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Biomedical subjects

L Michaels

Publications and source records attributed to L Michaels.

At least 19 recordsLinked to original sources
PubMed1992

A histologic study of nonmorphogenetic forms of hereditary hearing impairment.

It appears that many forms of syndromic and nonsyndromic hereditary hearing impairment are secondary to either neuroepithelial or cochleosaccular dysfunction. Making this distinction can be difficult in human temporal bone specimens; however, this added knowledge may ultimately provide prognostic and therapeutic information in hearing habilitation. Fundamental studies using animal models of different types of hereditary deafness may also prove useful in this respect.

Adult↗
PubMed1992

Image analysis in the discrimination of verrucous carcinoma and squamous papilloma.

Verrucous carcinoma is a differentiated variant of squamous cell carcinoma and may present diagnostic difficulties as it may be erroneously diagnosed as squamous papilloma. In this study, the sizes of the intermediate cells in these two conditions were measured by means of morphometric analysis. Biopsies from 28 patients with verrucous carcinoma, 25 patients with squamous papilloma, and ten squamous cell carcinomas were analysed. A significant difference was shown (P less than 0.001) by an uncorrelated t-test between verrucous carcinoma and squamous papilloma. The former had a mean cell area of 373 microns 2 and the latter 184 microns 2. Squamous cell carcinomas differed from the other two neoplasms by their large range of cell areas both within and between cases. Thus, image analysis can be of diagnostic help in cases where no firm initial histopathological diagnosis can be obtained. The diagnosis should be made on morphological grounds, but a mean cell area greater than 300 microns 2 supports a diagnosis of verrucous carcinoma whereas an area less than 250 microns 2 supports a diagnosis of squamous papilloma.

Adult↗
PubMed1992

The imaging characteristics of naso-sinus chondrosarcoma.

Eighteen patients with histologically-verified naso-sinus chondrosarcomata are reviewed, emphasizing their CT and MRI appearances. These tumours present with a soft tissue mass expanding and destroying bone and typically (89%) showing areas of nodular or plaque-like calcification on CT. The magnetic resonance characteristics are more specific and when present with the typical CT features are diagnostic of chondrosarcoma. They combine high signal on T2-weighted sequences, with differential enhancement on post-Gadolinium T1-weighted scans. The contrast enhancement is seen at the periphery of the tumour and the central chondromatous core does not enhance. These changes are dependent upon the vascularity of the tissues concerned and have been correlated exactly with the histopathology of the resected tumour specimens.

Adolescent↗
PubMed1991

Auditory epithelial migration. III. Development of the stratified squamous epithelium of the tympanic membrane and external canal in the mouse.

The development of the stratified squamous epithelium of the tympanic membrane and external auditory canal was studied in serial sections of 124 mouse ears aged from 11 gestational days to 100 days. A fold developed from the edge of the fundus of the primary canal. It possessed two regions: firstly the meatal plate, which produced the pars tensa-covering epithelium (zone 2) and most of the deep ear canal epithelium (zone 3), and secondly the fundal extension plate, which grew from that part of the fundus not forming the meatal plate. The fundal extension plate gave rise to the pars flaccida-covering epithelium (zone 1) and also to the adjacent deep canal epithelium (zone 3). A difference from human development was that zone 3 in the mouse, in both the meatal plate- and the fundal extension plate-derived areas, formed adnexal structures. In the early development of the meatal plate, zone 3, at its tip, was swollen and actively mitotic and extended always for a short distance on to the zone 2 side. Zone 2, first perceived two days after zone 3, became progressively attenuated, and by the fourth day after its formation was a single thin layer. It is suggested that the proximal part of zone 3, situated in the mature ear around the periphery of the tympanic membrane, is a generation center for unidirectional outward flux of epithelium which terminates in the mouse at the first adnexal structure. It may cause the whole of zone 2 to move in the same direction by negative contact inhibition.

Animals↗
PubMed1991

Stratified squamous epithelium in relation to the tympanic membrane: its development and kinetics.

The pathways of auditory epithelial migration on the human tympanic membrane and their rate of movement were investigated by Hopkins rod photography of dye markings. The origin of these pathways was determined in both the human and the mouse by studying the development of the stratified squamous epithelium of the tympanic membrane and external auditory meatus from earliest embryonic life to maturity. Two pathways of migration are present. In one, epithelium moves from the region covering the tip of the handle of the malleus upwards to the lateral process and then posterior-superiorly with all dye on the pars flaccida to its posterior superior edge. In the second, dye moves centrifugally and radially outwards from the edges of the handle and pars flaccida regions to the annulus. Rate of movement can be determined approximately only and by reference to anatomical landmarks. The first pathway was traced embryologically to migration possibly commencing in the fundus of the primordial first branchial groove. The second pathway has its source in the growth of the meatal plate. A study of the development of the early meatal plate in the mouse suggests that movement of epithelium over the pars tensa region could be the result of a "pulling" effect of mitotically active cells in a generation center at the edge of the tympanic membrane resulting from negative contact inhibition.

Adolescent↗
PubMed1991

Mode of growth of acquired cholesteatoma.

A histopathological study of acquired cholesteatoma in four temporal bones from two adults and one child is presented. The findings suggest that the cholesteatoma originated from the retraction pockets of the tympanic membrane and there was active growth of the squamous epithelium of the retraction pockets, which may be enhanced in the presence of otitis media.

Aged↗
PubMed1991

Congenital cholesteatoma.

We present a British series of eleven patients with primary cholesteatoma, including one patient with bilateral disease. Eight children presented with a history of hearing loss, while one child had had recurrent otitis media and another had had earache. Operative findings were: in five ears, cholesteatoma confined to the antero-superior segment with intact ossicles, in a further four, cholesteatomas extending throughout the mesotympanum with ossicular erosion in one, and in two ears posterior disease throughout the middle ear and mastoid, which had eroded the ossicles in both cases. The five cases of antero-superior cholesteatoma lend most support to Michaels' concept of epidermoid formation as a possible source of congenital cholesteatoma. With a greater awareness of the problem and careful examination of the antero-superior quadrant of the tympanic membrane, earlier diagnosis may be possible enabling removal of small intact cholesteatoma sacs and preserving the structures of the middle ear and therefore the hearing. A screening programme for infants included as part of their routine examination which would be undertaken by examiners who are trained to be more aware of the problem and skilled at otoscopy, would help in the earlier detection of such cases as is shown by reports from the U.S.A.

Child↗
PubMed1991

The temporal bone: an organ in search of a histopathology.

The pathology of the temporal bone and the inner ear in particular has been a neglected area for histopathologist. This review sets out to answer a number of questions on the topic: why is it neglected; how do you learn its anatomy; how do you process it; why do it; and who should do it? The histopathological features of cholesteatoma, otosclerosis and presbyacusis are discussed in detail and future areas of research are identified.

Cholesteatoma↗
PubMed1991

Atypical Ph negative chronic myeloid leukaemia presenting as sudden profound deafness.

A patient with atypical Ph negative chronic myeloid leukaemia presented with the sudden onset of profound deafness. He survived only eight months. Detailed histological investigation performed at necropsy showed loss of ganglion cells and afferent nerve fibres in the cochlea and vestibule associated with extensive fibrosis and new bone formation in the labyrinthine spaces. Both leucophoresis and high dose chemotherapy capable of rapid cytoreduction are recommended in patients with chronic myeloid leukaemia with profound hearing loss, as conventional chemotherapy is rarely followed by recovery.

Deafness↗