Human Auditory Ossicles Research Articles

Multiscale 3D organization of human auditory ossicles unveiled by synchrotron small-angle X-ray scattering tensor tomography

Multiscale 3D organization of human auditory ossicles unveiled by synchrotron small-angle X-ray scattering tensor tomography

Anatomic and morphometric examination of auditory ossicles in sheep.

It is important to know the morphometry of the auditory ossicles for middle ear surgical applications. The present study aims to investigate the morphometric measurements of sheep auditory ossicles and the relationship between these ossicles. In this study, 100 malleus, incus and stapes of 50 Akkaraman sheep were examined using at trinocular stereo microscope and a total of 19 morphometric measurements were taken. The mean values of the morphometric measurements were obtained, and correlation analysis was performed between each part of each auditory ossicle. Similarities were found between the measurements of the lengths of the malleus, manubrium mallei and incus, and the width of the base of the stapes with morphometric measurements in human auditory ossicles. A significant positive correlation was found between the length of the malleus with the length of the manubrium mallei, between the length of the incus with the lengths of the long crus and corpus incudis, between the length of the stapes with the lengths of the rostral crus, caudal crus, caput stapedis, and the length and width of the intercrural foramen. Due to the anatomic similarities between sheep and human auditory ossicles, it was concluded that the auditory ossicles of sheep are suitable for use in the training of human ear surgery applications.

The Presence of the Human Auditory Ossicles—Detected Postmortem by CT Scan—As a Taphonomic Indicator

Introduction: Three tiny bones compose the human ossicular chain: malleus, incus and stapes. Also known as auditory ossicles, they are united by joints in the middle ear cavity of the petrous part of the temporal bone. Completely developed two years after birth, the ossicular chain is involved in the physiological process of hearing, by which sound waves from the environment are converted into electrochemical impulses. In the last 500 years, most studies have focused on the morphogenesis, morphological variability and clinical pathology of the ossicular chain, whilst only a few studies have added relevant knowledge to anthropology and forensic science. The auditory ossicles and the enclosing petrous bone are some of the hardest in the human skeleton. This is reflected in a relative resistance to fire and in the possibility of preservation and fossilization in millions of years. Materials and Methods: The literature and four present-day forensic cases were included in studying the postmortem loss of the auditory ossicles in skeletal or decomposing remains. Results indicate that it can be ascribed to their destruction or physical displacement, by either macro-micro-faunal action and/or any other natural or artificial disturbance. Discussion: Physical displacement is closely connected to the depositional environment of the skeletal remains, such as burial, entombment (sarcophagus, coffin, vault…), submersion or exposure to natural elements. Auditory ossicles can be recovered in situ, or very close to their anatomical location, when the skeletal material has been involved in an archaeological excavation. In the case of accessible or disturbed remains, scavengers may remove the tiny ossicles and/or they can slip out of the middle ear cavity following skull movements. Entombment offers effective protection against the displacement of the auditory ossicles, whereas aquatic submersion and aquatic movement almost invariably displace them. Conclusion: the preservation of the human auditory ossicles should be critically considered in the comprehensive context of any forensic investigation on human remains since it can assist the reconstruction of their taphonomic history. Taphonomic histories of remains can add crucial information to forensic investigations (e.g., the Post Mortem Interval, PMI). The aim of this study, limited by scarce relevant literature, is to discuss the potential role of the ossicular chain, detected by postmortem imaging techniques, as a taphonomical indicator in decomposing and/or skeletonized bodies.

Internal vascular channel architecture in human auditory ossicles.

The vascular supply of the human auditory ossicles has long been of anatomical and clinical interest. While the external blood supply has been well‐described, there is only limited information available regarding the internal vascular architecture of the ossicles, and there has been little comparison of this between individuals. Based on high‐resolution micro‐CT scans, we made reconstructions of the internal vascular channels and cavities in 12 sets of ossicles from elderly donors. Despite considerable individual variation, a common basic pattern was identified. The presence of channels within the stapes footplate was confirmed. The long process of the incus and neck of the stapes showed signs of bony erosion in all specimens examined. More severe erosion was associated with interruption of some or all of the main internal vascular channels which normally pass down the incudal long process; internal excavation of the proximal process could interrupt vascular channels in ossicles which did not appear to be badly damaged from exterior inspection. An awareness of this possibility may be helpful for surgical procedures that compromise the mucosal blood supply. We also calculated ossicular densities, finding that the malleus tends to be denser than the incus. This is mainly due to a lower proportion of vascular channels and cavities within the malleus.

Morphometry of auditory ossicles in medieval human remains from Central Europe.

Human auditory ossicles, the malleus, the incus, and the stapes, are located in the tympanic cavity in the temporal bone and through forming a chain for the sound transmission from the tympanic membrane to the cochlea, they play an important role in the hearing process. Despite their clinical, phylogenetic, and evolutionary significance, the morphometry of the human ear bones has not been examined systematically. The ear ossicles are the smallest bones of the human skeleton, attaining their final size and morphology already at birth. Initially, they have been found to exhibit minimal morphometric variation, but further studies brought the opposite results. The aim of this study was to examine the morphometric variation of human auditory ossicles recovered from medieval and postmedieval subadult skeletons from Poland, Central Europe. The analysis involved in a total of 166 ear bones. Their measurements were performed on microscopic images using CorelDraw x4, according to a protocol of Quam and Rak with modification of Flohr et al. and Wadhwa et al. Our study showed a significant metric variation in the measurements taken at areas of the greatest morphological variability of the ossicles. We found that greater linear dimensions were associated with lower values of angular measurements. These results reveal the inherent variation found in these supposed functionally constrained structures. Representation of even greater number of populations, time periods, and developmental stages are needed. Further study will expand our understanding of the global scope of variation found in ear ossicular morphology and its functional implications for paleoanthropology.

Study on the mechanism of sound conduction of the reconstructive model of human auditory ossicles

Study on the mechanism of sound conduction of the reconstructive model of human auditory ossicles

Navigational guidelines and positional relationships of the human auditory ossicles from three-dimensional topography for ensuring safe and effective malleostapedotomy : Stereotactic topography of the auditory ossicles and its clinical implication.

The aims of the present study were to identify detailed positional relationship between the auditory ossicles and to provide theoretic navigational guidelines for optimal prosthesis adaptation and effective malleostapedotomy. Fifty sides of the temporal bone from donated cadavers were scanned by MicroCT and the malleus, incus, stapes and tympanic membrane were materialized three dimensionally using computer software. Dimensions between the auditory ossicles closely related to malleostapedotomy were measured twice. The grip site of malleus handle was mean 1.8mm superior and mean 1.3mm anterior, and linear distance between the grip site of malleus handle and the footplate of the stapes was mean 6.5mm. The stapes was not parallel to the tympanic membrane and rotated mean 10.7° posteriorly relative to the tympanic membrane. Surgeons should start with at least 8.75mm prosthesis to cover the upper limits of potential anatomy and then trim down to the individualization to the case. The ideal loop morphology has to be oval shape more than 1.4mm in the long diameter and 1.0mm in the short diameter. The wire of the prosthesis has to be bended at the two points: about 10° anteriorly at the most proximal point of the wire and about 50° superiorly at the stapes head point.

Corrigendum: Human auditory ossicles as an alternative optimal source of ancient DNA

Corrigendum: Human auditory ossicles as an alternative optimal source of ancient DNA

Human auditory ossicles as an alternative optimal source of ancient DNA

DNA recovery from ancient human remains has revolutionized our ability to reconstruct the genetic landscape of the past. Ancient DNA research has benefited from the identification of skeletal elements, such as the cochlear part of the osseous inner ear, that provides optimal contexts for DNA preservation; however, the rich genetic information obtained from the cochlea must be counterbalanced against the loss of morphological information caused by its sampling. Motivated by similarities in developmental processes and histological properties between the cochlea and auditory ossicles, we evaluate the ossicles as an alternative source of ancient DNA. We show that ossicles perform comparably to the cochlea in terms of DNA recovery, finding no substantial reduction in data quantity and minimal differences in data quality across preservation conditions. Ossicles can be sampled from intact skulls or disarticulated petrous bones without damage to surrounding bone, and we argue that they should be used when available to reduce damage to human remains. Our results identify another optimal skeletal element for ancient DNA analysis and add to a growing toolkit of sampling methods that help to better preserve skeletal remains for future research while maximizing the likelihood that ancient DNA analysis will produce useable results.

Auditory ossicles: a potential biomarker for maternal and infant health in utero

Background: Carbon (δ13C) and nitrogen (δ15N) isotope ratios of collagen from teeth and bone are used to study human nutrition and health. As bones are constantly remodelling throughout life, isotopic values of bone collagen represent an average of several years. In contrast, human teeth do not remodel and their primary dentine contains only the isotopic data from the time of formation. In contrast to all other bones, human auditory ossicles also appear not to remodel. As they develop in utero and finish formation in the first 2 years of life, their collagen should also represent isotopic values of these two relatively short periods.Aim: By comparing δ13C and δ15N data from ossicles and incremental dentine, this study aims to investigate how two developmental periods of the ossicles, in utero and the first 2 years of life, reflect in collagen obtained from the ossicles.Subject and methods: Ossicle and tooth samples of 12 individuals aged 0.5 ± 0.4 years to 13 ± 1 years from the nineteenth century St. Peter’s burial ground in Blackburn were collected and processed to obtain bulk bone and incremental dentine collagen which was measured for δ13C and δ15N.Results: Averaged δ13C and δ15N of ossicles are lower when compared to every age group except after 3 years of age. Average offset between ossicles and dentine of different groups ranges from 0.4–0.9‰ for δ13C and from 0.3–0.9‰ for δ15N, with highest counterbalance at birth and after the first 5 months after birth.Conclusions: There appears to be a systematic offset between the dentine and ossicle data. It seems that the second phase of development does not influence the isotopic values of collagen significantly and the data we are obtaining from ossicles represents the in utero period.

Ultra-high matrix mineralization of sperm whale auditory ossicles facilitates high sound pressure and high-frequency underwater hearing.

The auditory ossicles-malleus, incus and stapes-are the smallest bones in mammalian bodies and enable stable sound transmission to the inner ear. Sperm whales are one of the deepest diving aquatic mammals that produce and perceive sounds with extreme loudness greater than 180 dB and frequencies higher than 30 kHz. Therefore, it is of major interest to decipher the microstructural basis for these unparalleled hearing abilities. Using a suite of high-resolution imaging techniques, we reveal that auditory ossicles of sperm whales are highly functional, featuring an ultra-high matrix mineralization that is higher than their teeth. On a micro-morphological and cellular level, this was associated with osteonal structures and osteocyte lacunar occlusions through calcified nanospherites (i.e. micropetrosis), while the bones were characterized by a higher hardness compared to a vertebral bone of the same animals as well as to human auditory ossicles. We propose that the ultra-high mineralization facilitates the unique hearing ability of sperm whales. High matrix mineralization represents an evolutionary conserved or convergent adaptation to middle ear sound transmission.

Early bone tissue aging in human auditory ossicles is accompanied by excessive hypermineralization, osteocyte death and micropetrosis

Within the mineralized bone, osteocytes form a multifunctional mechanosensitive network orchestrating bone remodelling. A preserved osteocyte population is a crucial determinant of bone quality. In human auditory ossicles, the early decrease in osteocyte numbers but maintained integrity remains an unexplained phenomenon that might serve for sound transmission from air to the labyrinth. Here we analysed the frequency, size and composition of osteocyte lacunae in the auditory ossicles of 22 individuals from early postnatal period to old age. Mineralization of the bone matrix was determined using backscattered electron imaging. No signs of bone remodelling were observed above the age of 1 year. We detected characteristics of early bone tissue aging, such as decrease in osteocytes, lower total lacunar density and lacunar area, as well as high matrix mineralization accompanied by distinct accumulation of micropetrotic lacunae and decreased indentation depths. The majority of these changes took place in the first months and years of life, while afterwards only minor reorganization was present. With osteocyte apoptosis potentially being a consequence of low mechanical stimuli, the early loss of osteocytes without initiation of bone remodelling indicates an adaptive response conserving the architecture of the auditory ossicles and ensuring stable sound transmission throughout life.

Dissection of the Auditory Bulla in Postnatal Mice: Isolation of the Middle Ear Bones and Histological Analysis.

In most mammals, auditory ossicles in the middle ear, including the malleus, incus and stapes, are the smallest bones. In mice, a bony structure called the auditory bulla houses the ossicles, whereas the auditory capsule encloses the inner ear, namely the cochlea and semicircular canals. Murine ossicles are essential for hearing and thus of great interest to researchers in the field of otolaryngology, but their metabolism, development, and evolution are highly relevant to other fields. Altered bone metabolism can affect hearing function in adult mice, and various gene-deficient mice show changes in morphogenesis of auditory ossicles in utero. Although murine auditory ossicles are tiny, their manipulation is feasible if one understands their anatomical orientation and 3D structure. Here, we describe how to dissect the auditory bulla and capsule of postnatal mice and then isolate individual ossicles by removing part of the bulla. We also discuss how to embed the bulla and capsule in different orientations to generate paraffin or frozen sections suitable for preparation of longitudinal, horizontal, or frontal sections of the malleus. Finally, we enumerate anatomical differences between mouse and human auditory ossicles. These methods would be useful in analyzing pathological, developmental and evolutionary aspects of auditory ossicles and the middle ear in mice.

Dissection of the Auditory Bulla in Postnatal Mice: Isolation of the Middle Ear Bones and Histological Analysis

In most mammals, auditory ossicles in the middle ear, including the malleus, incus and stapes, are the smallest bones. In mice, a bony structure called the auditory bulla houses the ossicles, whereas the auditory capsule encloses the inner ear, namely the cochlea and semicircular canals. Murine ossicles are essential for hearing and thus of great interest to researchers in the field of otolaryngology, but their metabolism, development, and evolution are highly relevant to other fields. Altered bone metabolism can affect hearing function in adult mice, and various gene-deficient mice show changes in morphogenesis of auditory ossicles in utero. Although murine auditory ossicles are tiny, their manipulation is feasible if one understands their anatomical orientation and 3D structure. Here, we describe how to dissect the auditory bulla and capsule of postnatal mice and then isolate individual ossicles by removing part of the bulla. We also discuss how to embed the bulla and capsule in different orientations to generate paraffin or frozen sections suitable for preparation of longitudinal, horizontal, or frontal sections of the malleus. Finally, we enumerate anatomical differences between mouse and human auditory ossicles. These methods would be useful in analyzing pathological, developmental and evolutionary aspects of auditory ossicles and the middle ear in mice.

Innovative 3D Model of the Human Middle Ear in High Resolution with a Histological Microgrinding Method: A Feasibility Study and Comparison with μCT.

Conclusion. The development of a histological 3D model of the tympanic cavity visualizes the exact microanatomy of the sound conduction organ and is therefore essential for finite elements simulations and surgical training. Objectives. So far, no accurate histological 3D model of the sound conduction system existed in literature. For 3D reconstruction of the very fine structures inside and outside the auditory ossicles, a method based on histological slices allows a more differential analysis of both hard and soft tissues and could thus be superior to μCT. Method. A complete temporal bone was embedded in epoxy resin and microground in distances of about 34 μm. After photodocumentation of every plane, a 3D reconstruction was performed by using the Computer Aided Design (CAD) program Rhinoceros 5®. For comparison, a μCT of the same specimen resulted in a 3D model of the calcified structures in the middle ear. Results. The histological 3D model gives an excellent overview to all anatomical soft and bony tissues of the human auditory ossicles. Specifically the fine blood vessel system and the exact dimension of cartilage areas inside the ossicles can be illustrated much more precisely than with μCT data. The present technique also allows the evaluation of the fine connecting ligaments inside the tympanic cavity.

ヒト耳小骨の振動解析

ヒト耳小骨の振動解析

Selection of the implant to replace the human auditory ossicles based on the model coupled contours

In this work, based on the model of coupled circuits, decided actual plastic surgery ENT problem of individual selection of material to replace the auditory ossicles of the middle ear of man. Reference 8, figures 7, table 2

Osteocyte Apoptosis and Absence of Bone Remodeling in Human Auditory Ossicles and Scleral Ossicles of Lower Vertebrates: A Mere Coincidence or Linked Processes?

Considering the pivotal role as bone mechanosensors ascribed to osteocytes in bone adaptation to mechanical strains, the present study analyzed whether a correlation exists between osteocyte apoptosis and bone remodeling in peculiar bones, such as human auditory ossicles and scleral ossicles of lower vertebrates, which have been shown to undergo substantial osteocyte death and trivial or no bone turnover after cessation of growth. The investigation was performed with a morphological approach under LM (by means of an in situ end-labeling technique) and TEM. The results show that a large amount of osteocyte apoptosis takes place in both auditory and scleral ossicles after they reach their final size. Additionally, no morphological signs of bone remodeling were observed. These facts suggest that (1) bone remodeling is not necessarily triggered by osteocyte death, at least in these ossicles, and (2) bone remodeling does not need to mechanically adapt auditory and scleral ossicles since they appear to be continuously submitted to stereotyped stresses and strains; on the contrary, during the resorption phase, bone remodeling might severely impair the mechanical resistance of extremely small bony segments. Thus, osteocyte apoptosis could represent a programmed process devoted to make stable, when needed, bone structure and mechanical resistance.

Role of osteocyte apoptosis in peculiar ossicles of the hearing sense organ: preliminary observations on hearing loss and osteoporosis

Starting point of the present study is the osteocyte role in bone remodelling that allows bone adaptation to mechanical load [1-3]. Bone remodelling has been investigated in relation to the occurrence of apoptosis [4] to understand if and how the process of programmed cell death interferes with bone turnover. In 1998, in a study on human middle ear, Marotti et al. [5] demonstrated that: 1) over 40% of osteocytes are dead within the 2nd year of age (but the authors were not able to demonstrate if osteocyte death occurred by degeneration or apoptosis); 2) bone remodelling occurs only occasionally. Recently [6], we showed that: 1) osteocytes of human auditory ossicles die by apoptosis; 2) also osteocytes located inside scleral ossicles of lower vertebrate eye (reptiles and birds) phylogenetically so far from human auditory ossicles are widely affected by apoptosis (about 60%); 3) in scleral ossicles bone turnover never occur. It is to be noted that both auditory ossicles of human ear and scleral ossicles of vertebrate eye are peculiar bony segments continuously submitted to stereotyped stresses and strains, with specialized functions: the first are involved in sound wave transmission and the latter protect the eyeball against deformation during the movement and have a role in visual accomodation, providing attachment for the ciliary muscles. In both cases, bone remodelling might severely impair, by resorption, the mechanical resistance of these extremely small specialized bony segments. Thus, we suggested that in auditory and scleral ossicles, submitted to stereotyped loading for all life, bone mechanical adaptation is not needed and osteocyte programmed death could represent the mechanism to avoid bone remodelling and to make stable, when necessary, bone structure and mechanical resistance. More recently, to confirm this hypothesis, clinical data were collected from a cohort of patients aged 55-85 years affected by hearing loss. The main target of the present study is to exclude any correlation between hearing loss and osteoporosis. During osteoporosis, unbalanced bone turnover causes the bone depletion in skeletal segments; such condition, in the peculiar ossicles of human middle ear, should imply hearing impairment. Our preliminary observations indicate, instead, that osteoporotic patients do not show higher percentage of hearing loss with respect to non osteoporotic ones. This evidence is ascribable to osteocyte apoptosis of auditory ossicles that avoid bone remodelling, thus assuring the integrity of such bony segments also in osteoporotic conditions.

Auditory ossicles from southwest Asian Mousterian sites

The present study describes and analyzes new Neandertal and early modern human auditory ossicles from the sites of Qafzeh and Amud in southwest Asia. Some methodological issues in the measurement of these bones are considered, and a set of standardized measurement protocols is proposed. Evidence of erosive pathological processes, most likely attributed to otitis media, is present on the ossicles of Qafzeh 12 and Amud 7 but none can be detected in the other Qafzeh specimens. Qafzeh 12 and 15 extend the known range of variation in the fossil H. sapiens sample in some metric variables, but morphologically, the new specimens do not differ in any meaningful way from living humans. In most metric dimensions, the Amud 7 incus falls within our modern human range of variation, but the more closed angle between the short and long processes stands out. Morphologically, all the Neandertal incudi described to date show a very straight long process. Several tentative hypotheses can be suggested regarding the evolution of the ear ossicles in the genus Homo. First, the degree of metric and morphological variation seems greater among the fossil H. sapiens sample than in Neandertals. Second, there is a real difference in the size of the malleus between Neandertals and fossil H. sapiens, with Neandertals showing larger values in most dimensions. Third, the wider malleus head implies a larger articular facet in the Neandertals, and this also appears to be reflected in the larger (taller) incus articular facet. Fourth, there is limited evidence for a potential temporal trend toward reduction of the long process within the Neandertal lineage. Fifth, a combination of features in the malleus, incus, and stapes may indicate a slightly different relative positioning of either the tip of the incus long process or stapes footplate within the tympanic cavity in the Neandertal lineage.