Cochlear Parameters Research Articles

Diagnostic Value of 3D Segmentation in Understanding the Anatomy of Human Inner Ear Including Malformation Types.

To understand the anatomical and dimensional variations of the human inner ear using 3-dimensional (3D) segmentation within the Middle East population. Retrospective study. King Abdullah Ear Specialist Center (KAESC) Riyadh, Saudi Arabia. Forty computed tomography (CT) images of patients with sensorineural hearing loss who underwent cochlear implant (CI) were taken for analysis. Three-dimensional images showing the anatomical variations of the inner ear including various pathological conditions, cochlear parameters including basal turn diameter ("A" value), "B" value which is perpendicular to "A" value, cochlear height, length, and width of the internal auditory canal (IAC), intercochlear spacing, and electrode angular insertion depth (AID). Out of 40 CT image data sets, 12 had normal inner-ear anatomy (NA), 4 with enlarged vestibular aqueduct syndrome (EVAS), 8 with only 2 turns of the cochlea (2TL), 7 with incomplete partition (IP) type II, 5 with cochlear hypoplasia, 1 with common cavity, and 3 with abnormal IAC. Taking the NA, EVAS, 2TL, and the IP type II cases altogether, age of the patient had no correlation with the "A" value; however, the "A" value had a linear correlation with the "B" value. The age of the patient had an increasing logarithmic correlation with the IAC length and the intercochlear spacing. The "A" value did not have any meaningful correlation with the cochlear height. Three data sets showed asymmetric inner-ear malformation types on either side of the ears. All these 40 cases were implanted with various CI electrode array variants and the corresponding postoperative plain film X-ray images showing the electrode AID are given separately in figures. Three-dimensional segmentation of the inner ear from the temporal bone CT is a valuable clinical and training tool for surgeons and radiologists especially in difficult cases which will certainly help to understand the overall anatomical and dimensional variations.

The inner ear of the Paranthropus specimen DNH 22 from Drimolen, South Africa.

Morphological variation within the southern African hypodigm of Paranthropus has been the focus of major interest since the earliest discoveries in the "Cradle of Humankind." Given the relevance of the bony labyrinth for investigating fossil primate paleobiodiversity, this article aims to provide additional evidence for assessing the degree of regional variation within Paranthropus through the comparative analysis of the inner ear of DNH 22. As comparative material, 18 southern African hominin specimens from Sterkfontein, Swartkrans, and Makapansgat (plus published data from Kromdraai B), attributed to Australopithecus, early Homo or Paranthropus, as well as 10 extant human and 10 extant common chimpanzee specimens are investigated. A landmark-based geometric morphometric method is applied for quantitatively assessing labyrinthine morphology. Additionally, cochlear parameters and oval window area are measured. In terms of semicircular canal and cochlear shape, DNH 22 most resembles the Paranthropus specimen SKW 18 from Swartkrans. Both specimens differ from the other Paranthropus specimens investigated in this study by an anteroposteriorly large posterior semicircular canal and a cochlea with loose turns in the apical portion. Conversely, the oval window area in DNH 22 closely fits the range observed in Paranthropus from Swartkrans and Kromdraai B. The inner ear of the DNH 22 specimen represents a unique opportunity to provide further insight into the early hominin labyrinthine variation pattern. In particular, the description of DNH 22 raises critical questions on the diversity of the vestibular system and evolutionary pattern of the auditory apparatus in Paranthropus.

Added Value of MDCT in Cochlear Parameters Assessment in Patients with Sensory Neural Hearing Loss Candidates for Cochlear Implantation

The aim of this study is to detect the variations in cochlear size which may help in selection of the best cochlear implant electrode length and may also influence the insertion depth angles of the electrode arrays. To achieve this goal, 40 patients (21 females and 19 male) were included, their age ranged from 4 to 57 years (mean 24.63±17.30 years), pre- and post-operative non-contrast CT examination of the petrous bone was performed. It showed that, the cochlear distance (diameter A) ranged between 7.10 – 10.10mm (mean 8.53 ± 0.56mm) ,The cochlear duct length ranged between 25.50 – 38.0mm (mean 31.45 ± 2.33mm), postoperative, insertion depth angles ranged between 405 to 500o (mean 450.17±36.77), for advanced bionics, 211.0 – 420.0o (mean 367.56 ± 71.81o) for cochlear nucleus, 371.0 – 520.0o (mean 456.14 ± 61.33o) for Flex 28, and 475.0 – 598.0o (mean 513.06 ± 31.76 o) for Med-El standard electrode, a non-significant correlation was found between the insertion depth angles and the cochlear distance. A statistically significant positive correlation was found between the insertion depth angle and length of the electrode array. Therefore, it is concluded that assessing the cochlear parameters helps to choose the optimal electrode to provide proper cochlear coverage while avoiding insertional trauma.

Hydrogen-rich saline alleviates experimental noise-induced hearing loss in guinea pigs

Objective. To examine the efficiency of hydrogen-rich saline in the treatment of intensive noise-induced cochlear injury. Materials and methods. Forty guinea pigs were assigned to one of four groups: HS+NOISE (i.p. injection hydrogen-rich saline), NS+NOISE (i.p. injection normal saline), NOISE ALONE (noise control), and NO TREATMENT (normal control) groups. The HS+NOISE, NS+NOISE, and NOISE ALONE groups were exposed to intensive noise (4 h at 115 dB SPL noise of 4000±100 Hz). The auditory brainstem response (ABR) was used to examine the hearing threshold in each group. Distortion product otoacoustic emission (DPOAE) was used to examine outer hair cell function. We also examined cochlear morphology to evaluate inner and outer hair cell trauma induced by noise exposure. Hydrogen-rich saline was administered twice daily for 6 days (2.5 ml/kg, i.p.) 24 h after noise exposure. Results. Baseline ABR thresholds and DPOAE values were normal in all groups at the measured frequencies (2, 4, 8, and 16 kHz) before noise exposure. The ABR threshold shift was 50–55 dB across the frequencies tested, and average DPOAE declined in the NOISE ALONE, NS+NOISE, and HS+NOISE groups 24 h after noise exposure. However, the changes in cochlear parameters were different between groups. The HS+NOISE group showed a significantly decreased ABR threshold value as compared with the NS+NOISE or NOISE ALONE group (P<0.01) on day 7. The mean DPOAE recovered to some extent in the three noise exposure groups, but at most frequencies the HS+NOISE group showed significantly increased DPOAE on day 7 as compared with the NS+NOISE group or NOISE ALONE group (P<0.01). Surface Corti organ preparations stained with succinate dehydrogenase (SDH) showed that most outer hair cells (OHCs) were still dropsical and a few were missing 7 days after noise exposure in the NS+NOISE group. Only a few OHCs were slightly dropsical in the HS+NOISE group. The numbers of missing hair cells 7 days after noise exposure were significantly greater in the NOISE ONLY and NS+NOISE groups than the HS+NOISE group (P<0.01). Conclusions. Hydrogen-rich saline can alleviate experimental noise-induced hearing loss in guinea pigs, partially by preventing the death of cochlear hair cells after intensive noise exposure.

Effects of middle-ear immaturity on distortion product otoacoustic emission suppression tuning in infant ears

Distortion product otoacoustic emission (DPOAE) measures of cochlear function, including DPOAE suppression tuning curves and input/output (I/O) functions, are not adultlike in human infants. These findings suggest the cochlear amplifier might be functionally immature in newborns. However, many noncochlear factors influence DPOAEs and must be considered. This study examines whether age differences in DPOAE I/O functions recorded from infant and adult ears reflect maturation of ear-canal/middle-ear function or cochlear mechanics. A model based on linear middle-ear transmission and nonlinear cochlear generation was developed to fit the adult DPOAE I/O data. By varying only those model parameters related to middle-ear transmission (and holding cochlear parameters at adult values), the model successfully fitted I/O data from infants at birth through age 6 months. This suggests that cochlear mechanics are mature at birth. The model predicted an attenuation of stimulus energy through the immature ear canal and middle ear, and evaluated whether immaturities in forward transmission could explain the differences consistently observed between infant and adult DPOAE suppression. Results show that once the immaturity was compensated for by providing infants with a relative increase in primary tone level, DPOAE suppression tuning at f2= 6000 Hz was similar in adults and infants.

The spiral model of pitch: Interrelations with musical and psychoacoustic scales and with cochlear parameters

A spiral model of pitch can represent pitch chroma and pitch height. Its arclength provides the frequency-position map of the cochlea, and, when scaled by the number of auditory-ganglion cells, provides the Mel scale. Pitch-like scales fall into three groups. Group I is typified by the Cent scale, which can be expressed as a pitch spiral. Other Group-I scales are musical notation, logarithmic scales of frequency, Fechners Law for complex tones, and the pitch helix. Group II is typified by Greenwoods cochlear map, which is simply related to the arclength of the pitch spiral. Other Group-II scales are the sums of the number of (a) equivalent-rectangular bandwidths (NERBs); (b) difference limens for frequency (NDLFs); and (c) inner-hair cells (NIHCs) and are consistent with critical ratios. Group III is typified by the Mel Scale, which can be derived from the pitch spiral and the distribution of auditory-ganglion cells. Other Group-III scales are the sums of the number of (a) auditory ganglion cells (NSGCs), (b) frequency-modulation-difference limens (NFMDLs), and (c) Barks (NBARKs). The pitch spiral seems a basic concept from which other pitch-like scales can be derived.

Noise-induced cochlear hypoxia is intensity dependent, correlates with hearing loss and precedes reduction of cochlear blood flow.

Anesthetized and artificially ventilated guinea pigs were exposed to broad-band noise of 95, 101, 106 or 115 dB SPL for 30 min and studied for 180 min after cessation of noise. The partial pressure of oxygen (pO2) in the perilymph, the cochlear blood flow (CoBF) and auditory-evoked potentials were continuously recorded. Arterial blood pressure, electrocardiogram, inspiratory and expiratory gas levels, arterial blood gas levels and acid-base status were kept stable to exclude influences of these parameters on cochlear parameters. Exposure to 95 dB SPL did not affect perilymphatic pO2 or CoBF. Cochlear microphonics (CMs) were reduced, but compound action potentials of the auditory nerve (CAPs) and auditory brainstem potentials (ABRs) increased after exposure to this low-level noise. Perilymphatic pO2 decreased during exposure to 101 dB SPL and then further decreased during the subsequent 60 min after cessation of the noise. CoBF did not change significantly during and 30 min after noise but then paralleled the decline of perilymphatic pO2. However, both parameters showed a clear indication of recovery in the second and third hours after noise. At 101 dB SPL, CMs were again reduced immediately, CAPs were unaltered and ABRs again increased. Exposure to 106 and to 115 dB SPL resulted in a decrease in both perilymphatic pO2 and CoBF; this decrease began during the exposure but became progressively worse after the noise. Hearing loss was observed immediately with exposure and showed no signs of further deterioration after cessation. The observed time courses of changes are important. They reveal that hearing loss and cochlear hypoxia precede reduction in CoBF due to noise exposure. The potential mechanisms underlying these effects are discussed.

Effects of perilymph viscosity on low-frequency intracochlear pressures and the cochlear input impedance of the cat.

Cochlear model calculations are shown to be in reasonable agreement with recent low-frequency measurements of intracochlear pressures and the cochlear input impedance of the cat [V. Nedzelnitsky, J. Acoust. Soc. Am. 68, 1676-1689 (1980); T. J. Lynch, III, V. Nedzelnitsky, and W. T. Peake, J. Acoust. Soc. Am. 72, 108-130 (1982)]. Included in the cochlear model are perilymph viscosity, the measured variation of the area of the scala vestibuli with distance from the stapes [P. Dallos, J. Acoust. Soc. Am. 48, 489-499 (1970)], and finite impedance of the round window membrane. The WKB approximation and its extension to the low-frequency region is used in order to exhibit explicitly the dependence of the model results on the cochlear parameters.

Model calculations of low‐frequency intracochlear pressures and the cochlear input impedance of the cat and guinea pig

Recent low‐frequency measurements of intracochlear pressures and the cochlear input impedance of the cat [V. Nedzelnitsky, J. Acoust. Soc. Am. 68, 1676–1689 (1980); T. J. Lynch, III, V. Nedzelnitsky, and W. T. Peake, J. Acoust. Soc. Am. 72, 108–130 (1982)] and the guinea pig (A. Dancer and R. Franke, Hear. Res. 2, 192–205 (1980)] are shown to be in reasonable agreement with the results of cochlear model calculations. Included in the cochlear model are perilymph viscosity, the measured variation of the area of the scala vestibuli with distance from the stapes [P. Dallos, J. Acoust. Soc. Am. 48, 489–499 (1970)], and the finite impedance of the round window membrane. Approximate analytic expressions for the fluid pressures in the scalae are derived so as to explicitly exhibit the dependence of the model results on cochlear parameters. [This work was supported by NSF.]

Unified computational model of stimulated and spontaneous acoustic emissions in the external auditory meatus

We consider two‐dimensional cochlear models which may contain active elements and nonlinearities, and which give retrograde waves on the basilar membrane because of assumed discontinuities in cochlear parameters. Using a conventional middle‐ear model and applying frequency and time‐domain methods, we calculate the properties of stimulated [D. T. Kemp, J. Acoust. Soc. Am. 64, 1386–1391 (1978)] and spontaneous [P. M. Zurek, J. Acoust. Soc. Am. 69, 514–523 (1981)] acoustic emissions, and compare the results with experimental data. We assume that spontaneous emission is associated with the cochlear response to thermal noise. [This work was supported by NSF.]

A recursive incremental model for noninvasive cochlear measurements

In recent years a number of models have been developed to correlate the cochlear mechanics to measurements obtained by several researchers. This paper proposes a model which, rather than proceed in this manner, describes the cochlear mechanics as an energy interchange process between the stapes and the cochlea. The present approach tries to focus this problem through the application of an incremental model successfully used in the description of speech analysis‐synthesis problems. The model describes the cochlea as a chain of incremental sections; hence, by dividing the model into simple sections, simple solutions of the general differential equations can be found for each section and thus for the whole. By means of the boundary conditions between two adjacent sections, the energy flow can be related with the transmission parameters of the sections, establishing a close relationship between the wave propagation characteristics in a given section and those in the stapes. This leads to the possibility of the measurement of cochlear parameters by noninvasive methods.

Short-wave world revisited: Resonance in a two-dimensional cochlear model

According to the type of wave motion occurring, the length of the cochlea can be divided into three parts: in the first part there is a travelling wave with location-dependent propagation velocity, in the second the motion is dominated by resonance and in the third the wave is rapidly attenuated. This paper investigates two-dimensional aspects of wave motion in the second region for a simple cochlear model. The partition impedance is approximated by a linear function of the location χ and the integral equation for two-dimensional fluid motion is solved analytically. It is shown that for the commonly used cochlear parameters the fluid wave motion in the resonance region is predominantly two-dimensional, i.e., characterized as occurring in a short-wave world. Several physical aspects of this type of fluid motion are discussed.