J. Marquet

Histological Study of the Thin Replacement Membrane of Human Tympanic Membrane Perforations

A histological study was done on the thin, nearly transparent replacement membrane of tympanic membrane perforations. Human tympanic membranes that were rejected for transplantation, were studied by light and electron microscopy. The abrupt reduction in thickness at the margin of the covered perforation, is entirely due to the reduction of the lamina propria. Even in the thinnest parts of the replacement membrane, a lamina propria is present, separated by continuous basement membranes from the epithelium and mucosa, and measuring no more than some 2-3 microns in thickness. This lamina propria consists of fibrils and interfibrillar matrix, but fibroblasts appear to be lacking. The epithelial layer does not contain basal cells, confirming the thesis that the upper layers are not generated by in situ proliferation, but that they have migrated from the periphery.

The involvement of the cochlear nerve in neurinomas of the eighth cranial nerve

SummaryIn view of recent controversies concerning the preservation of hearing in acoustic neurinoma surgery, we examined the courses of the vestibular and cochlear nerve fibers in 12 intact acoustic neurinomas studied in our department. Due to its lack of specificity, the Luxol fast blue stain was found to be inadequate for our study of the nerve fibers. In contrast, Verhoeffs stain proved to be satisfactory when combined with a highly specific immunohistochemical technique. There were macroscopically visible adherences between the tumor and the cochlear nerve in 9 out of the 12 specimens. From those specimens, histological sections were obtained in which both the cochlear nerve and tumor could be clearly identified. In these specimens the cochlear nerve was involved in the tumoral process and there was no clear cleavage plane between the nerve and the tumor. However, all these patients suffered only from minimal losses of hearing as a result of their tumors.

A pharyngeal hairy polyp causing neonatal airway obstruction: a case study

A case of neonatal respiratory distress due to an oropharyngeal hairy polyp is reported with its MRI assessment. The place of hairy polyps in the differential diagnosis of upper respiratory tract obstruction is discussed. Early and rapid diagnosis and treatment may be lifesaving for the newborn.

Psychoacoustical Tuning Curves Normative Data for Clinical Use

This normative study presents a clinically applicable method with which to obtain Psychoacoustical Tuning Curves: data are obtained with clinical audiometers, and measurements are performed on normal-hearing non-trained volunteers. A simultaneous masking method with test frequency of 4,000 Hz was used, withmasking being incremented in 5 dB or 1 dB steps. One group of subjects was tested three times with 5 dB incrementing steps to evaluate the methods reproducibility. A second group of subjects was measured twice with 1 dB incrementing steps, to compare the reproducibility of the 1-dB step measurements, and the difference between the 1-dB step and 5-dB step measurements. All the data were evaluated as normative values. The method presented proves to have a good reproducibility. Although testing with 1-dB incrementing steps provides more accurate measurements and curves with steeper slopes, the 5-dB incrementing step method is more practicable. Interest variability evaluation indicates that differences between two measurements performed on the same person exceeding 120 Hz (2 SD) bandwidth can be interpreted as significant.

Normal growth pattern of the middle ear cleft in the human fetus.

The normal growth pattern of the middle ear cleft was studied on macro- and histological sections of the human fetus. When compared with adult temporal bones, the inclination of the tympanic ring remains unaltered throughout fetal development. Expansion of the middle ear cleft is caused by intrinsic growth and by lateral displacement of its constituent elements: tympanic ring, otic capsule and squamous bone. Not only are the two mutually different modes of growth movement quite dissimilar in magnitude and direction, but so is their resultant vector for each constituent; this dissimilarity in growth movement leads to a characteristic change in shape of the middle ear cleft and to curvature of the tympanic membrane. The intrinsic growth of these elements is simultaneously accompanied by remodelling of their shape; lateral displacement of the squamous bone and tympanic ring is caused by the pressure of the enlarging brain. The consequences of developmental disturbances on the normal growth pattern are discussed.

Differentiation of cartilage and bone in human fetal temporal bones with Luxol fast blue stain

SummaryA modified Luxol fast blue technique was used to study the development of the temporal bone. This staining method makes it possible to make a clear distinction between the primitive cartilage present and the new forming bone. Although these tissues both contain a significant amount of collagen, their staining properties with the Luxol dyes are widely dissimilar, due to the different physicochemical properties of the collagen types involved in these tissues. The differentiation of mesenchymatous tissue into ligaments and joints can also be very clearly demonstrated with this technique. In studying the endochondral ossification process of the otic capsule and middle ear, the modified Luxol fast blue stain is a valuable technique that is complementary to more conventional staining methods.

Keratinization of middle ear cholesteatomas

SummaryA histochemical study was performed to clarify further the role played by epidermal transglutaminase (ETgase) in the keratinization of aural cholesteatoma. Weakly and strongly keratinized epidermal tissues and healthy middle ear mucosa were included as references. A first assay revealed the distribution of non-specified acyl donor substrates. In a second assay, the topography of involucrin was assessed immunohistochemically. In both epidermal and cholesteatoma matrix tissues, the presence of acyl donors was not restricted to the sites of (E)Tgase activity, but was almost uniformly extended throughout living layers. In reference tissues, residual acyl donors were poorly detected in horny layers, while they were more abundant in the stratum corneum of the cholesteatomas studied. The presence of involucrin along the cell membrane was observed at varying distances throughout the spinous and granular layers, depending upon the epidermal and matrix configurations. In thick epithelia, involucrin rapidly became concentrated at the cell periphery (in spinous kerationcytes), while in thin epithelia it was usually associated with cell flattening. This latter staining profile was observed more frequently in cholesteatomatous tissues. In addition, we regularly noticed an immediately suprabasal accumulation of involucrin, suggesting a locally hyperproliferative state of the matrix. An insufficient availability of acyl donors, especially involucrin, could not be used to explain the defective ETgase-mediated cross-linking of cholesteatoma cell membranes during terminal stages of differentiation. The present investigation may be the first to demonstrate the presence of involucrin in middle ear mucosa.

A scanning electron microscope study of preserved allograft tympanic membranes: a comparison with autogenous grafts, xenografts and the normal eardrum

SummaryScanning electron microscopy was used to investigate the surface architecture of the human tympanic membrane. The morphology of the eardrum was compared with the surface structures of preserved tympanic membranes (allografts), fresh air-dried temporalis fascia and preserved calf jugular veins (xenografts). The role of the physical structure and the composition of the extracellular matrix in the regeneration of a tympanic graft is discussed.

Effect of isepamicin dosing scheme on concentration in cochlear tissue.

To investigate the possible effect of the dosing scheme of aminoglycosides on their concentration in the cochlear tissue, we gave two groups of 12 guinea pigs subcutaneous doses of 45 mg of isepamicin (ca. 30 mg of active product) per kg of body weight daily for eight consecutive days. The first group received the drug by continuous infusion, while the second group received it by single daily injection. On the final day of administration, the animals were sacrificed and the cochlear tissue was removed. The tissues from the cochleas of pairs of guinea pigs were pooled. The isepamicin concentrations in the cochlear duct tissue (organ of Corti plus lateral wall) and the cochlear nerve tissue were determined separately. Hearing levels before and after treatment were assessed by means of frequency-specific auditory brain stem responses (ABR). The creatinine level in serum was determined on the last day of the administration. None of the animals in either group showed signs of renal insufficiency or of hearing impairment. The median isepamicin concentration in the cochlear duct was 2.40 micrograms/mg of protein after continuous administration and 2.50 micrograms/mg of protein after once-daily administration, compared with the concentration in the cochlear nerve, where it was 1.93 micrograms/mg of protein after continuous administration and 2.59 micrograms/mg of protein after once-daily administration. These differences are statistically insignificant. The results give evidence for linear uptake kinetics of isepamicin in the inner ear tissue and may be directly relevant to the clinical dosing of the drug.

Early ossification within the human fetal otic capsule: morphological and microanalytical findings

Besides the use of conventional techniques such as light and polarization microscopy, the present paper proposes the combined use of transmission electron microscopy, secondary and backscattered electron imaging, energy dispersive X-ray analysis and computed tomography for the diagnostic evaluation of ear pathology in the human fetus. These methods were used to revisit the primary calcification front of the fetal otic capsule between 16 and 23 weeks gestational age. Ultramicroscopic evaluation demonstrates similar fetal bone formation to that found in other bones of the human fetus. The formation of the endosteal and periosteal layers is a typical example of early intra-membranous ossification. The enchondral layer is made up of fibrillar bone, laid down around the calcified cartilage remnants. Microchemical analysis indicates a significantly higher Ca/P ratio in the endochondral layer with respect to the endosteum and periosteum. The consequences of a lower Ca/P ratio in the endosteal layer are discussed in view of calcium homeostasis and inner ear function.