Growth patterns of facial muscles at the angle of the mouth: A histological study using midterm and near-term human fetuses.

At the angle of the mouth, spoke-like muscle bundles converge at the "modiolus," which is believed to appear in utero. The aim of this study was to investigate the growth of the modiolus histologically. We studied frontal histological sections of the face from 12 midterm and six near-term fetuses. At midterm, a convergence of the levator anguli oris (LAOM) and depressor anguli oris (DAOM) was frequently present, and another convergence of the LAOM with the platysma (PM) or orbicularis oris (OOM) was also often evident. At near-term, muscle fiber merging or interdigitation was classified into nine combinations, five of which were frequently seen: LAOM-PM, LAOM-DAOM, zygomaticus major (ZMM)-orbicularis oris (OOM), buccinator (BM)-LAOM, and BM-PM. These combinations existed at slightly different depths and/or sites, thus allowing the angle of the mouth to receive multiple muscles. Notably, tissues interposed between the muscle fibers were limited to a thin epimysium at each crossing or interdigitation. Therefore, the LAOM, DAOM, OOM, BM, and PM appear to form a basic configuration at birth, but the development and growth were much delayed than the classical description. The modiolus is not a specific fibromuscular structure but simply represents a cluster of muscle convergence sites. Even at meeting between an elevator and depressor, a specific fibrous structure seems unlikely to connect the epimysium for the muscle convergence. Instead, the central nervous system appears to regulate the activity of related muscles to minimize tension or friction stress at the meeting site.

"Untying the knot": The primitive orofacial muscle architecture in the gorilla (Gorilla gorilla) as a key to the evolution of hominin facial movement.

The anatomical underpinnings of primate facial expressions are essential to exploring their evolution. Traditionally, it has been accepted that the primate face exhibits a "scala natura" morphocline, ranging from primitive to derived characteristics. At the primitive end, the face consists of undifferentiated muscular sheets, while at the derived end there is greater complexity with more muscles and insertion points. Among these, the role of the human modiolus ("knoten" in German) has been emphasized. Recent studies have challenged this view by revealing significant complexity in the faces of several non-human primates, thereby rejecting the linear notion of facial evolution. However, our knowledge of the facial architecture in gorillas, the second closest living relatives to modern humans, remains a significant gap in the literature. Here, we present new findings based on dissection and histological analysis of one gorilla craniofacial specimen, alongside 30 human hemifaces. Our results indicate that while the number and overall arrangement of facial muscles in the gorilla are comparable to those of chimpanzees and modern humans, several orofacial features distinguish the gorilla's anatomy from that of hominins. Among these are the absence of a modiolus, the continuity of muscular fibers over the region of the mouth corner, the flat (uncurving) sheet of the orbicularis oris muscle, and the insertion of direct labial tractors both anterior and posterior to it. Collectively, the anatomical characteristics observed in the gorilla suggest that the complex anatomy of the hominin face should be considered synapomorphic (shared-derived) within the Pan-Homo clade.

The three layered structure of orbicularis oris and buccinator complex with partial connection at the modiolus and partial direct continuation.

PURPOSE: This study aimed to clarify the structural arrangement of the orbicularis oris (OOr), the buccinator, and the other perioral muscles around the modiolus. METHODS: The perioral muscles in seventeen cadavers fixed with formalin were dissected in situ and/or in isolated muscle specimens, and their layers were reconstructed schematically upon pantomographic view of the skeleton to evaluate their actions. RESULTS: The buccinator was composed of three parts including upper and lower oblique parts in its superficial layer and a middle transverse part in its deep layer. The superior and inferior OOr were composed of an inner marginal part (IM) and an outer labial part (OL) in each. The perioral muscles as a whole were arranged in three layers. The first layer consisted of the depressor anguli oris and the OL of superior OOr connected at the modiolus in a vertical direction. The second layer consisted of the upper and inner oblique part of buccinator and a part of the OL of inferior OOr connected at the modiolus in a horizontal direction. The third layer contained the middle transverse part of buccinator continuous with the IM of both OOr and a part of the OL of inferior OOr without connection to the modiolus. CONCLUSIONS: The different arrangement of the three layers of perioral muscles around the modiolus could serve as a good basis to predict the actions of the individual perioral muscles on the movement of lips in open/close of the oral fissure and widening/narrowing of the lip width.

Evaluation of CI electrode position from imaging: comparison of an automated technique with the established manual method.

BACKGROUND: A manual evaluation of the CI electrode position from CT and DVT scans may be affected by diagnostic errors due to cognitive biases. The aim of this study was to compare the CI electrode localization using an automated method (image-guided cochlear implant programming, IGCIP) with the clinically established manual method. METHODS: This prospective experimental study was conducted on a dataset comprising N=50 subjects undergoing cochlear implantation with a Nucleus® CI532 or CI632 Slim Modiolar electrode. Scalar localization, electrode-to-modiolar axis distances (EMD) and angular insertion depth (aDOI) were compared between the automated IGCIP tool and the manual method. Two raters made the manual measurements, and the interrater reliability (±1.96·SD) was determined as the reference for the method comparison. The method comparison was performed using a correlation analysis and a Bland-Altman analysis. RESULTS: Concerning the scalar localization, all electrodes were localized both manually and automatically in the scala tympani. The interrater differences ranged between ±0.2 mm (EMD) and ±10° (aDOI). There was a bias between the automatic and manual method in measuring both localization parameters, which on the one hand was smaller than the interrater variations. On the other hand, this bias depended on the magnitude of the EMD respectively aDOI. A post-hoc analysis revealed that the deviations between the methods were likely due to a different selection of mid-modiolar axis. CONCLUSIONS: The IGCIP is a promising tool for automated processing of CT and DVT scans and has useful functionality such as being able to segment the cochlear using post-operative scans. When measuring EMD, the IGCIP tool is superior to the manual method because the smallest possible distance to the axis is determined depending on the cochlear turn, whereas the manual method selects the helicotrema as the reference point rigidly. Functionality to deal with motion artifacts and measurements of aDOI according to the consensus approach are necessary, otherwise the IGCIP is not unrestrictedly ready for clinical use.

Quality-assured training in the evaluation of cochlear implant electrode position: a prospective experimental study.

BACKGROUND: The objective of this study was to demonstrate the utility of an approach in training predoctoral medical students, to enable them to measure electrode-to-modiolus distances (EMDs) and insertion-depth angles (aDOIs) in cochlear implant (CI) imaging at the performance level of a single senior rater. METHODS: This prospective experimental study was conducted on a clinical training dataset comprising patients undergoing cochlear implantation with a Nucleus® CI532 Slim Modiolar electrode (N = 20) or a CI512 Contour Advance electrode (N = 10). To assess the learning curves of a single medical student in measuring EMD and aDOI, interrater differences (senior-student) were compared with the intrarater differences of a single senior rater (test-retest). The interrater and intrarater range were both calculated as the distance between the 0.1th and 99.9th percentiles. A "deliberate practice" training approach was used to teach knowledge and skills, while correctives were applied to minimize faulty data-gathering and data synthesis. RESULTS: Intrarater differences of the senior rater ranged from - 0.5 to 0.5 mm for EMD and - 14° to 16° for aDOI (respective medians: 0 mm and 0°). Use of the training approach led to interrater differences that matched this after the 4th (EMD) and 3rd (aDOI) feedback/measurement series had been provided to the student. CONCLUSIONS: The training approach enabled the student to evaluate the CI electrode position at the performance level of a senior rater. This finding may offer a basis for ongoing clinical quality assurance for the assessment of CI electrode position.

PCR and histology identify new bivalve hosts of Apicomplexan-X (APX), a common parasite of the New Zealand flat oyster Ostrea chilensis.

Apicomplexan-X (APX) is a significant pathogen of the flat oyster Ostrea chilensis in New Zealand. The life cycle and host range of this species are poorly known, with only the zoite stage identified. Here, we report the use of molecular approaches and histology to confirm the presence of APX in samples of green-lipped mussels Perna canaliculus, Mediterranean mussels Mytilus galloprovincialis and hairy mussels Modiolus areolatus collected from widely distributed locations in New Zealand. The prevalence of APX infection estimated by PCR was 22.2% (n = 99) and 50% (n = 30) in cultured green-lipped mussels from Nelson and Coromandel, respectively; 0.8% (n = 258), 3.3% (n = 150) and 35.3% (n = 17) in wild Mediterranean mussels from Nelson, Foveaux Strait and Golden Bay, respectively; and 46.7% (n = 30) in wild hairy mussels from Foveaux Strait. Histology detected all cases of PCR that were positive with APX and appeared to be more sensitive. The prevalence of APX estimated by histology in green-lipped mussels from Coromandel was 60% versus 50% by PCR, and 4.3%, 10.7% and 52.9% by histology versus 0.8%, 3.3% and 35.3% by PCR in wild Mediterranean mussels from Nelson, Foveaux Strait and Golden Bay, respectively. The specific identity of the parasite found in mussels was determined by sequencing PCR products for a portion (676 bp) of the 18S rRNA gene; the resulting sequences were 99-100% similar to APX found in flat oysters. Phylogenetic analyses also confirmed that all isolates from green-lipped, Mediterranean and hairy mussels grouped with APX isolates previously identified from flat oysters. This study indicates the wide geographical distribution of APX and highlights the potentially multi-host specific distribution of the parasite in commercially important bivalve shellfish.

Cochleostomy and facial recess packing alter cochlear implant electrode location in a human cochlea model.

PURPOSE: Determine the effect of cochleostomy and facial recess packing on cochlear implant electrode distance from the modiolus. MATERIALS AND METHODS: Two otolaryngology residents (PGY5 and PGY6) and one attending ear surgeon performed electrode insertions on a human cochlea model using perimodiolar (Cochlear® Slim Modiolar 532™, CI532) and lateral wall electrodes (Cochlear® Slim Straight 522™, CI522) via a cochleostomy. Packing material was simulated using cotton and placed in the cochleostomy and facial recess under the following conditions: 1) inferior to the electrode, 2) superior, 3) both inferior and superior, and 4) no packing. Distance of the electrode from the modiolus at the proximal, middle, and distal basal turn of the cochlea were measured by photomicrograph analysis. RESULTS: Packing superior to the CI532 resulted in a significant decrease in distance from the modiolus at the middle and distal basal turn compared to the inferior condition, with the largest effect in the middle basal turn (0.25 mm vs. 1.92 mm, respectively, p < 0.001). For the CI522, packing superior similarly resulted in decreased distance to the modiolus when compared to the inferior packing condition at the middle and distal basal turn regions, with the largest effect in the middle basal turn (1.25 mm vs. 1.75 mm, respectively, p = 0.002). CONCLUSIONS: Packing of the cochleostomy site and facial recess has a significant effect on electrode distance from the modiolus in the middle and distal basal turn using a model of a human cochlea. Effects were more pronounced when using the perimodiolar (CI532) electrode.

Renaissance-Europe-16th Century continued.

This chapter is limited to the text of Della Cruce, which contains the most comprehensive account of the instruments used in cranial surgery at the time. Of particular importance is Della Cruce's attitude to what he called non-perforating straight trepans, which in general he disliked. It may be noted that his text was the last to describe this sort of instrument. In the succeeding centuries, changes to penetrating instruments were all variations on the shape of different kinds of crown trepan. Like Berengario, Della Cruce described brace and bit trepans with interchangeable bits. Various methods were employed to prevent them penetrating too deeply.

Rome-Celsus (ca 25BC to ca. 50AD).

Celsus gave an adequate description of the bones and sutures of the calvarium. His classification of injuries was simple including fissures and depressions. He is the first to relate specific symptoms to specific tissue injury. In addition, he was aware that fractures could be present in the absence of typical findings. He was also the first to note the meningeal vessels could rupture producing severe localized pain. His treatment was more conservative than that of Hippocrates. Plasters were to be used and if there was no deterioration trepanation was avoided. He described the use of the crown trepan (modiolus) and the instrument with a smaller tip which expands rapidly to prevent penetration. He also described the technique of rotating the trepan between the palms. His description of operations for depressed fractures were unusually clear and relevant even by modern standards. His wound care is strikingly different from that of Hippocrates as he advocates various dressings soaked in vinegar and as time passes plasters should be softened with rose oil. Regrettably, Celsus influence would not be felt until the time of the Renaissance, because his texts were lost. However, his "De Medicina" was rediscovered and became the first medical text to be published using the new moveable type printing press, in the year 1478. Thus, his influence was minimal in the Arabic world and the early Renaissance. Thereafter it was profound.

Endoscopic Temporalis Tendon Extension (ETTE).

Many techniques have been proposed to restore facial symmetry in facial nerve palsies. This study presents our surgical approach called Endoscopic Temporalis Tendon Extension (ETTE). After nasotracheal intubation, a 4 cm skin incision is made at the nasolabial fold. Under endoscopic view, the medial face of the masseter muscle is detached from the mandibular ramus. The coronoid process is then sectioned by Piezosurgery®. Finally, a fascia lata graft is suspended between the temporalis tendon and the orbicularis oris. ETTE is a mixed technique, with a static suspension component and a dynamic contraction one. The preservation of the temporalis muscle insertion in temporal fossa allows for an optimal contraction. A fascia lata graft is necessary for reasons of length. The scar produced by the nasolabial incision allows to recreate the missing nasolabial fold. The endoscopic assistance provides greater precision during the procedure and entails a shorter learning curve.

Dependability of Electrode to Modiolus Distance in Patients Specific Electrode Selection: A Cadaveric Model Study.

OBJECTIVE: This study aims to discern the disparities in the electrode-to-modiolus distance (EMD) between cochleostomy and round window approaches when performed sequentially in the same temporal bone. Additionally, the study seeks to identify the cochlear metrics that contribute to these differences. METHODOLOGY: A cross-sectional study was conducted, involving the sequential insertion of a 12-electrode array through both round window and cochleostomy approaches in cadaveric temporal bones. Postimplantation high-resolution CT scans were employed to calculate various parameters. RESULTS: A total of 12 temporal bones were included in the imaging analysis, revealing a mean cochlear duct length of 32.892 mm. The EMD demonstrated a gradual increase from electrode 1 (C1) in the apex (1.9 ± 0.07 mm; n = 24) to electrode 12 (C12) in the basal turn (4.6 ± 0.24 mm; n = 12; p < 0.01). Significantly higher EMD values were observed in the cochleostomy group. Correlation analysis indicated a strong positive correlation between EMD and cochlear perimeter (CP) (rs = 0.64; n = 12; p = 0.03) and a strong negative correlation with the depth of insertion (DOI) in both the middle and basal turns (rs = - 0.78; n = 20; p < 0.01). Additionally, EMD showed a strong negative correlation with the DOI-CP ratio (rs = -0.81; n = 12; p < 0.01). CONCLUSION: The cochleostomy group exhibited a significantly higher EMD compared with the round window group. The strong negative correlation between EMD and DOI-CP ratio suggests that in larger cochleae with shallower insertions, EMD is greater than in smaller cochleae with deeper insertions. LEVEL OF EVIDENCE: NA Laryngoscope, 134:4736-4744, 2024.

Elevated modiolus density on high-resolution computed tomography as an indicator of cochlear neurodysplasia: a retrospective case-control study.

Background: Cochlear neurodysplasia (CND) is recognized as a contributing factor to sensorineural hearing loss in children. This study aimed to investigate the relationship between modiolus density on high-resolution computed tomography (HRCT) and CND, and to evaluate its performance in diagnosing CND. Methods: This retrospective study collected HRCT images of 34 patients diagnosed with unilateral neurological hearing loss in the Children's Hospital of Chongqing Medical University from March 2018 to December 2023, who were also diagnosed with unilateral CND by computed tomography (CT) and magnetic resonance imaging (MRI) hydroimaging. CT values of the modiolus and petrous bone were measured on the affected and healthy sides, in addition to determining the width of cochlear nerve foramina and the width of internal auditory tract. The receiver operator characteristic (ROC) curve was used to evaluate the diagnostic performance of these features. Simultaneously, comparisons were conducted with parameters obtained from normal children. A total of 29 patients without CND were randomly selected as a control group. Results: The unilateral sensorineural hearing loss group had 34 patients, comprising 18 males and 16 females, with a median age of 4.5 years, ranging from 0.7 to 11 years. The normal children group consisted of 20 males and 9 females, with a median age of 5.9 years, ranging from 0.5 to 12.0 years. Statistically significant differences were observed in the CT values of the modiolus, modiolus/petrous bone CT value ratio, width of cochlear nerve foramina, and width of internal auditory tract between the affected and healthy sides in patients with unilateral sensorineural hearing loss (P<0.05). The area under the ROC curve (AUC) of the modiolus CT value and the width of cochlear nerve foramina for the diagnosis of unilateral sensorineural hearing loss was 0.98 [95% confidence interval (CI): 0.95-1.00] and 0.99 (95% CI: 0.98-1.00), respectively. the modiolus density was significantly elevated in the affected sides in patients with unilateral CND. The optimal cut-off value of modiolus CT values was 983 Hounsfield unit (HU). Conclusions: The elevated density of the modiolus on HRCT holds significant value in diagnosing CND.

Ti3 C2 Tx MXene Composite 3D Hydrogel Potentiates mTOR Signaling to Promote the Generation of Functional Hair Cells in Cochlea Organoids.

Organoids have certain cellular composition and physiological features in common with real organs, making them promising models of organ formation, function, and diseases. However, Matrigel, the commonly used animal-derived matrices in which they are developed, has limitations in mechanical adjustability and providing complex physicochemical signals. Here, the incorporation of Ti3 C2 Tx MXene nanomaterial into Matrigel regulates the properties of Matrigel and exhibits satisfactory biocompatibility. The Ti3 C2 Tx MXene Matrigel composites (MXene-Matrigel) regulate the development of Cochlear Organoids (Cochlea-Orgs), particularly in promoting the formation and maturation of organoid hair cells. Additionally, regenerated hair cells in MXene-Matrigel are functional and exhibit better electrophysiological properties compared to hair cells in Matrigel. MXene-Matrigel potentiates the amycin (mTOR) signaling pathway to promote hair cell differentiation, and mTOR signaling inhibition restrains hair cell differentiation. Moreover, MXene-Matrigel facilitates innervation establishment between regenerated hair cells and spiral ganglion neurons (SGNs) growing from the Cochlea modiolus in a co-culture system, as well as promotes synapse formation efficiency. The approach overcomes some limitations of the Matrigel-dependent culture system and greatly accelerates the application of nanomaterials in organoid development and research on therapies for hearing loss.

High Signal Intensity of the Cochlear Modiolus on Unenhanced T1-Weighted Images in Classical Infratentorial Superficial Siderosis.

Background: Superficial siderosis (SS) results from chronic bleeding in the subarachnoid space. SS can be classified as infratentorial SS (i-SS) and supratentorial SS (s-SS). The cochlear modiolus (CM) normally shows low signal intensity (SI) on Tl-weighted images (T1WI). We noticed persistently high SI of the CM on unenhanced thin-sliced T1WI in patients with i-SS. The purpose of this study was to evaluate the correlation between SS and high SI of the CM on unenhanced T1WI. Methods: This retrospective study analyzed three cases with i-SS, eight cases with s-SS, and 23 normal controls (NC) evaluated on unenhanced thin-sliced T1WI with a three-dimensional spoiled gradient-recalled echo sequence. CM-T1SI scores of 0, 1, and 2 indicated low, iso, and high SI, respectively. In cases with scores of 2 evaluated several times, all scores were reviewed for each case. The CM-T1SI ratio was defined as the contrast ratio between the CM and the cerebellum. Differences between the three groups were statistically analyzed based on the CM-T1SI score and ratio. Receiver operative curve (ROC) analysis was used to determine the cut-off values for differentiating the i-SS group from the NC group based on the CM-T1SI ratio. Results: Two patients with i-SS had a score of 2 on all evaluations. The CM-T1SI score and ratio differed significantly between the i-SS and NC groups. The accuracy of the CM-T1SI ratio for discriminating i-SS from NC was 98.9% at a cutoff value of 0.628. Conclusion: High SI of the CM on unenhanced TIWI can be an additional characteristic finding of i-SS.

Toward a cochlear implant electrode array with shape memory effect for post-insertion perimodiolar positioning.

For cochlear implants (CI) a final position of the electrode array (EA) along the inner wall of the spirally shaped cochlea is considered to be beneficial because it results in a closer proximity to the auditory nerve fibers. A shape memory effect (SME) could facilitate such shift of the EA toward the cochlear inner wall, but its implementation remains to be solved. The current study presents an EA prototype featuring the SME with minute adjustments of the material properties of Nitinol, a shape memory alloy, in combination with a suitable cooling strategy to prevent premature curling. Ten samples were successfully inserted by a CI surgeon into an artificial cochlear model submerged into a temperature-controllable water bath to simulate temporary hypothermia of the inner ear (31°C). Gentle insertions were possible, with an average insertion speed of 0.81 ± 0.14 mm/s. After recovery of body temperature, the desired position shift toward the modiolus was observed in all trials. Angular insertion depth increased by approximately 81.8° ± 23.4°. We demonstrate for the first time that using the body temperature responsive SME for perimodiolar EA positioning is feasible and does not impede a gentle surgical insertion.

Complications of Cochleostomy Versus Round Window Surgical Approaches: A Systematic Review and Meta-Analysis.

We conducted a systematic review and meta-analysis to compare round window (RW) and cochleostomy (C) surgical approaches for the placement of cochlear implants (CIs). After obtaining the Institutional Review Board (IRB) approval, 213 peer-reviewed articles published between January 1, 2000, and August 1, 2021, comparing RW and C approaches were identified via a search on Google Scholar, Cochrane, and PubMed. The inclusion criteria were articles having an English version and involving only human subjects (cadaveric or alive). Statistical analysis of compiled electrode-to-modiolus distances was performed with two-sample independent t-tests. Live patients were categorized as having complete hearing preservation (<10 dB threshold shift), partial hearing preservation (10-20 dB shift), or minimal hearing preservation (>20 dB shift). Chi-squared testing was used to compare the distribution of hearing preservation categories between surgical approaches. Due to the heterogeneous nature of the data, only summative information was provided on the effects of approaches on trauma, electrical impedance, speech perception, vestibular dysfunction, ease of scala tympani insertion, and scalar shift. A total of 3,797 CI patients were evaluated. The RW approach resulted in a smaller (0.15 mm smaller on average, p<0.05) electrode-to-modiolus distance when compared to the C approach. The RW approach (93.0%) led to statistically better hearing preservation than the C approach (84.3%) (p<0.05). The RW approach was also associated with better outcomes in terms of speech perception, ease of scala tympani insertion, and reduced scalar shift. No difference between approaches was found with regard to trauma, electrical impedance, and vestibular dysfunction. Based on our findings, the RW approach appears to have several benefits compared to the C approach.

MR Imaging of Cochlear Modiolus and Endolymphatic Hydrops in Patients With Menière's Disease.

Background: Menière's disease (MD) is an inner ear disorder characterized by recurrent episodes of spontaneous vertigo, unilateral low-frequency sensorineural hearing loss, tinnitus, and aural fullness. Current diagnosis still often has to rely on subjective and audiometric criteria only, although endolymphatic hydrops is recognized as the pathophysiological substrate of the disease, having been demonstrated in anatomical pathological studies and by magnetic resonance (MRI). The modiolus has a close functional and anatomical relationship with the cochlear nerve and membranous labyrinth and can be evaluated with MRI but no data exist on the modiolar size in MD. Purpose: Our purpose is to examine the following hypothesis. Is cochlear modiolus smaller in symptomatic ears in MD? Methods: We used a retrospective 3 Tesla MR study (heavily T2-weighted 3D fast asymmetric spin-echo images and 0.5 mm slice thickness) comparing the mean modiolar area (MMA) in the index and best ears of eight patients with definite MD based on audiometric data. The obtained MMA values were compared against the audiometric data and the presence of vestibular endolymphatic hydrops. Results: No differences were seen in MMA between best and worst ears. Ears with a pure tone average (PTA) ≥25 dB and more pronounced endolymphatic hydrops showed lower MMA (not statistically significant). Two patients with extreme endolymphatic hydrops showed a noteworthy ipsilateral decrease in the cochlear modiolus area. Conclusion: No differences were seen in MMA between best and worst ears in definite MD. Worse hearing function (PTA ≥ 25dB) and more pronounced endolymphatic hydrops seem to be associated with lower MMA. This might be related to bone remodeling as a consequence of endolymphatic hydrops. Further research is needed to corroborate and explore these findings.

Cochlear Pathomorphogenesis of Incomplete Partition Type II in Slc26a4-Null Mice.

Incomplete partition type II (IP-II) is frequently identified in ears with SLC26A4 mutations. Cochleae with IP-II are generally observed to have 1½ turns; the basal turns are normally formed, and the apical turn is dilated or cystic. The objective of this study was to characterize the pathomorphogenesis of the IP-II cochlear anomaly in Slc26a4-null mice. Otic capsules were dissected from Slc26a4Δ/+ and Slc26a4Δ/Δ mice at 1 and 8 days of age and at 1 and 3 months of age. X-ray micro-computed tomography was used to image samples. We used a multiplanar view and three-dimensional reconstructed models to calculate the cochlear duct length, cochlear turn rotation angle, and modiolus tilt angle. The number of inner hair cells was counted, and the length of the cochlear duct was measured in a whole-mount preparation of the membranous labyrinth. X-ray micro-computed tomography mid-modiolar planar views demonstrated cystic apical turns in Slc26a4Δ/Δ mice resulting from the loss or deossification of the interscalar septum, which morphologically resembles IP-II in humans. Planes vertical to the modiolus showed a similar mean rotation angle between Slc26a4Δ/+ and Slc26a4Δ/Δ mice. In contrast, the mean cochlear duct length and mean number of inner hair cells in Slc26a4Δ/Δ mice were significantly smaller than in Slc26a4Δ/+ mice. In addition, there were significant differences in the mean tilt angle and mean width of the modiolus. Our analysis of Slc26a4-null mice suggests that IP-II in humans reflects loss or deossification of the interscalar septum but not a decreased number of cochlear turns.

Presence of the spiral ganglion cell bodies beyond the basal turn of the human cochlea.

The purpose of this study was to obtain a better understanding of the number and distribution of spiral ganglion cell bodies (SGCB) in the central modiolus trunk of the human cochlea with normal hearing as well as with hearing loss due to various pathological conditions. A literature review was performed using the key words 'human spiral ganglion cell population', 'analysis of spiral ganglion cell population', 'survival of human spiral ganglion cells', 'human Rosenthal's canal', 'human ganglion cell counts', and 'distribution of human spiral ganglion cells' to identify articles published between 1968 and 2018. Articles were included if the number of SGCB in the four segments of the human cochlea and angular depth distribution of the SGCB were stated. Of 236 articles initially identified, 19 articles met the inclusion criteria. SGCB inside the Rosenthal's canal (RC) in the modiolus trunk extended to an angular depth of 630-680° which is near the end of the second turn of the cochlea. SGCBs in Segment IV of the cochlea account for approximately 25-30% of the entire SGCB population irrespective of the cochlear condition (normal vs. pathologic). In normal hearing subjects, the total number of SGCB ranged between 23,910 and 33,702 and in patients with hearing loss between 5733 and 28,220. This literature review elaborates on the current state of knowledge about the number and distribution of SGCB in the human cochlea.

The complete mitochondrial genome of a marine mussel, Modiolus comptus (Mollusca: Mytilidae), and its phylogenetic implication.

In this study, the complete mitochondrial genome of Modiolus comptus was determined and annotated for the first time. The 15,591 bp circular genome has a base composition of 24.3% A, 38.6% T, 12.5% C, and 24.5% G, demonstrating a bias of higher AT content (63.0%) than GC content (27.0%). The mitochondrial genome contains 12 protein-coding genes (PCGs), 20 transfer RNA genes (tRNA), 2 ribosomal RNA genes (12S rRNA and 16S rRNA), and one control region. All genes of M. comptus were encoded on the heavy strand, except trnT(ugu) gene. The whole mitochondrial genome of M. comptus and 21 mitogenomes of other Mytilidae species were used for phylogenetic analysis. The result indicated the newly sequenced species had the closest relationship with Modiolus nipponicus (MK721547) and was clustered within the clade of genus Modiolus.