The incudostapedial articulation in Down's syndrome (trisomy 21): a temporal bone study.

HYPOTHESIS: Anomaly in the incudostapedial articulation (IS) may be responsible for persistent conductive hearing loss (HL) in Down's syndrome (DS) patients. Our goal was to perform a detailed histopathologic assessment of the role of the IS joint in the conductive HL. BACKGROUND: In addition to other disabilities, 38% to 78% of patients with Down's syndrome (Trisomy 21) have CHL, some of which are persistent despite maximum treatment. The cause of the persistent conductive HL remains unclear. METHODS: Retrospective analysis of temporal bone histopathology. Analyses of the midsection through the IS joint of 21 temporal bones (13 subjects) patients with DS and 31 temporal bones (18 subjects) from healthy subjects, performed by 2 blinded authors. The length of 7 different parameters of the width of the IS joint was measured and compared between the 2 groups. RESULTS: The IS joint of patients with DS was significantly wider than the normal control. As opposed to the control, it did not decrease because of age. CONCLUSION: The persistent conductive HL in some patients with DS might be caused by anomaly of the IS joint. In severe cases, corrective surgery should be considered.

The pathogenesis of acquired cholesteatoma of the human middle ear: support for the migration hypothesis.

HYPOTHESIS: That acquired cholesteatoma of the human middle ear and mastoid process can be caused by migration of squamous epithelium from the tympanic membrane. OBJECTIVE: To provide histologic evidence in humans of the potential for medial epithelial migration toward the middle ear. BACKGROUND: The origin of cholesteatomas of the middle ear complex of humans is still not clearly understood. The most popular theory, the medial migration of squamous epithelium from the external auditory canal/tympanic membrane through a perforation of the tympanic membrane to form a cholesteatoma, was first proposed over a century ago independently by Bezold (1899) and Habermann (1899) based on their observations during surgery. Neither author had histologic proof. Despite much experimental efforts in animals, histologic evidence in the human continues to be the missing link. METHOD: We examined the histologic sections of the temporal bones of 60 children aged 1 day to 12 years with evidence of acute otitis media. We present our findings in the temporal bones of 3 infants. RESULTS: We find evidence of the propensity of the squamous epithelium of the tympanic membrane particularly in the pars flaccida to become very active and to migrate medially toward the middle ear. CONCLUSION: Our concept is that this material supports the migration theory that cholesteatomas are formed by the medial migration of the stimulated squamous epithelium of the tympanic membrane.

Selective inner hair cell loss in prematurity: a temporal bone study of infants from a neonatal intensive care unit.

Premature birth is a well-known risk factor for sensorineural hearing loss in general and auditory neuropathy in particular. However, relatively little is known about the underlying causes, in part because there are so few relevant histopathological studies. Here, we report on the analysis of hair cell loss patterns in 54 temporal bones from premature infants and a control group of 46 bones from full-term infants, all of whom spent time in the neonatal intensive care unit at the Hospital de Niños in San Jose, Costa Rica, between 1977 and 1993. The prevalence of significant hair cell loss was higher in the preterm group than the full-term group (41% vs. 28%, respectively). The most striking finding was the frequency of selective inner hair cell loss, an extremely rare histopathological pattern, in the preterm vs. the full-term babies (27% vs. 3%, respectively). The findings suggest that a common cause of non-genetic auditory neuropathy is selective loss of inner hair cells rather than primary damage to the cochlear nerve.

Anatomy of the distal incus in humans.

The anatomy of the distal incus, including the lenticular process, was examined in histological sections from 270 normal cadaveric human temporal bones aged between less than 1 month and 100 years. All but nine of these sectioned specimens showed signs of a bony connection between the long process of the incus and the flattened plate of the lenticular process, and in 108 specimens a complete bony attachment was observed in a single 20 microm section. In these 108 ears, the bony lenticular process consisted of a proximal narrow "pedicle" connected to a distal flattened "plate" that forms the incudal component of the incudo-stapedial joint. A fibrous joint capsule extended from the stapes head to the pedicle of the lenticular process on all sides, where it was considerably thickened. Three-dimensional reconstructions made from serial 20 microm sections of four bones provided views from all directions that easily convey the anatomical features of this region. Morphometric measurements of the bony architecture of the distal incus in 103 temporal bones were made, including lengths and cross-sectional areas, estimates of the percentage of lacunae containing osteocytes, and the degree of bone resorption. These measurements, analyzed as a function of age, provided an anatomic description over a large age range that can serve as a normal baseline against which structural pathology can be compared. Although none of the bony dimensions showed significant age dependence, the estimated percentage of bony lacunae that contain osteocytes decreased significantly with age. The results have implications for the roles of specific components on the coupling of ossicular motion across the incudo-stapedial joint, and provide insights regarding bone resorption at the level of the distal incus, which occurs clinically in some patients with chronic otitis media or after stapedectomy.

The incudostapedial articulation: new concepts.

HYPOTHESIS: To study the detailed anatomy of the incudostapedial joint (ISJ). BACKGROUND: Detailed study of the anatomy of the ISJ has been surprisingly neglected and continues to be controversial. METHODS: We studied the joint in 86 temporal bones from 51 subjects, aged 12 to 104 years, by light microscopy and three-dimensional images of computer-based reconstructions. RESULTS: In the course of this study, we found that the lenticular process is extremely delicate, consisting of thin trabeculae and spaces filled with areolar tissue. The ISJ is at least partially a bichambered diarthrodial joint divided by a fibrous articular disk into unequal joint spaces. This disk could be identified in all 86 specimens. In addition, we identified for the first time a concavity on the anterior face of the inferior end of the long process of the incus. The asymmetric joint capsule of the ISJ, which completely envelops the lenticular process, extends to this incudal concavity, thereby incorporating part of the long process into the joint complex. We also found that the attachment of the tendon of the stapedius muscle to be more complex than previously described with contributions to the posterior and probably the inferior joint capsule. CONCLUSION: On the basis of its finely cohesive anatomic structure, we believe that the incudostapedial articulation should be considered to be a single complex and to be a single entity physiologically.

Anatomy of the round window and hook region of the cochlea with implications for cochlear implantation and other endocochlear surgical procedures.

HYPOTHESIS: The goal of this study was to create a three-dimensional model of the anatomy of the hook region to identify the optimal site for cochleostomy in cochlear implant surgery. BACKGROUND: The anatomy of the hook region is complex, and spatial relationships can be difficult to evaluate using two-dimensional histological slides or cadaveric temporal bones. METHODS: The right temporal bone of a 14-year-old adolescent boy was used to create a three-dimensional model. Sections containing the round window membrane (RWM) and surrounding cochlear structures were stained, digitized, and imported into a general purpose three-dimensional rendering and analysis software program (Amira, version 4.1). Three-dimensional models of the RWM, basilar membrane, osseous spiral lamina, spiral ligament, cochlear aqueduct, inferior cochlea vein, scala media, ductus reuniens, scala vestibuli, scala tympani, and surrounding bone were generated. The relationship between these structures and the RWM and adjacent otic capsule was evaluated. Histological sections from a different temporal bone were also analyzed. This temporal bone was sectioned in a plane perpendicular to the axis corresponding to the surgical view of the RWM, seen through the facial recess. RESULTS: The anteroinferior margin of the RWM or adjacent otic capsule was identified as the site for a cochleostomy that will avoid damage to critical cochlear structures and allow implantation directly into the scala tympani. The model can be downloaded from: https://research.meei.harvard.edu/otopathology/3dmodels. CONCLUSION: This three-dimensional model has implications for surgical procedures to the inner ear that aim to minimize insertional trauma.

Tuberculous otitis in infants: temporal bone histopathology and clinical extrapolation.

HYPOTHESIS: The study of infant temporal bones with tuberculosis (TB) of the middle ear and mastoid could provide information to assist with clinical diagnosis in this population. BACKGROUND: The TB pandemic has become a critical global public health problem. With the rising incidence of the disease, otolaryngologists might encounter an increased frequency of otologic TB. Pediatric temporal bone reports of TB are rare. METHODS: Light microscopic examination was performed on both temporal bones from an infant who died as a result of miliary TB. RESULTS: The tympanic membranes were thickened with dilated blood vessels, yet were intact without perforations. Purulence, granulation tissue, and classic tubercles were observed in the middle ears and mastoids. Serous labyrinthitis and inflammatory cells surrounding the Cranial Nerve VIII in the internal auditory canal were observed in the inner ear. CONCLUSIONS: The histological findings suggest that a clinical presentation of infantile tuberculous otitis media and mastoiditis could be a patient with otoscopic findings consistent with common otitis media with an intact tympanic membrane, likely in conjunction with inner ear symptoms. Lacking the classic finding of multiple tympanic membrane perforations, tuberculous otitis might be underappreciated in this population.

Three-dimensional virtual model of the human temporal bone: a stand-alone, downloadable teaching tool.

OBJECTIVE: To develop a three-dimensional virtual model of a human temporal bone based on serial histologic sections. BACKGROUND: The three-dimensional anatomy of the human temporal bone is complex, and learning it is a challenge for students in basic science and in clinical medicine. METHODS: Every fifth histologic section from a normal 14-year-old male was digitized and imported into a general purpose three-dimensional rendering and analysis software package called Amira (version 3.1). The sections were aligned, and anatomic structures of interest were segmented. RESULTS: The three-dimensional model is a surface rendering of these structures of interest, which currently includes the bone and air spaces of the temporal bone; the perilymph and endolymph spaces; the sensory epithelia of the cochlear and vestibular labyrinths; the ossicles and tympanic membrane; the middle ear muscles; the carotid artery; and the cochlear, vestibular, and facial nerves. For each structure, the surface transparency can be individually controlled, thereby revealing the three-dimensional relations between surface landmarks and underlying structures. The three-dimensional surface model can also be "sliced open" at any section and the appropriate raw histologic image superimposed on the cleavage plane. The image stack can also be resectioned in any arbitrary plane. CONCLUSION: This model is a powerful teaching tool for learning the complex anatomy of the human temporal bone and for relating the two-dimensional morphology seen in a histologic section to the three-dimensional anatomy. The model can be downloaded from the Eaton-Peabody Laboratory web site, packaged within a cross-platform freeware three-dimensional viewer, which allows full rotation and transparency control.