Cochlear implant surgery is a procedure performed to treat profound hearing loss. Clinical results suggest that implanting the electrode in the scala tympani, one of the two principal cavities inside ...the cochlea, may result in better hearing restoration. Segmentation of intracochlear cavities could thus aid the surgeon to choose the point of entry and angle of approach that maximize the likelihood of successful implant insertion, which may lead to more substantial hearing restoration. However, because the membrane that separates the intracochlear cavities is too thin to be seen in conventional in vivo imaging, traditional segmentation techniques are inadequate. In this paper, we circumvent this problem by creating an active shape model with micro CT (μCT) scans of the cochlea acquired ex vivo. We then use this model to segment conventional CT scans. The model is fitted to the partial information available in the conventional scans and used to estimate the position of structures not visible in these images. Quantitative evaluation of our method, made possible by the set of μCTs, results in Dice similarity coefficients averaging 0.75. Mean and maximum surface errors average 0.21 and 0.80 mm.
The mammalian cochlea has historically resisted attempts at high-resolution, non-invasive imaging due to its small size, complex three-dimensional structure, and embedded location within the temporal ...bone. As a result, little is known about the relationship between an individual's cochlear pathology and hearing function, and otologists must rely on physiological testing and imaging methods that offer limited resolution to obtain information about the inner ear prior to performing surgery. Micro-optical coherence tomography (μOCT) is a non-invasive, low-coherence interferometric imaging technique capable of resolving cellular-level anatomic structures. To determine whether μOCT is capable of resolving mammalian intracochlear anatomy, fixed guinea pig inner ears were imaged as whole temporal bones with cochlea in situ. Anatomical structures such as the tunnel of Corti, space of Nuel, modiolus, scalae, and cell groupings were visualized, in addition to individual cell types such as neuronal fibers, hair cells, and supporting cells. Visualization of these structures, via volumetrically-reconstructed image stacks and endoscopic perspective videos, represents an improvement over previous efforts using conventional OCT. These are the first μOCT images of mammalian cochlear anatomy, and they demonstrate μOCT's potential utility as an imaging tool in otology research.
Studies suggest lateral wall (LW) scala tympani (ST) height decreases apically, which may limit insertion depth. No studies have investigated the relationship of LW ST height with translocation rate ...or location.
Retrospective review.
Cochlear implant program at tertiary referral center.
LW ST height was measured in preoperative images for patients with straight electrodes. Scalar location, angle of insertion depth (AID), and translocation depth were measured in postoperative images. Audiologic outcomes were tracked.
In total, 177 ears were identified with 39 translocations (22%). Median AID was 443° (interquartile range IQR, 367°-550°). Audiologic outcomes (126 ears) showed a small, significant correlation between consonant-nucleus-consonant (CNC) word score and AID (
= 0.20,
= .027), although correlation was insignificant if translocation occurred (
= 0.11,
= .553). Translocation did not affect CNC score (
= .335). AID was higher for translocated electrodes (503° vs 445°,
= .004). Median translocation depth was 381° (IQR, 222°-399°). Median depth at which a 0.5-mm electrode would not fit within 0.1 mm of LW was 585° (IQR, 405°-585°). Median depth at which a 0.5-mm electrode would displace the basilar membrane by ≥0.1 mm was 585° (IQR, 518°-765°); this was defined as predicted translocation depth (PTD). Translocation rate was 39% for insertions deeper than PTD and 14% for insertions shallower than PTD (
= .008).
AID and CNC are directly correlated for straight electrodes when not translocated. Translocations generally occur around 380° and are more common with deeper insertions due to decreasing LW ST height. Risk of translocation increases significantly after 580°.
To describe the tip fold over rate, scalar localization, and speech perception outcomes of the CI532 Slim Modiolar Electrode.
All patients receiving the CI532 implant before June 2018.
Outcome ...measures for adults patients include pre- and postoperative speech perception, operative report details, electrode position as determined by X-ray and cone beam computed tomography. Comparison made with previous experience with the Contour perimodiolar electrode (CI512). In the pediatric population tip fold-over rate, measured by intraoperative X-ray, was the exclusive outcome.
One hundred twenty-five CI532 devices were implanted in adults and 69 in children. Electrode tip fold-over occurred in eight adults cases and none among children (4.1%). Cone beam CT scans of 120 out of 125 adult patients confirmed scala tympani (ST) position in all but one case where the electrode had been placed into scala vestibuli. There were no translocations from ST to scala vestibuli. This compares favorably with the CI512 translocation rate of 17%. Speech perception outcomes demonstrated good performance with mean preop phoneme scores of 16.2% (±13) increasing to 64.2% (±14) and 71.6 (±16) 3 and 12-months postop, respectively. Compared with a matched group of CI512 recipients, CI532 recipient phoneme scores were significantly higher 3 and 12-months postop by 4 and 7%, respectively.
The slim modiolar, CI532 electrode has provided very reliable ST position with a low rate of tip fold over. A trend toward better speech perception scores in CI532 compared with CI512 was observed.
Partindo do pressuposto de que no projeto pedagógico de Sócrates, Alcibíades foi considerado um grande fracasso, proponho retomar o Banquete de Platão, cotejado com Vida de Alcibíades de Plutarco e ...História da Guerra do Peloponeso de Tucídides, para pensar o movimento das paixões na figura do controverso general e político ateniense, discípulo apaixonado por Sócrates, cuja estrutura psíquica se situa entre a dimensão dos desejos voltados para os apetites e para a glória individual. Na sua ânsia de viver intensamente, Alcibíades revela ter consciência e até mesmo prazer em ser um não-filósofo que dialoga e teme o discurso de seu outro, o filósofo, representado por Sócrates. Proponho, pois, que o impedimento de Alcibíades para se tornar filósofo é o fato de não atingir o percurso final da scala amoris, visto desejar com intensidade o indivíduo Sócrates, apesar da ausência de beleza corpórea de seu amado, além de reconhecer e louvar suas belas ações, o que permite pensar que atingiu a esfera da beleza das almas.
Objectives
To use synchrotron radiation phase‐contrast imaging (SR‐PCI) to visualize and measure the morphology of the entire cochlear scala tympani (ST) and assess cochlear implant (CI) electrode ...trajectories.
Methods
SR‐PCI images were used to obtain geometric measurements of the cochlear scalar diameter and area at 5‐degree increments in 35 unimplanted and three implanted fixed human cadaveric cochleae.
Results
The cross‐sectional diameter and area of the cochlea were found to decrease from the base to the apex. This study represents a wide variability in cochlear morphology and suggests that even in the smallest cochlea, the ST can accommodate a 0.4 mm diameter electrode up to 720°. Additionally, all lateral wall array trajectories were within the anatomically accommodating insertion zone.
Conclusion
This is the first study to use SR‐PCI to visualize and quantify the entire ST morphology, from the round window to the apical tip, and assess the post‐operative trajectory of electrodes. These high‐resolution anatomical measurements can be used to inform the angular insertion depth that can be accommodated in CI patients, accounting for anatomical variability.
Level of evidence
N/A. Laryngoscope, 134:2889–2897, 2024
This is the first study to use synchrotron radiation phase‐contrast imaging to visualize and quantify the entire scala tympani morphology, and assess the post‐operative trajectory of electrodes. These high‐resolution anatomical measurements can be used to inform the angular insertion depth that can be accommodated in CI patients, accounting for anatomical variability.
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.
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.
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.
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.
•Ear canal and intracochlear pressures are described during shock wave exposure.•Tympanic membrane rupture was observed for impulses over 22 kPa peak pressure.•Evidence for a bone-conducted component to shock wave exposure observed.•Results can be used to update and extend hearing hazard assessment tools.
•A fabrication process for patient-specific artificial scala tympani models is described.•Intracochlear frictional properties are reproduced by an easily applied polymer brush coating.•Measurements ...of insertion forces of cochlear implant electrode arrays show a very good agreement with measurements on cadaver specimens.•The model enables large scale cochlear implant electrode array evaluation studies and insertion experiments.
Electrode array insertion into the inner ear is a critical step in cochlear implantation, and artificial scala tympani models can be a valuable tool for studying the dynamics of this process.
This technical note describes the fabrication of electrode array dummies and scala tympani models that address shortcomings of previously published cochlear models. In particular, we improve the reproduction of frictional properties with an easy-to-apply polymer brush coating that creates hydrophilic surfaces, and produce geometries with accurate macro-anatomy based on microtomographic scans. The presented methods rely only on commonly available materials and tools and are based on publicly available data.
Our validation shows very good agreement of insertion forces both in terms of linear insertion depth and insertion speed compared to previously published measurements of insertions in cadaveric temporal bones.
1) Compare rates of scala tympani (ST) insertion between Nucleus CI422 Slim Straight electrodes and Nucleus CI512 Contour Advance electrodes; 2) examine audiometric performance with both electrode ...arrays, while controlling for electrode location.
Tertiary academic hospital.
Fifty-six post-lingually deafened adults undergoing cochlear implant (CI).
Primary outcome measures of interest were scalar electrode location and postoperative audiologic performance.
Fifty-six implants in 49 patients were included; 20 were implanted with Nucleus CI422 Slim Straight electrodes, and 36 were implanted with Nucleus CI512 Contour Advance electrodes. Overall, 62.5% (35 of 56) of implants had all electrodes located within the ST. Significantly, higher rates of ST insertion (90%) were observed for Nucleus CI422 Slim Straight electrodes when compared with Nucleus CI512 Contour Advance electrodes (47.2%) (p = 0.002). In regards to audiologic performance, consonant-nucleus-consonant (CNC) scores were significantly higher for Nucleus CI422 Slim Straight electrodes (55.4%) compared with Nucleus CI512 Contour Advance electrodes (36.5%) (p = 0.005). In addition, AzBio scores were better for Nucleus CI422 Slim Straight electrodes (71.2%) when compared with Nucleus CI512 Contour Advance electrodes (46.7%) (p = 0.004). Controlling for ST insertion, higher AzBio scores were again observed for Nucleus CI422 Slim Straight electrodes (p = 0.02).
The results of this study demonstrate that the Nucleus CI422 Slim Straight electrode is more likely to reside entirely within the ST when compared with the Nucleus CI512 Contour Advance electrode. Furthermore, AzBio scores were superior for patients with Nucleus CI422 Slim Straight electrodes in all patients, as well as those with only ST insertions.
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