Basal Turn Of Cochlea Research Articles

Gene expression analysis of oxidative stress-related genes in the apical, middle, and basal turns of the cochlea

It can be observed from aminoglycoside-induced hair cell damage that the cochlea basal turn is more susceptible to trauma than the apex. Drug-induced hearing loss is closely related to oxidative damage. The basilar membrane directly exposed to these ototoxic drugs exhibits differences in damage, indicating that there is an inherent difference in the sensitivity to oxidative damage from the apex to the base of the cochlea. It has been reported that the morphology and characteristics of the cochlea vary from the apex to the base. Therefore, we investigated oxidative stress-related gene expression profiles in the apical, middle, and basal turns of the cochlea. The Oxidative Stress RT2 Profiler™ PCR Array revealed that three of the 84 genes (Mb, Mpo, and Ncf1) were upregulated in the middle turn compared to their level in the apical turn. Moreover, eight genes (Mb, Duox1, Ncf1, Ngb, Fmo2, Gpx3, Mpo, and Gstk1) were upregulated in the basal turn compared to their level in the apical turn. The qPCR verification data were similar to that of the PCR Array. We found that MPO was expressed in the rat cochlea and protected against gentamicin-induced hair cell death. This study summarized the data for the gradient of expression of oxidative stress-related genes in the cochlea and found potential candidate targets for prevention of ototoxic deafness, which may provide new insights for cochlear pathology.

Reliability of Neuronavigation in Localizing the Internal Acoustic Canal during Middle Fossa Approach

Abstract Objective The absence of precise landmarks in the middle fossa floor and frequent anatomical variations make it difficult to localize the internal acoustic canal (IAC) during the middle fossa approach (MFA). We aimed to investigate the reliability and utility of the neuronavigation system (NNS) in the MFA and to delineate specific technical considerations regarding NNS during the approach. Method One-millimeter-thin section computed tomography scans were performed on five formalin-fixed human cadavers (10 sides). During the MFA, structures, such as the IAC, vestibule and cochlea hidden in the temporal bone were investigated under NNS guidance. Results All the superficial landmarks, such as the foramen spinosum and ovale were correctly localized by NNS. Deeper landmarks, such as the central part of the IAC lying beneath the surface of the petrous apex could not be localized via NNS. The exact area of bone removal along roof of IAC was determined by using the orientation provided by the probe placed between the basal turn of cochlea and the vestibule. We were able to validate the location of the IAC via a medial to lateral drilling by using the navigation this reference point. Conclusion The NNS can be used effectively during the MFA, and localizing superficial landmarks on the middle fossa floor with a higher accuracy may prove helpful in identifying the IAC from above. By referring to the cochlea–vestibule junctional area, the exact location of the trace of the IAC can be revealed.

Morphometry around Cochleostomy Site to Aid Safe Cochlear Implantation.

In morphologically normal-appearing inner ears, measurements of the distance between the round window and carotid canal (RCD), the maximum diameter of the basal turn of the cochlea next to the round window (BD), and the thickness of the promontory (PT) just lateral to the basal turn may be used as guide for safe cochleostomy and implant placement. From January to March 2022, a cross-sectional observational study was carried out in a tertiary care hospital. The round window to carotid canal distance (RCD), the largest diameter of the cochlea's basal turn next to the round window (BD), and the thickness of the promontory immediately lateral to the basal turn (PT) were measured using CT temporal bone images of 150 persons without cochlear abnormalities. The values obtained were compared using Paired T-test for significance of difference between both genders and sides. A total of 150 participants-75 men and 75 women-with a mean age of 37.5 years were enrolled in the study. With a range of 7.18 mm to 10.52 mm, the mean RCD was 8.84 mm (SD 0.8 mm). The mean BD was 2.27 mm (SD 0.4 mm), while the mean PT was 1.15 mm (SD 0. mm). The values obtained did not differ significantly in both the genders and the right and left sides (p = 0.37 and 0.24, respectively). The present study has defined and calculated pertinent measures at cochleostomy site that will aid safe electrode insertion and prevent misplacement.

Effect of perinatal and postnatal thiamine deficiency on auditory pathway of the Wistar-Albino rats.

In this study, we created an animal model to demonstrate the effects of thiamine on the hearing pathways of new-borns during pregnancy and lactation by inducing a dietary thiamine deficiency in the mother. The study included 16 female Wistar albino rats. The animals were separated into four groups and provided the appropriate amounts of dietary thiamine according to their groups during pre-pregnancy, pregnancy, and lactation periods. Three pups from each mother were included in the study, and 12 pups were selected from each group. On the fortieth day after birth, the auditory pathways of 48 pups in the 4 groups were examined electro physiologically and ultra-structurally. In Group N-N, morphology of hair cells stereocilia degeneration was not obtained in all turns of cochlea. In Group N-T, Inner Hair Cells (IHCs) and Outher Hair Cells (OHCs) stereocilia didn't show degeneration in all turns of cochlea but had rupture inrows of HCs stereocilia. In group T-N IHCs stereocilia less degeneration was observed in all turns of cochlea. OHC stereocilia partial loss was observed only in basal turn of cochlea. In Group T-T IHCs stereocilia was observed less degeneration and rupture in all turns of cochlea. Thiamine is vital for the development of cochlear hair cells during both prenatal and postnatal periods. Even partial deficiency of thiamine causes significant degeneration to the auditory pathway. The level of evidence of this article is 5. This article is an experimental animal and laboratory study.

Symptoms: Sudden Hearing Loss and Aural Fullness

Symptoms: Sudden Hearing Loss and Aural Fullness

Two Cases of Cochlear Implantation in Patients With Unilateral Profound Hearing Loss Due to Intralabyrinthine Schwannoma

When vestibular schwannoma originates from the segment within the labyrinth of the vestibulocochlear nerve, it is termed intralabyrinthine schwannoma (ILS). As most of the cases are presented with profound sensorineural hearing loss on the affected side, for auditory rehabilitation, cochlear implantation can be considered simultaneously as the tumor removal. Successful results of cochlear implantation were reported in patients with ILS even after partial resection of the mass. In this study, we report the cases of two patients with ILS with unilateral deafness. In one patient, a mass found in the basal turn of cochlea was removed totally and a cochlear implantation electrode was fully inserted. In the other patient, a mass found in the basal turn and vestibule was partially removed and an electrode was inserted. Postoperatively, hearing was improved and tinnitus was reduced.

Disruption of the autism-related gene Pak1 causes stereocilia disorganization, hair cell loss, and deafness in mice

Several clinical studies have reported that hearing loss is correlated with autism in children. However, little is known about the underlying mechanism between hearing loss and autism. p21-activated kinases (PAKs) are a family of serine/threonine kinases that can be activated by multiple signaling molecules, particularly the Rho family of small GTPases. Previous studies have shown that Pak1 mutations are associated with autism. In the present study, we take advantage of Pak1 knockout (Pak1−/−) mice to investigate the role of PAK1 in hearing function. We find that PAK1 is highly expressed in the postnatal mouse cochlea and that PAK1 deficiency leads to hair cell (HC) apoptosis and severe hearing loss. Further investigation indicates that PAK1 deficiency downregulates the phosphorylation of cofilin and ezrin-radixin-moesin and the expression of βII-spectrin, which further decreases the HC synapse density in the basal turn of cochlea and disorganized the HC stereocilia in all three turns of cochlea in Pak1−/− mice. Overall, our work demonstrates that the autism-related gene Pak1 plays a crucial role in hearing function. As the first candidate gene linking autism and hearing loss, Pak1 may serve as a potential target for the clinical diagnosis of autism-related hearing loss.

Surgical anatomy of basal turn in relation to middle cranial fossa and round window as pertaining to middle fossa cochlear implant technique.

The purpose of this investigation was to evaluate the relation of the basal turn of cochlea with middle cranial fossa and round window as pertaining to middle cranial fossa cochlear implant technique. Fifty-four formalin preserved temporal bones were micro-dissected to expose the basal turn. The point (f) was marked on the basal turn of cochlea where there was minimum distance of basal turn of cochlea from the floor of middle cranial fossa (f1). The f-f1 distance, the angle (∠smf) and distance of point "f" from the round window (s-f) was measured. The mean minimum distance between basal turn of cochlea and floor of middle cranial fossa (f-f1) was 2.0 ± 0.7mm.The point f was at mean distance (s-f) and angle (∠smf) of 14.7 ± 1.6mm and 217° ± 13.7° from round window, respectively. The information may be helpful for designing appropriate electrode array for middle fossa technique especially for deciding the length of electrode array towards round window, as otherwise electrode may extend into vestibule of inner ear. In the cases where bone thickness between superior part of basal turn of cochlea and middle cranial fossa is < 1.5mm, surgeon should be extra cautious.

Impact of the Surgical Approach: A Comparative Study between Transcanal and Posterior Tympanotomy Approach for Cochlear Implantation

Abstract Introduction The aim of our study is to compare the surgical complications of the transcanal and posterior tympanotomy approach and to evaluate the advantages and disadvantages of both techniques. Materials and Methods It is a prospective study involving 252 pediatric cochlear implant patients operated in the Department of ENT, GMERS Medical College and General Hospital, Gandhinagar, Gujarat, India. Out of these, 126 patients were operated by transcanal approach (group A) and 126 patients were operated by posterior tympanotomy approach (group B). Results No significant difference in the mean duration of surgery (p &gt; 0.064) was observed in both the groups. Major complications occurred in 60.2% of group A and 3.1% of group B and minor complications occurred in 65% of group A and 3.1% in group B, which is highly significant (p &lt; 0.0134). The categories of auditory perception, speech intelligibility rating scales, meaningful auditory integration scale, and meaningful use of speech scale were assessed in both groups. Conclusion Complication rate in the transcanal approach is higher as compared with posterior tympanotomy approach. A complete alignment and introduction of electrode array into the basal turn of cochlea is more favorable in the posterior tympanotomy approach. Transcanal technique even as an alternative may not be useful. Outcomes may be affected depending upon the technique chosen.

Correlation between Carotid–Cochlear and Sensorineural Hearing Loss: A Cross-Sectional Study

Abstract Background Sensorineural hearing loss is a condition with several etiologies and varies with the age of the individual. Carotid–cochlear interval is the minimum distance between basal turn of cochlea and the genu of petrous part of internal carotid artery. It is believed that constant pulsations from carotid can cause fluid pressure changes within the cochlea leading to damage to hair cells causing hearing loss. Objective To study the correlation between carotid–cochlear interval and degree of hearing loss at different frequencies in patients with sensorineural deafness and compare this interval with normal subjects. Methods Seventy cases with sensorineural hearing loss between 18 and 60 years undergoing HRCT temporal bone were grouped together and 70 cases with normal hearing undergoing CT nose and paranasal sinuses were grouped together. Carotid–cochlear interval measured in both the groups was correlated with the degree and frequency of hearing loss and compared with normal subjects. Results The mean carotid–cochlear interval in sensorineural hearing loss and in normal subjects was found to be 1.30 + 0.68 (SD) mm and 1.83 + 0.74 (SD) mm, respectively with p &lt; 0.001. The coefficient of correlation between carotid–cochlear interval and pure tone average in patients with sensorineural deafness was r = −0.740 with p-value &lt; 0.001. Conclusion Carotid–cochlear interval is significantly low in patients with sensorineural hearing loss and bears a strong negative correlation with the degree of hearing loss at mid- and high-frequency ranges. Thus we hypothesize that pulsations from carotid artery cause damage to hair cells in the organ of Corti producing audiological symptoms such as hearing loss.

The Human Cochlear Aqueduct and Accessory Canals: a Micro-CT Analysis Using a 3D Reconstruction Paradigm.

We sought to study the anatomic variations of the cochlear aqueduct and its accessory canals in human temporal bones using micro-CT and a 3D reconstruction paradigm. More knowledge about the anatomic variations of these structures, particularly at the basal turn of the cochlea and round window niche, may be important to better preserve residual hearing as well as the neural supply during cochlear implant surgery. An archival collection of 30 human temporal bones underwent micro-CT and 3D reconstruction. A surface enhancement paradigm was applied. The application displays reconstructed slices as a 3D object with realistic 3D visualization of scanned objects. Virtual sectioning or "cropping" of the petrous bone presented subsequent areas. Thereby, the bony canals could be followed from inside the basal turn of cochlea and middle ear to the jugular foramen. The cochlear aqueduct was always paralleled by an accessory canal containing the inferior cochlear vein. It ran from the basal turn of the cochlea and exited laterally in the jugular foramen. In 70% of the cases, a secondary accessory canal was observed and it derived mostly from a depression or infundibulum located in the floor of the round window niche. This canal also exited in the jugular foramen. The secondary accessory canal occasionally anastomosed with the primary accessory canal suggesting that it contains a vein that drains middle ear blood to the cranial sinus. Micro-CT with 3D surface reconstruction paradigm offers new possibilities to study the topographic anatomy of minor details in the human inner ear. The technique creates simulated transparent "castings" of the labyrinth with a coinciding surface view through enhancement of contrast between boundaries. Accessory canals that drain blood from the cochlea, spiral ganglion, and middle ear could be characterized three-dimensionally.

Surgical anatomy of the round window-Implications for cochlear implantation.

The round window is an important portal for the application of active hearing aids and cochlear implants. The anatomical and topographical knowledge about the round window region is a prerequisite for successful insertion for a cochlear implant electrode. To sum up current knowledge about the round window anatomy and to give advice to the cochlear implant surgeon for optimal placement of an electrode. Systematic Medline search. Search term "round window[Title]" with no date restriction. Only publications in the English Language were included. All abstracts were screened for relevance, that is a focus on surgical anatomy of the round window. The search results were supplemented with hand searching of selected reviews and reference lists from included studies. Subjective assessment. There is substantial variability in size and shape of the round window. The round window is regarded as the most reliable surgical landmark to safely locate the scala tympani. Factors affecting the optimal trajectory line for atraumatic electrode insertion are anatomy of the round window, the anatomy of the intracochlear hook region and the variable orientation and size of the cochlea's basal turn. The very close relation to the sensitive inner ear structures necessitates a thorough anatomic knowledge and careful insertion technique, especially when implanting patients with residual hearing. In order to avoid electrode migration between the scalae and to achieve protect the modiolus and the basilar membrane, it is recommended to aim for an electrode insertion vector from postero-superior to antero-inferior.

Two Cases of Electrode Kinking in Cochlear Implantation

Less traumatic electrode insertion along the basal turn of cochlea is essential to cochlear implantation. However, immoderate attempts to insert the electrode beyond the point of resistance can result in electrode kinking within the basal turn of cochlea. Electrode kinking tends to occur 1) in the use of contour or hugging type of electrode, 2) in the cochlear ossification or fibrosis, and 3) in wrong angle insertion in the approach of round window membrane or cochleostomy near the round window. Intra-operative radiologic evaluation and intra-operative measurement of the neural response telemetry or auditory nerve response telemetry during cochlear implantation is essential to check the status and proper insertion of electrode. Recently, we experienced two cases of electrode kinking in cochlear implantation and discovered that both patients showed abnormal impedances and crumpled electrode in X-ray. Based on these cases, we suggest routine impedance and radiologic measurement during the cochlear implantation. Key words: Cochlea ㆍ Cochlear implantation ㆍ Electrode ㆍ Ossificaition

Unusual narrowing in basal turn of cochlea and cochlear implantation

Unusual narrowing in basal turn of cochlea and cochlear implantation

The impact of the cochlear-carotid interval on tinnitus perception.

We hypothesized that the cochlear-carotid interval (CCI), which is defined as the smallest distance along the petrous segment of the internal carotid artery and basal turn of cochlea, may be associated with direct stimulation of hair cells, thereby affecting tinnitus perception. The aim of this study was to investigate the relationships between the CCI, tinnitus perception, and accompanying hearing loss in patients with tinnitus. The CCI on both sides was measured independently by two observers from the temporal 3D b-FFE MR images of 25 patients with tinnitus and 20 age/gender matched control subjects. The relationships between CCI, tinnitus visual analog scale (VAS), and tinnitus handicap inventory (THI) were investigated. CCI ranged 0.2-5.6mm (1.9±1.5) on the right and 0.1-5.4mm (2.2±1.6) on the left side in the patient group and 0.5-5.4 (1.9±1.4) mm on the right and 0.3-6.7 (2.3±1.7) on the left side in the control group. The differences between the two groups were not statistically significant (p>0.05). CCI showed a strong negative correlation with THI and VAS scores on both sides. Correlation of audiologic findings with CCI revealed a significant negative correlation with pure tone average of the ipsilateral ear most affectedly at high frequencies. The strong negative correlation of CCI with tinnitus-related distress and accompanying sensorineural hearing loss predominantly at high frequencies suggests that further studies on patients with tinnitus that focus on this small area may help to improve the knowledge of tinnitus pathophysiology.

Contrast perilymphatic MRI findings of inner ear in sudden hearing loss with vertigo

Objective To explore the contrast perilymphatic MRI characteristics of inner ears with sudden hearing loss with vertigo. Methods Forty three patients with sudden hearing loss with vertigo and 35 patients with unilateral tinnitus diagnosed by the department of Otolaryngology-Head and Neck Surgery were retrospectively included. Forty eight ears (38 ears with unilateral sudden hearing loss and 10 ears in 5 cases with bilateral sudden hearing loss) were regarded as sudden hearing loss group, 35 asymptomatic ears (the opposite ears of the unilateral tinnitus ears) as control group. Thirty eight opposite ears of the 38 unilateral sudden hearing loss ears and 35 ears of the control group showed normal in the pure tone audiometry exam. One hundred and twenty one ears (48 hearing loss ears, 38 opposite ears of the 38 unilateral sudden hearing loss ears and the 35 control group's ears) underwent contrast perilymphatic MR exams, 0.4 to 0.5 ml gadolinium hydrate diluted with saline was injected through the tympanic membrane, twenty four hours later, three-dimensional fluid attenuated inversion recovery (3D-FLAIR) sequence was performed using a 3.0 T MRI scanner. After the contrast perilymphatic MR exam, success in the exam was judged through the raw image. The signal intensity ratio (SIR) of cochlea basal turn and homolateral brain stem was quantitatively calculated. The SIR difference of 48 ears with sudden hearing loss and 35 asymptomatic ears in control group was analyzed by t test. The SIR difference of the 38 unilateral sudden hearing loss ears and the contralateral asymptomatic ears was also analyzed. The presence of endolymphatic hydrops was judged. Results The contrast perilymphatic MRI of 121 inner ears with intratympanic gadolinium injection were all successful. Endolymphatic hydrops were observed in 12 sudden hearing loss ears with the occurrence rate of 25%(12/48). The SIR of basal turn and homolateral brain stem of the sudden hearing loss ears (2.062±0.907) were lower than the SIR of the control groups' asymptomatic ears (2.703± 0.640) with significant difference between them (t=3.619,P=0.001), the SIR of basal turn and homolateral brain stem of the unilateral sudden hearing loss ears (1.941±0.860) were also lower than the SIR of the contralateral asymptomatic ears (2.411±0.670) with statistical difference between them (t =3.270,P=0.002). Conclusions Endolymphatic hydrops were observed in sudden hearing loss with vertigo. The SIR of the cochlea in sudden hearing loss ears were lower than that of the asymptomatic ears, indicating the abnormal permeability of the round window membrane. Key words: Hearing loss; Sudden; Magnetic resonance imaging

Congenital Anomaly of Cochlea: A Case Report

Congenital malformations of inner ear are rare anomalies. These occur due to arrested development at different stages of embryogenesis. One rare anomaly of inner ear is Mondini dysplasia. Possibly it occurs due to arrested development of cochlea in its embryonic stage at about sixth week of gestation. In this anomaly only basal turn of cochlea is developed. There is deficient interscalar septum for distal one & half turn. Thus bony cochlea is restricted to 1.5 turns only. This causes sensorineural hearing loss. One such anomaly was recognized clinically in a 4yrs old girl who presented with congenital deafness. Thorough systemic & specific examination was done.Radiological examination (Computed Tomography) revealed, that there was defect in the turn of cochlea i.e. cochlea was only one half turn.

Insertion Depth Angles of Cochlear Implant Arrays With Varying Length

The aim of the study is to investigate the insertion depth angles for different types of electrode arrays and its variability depending on the individual cochlear size. Preoperative estimation of the insertion depth angles for different electrode arrays can help surgeons choose the optimal electrode length, especially for low-frequency residual hearing preservation. Four different electrode arrays varying in lengths (20, 24, 28, and 31 mm) were inserted in 10 temporal bones to quantify the insertion depth angle of each inserted electrode. High-resolution 3D radiographs provided by Flat Panel Computed Volume Tomography (FPCT) were used to determine electrode array insertion depth angle and diameter of the cochlea's basal turn. The high-resolution FPCT images from all electrode arrays inserted into the temporal bones allowed reliable measurements of insertion depth angles. In particular, statistically significant different insertion depth angles between the various array types were identified. The insertion of the 20-, 24-, 28-, and 31-mm arrays yielded a mean insertion depth angle of 341 degrees (SD, 22 degrees), 477 degrees (SD, 36 degrees), 587 degrees (SD, 42 degrees), and 673 degrees (SD, 38 degrees), respectively. Furthermore, a statistically significant negative correlation between insertion depth angle and diameter of the cochlea's basal turn was found for the 20- and 31-mm arrays. The results suggest an individually adapted length of electrode arrays, which should be taken into account for an improved decision paradigm for patients scheduled for cochlear implantation. This is of particular importance for patients with low-frequency residual hearing.

Diet-Induced Obesity Exacerbates Auditory Degeneration via Hypoxia, Inflammation, and Apoptosis Signaling Pathways in CD/1 Mice

The aim of this study was to investigate the mechanisms of diet-induced obesity on hearing degeneration in CD/1 mice. Sixty 4-week-old male CD/1 mice were randomly and equally divided into 2 groups. For 16 weeks, the diet-induced obesity (DIO) group was fed a high fat diet and the control group was fed a standard diet of 13.43 % kcal fat. The morphometry, biochemistry, auditory brainstem response thresholds, omental fat, and histopathology of the cochlea were compared between the beginning and end of the study (4 vs. 20 weeks old). The results show that the body weight, fasting plasma triglyceride concentrations, and omental fat weight were higher in the DIO group than in the control group at the end of experiment. The auditory brainstem response thresholds at high frequencies were significantly elevated in the DIO group compared to those of the control group. Histology studies showed that, compared to the control group, the DIO group had blood vessels with smaller diameters and thicker walls in the stria vascularis at the middle and basal turns of the cochlea. The cell densities in the spiral ganglion and spiral ligament at the basal turn of the cochlea were significantly lower in the DIO group. Immunohistochemical staining showed that hypoxia-induced factor 1 (HIF-1), tumor necrosis factor alpha (TNF-α), nuclear factor kappa B (NF-κB), caspase 3, poly(ADP-ribose) polymerase-1, and apoptosis inducing factor were all significantly more dense in the spiral ganglion and spiral ligament at the basal turn of cochlea in the DIO group. Our results suggest that diet-induced obesity exacerbates hearing degeneration via increased hypoxia, inflammatory responses, and cell loss in the spiral ganglion and spiral ligament and is associated with the activation of both caspase-dependent and -independent apoptosis signaling pathways in CD/1 mice.

Characterization of neuronal cell death in the spiral ganglia of a mouse model of endolymphatic hydrops.

Spiral ganglion neurons (SGN) in the Phex male mouse, a murine model of postnatal endolymphatic hydrops (ELH) undergo progressive deterioration reminiscent of human and other animal models of ELH with features suggesting apoptosis as an important mechanism. Histologic analysis of the mutant's cochlea demonstrates ELH by postnatal Day (P) 21 and SGN loss by P90. The SGN loss seems to occur in a consistent topographic pattern beginning at the cochlear apex. SGN were counted at P60, P90, and P120. Semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR), quantitative PCR, and immunohistochemical analyses of activated caspase-3, caspase-8, and caspase-9 were performed on cochlear sections obtained from mutants and controls. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling assay (TUNEL) was carried out on 2 mutants and 2 controls. Corrected SGN counts in control mice were greater in the apical turn of the cochleae at P90 and P120, respectively (p < 0.01). Increased expression of activated caspase-3, caspase-8, and caspase-9 was seen in the mutant. At later time points, activated caspase expression gradually declined in the apical turns and increased in basal turns of the cochlea. Quantitative and semiquantitative PCR analysis confirmed increased expression of caspase-3, caspase-8, and caspase-9 at P21 and P40. TUNEL staining demonstrated apoptosis at P90 in the apical and basal turns of the mutant cochleae. SGN degeneration in the Phex /Y mouse seems to mimic patterns observed in other animals with ELH. Apoptosis plays an important role in the degeneration of the SGN in the Phex male mouse.