Stimulation efficiency of an actuator driven piston at the biological interface to the inner ear

Direct acoustic cochlear stimulation uses piston motion to substitute for stapes footplate (SFP) motion. The ratio of piston to stapes footplate motion amplitude, to generate the same loudness percept, is an indicator of stimulation efficiency. We determined the relationship between piston displacement to perceived loudness, the achieved maximum power output and investigated stapes fixation and obliteration as confounding factors. The electro-mechanical transfer function of the actuator was determined preoperatively on the bench and intraoperatively by laser Doppler vibrometry. Clinically, perceived loudness as a function of actuator input voltage was calculated from bone conduction thresholds and direct thresholds via the implant. The displacement of a 0.4 mm diameter piston required for a perception equivalent to 94 dB SPL at the tympanic membrane compared to normal SFP piston displacement was 27.6–35.9 dB larger, consistent with the hypothesis that the ratio between areas is responsible for stimulation efficiency. Actuator output was 110 ± 10 eq dB SPLFF @1Vrms ≤ 3 kHz and decreased to 100 eq dB SPLFF at 10 kHz. Output was significantly higher for mobile SFPs but independent from obliteration. Our findings from clinical data strongly support the assumption of a geometrical dependency on piston diameter at the biological interface to the cochlea.

The ear

The delicate yet definitive deflections of the pinna (wing/fin) of the external ear contribute to the collection of sound. The external acoustic meatus is responsible for the transmission of sounds to the tympanic membrane, which in turn separates the external ear from the middle ear. The middle ear is an air filled (from the nasopharynx via the eustachian tube), mucous membrane lined space in the petrous temporal bone. It is separated from the inner ear by the medial wall of the tympanic cavity – bridged by the trio of ossicles. The inner ear refers to the bony and membranous labyrinth and their respective contents. The osseus labyrinth lies within the petrous temporal bone. It consists of the cochlea anteriorly, semicircular canals posterosuperiorly and intervening vestibule – the entrance hall to the inner ear whose lateral wall bears the oval window occupied by the stapes footplate.

On the hearing effects of a cholesteatoma growing: A biomechanical study

Chronic otitis media enables the appearance of a benign middle ear tumor, known as a cholesteatoma, that may compromise hearing. To evaluate the influence of a cholesteatoma growth on the hearing function, a computational middle ear model based on the finite element method was used and three different size of cholesteatoma were modeled. The cholesteatoma solidification and the consequent degradation of the ossicles were also simulated as two condition that commonly occurs during cholesteatoma evolution. A sound pressure level of 80 dB SPL was applied in the tympanic membrane and a steady state analysis was performed for frequencies from 100 Hz to 10 kHz. The displacements of both the tympanic membrane and the stapes footplate were measured. The results were compared with a healthy case and it was shown that the cholesteatoma development leads to a decrease in the umbo and stapes displacements. The ossicles degradation simulation showed the higher difference comparing with the cholesteatoma in an initial stage, with lower displacements in the stapes footplate mainly for high frequencies. The observed displacement differences are directly connected to hearing loss, being possible to conclude that cholesteatoma evolution in the middle ear will lead to hearing problems, mainly in an advanced stage.

3D Finite Element Modeling of Blast Wave Transmission From the External Ear to a Spiral Cochlea

Blast-induced injuries affect the health of veterans, in which the auditory system is often damaged, and blast-induced auditory damage to the cochlea is difficult to quantify. A recent study modeled blast overpressure (BOP) transmission throughout the ear utilizing a straight, two-chambered cochlea, but the spiral cochlea's response to blast exposure has yet to be investigated. In this study, we utilized a human ear finite element (FE) model with a spiraled, two-chambered cochlea to simulate the response of the anatomical structural cochlea to BOP exposure. The FE model included an ear canal, middle ear, and two and half turns of two-chambered cochlea and simulated a BOP from the ear canal entrance to the spiral cochlea in a transient analysis utilizing fluid-structure interfaces. The model's middle ear was validated with experimental pressure measurements from the outer and middle ear of human temporal bones. The results showed high stapes footplate displacements up to 28.5µm resulting in high intracochlear pressures and basilar membrane (BM) displacements up to 43.2µm from a BOP input of 30.7kPa. The cochlea's spiral shape caused asymmetric pressure distributions as high as 4kPa across the cochlea's width and higher BM transverse motion than that observed in a similar straight cochlea model. The developed spiral cochlea model provides an advancement from the straight cochlea model to increase the understanding of cochlear mechanics during blast and progresses towards a model able to predict potential hearing loss after blast.

Congenital ossicular chain anomaly. Columella stapes

Congenital anomalies of the ossicular chain are a rare condition in clinical practice. In literature described different variants of the ossicular chain anomaly from stapes footplate ankylosis to complete aplasia of the ossicular chain, oval, and round window. Possible congenital ossicular chain anomaly should be suspected in case of non-progressive conductive hearing loss with a normal ear drum during an otoscopic examination, without a history of previous ear infections or trauma. In this article, we described the clinical case of congenital ossicular chain anomaly presented as fixed incus. Stapes was presented as single, straight, broad crus that were attached to the central part of the footplate. Stapedius tendon was absent. The footplate was completely mobile. Exploratory tympanotomy was performed to confirm a diagnosis of congenital ossicular chain anomaly. The ossicular chain was reconstructed with PORP titanium prosthesis. Furthermore, a literature review was done, conclusions presented.

Conductive hearing loss after surgical treatment of otosclerosis—long-term observations

Introduction: Surgical treatment of otosclerosis has been a commonly accepted method of treatment for many years. The improvement of hearing after surgery is sometimes even spectacular, and good results are obtained in many centres in over 90% of the entire operated population. However, in the years following the procedure, some patients develop permanent or progressive conductive hearing loss. The aim of the study is to present a group of patients with conductive hearing loss that appeared after the first otosclerosis surgery and to analyse the causes of its occurrence. Material and Methods: Retrospective analysis was performed on patients who were first operated on in the years 2000-2009. Their medical records were analysed by the end of 2019, which made it possible to obtain results on at least 10 years of postoperative follow-up. The group consisted of 1118 patients, aged 14-82, including 802 women and 316 men. Results: Reoperations due to conductive hearing loss were performed on 93 patients, who accounted for 8.3% of the originally operated patients. They were much more often performed on patients after stapedectomies (19.7%) than on patients after stapedotomy (5.5%). Intraoperatively, prosthesis displacement was found to be the most frequent observation (44.1%) and was often associated with erosion or necrosis of the long process of incus (28%). Less frequent reasons of hearing loss were: adhesions around the prosthesis (10.8%), too small hole in the stapes footplate (8.6%), too short prosthesis (8.6%), progression of otosclerosis (7.5%), too long prosthesis (6.4%), presence of a granuloma around the prosthesis (5.4 %), and displacement of incus (4.3%). Conclusions: Surgical treatment in otosclerosis is a widely accepted and good method. It allows improvement in hearing in the vast majority of patients treated in this way. Unfortunately, over the years, some patients develop conductive hearing loss again. Reoperation gives a chance to find the cause and improve hearing in most of these cases.