METHODS: Seventeen ears from nine subjects who were diagnosed as having SCDS (five ears from three cases) or LVAS (12 ears from six cases) were studied. Ears were evaluated by 3-T MRI performed 4 hours after intravenous injection of gadodiamide hydrate. Imaging data concerning the degree of EH in the cochlea and the vestibule were compared with clinical symptoms and hearing levels for all ears. RESULTS: All ears showed air-bone gaps at low frequencies on pure tone audiometry. None of the subjects with SCDS had episodes of acute sensorineural hearing loss (SNHL) or vestibular symptoms, except for one patient who complained of head vibration induced by loud noise. Conversely, five of six subjects with LVAS had episodes of acute SNHL or vestibular symptoms. Four of five ears with SCDS showed severe EH in the cochlea, and two ears showed mild EH in the vestibule. All ears with LVAS showed mild to severe EH in both the cochlea and vestibule. CONCLUSIONS: The present study demonstrated the existence of EH in ears with pathologic third window lesions, which might affect patients' auditory or vestibular symptoms. LEVEL OF EVIDENCE: 4 Laryngoscope, 126:1446-1450, 2016.

Oval Window Temperature Changes in an Endoscopic Stapedectomy.

OBJECTIVES: Following the initial use of endoscopes in otology, the pros and cons of these instruments have been questioned increasingly. These instruments cause an increase in temperature that needs to be investigated. In this study, the authors aimed to investigate the temperature increase caused by endoscopes and light sources in the perilymph by performing a stapedotomy in an animal model under anesthesia. STUDY DESIGN: The study was performed in a guinea pig model. METHODS: In the animal model, a simulated otologic stapes surgery was performed at room temperature. The body temperatures of the guinea pigs were monitored; the temperature increase caused by the 0-degree rigid endoscopes with diameters of 3 and 4  mm as well as the light sources, including halogen, light-emitting diode (LED), and xenon lamps, were monitored following the stapedotomy to measure and document the continuous temperature increase in the perilymph using sensors placed at the oval window. RESULTS: Rigid endoscopes cause a temperature increase in the tympanum regardless of their diameter when used with xenon and halogen light sources. The LED light caused a relatively small temperature increase. CONCLUSIONS: The endoscopic instruments used in the stapes operation caused a temperature increase in the oval window. The authors concluded that this heat could easily be transmitted to the cochlea by the perilymph, which has obstructed contact with the outer environment following stapedomy, resulting in neurosensorial damage.

[Direct acoustic cochlear stimulation for therapy of severe to profound mixed hearing loss: Codacs™ Direct Acoustic Cochlear Implant System]. / Direkte akustische cochleäre Stimulation für die Therapie der hochgradigen kombinierten Schwerhörigkeit: Codacs™ Direct Acoustic Cochlear Implant System.

OBJECTIVE: Implantable hearing aids have become a valid option for the therapy of various forms of hearing loss. The Codacs™ Direct Acoustic Cochlear Implant System is the first vibratory implant available for patients with severe to profound mixed hearing loss (MHL). By directly coupling sound energy into the perilymph, a very high maximum power output (MPO) is achieved over a broad frequency range. Via a conventional stapedotomy, the vibratory energy of the electromagnetic actuator is transferred directly to the perilymph through the oval window. PATIENTS AND METHODS: This article describes the technical principle, basic surgical aspects and audiological outcomes of two clinical studies. Additional coupling procedures and extensions to the spectrum of indications are also discussed. Surgically, the two-component system can either be implanted via a purely transmastoid approach with posterior tympanotomy, or additionally via transmeatal access to the stapes footplate. Pre- and postoperative audiological results of patients wearing conventional hearing aids and with severe to profound MHL, who were implanted with the Codacs™ system at the Medical University Hannover, were compared. RESULTS: Significant improvements over conventional hearing aids could be achieved with initial bone conduction thresholds between 44 and 63 dB HL (Ø 54 dB HL) and an air-bone gap between 19 and 51 dB HL (Ø 34 dB HL) in patients with MHL caused by advanced otosclerosis or tympanosclerosis and an intact posterior wall of the auditory canal. The mean functional gain was 50 ± 9 dB (0.5-4 kHz) and the monosyllabic word score was 85% at 65 dB presentation level compared to conventional hearingaids with 25%. Speech intelligibility in noise (S0N0) improved by 7.1 to Ø 0.3 dB SNR with Codacs™. The mean bone conduction threshold remained unchanged or showed a minimal increase in the low-frequency range. CONCLUSION: The CODACS system provides an effective new treatment for patients with severe to profound MHL for the first time.

Improving cochlear implant properties through conductive hydrogel coatings.

Conductive hydrogel (CH) coatings for biomedical electrodes have shown considerable promise in improving electrode mechanical and charge transfer properties. While they have desirable properties as a bulk material, there is limited understanding of how these properties translate to a microelectrode array. This study evaluated the performance of CH coatings applied to Nucleus Contour Advance cochlear electrode arrays. Cyclic voltammetry and biphasic stimulation were carried out to determine electrical properties of the coated arrays. Electrical testing demonstrated that CH coatings supported up to 24 times increase in charge injection limit. Reduced impedance was also maintained for over 1 billion stimulations without evidence of delamination or degradation. Mechanical studies performed showed negligible effect of the coating on the pre-curl structure of the Contour Advance arrays. Testing the coating in a model human scala tympani confirmed that adequate contact was maintained across the lateral wall. CH coatings are a viable, stable coating for improving electrical properties of the platinum arrays while imparting a softer material interface to reduce mechanical mismatch. Ultimately, these coatings may act to minimize scar tissue formation and fluid accumulation around electrodes and thus improve the electrical performance of neural implants.

The effect of rocking stapes motions on the cochlear fluid flow and on the basilar membrane motion.

The basilar membrane (BM) and perilymph motion in the cochlea due to rocking stapes motion (RSM) and piston-like stapes motion (PSM) is modeled by numerical simulations. The full Navier-Stokes equations are solved in a two-dimensional box geometry. The BM motion is modeled by independent oscillators using an immersed boundary technique. The traveling waves generated by both stimulation modes are studied. A comparison of the peak amplitudes of the BM motion is presented and their dependence on the frequency and on the model geometry (stapes position and cochlear channel height) is investigated. It is found that the peak amplitudes for the RSM are lower and decrease as frequency decreases whereas those for the PSM increase as frequency decreases. This scaling behavior can be explained by the different mechanisms that excite the membrane oscillation. Stimulation with both modes at the same time leads to either a slight increase or a slight decrease of the peak amplitudes compared to the pure PSM, depending on the phase shift between the two modes. While the BM motion is dominated by the PSM mode under normal conditions, the RSM may lead to hearing if no PSM is present or possible, e.g., due to round window atresia.

The enigmatic root cell - emerging roles contributing to fluid homeostasis within the cochlear outer sulcus.

Despite their curious morphology prompting numerous hypotheses of their normal function, the root cells lining the cochlear outer sulcus have long evaded physiological characterization. A growing body of evidence now suggests that they regulate the solute content of the endolymph and/or the perilymph, and may be essential in safe-guarding the global homeostasis of the cochlea. Immuno-labeling experiments have demonstrated polarized expression of key ion transport proteins, and recent electrophysiological recordings have identified specific membrane conductances. These studies have painted a clearer picture of how this unusual cell type may contribute to the maintenance of sound transduction, and how they may be central to pathological processes associated with various forms of hearing loss. This article is part of a Special Issue entitled "Annual Reviews 2013".

Influence of an intraoperative perilymph gusher on cochlear implant performance in children with labyrinthine malformations.

OBJECTIVES: To assess the effect of an intraoperative perilymph fluid gusher during cochlear implantation on speech perception abilities in pediatric patients with labyrinthine anomalies. SETTING: Tertiary care academic referral center. METHODS: Seventy subjects with labyrinthine malformations who received a cochlear implant were identified in our pediatric cochlear implant database. In 30 cases, an intraoperative perilymph fluid gusher was encountered during surgery. Fifteen children with GJB2 positive hereditary hearing loss served as controls. Multiple speech perception measures were obtained with the cochlear implant. The best score for each subject over time was determined as a speech reception index in quiet. This index was compared among groups and malformation types. RESULTS: The speech reception index in quiet demonstrated overall good performance scores of cochlear implantation in children with incomplete partitioning/enlarged vestibular aqueduct type malformations. Children with hypoplastic malformations, on the other hand, showed variable outcomes with many children demonstrating only limited long-term speech discrimination abilities. The presence or absence of a perilymph gusher did not significantly influence results after cochlear implantation. CONCLUSION: This report documents the variable outcomes of pediatric cochlear implantation in children with inner ear malformations. More importantly, anatomic parameters, such as the classification of the anomaly and the presence of a viable cochlear nerve, seem to influence performance measures substantially. The presence of a perilymph gusher did not influence outcomes in both hypoplastic and incomplete partitioning/enlarged vestibular aqueduct type malformations. LEVEL OF EVIDENCE: 2b Individual retrospective cohort study.

Differences in the perilymph fluid stimulation before and after experimental stapedotomy.

A stapedotomy surgery using a piston stapes prosthesis significantly modifies the perilymph fluid stimulation level and always leads to alteration of conditions in sound transmission through the cochlea. This paper shows the results of non-contact measurements of the stapes head velocity, a Teflon piston stapes prosthesis velocity and round window velocity conducted in freshly harvested human cadaver temporal bone specimens. The vibration patterns were measured within the frequency range of 0.4-10 kHz at the sound pressure level of 90 dB administered to the external auditory canal in the same specimen before and after experimental stapedotomy. It was shown that the vibrations of the stapes Teflon piston prosthesis and the physiological stapes are similar and approximately five-fold lower amplitude of the round window membrane vibrations compared to a physiologic situation is caused by piston shape of the stapes prosthesis. The results in this report are the part of a larger study designed to develop a new type of chamber stapes or whole middle ear prosthesis.

Electrophysiological monitoring of hearing function during cochlear perilymphatic perfusions.

CONCLUSION: The cochlear perilymphatic perfusion produces, by itself, significant effects in the cochlear physiology that could be associated with the surgical procedure. These effects need to be well characterized to allow a reliable quantification of the effects of the experimental agent being tested. OBJECTIVES: The study focused on the accurate description of the electrophysiological effects on the cochlear potential recordings of perilymphatic perfusions. METHODS: Two successive cochlear perilymphatic perfusions were carried out. The first used artificial perilymph. The second used artificial perilymph alone or a kainic acid (KA) solution in artificial perilymph. The compound action potential of the auditory nerve (CAP-AN) was recorded: (1) before the first perfusion, (2) after the first perfusion and (3) after the second perfusion, and compared between groups. RESULTS: The first intracochlear perfusion with artificial perilymph produced significant effects in the CAP-AN that could be related to the surgical procedure. These effects were analysed separately from the effects produced by the KA. In particular, the KA administered intracochlearly produced a significant increase in the latency and a decrease in the amplitude of the CAP-AN N1 wave compared with the controls that were perfused twice with artificial perilymph.

Ear canal pressure variations versus negative middle ear pressure: comparison using distortion product otoacoustic emission measurement in humans.

OBJECTIVE: For more than a century, positive and/or negative ear canal air pressure (ECP) has often been employed to simulate negative middle ear pressure (MEP) in exploring the latter's effect on hearing sensitivity and outcomes of various physiological assessments of the auditory system. However, systematic investigation is lacking on validation of these practices. This study was aimed at comparing these air pressure variations in humans in terms of effect on distortion product otoacoustic emissions (DPOAEs) and discussing certain issues pertaining to the middle ear transfer function. DESIGN: The 2f1 - f2 DPOAE was measured for nine f2 frequencies from 600 to 8000 Hz in 27 adult ears under four air pressure conditions: normal MEP, negative MEP, and positive and negative ECPs. The subjects voluntarily induced negative MEPs with magnitudes ranging from -40 to -420 daPa, as estimated by the tympanometric peak pressure. For each negative MEP, positive and negative ECPs were applied, respectively, at the same magnitude in absolute value as the negative MEP after it was equalized. Negative MEP and ECP variations were compared in terms of change in DPOAE level. RESULTS: Positive ECP resembled negative MEP, showing a distinct frequency-specific model of effect on DPOAE level: (1) DPOAEs were attenuated the greatest for frequencies at and below 1000 Hz, which increased from 4-6 to 10-12 dB with increasing the pressure for the tested range; (2) DPOAE attenuation decreased with increasing frequency and was minimal at 2000 Hz; and (3) DPOAE level significantly declined for the frequencies between 2000 and 6000 Hz and tended to increase for high frequencies. Compared with a negative MEP, an equivalent negative ECP yielded a smaller reduction of DPOAE levels for frequencies below 2000 Hz, as well as 3000 Hz, but greater reduction for frequencies above 4000 Hz. One phenomenon that occurred under all three air pressures was a minimal change of the DPOAE level at 2000 Hz. This resulted in a peak at 2000 Hz in the DPOAE level change versus frequency function. CONCLUSIONS: Effects of negative MEP and ECP variations on DPOAEs in human ears are comparable, to a great extent, to findings from previous studies on hearing sensitivity in humans and tympanic membrane vibration at the umbo in human temporal bones. The present study demonstrates that positive ECP can be used to simulate negative MEP in research on the middle ear function in live humans. Results also suggest that long-lasting beliefs regarding the ECP effect on the middle ear conduction should be amended: (1) only positive ECP, not negative ECP, attenuates sound transmission more for low frequencies than for high frequencies, and (2) positive ECP has a greater effect than negative ECP only for low frequencies and not for high frequencies. Discussion of the present results together with those from previous studies sheds light on the middle ear dynamics under diverse pressure changes across the tympanic membrane and proposes that distorted configuration of the tympanic membrane and ossicular chain is the key factor in the effect of MEP or ECP on the middle ear sound transmission for low frequencies.

Cochlin-tomoprotein (CTP) detection test identifies traumatic perilymphatic fistula due to penetrating middle ear injury.

CONCLUSIONS: The cochlin-tomoprotein (CTP) detection test can be used to make a definite, objective diagnosis of traumatic perilymphatic fistula (PLF), and therefore offers valuable information on patient selection for surgical treatment. OBJECTIVES: Penetrating middle ear injury can cause traumatic PLF, which is a surgically treatable otologic emergency. Recently, we have reported on CTP, a novel perilymph-specific protein. The purpose of this study was to determine if the CTP detection test is useful for the diagnosis of traumatic PLF. METHODS: This was a prospective study of CTP detection in penetrating middle ear injury cases with tympanic membrane perforation and hearing loss. RESULTS: A total of seven individuals were included in this study. CTP was detected in three of four cases with posterosuperior quadrant perforation of the tympanic membrane. In one of these three cases, even though the high resolution CT scan was not suggestive of PLF and the perilymph leakage could not be visualized intraoperatively, the CTP detection test was able to detect PLF. In two cases, the preoperative positive test results enabled us to make a diagnosis of PLF and a decision for surgical treatment. CTP was not detected in the cases with anterior or inferior tympanic membrane perforation.

[Traumatic perilymphatic fistulae : about 13 cases]. / Fistules péri lymphatiques post traumatiques : a propos 13 cas.

BACKGROUND: Post-traumatic peri-lymphatic fistulas have been described following ear and temporal bone injury, particularly in the setting of temporal bone fractures. The symptoms and signs of perilymphatic fistulae (PLF) are very varied and frequently misleading. The diagnosis can be suspected on the bases of the clinical and the audiometrial findings. Indications for exploratory surgery in cases of trauma are vague and not well described. AIM: To assess the principal clinical and radiologic signs of PLF. METHOD: Study of 13 patients with different symptoms of posttraumatic peri-lymphatic fistulae. RESULTS: Ten patients had vertigo, and 2 presented otoliquorreha. Two patients had tympanic perforation. Nine patients presented neurosensorinal hearing loss and 5 were completely deaf. A CT Scann was realized in 12 cases and showed the fracture in 10 cases (91%) with a pneumolabyrinth in 4 cases. Medical and postural treatment was indicated for all the patients then a surgery was indicated in all of them in an average wait of 4 months realizing an ear exclusion in one case and a filling-up for 12 patients. Vertigo improved in 10 cases and the hearing loss in 2 cases. CONCLUSION: The diagnostic of perilymphatic fistulae is not easy. The trauma and the clinical signs can help but the confirmation is surgical. The indication of surgery and its timing are still discussed.