Comparative study of efficiency and characteristics of FMT and DRT installed in human cadavers for round-window stimulation.

Acoustic hearing aids generate amplified sound in the ear canal, and they are the standard of care for patients with mild to moderate sensorineural hearing loss. However, because of their limited frequency bandwidth, gain, and feedback, there is substantial room for improvement. Active middle ear implants, which directly vibrate the middle ear and cochlea, are an alternative approach to conventional acoustic hearing aids. They provide an opportunity to improve sound quality and speech understanding with amplification rehabilitation. For floating-mass type and direct-rod type (DRT) middle ear transducers, a differential floating-mass transducer (DFMT) and a tri-coil bellows transducer (TCBT), respectively, were fabricated to measure the output characteristics in four human temporal bones. Both were fabricated to have similar output forces per unit input and were placed in four human temporal bones to measure their output performances. The TCBT resulted in higher output than did the DFMT throughout the audible frequency range, and the output was more prominent at lower frequency ranges. In this study, we showed that DRT was a more effective method for round window stimulation. Because of its frequency characteristics and vibration efficiency, this implantation method can be utilized as a driving solution for middle ear implants.

The biomechanical characteristics of human vestibular aqueduct: a numerical-based model construction and simulation.

Vestibular aqueduct is a precise structure embedded in the temporal bone and plays a key role in the physiological function of inner ear by maintaining the endolymphatic circulation and buffering the impact from intracranial pressure. Although the alterations on the morphology or volume of vestibular aqueduct result in variety of diseases, the approaches of evaluating the condition of vestibular aqueduct are still unsatisfing because the pathological sections utilized for the 3D construction model most likely undergoes morphological changes. In this study, the vestibular aqueduct images obtained by CT scanning were processed by finite element method to construct the 3D model. To assess if this numerical model reflects the actual biomechanical properties of vestibular aqueduct, the fluid-solid coupling calculation was applied to simulate the endolymphatic flow in the vestibular aqueduct. By measuring the dynamics of endolymphatic flow, and the pressure and displacement on round membrane under external pressure, we found the numerical 3D model recapitulated the biomechanical characteristics of the real vestibular aqueduct. In summary, our approach of 3D model construction for vestibular aqueduct will provide a powerful method for the research of vestibular aqueduct-related diseases.

Assessment of surgical treatment of Eagle's syndrome.

INTRODUCTION: The aim of the study was to assess the effectiveness of surgical treatment of patients with Eagle's syndrome, taking into account both early and late results. MATERIAL AND METHODS: The study group consisted of 15 patients who underwent resection of the styloid process due to Eagle syndrome in the period of 2005-2017. During the follow-up visit, the patients were asked to fill in a post-operative questionnaire that compared the pre-operative symptoms and their severity with the patients' current health condition. The VAS pain scale was used to assess each symptom, and the Laitinen scale was used to assess the quality of life. Data from patients' medical records were also included. The results of the surveys were subjected to statistical analysis. RESULTS: The study showed that in 11 out of 15 cases there was a significant improvement in the level of pain (70.5% on average) and an improvement in quality of life (on average 65%) comparing to the pre-operative condition. The Wilcoxon test for binding pairs, the Mann-Whitney test, the Kruskal-Wallis test and the Spearman correlation coefficient were used in the statistical analysis. There were statistically significant correlations between the recorded improvement rate and the length of the resected styloid process and its setting. DISCUSSION: The study proved that resection of prolonged styloid process from extraoral approach in most cases is an effective method of treatment of Eagle syndrome, that carries low risk of complications.

Repair of subtotal tympanic membrane perforations: A temporal bone study of several tympanoplasty materials.

The aim of this project was to investigate the effects of different types of graft material, and different remaining segments of the native TM on its motion. In twelve human temporal bones, controlled TM perforations were made to simulate three different conditions. (1) Central perforation leaving both annular and umbo rims of native TM. (2) Central perforation leaving only a malleal rim of native TM. (3) Central perforation leaving only an annular rim of native TM. Five different graft materials (1) perichondrium (2) silastic (3) thin cartilage (4) thick cartilage (5) Lotriderm® cream were used to reconstruct each perforation condition. Umbo and stapes vibrations to acoustic stimuli from 250 to 6349 Hz were measured using a scanning laser Doppler vibrometer. Results showed that at low frequencies: in the Two Rims condition, all grafting materials except thick cartilage and Lotriderm cream showed no significant difference in umbo velocity from the Normal TM, while only Lotriderm cream showed a significant decrease in stapes velocity; in the Malleal Rim condition, all materials showed a significant decrease in both umbo and stapes velocities; in the Annular Rim condition, all grafting materials except Lotriderm and perichondrium showed no significant difference from the Normal TM in stapes velocity. Umbo data might not be reliable in some conditions because of coverage by the graft. At middle and high frequencies: all materials showed a significant difference from the Normal TM in both umbo and stapes velocities for all perforation conditions except in the Annular Rim condition, in which silastic and perichondrium showed no significant difference from the Normal TM at umbo velocity in the middle frequencies. In the low frequencies, the choice of repair material does not seem to have a large effect on sound transfer. Our data also suggests that the annular rim could be important for low frequency sound transfer.

The effect of blast overpressure on the mechanical properties of the human tympanic membrane.

The rupture of the tympanic membrane (TM) is one of the major indicators for blast injuries due to the vulnerability of TM under exposure to blast overpressure. The mechanical properties of the human TM exhibit a significant change after it is exposed to such a high intensity blast. To date, the published data were obtained from measurement on TM strips cut from a TM following an exposure to blast overpressure. The dissection of a TM for preparation of strip samples can induce secondary damage to the TM and thus potentially lead to data not representative of the blast damage. In this paper, we conduct mechanical testing on the full TM in a human temporal bone. A bulging experiment on the entire TM is carried out on each sample prepared from a temporal bone following the exposure to blast three times at a pressure level slightly below the TM rupture threshold. Using a micro-fringe projection method, the volume displacement is obtained as a function of pressure, and their relationship is modeled in the finite element analysis to determine the mechanical properties of the post-blast human TMs, the results of which are compared with the control TMs without an exposure to the blast. It is found that Young's modulus of human TM decreases by approximately 20% after exposure to multiple blast waves. The results can be used in the human ear simulation models to assist the understanding of the effect of blast overpressure on hearing loss.

Styloidogenic Jugular Venous Compression Syndrome: Clinical Features and Case Series.

BACKGROUND: Styloidogenic jugular venous compression syndrome (SJVCS) is a rare cause of idiopathic intracranial hypertension (IIH). OBJECTIVE: To elucidate the pathophysiology and the hemodynamics of SJVCS. METHODS: We conducted a retrospective review of medical records, clinical images, dynamic venography, and manometry for consecutive patients with SJVCS undergoing microsurgical decompression from April 2009 to October 2017. Patients with IIH with normal venography and manometry findings served as controls. RESULTS: Data were analyzed for 10 patients with SJVCS who presented with headaches. Neck flexion exacerbated headaches in 7 patients. Eleven patients with IIH provided control data for normal intracranial venous pressure and styloid process anatomy. Patients with SJVCS had bilateral osseous compression of venous outflow. The styloid processes were significantly longer in patients with SJVCS than in those with IIH (mean [standard deviation (SD)] distance, 31.0 [10.6] vs 19.0 [14.1] mm; P < .01). The styloid process-C1 lateral tubercle distance was shorter in patients with SJVCS than in those with IIH (mean [SD] distance, 2.9 [1.0] vs 9.9 [2.8] mm; P < .01). Patients with SJVCS had significantly higher global venous pressure and a higher pressure gradient across the stenosis site than controls (mean [SD] pressure, 2.86 [2.61] vs 0.13 [1.09] cm H2O; P = .09). All 10 patients with SJVCS experienced venous pressure elevation during contralateral neck turning (mean [SD] pressure, 4.29 [2.50] cm H2O). All 10 patients with SJVCS underwent transcervical microsurgical decompression, and 9 experienced postoperative improvement or resolution of symptoms. One patient had transient postoperative dysphagia and facial drooping, and another patient reported jaw numbness. CONCLUSION: SJVCS is a novel clinical entity causing IIH. Patients should be evaluated with dynamic venography with manometry. Surgical decompression with removal of osseous overgrowth is an effective treatment in select patients.

The potential protective effects of temporal bone pneumatization: A shock absorber in temporal bone fracture.

OBJECTIVES: We hypothesize that when temporal bone fractures occur, the pneumatic cells in the temporal bone are able to absorb most of the impact force during a traumatic event. This study aims to correlate the degree of pneumatization of the temporal bone with the severity of temporal bone fracture (TBF). METHODS: Charts and computed tomography scans representing 54 TBFs, diagnosed from 2012 to 2017 at a single tertiary hospital, were retrospectively reviewed. Temporal bone pneumatization (TBP) in the petrous apex and mastoid region was evaluated using previously published classification systems. TBP classifications and fracture types were correlated with TBF complications such as sensorineural hearing loss (SNHL), facial nerve palsy (FNP), and vestibular dysfunction. RESULTS: Patients with increased pneumatization of the temporal bone had significantly fewer and less severe SNHL. SNHL more strongly correlated with the degree of pneumatization in the mastoid (P = 0.005) than that in the petrous apex (P = 0.024). On the other hand, the degree of TBP correlated poorly with FNP and vestibular dysfunction. However, the mastoid hypopneumatization demonstrated significant correlation with otic-capsule violations (P = 0.002). Fractures with otic-capsule violation were 4 times more likely to have vestibular dysfunction (P = 0.043) and 3 times more likely to have SNHL (P = 0.006). FNP was not associated with otic-capsule violating fractures but was 3.5 times more common in comminuted fractures (P = 0.025). CONCLUSIONS: The degree of temporal bone pneumatization was negatively correlated to the incidence of otic-capsule violation and the severity of hearing impairment in patients with temporal bone fracture. This study substantiated the potential protective effect of temporal bone pneumatization in TBFs.

Sensor-actuator component for a Floating Mass Transducer-based fully implantable hearing aid.

We propose a novel system based on the Floating Mass Transducer (FMT) to be used as the active component of a fully implantable, Vibrant Soundbridge-like middle ear implant. The new system replaces the external microphone used in the currently available design with an implantable piezoelectric sensor that is inserted into the incudostapedial joint and picks up the vibrations transmitted to the long process of the incus. The FMT is coupled to the round window of the cochlea. We characterize the system by measuring the gain in intracochlear sound pressure using laser Doppler vibrometry at a surgically installed "third window" into the cochlea of six temporal bones. Closed-loop feedback oscillations limit the system's available output. We show that using an adaptive control algorithm, a mean functional gain of up to 40 dB is achieved, which is similar to Soundbridge functional gain. The concept matches the FMT's one-point fixation philosophy and offers several advantages over other designs, namely an easy and time-efficient surgery, reversibility of implantation, and natural hearing for the prospective patient.

Dual-laser measurement and finite element modeling of human tympanic membrane motion under blast exposure.

Hearing damage is one of most prevalent injuries in military personnel and civilians exposed to a blast. However, the mechanism of how the blast overpressure interacts with the tympanic membrane (TM) and impairs the peripheral auditory system still remains unclear. A 3D finite element (FE) model of the human ear has been developed to predict the blast overpressure transmission through the ear (Leckness et al., 2018), but the model needs to be further validated in TM response to blast pressure. This paper reports the first-ever approach using two laser Doppler vibrometers (LDVs) to measure the motion of the TM when the ear was exposed to a blast. Five fresh human temporal bones were used in this study with a pressure sensor inserted near the TM to measure the pressure reaching the TM (P1). The temporal bone was mounted in a "head block" and exposed to blast at the overpressure around 35 kPa measured at the entrance of the ear canal (P0). The movements of the TM at the umbo and the "head block" were measured simultaneously by two LDVs and the exact motion of the TM was determined by subtracting the head block motion from the TM data. Results include that the maximum TM velocity was 12.62 ±â€¯3.63 m/s (mean ±â€¯SD) and the displacement was 0.78 ±â€¯0.26 mm. The peak-to-peak displacement normalized by the P0 pressure was 22.9 ±â€¯6.6 µm/kPa. The frequency domain analysis indicated that the spectrum peaks were located at frequencies below 3 kHz. The TM motion was then compared with that calculated from the FE model of the human ear with the measured P0 pressure wave applied at the ear canal entrance. The FE model-derived TM displacement under blast overpressure was consistent with the experimental results. This study provides a new methodology to determine the behavior of the middle ear in response to blast overpressure. The experimental data are critical for validating the FE model of the human ear for blast wave transduction and understanding the TM damage induced by blast exposure.

Influence of angular positioning of the prosthesis in stapes surgeries with a NiTiBond prosthesis: Investigation in cadaveric temporal bones.

In incus stapedotomy surgeries, the longitudinal direction of the piston prosthesis should ideally be perpendicular to the stapes footplate. However, in reality, some amounts of angular deviation of the prosthesis from the ideal angular position is unavoidable due to anatomical constraints and surgical conditions. This study aims to evaluate the influence of angular positioning of the prosthesis on surgical outcomes in incus stapedotomy and to provide surgical guidelines related to practical tolerance of the angular positioning. In this study, this influence was assessed with a Kurz NiTiBond prosthesis (0.4-mm diameter) and fenestra sizes of 0.5- and 0.6-mm diameter in cadaveric temporal bones (n = 7 including 2 preliminary tests). Angular position of the prosthesis relative to the footplate was modulated by rotating the stapes about the long and short axes of the footplate. At each angular position, the tympanic membrane was acoustically stimulated in the frequency range of 0.2-10 kHz, and motion of the prosthesis was measured using a Laser Doppler vibrometer (LDV). Furthermore, micro-computed tomography (micro-CT) data of the middle-ear ossicles were used for anatomical analysis of angular positioning of the prosthesis. The results showed that changes of angular position of the prosthesis relative to the stapes footplate do not cause significant changes of prosthesis motion until a certain angular position threshold, and sharply attenuate prosthesis motion when the angular position reaches the threshold. The threshold of the angular position, as the tilting angle of the prosthesis from the direction normal to the stapes footplate, was 26.9 ±â€¯2.5° with the fenestration hole of 0.5-mm diameter and 30.6 ±â€¯3.0° with the fenestration hole of 0.6-mm diameter (n = 5, p < 0.01 for difference between the two fenestra sizes). Analysis of the middle-ear anatomy in this study revealed that the tolerances of the angular positions of the prosthesis does not always cover possible positions of prosthesis crimping. This study suggests that if an anterior offset of the stapes head and/or the thickened footplate is suspected, efforts to locate prosthesis crimping closer to the tip of the incus and/or to make a sufficiently large fenestration hole are favorable.

Temporal bone contrast-enhanced high-resolution CT evaluation of pulsatile tinnitus after sigmoid sinus wall reconstruction.

BACKGROUND: Sigmoid sinus wall reconstruction (SSWR) is a proven effective treatment for pulsatile tinnitus (PT) caused by sigmoid sinus wall dehiscence (SSWD) with or without sigmoid sinus diverticulum (SSD); however, comprehensive analysis of the postoperative imaging manifestations has not yet been reported. PURPOSE: To analyze temporal bone computed tomography (CT) imaging features following SSWR in patients with PT. MATERIAL AND METHODS: Following SSWR, temporal bone contrast-enhanced high-resolution CT (HRCT) images from 33 PT cases were retrospectively analyzed. Patients were divided into two groups based on follow-up interval: a short-interval group (≤18 months, 12 cases) and a long-interval group (>18 months, 21 cases). The mending material density and morphology was analyzed. Postoperative changes of the venous sinus were evaluated. Imaging manifestations of the normal temporal bone and mastoid air cells adjacent to the operative field were observed. RESULTS: The order of CT values of mending materials was significantly lower in the short-interval group than in the long-interval group (Z = -4.716, P < 0.001); the incidence of complete newly remodeled cortical bone on the rim of the mending materials was significantly higher in the long-interval group than in the short-interval group ( P < 0.001). Eleven patients (33.3%) showed varying degrees of remnant SSWD. The mending materials and normal mastoid bone structure showed complete fusion (n = 12, 36.4%), partial fusion (n = 16, 48.5%), or complete separation (n = 5, 15.2%). CONCLUSION: Temporal bone contrast-enhanced HRCT can be used to observe imaging features of the mending materials, venous sinus, adjacent normal temporal bone and mastoid air cells following SSWR.

Imaging of Tinnitus.

Although not all patients with tinnitus require imaging, patients with tinnitus and asymmetric hearing loss, additional neurologic findings, or pulsatile tinnitus should be evaluated with an appropriately tailored imaging study. Choice of imaging study should be guided by type of hearing loss and additional physical examination findings, such as middle ear lesion, presence of carotid bruit, or pulsatile tinnitus extinguished by jugular compression.

Hemorrhage within the tympanic membrane without perforation.

BACKGROUND: Hemotympanum refers to both the presence of blood in the middle ear cavity and to ecchymosis of the tympanic membrane (TM), and a systematic study of intra-TM (iTM) hemorrhage without bleeding in the middle ear cavity has not been conducted. The goals of our study were to analyze the causes of iTM hemorrhage without TM perforation or bleeding in the middle ear cavity, and to demonstrate the clinical characteristics of the disease. METHODS: This Case series study included five patients with iTM hemorrhage between August 2014 and August 2017. An iTM hemorrhage was diagnosed when otoendoscopic examination demonstrated minor bleeding behind the intact TM, a hemorrhage was observed between the TM annulus and the epidermal layer, and temporal bone computed tomography revealed thickening of the TM without soft tissue density within the tympanic cavity or temporal bone fracture. Initial symptoms, and serial findings of otoendoscopy and pure tone audiometry (PTA) were investigated. RESULTS: iTM hemorrhage developed due to blunt head trauma in two patients, descent barotrauma during scuba diving in two patients, and spontaneous epistaxis in one patient. Otalgia and ear fullness were the most common symptoms, but PTA showed no or minimal conductive hearing loss in all patients. CONCLUSIONS: An iTM hemorrhage may develop after blunt head trauma, barotrauma due to scuba diving, or spontaneous epistaxis; otological symptoms included otalgia, tinnitus, and aural fullness. An iTM hemorrhage resolved spontaneously without specific treatment, usually within 1 month.

Patients' experiences of living with superior canal dehiscence syndrome.

OBJECTIVE: The study investigated how the symptoms of superior canal dehiscence syndrome (SCDS) affected patients in their daily life, and how patients coped with the disease. DESIGN: This was a qualitative study; semi-structured interviews were performed and analysed according to the systematic text condensation method. STUDY SAMPLE: Twelve of 13 identified patients with SCDS in the county of Norrbotten, Sweden, were included in the study. RESULTS: Five main categories were created based on the patients' experiences of living with SCDS: (1) Experiencing strange symptoms: One "new" symptom was identified - mental fatigue. (2) A restricted life socially, physically and at work: All patients experienced some extent of limitation in their daily life. (3) To accept and to protect oneself: All patients had developed strategies to protect their ears from noise. (4) Misunderstood in health care: The diagnosis was sometimes delayed several years due to lack of knowledge among healthcare workers. (5) Carefully considering treatment (surgery): Symptoms were weighed against the risk of side effects. CONCLUSIONS: SCDS was rendered an invisible disability. In the present study, we identified mental fatigue as a symptom not previously considered in the literature.

Redesign of the Hannover Coupler: Optimized Vibration Transfer from Floating Mass Transducer to Round Window.

INTRODUCTION: In order to reduce the large variations in clinical outcomes of patients with implanted MED-EL Floating Mass Transducer (FMT) at the round window (RW), several approaches were proposed to optimize FMT-RW coupling. Our previous study showed improved FMT-RW coupling by applying static RW loads utilizing the "Hannover Coupler" (HC) FMT-prosthesis but also demonstrated insufficient low frequency performance. Hence, a redesigned HC version (HCv2) was investigated in this study. METHODS: Experiments were performed in ASTM F2504-05 compliant fresh human temporal bones. The HCv2 is a FMT-prosthesis redesigned from a previous prototype to specifically improve low frequency performance. Stapes footplate (SFP) displacements in response to acoustic stimulation of the tympanic membrane and to FMT-RW stimulation at varying static force (0-100 mN) were measured by Laser-Doppler vibrometry. RESULTS: SFP displacements were highly dependent on the applied RW load and had a global maximum at 15 mN when averaged at speech relevant frequencies (0.5-4 kHz). SFP responses at frequencies ≤ 1 kHz were up to 25 dB higher than responses achieved with the previous HC version. CONCLUSION: Optimizing the HC prosthesis design resulted in improved SFP responses to RW stimulation especially at lower frequencies (≤1 kHz).

Piezoelectric Actuator with Frequency Characteristics for a Middle-Ear Implant.

The design and implementation of a novel piezoelectric-based actuator for an implantable middle-ear hearing aid is described in this paper. The proposed actuator has excellent low-frequency output characteristics, and can generate high output in a specific frequency band by adjusting the mechanical resonance. The actuator consists of a piezoelectric element, a miniature bellows, a cantilever membrane, a metal ring support, a ceramic tip, and titanium housing. The optimal structure of the cantilever-membrane design, which determines the frequency characteristics of the piezoelectric actuator, was derived through finite element analysis. Based on the results, the piezoelectric actuator was implemented, and its performance was verified through a cadaveric experiment. It was confirmed that the proposed actuator provides better performance than currently used actuators, in terms of frequency characteristics.

Surgical management of patients with Eagle syndrome.

OBJECTIVE: Eagle syndrome, a spectrum of disease resulting from an elongated styloid process and/or calcified stylohyoid ligament, lacks standardized recommendations regarding indications for surgical intervention and approach. STUDY DESIGN: Retrospective cohort study. SETTING: Single tertiary care institution. SUBJECTS: Patients treated surgically for Eagle syndrome between January 2011 and June 2017. METHODS: Patients were diagnosed with Eagle syndrome based on thorough clinical workup and assessment. The primary outcome was improvement in pain severity following surgery, with complete resolution of pain being considered clinically meaningful. Wilcoxon rank-sum tests and Fisher's exact were used to compare numerical and categorical variables, respectively. RESULTS: Twenty-one patients were diagnosed with Eagle syndrome and underwent surgical resection of the styloid process. Patients most often complained of neck pain (81%), throat pain (62%), and ear pain (48%). Among these patients, 57% of procedures featured a transcervical approach, while the remaining 43% were transoral. The vast majority (90%) of patients experienced improvement in pain severity from a median of 6.0 before surgery to 0.0 afterwards (p < 0.01) as 62% experienced complete resolution. Using multivariable linear regression to model changes in pain severity, neck pain (ß = -1.69, p < 0.01) and jaw pain (ß = -0.93, p = 0.03) predicted greater relief, while headache (ß = 0.82, p = 0.04) predicted an inferior response. Adverse events were uncommon and typically resolved within three months, with 24% experiencing first bite syndrome and 19% reporting numbness. CONCLUSIONS: Transcervical and transoral styloidectomy are effective treatments for Eagle syndrome with minimal adverse effects. Patients with classic symptoms of neck or jaw pain benefit most from surgery.

Intracochlear pressure measurements during acoustic shock wave exposure.

INTRODUCTION: Injuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa. METHODS: Eight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead. RESULTS: Measurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher. CONCLUSIONS: Intracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.

Volumetric evaluation of temporal bone structures in the cases with bilateral tinnitus: clinical and morphometrical study.

BACKGROUND: Tinnitus is the recognition of sound in the absence of any external auditory stimulus to the noise of ringing in the ears. Middle ear aeration carries important role for ossicular coupling and normal hearing. There is restricted morphometric data on the cases with bilateral tinnitus. MATERIALS AND METHODS: In this study we evaluated hearing findings of 18 cases with subjective nonpulsatile bilateral tinnitus and also morphometry and volumetry of temporal bone substructures on the computed tomography images using stereological method compared with the gender and age matched 12 healthy subjects. Duration of tinnitus, exposing acoustic trauma or/and high level noise levels, evaluation of middle ear volume, jugular bulb levels, distances between jugular bulb and both oval window and middle ear were evaluated. RESULTS: Both males and females with tinnitus showed worse hearing thresholds through bone and air conductions than healthy subjects but it was not statistically significant. Pure tone thresholds through bone and air conductions were not statistically different in both sexes with bilateral tinnitus. Right middle ear volume of the cases with bilateral tinnitus was mean 5.57 cm3 for males and 5.64 cm3 for females; and also the left middle ear volume of the cases with bilateral tinnitus was mean 5.87 cm3 for males and 5.65 cm3 for females. There were no significant differences between the cases with bilateral tinnitus and the control subjects according to the side of the body. CONCLUSIONS: The data on the hearing findings and morphometrical evaluation of the cases with bilateral tinnitus may be important for anatomists and clinicians. (Folia Morphol 2018; 77, 1: 57-64).