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Biomedical subjects

F H Linthicum

Publications and source records attributed to F H Linthicum.

At least 37 records · Page 2Linked to original sources
PubMed1998

Morphology of the developing human endolymphatic sac.

The adult human endolymphatic sac (ES) has been described as a complex network of interconnected tubules. Embryologic examination describes the human ES as a single-lumen, pouch-like structure. Transition from saccular shape to tubules during the entire fetal period has not been previously reported. Tubular ES structure is thought to be unique to humans. Animal investigations describe similar saccular appearance, but without tubules in mature sacs. The authors examined 45 human fetal temporal bones to trace ES development and reviewed six types of animal sacs. Results in humans reveal tubular structure as early as 26 weeks' gestation. Maturation variably occurred in the fetal period and postnatally. For the first time, the tubular system is noted in the animal, the rhesus monkey. These findings suggest that the tubular system may represent more advanced specialized function.

Adolescent↗
PubMed1998

Mastoid size and otitis media with effusion: question of correlation.

OBJECTIVES/HYPOTHESIS: To determine the incidence of otitis media (OME) with effusion on histologic examination in temporal bones with mastoid cavities reduced by the fenestration procedure for otosclerosis. STUDY DESIGN: Temporal bone histologic study. METHODS: Light-microscopic examination of serially sectioned temporal bones. RESULTS: The incidence of otitis media with effusion in temporal bones with prior fenestration operation was not any more frequent than the control group of temporal bones with surgically unaltered mastoid cavity. CONCLUSIONS: There is no increased incidence of otitis media with effusion in temporal bones with prior fenestration operation.

Aged↗
PubMed1997

Cochlear implantation in common cavity malformations using a transmastoid labyrinthotomy approach.

The transmastoid facial recess approach has become the standard technique for cochlear implantation. Although this approach has been used for implantation in patients with common cavity deformities, it is not without increased risk to the facial nerve. Using a direct approach to the common cavity that circumvents the facial recess, we have successfully implanted four patients with common cavity deformities. An aberrant facial nerve in one patient would have precluded placement of the electrode array using standard cochlear implant techniques. As demonstrated in these four patients, the direct approach to the common cavity is an effective approach for placement of the electrode array, minimizes risk to the facial nerve, and may decrease the likelihood of postoperative cerebrospinal fluid leaks. Intraoperative video footage demonstrates the feasibility and facility of this approach in patients with common cavity deformities.

Child↗
PubMed1997

Effect of adult-onset deafness on the human central auditory system.

Degenerative change in the central auditory system was assessed in seven subjects with profound bilateral adult-onset deafness. The degree of transneuronal atrophy was determined by measuring cell size at three levels of the brain stem auditory pathway (anteroventral cochlear nucleus, medial superior olivary nucleus, and inferior colliculus). Within subjects, the relative degree of cell shrinkage was similar across all levels of the central pathway. Across subjects, the best neuronal preservation was seen in a case of viral labyrinthitis with 1 year of bilateral dearness and a near-normal population of cochlear ganglion cells. Reduction in cell size was greatest in cases of bacterial labyrinthitis or Scheibe degeneration with reduced populations of ganglion cells and longer periods of deafness. At the level of the cochlear nucleus, there was no consistent difference in cell size between the side stimulated by a functioning prosthetic device and the nonstimulated side.

Adult↗
PubMed1997

Marrow-mesenchyme connections in the fetal and newborn tympanum. A new entity.

Examinations of 41 human fetal, 8 infant, and 8 juvenile temporal bones prepared for light microscopic evaluation revealed direct connections between the hematopoietic bone marrow and the unresolved mesenchyme in the middle ear. The connections first appeared at 15 weeks of gestation and became bridged by fibrous tissue, in most cases, by the postpartum age of 10 months. Between 16 and 18 months after birth, the marrow-mesenchyme connections gradually disappeared. The areas in which the connections were most numerous were the anterior epitympanum, the sinus tympani medial to the stapedius muscle, and transitory bone that occupies the area that will become the aditus of the antrum. Immunohistochemical staining demonstrated the existence of mature leukocytes in these connections. These connections may help protect the middle ear against bacterial invasion during the postnatal period.

Bone Marrow↗
PubMed1996

Mutational spectrum in the neurofibromatosis type 2 gene in sporadic and familial schwannomas.

Using a heteroduplex approach and direct sequencing, we have completed the screening of approximately 88% of the neurofibromatosis type 2 (NF2)-coding sequence of DNA extracted from 33 schwannomas from NF2 patients and from 29 patients with sporadic schwannomas. The extensive screening has resulted in the identification of 33 unique mutations. Similarly to other human genes, we have shown that the CpG sites are more highly mutable in the NF2 gene. The frequency, distribution, and types of mutations were shown to differ between the sporadic and familial tumors. The majority of the mutations resulted in protein truncation and were consistent with more severe phenotype, however three missense mutations were identified during this study and were all associated with milder manifestations of the disease.

Codon↗
PubMed1996

Facial nerve schwannoma: nerve fibre dissemination.

Biopsy of a middle ear mass can lead to facial paralysis when the mass is a facial nerve schwannoma. Immunostaining techniques were used to determine if nerve fibres might be present within the tumour mass. Nerve fibres were found to be widely disseminated throughout the tumour in eight of 23 facial nerve schwannomas. Antibodies to neurofilaments demonstrated single fibres, or small groups of fibres, that are very difficult to see with routine haematoxylin and eosin stains. The presence of fibres throughout some tumours makes biopsy of them likely to result in facial dysfunction.

Biopsy↗
PubMed1996

Temporal bone findings in Alzheimer's disease.

Sensorineural hearing loss has been reported in Alzheimer's disease (AD) and a topographically specific pattern of degeneration in the central auditory system has been described. Although peripheral visual and olfactory systems have been extensively studied, there is no report of peripheral auditory system abnormalities in AD patients. Comparison of temporal bones from eight AD patients with those from eight non-AD controls revealed a significant difference in the percentage of remaining hair cells, peripheral processes, and spiral ganglion cells in the basal cochlear turn but no significant differences in the overall percentage between the two groups. Furthermore, special stains (thioflavin S and Bielschowsky's silver impregnation) of temporal bone nervous tissue from AD patients did not show neuritic plaques and neurofibrillary tangles. It is unclear whether the differences between the two groups in the basal portion of the cochlea are due to AD or some other process, such as presbycusis. However, lack of significant degeneration in other parts of the cochlea and absence of neurofibrillary tangles and neuritic plaques in all eight patients may suggest that the peripheral auditory system, unlike the peripheral visual and olfactory systems, is not involved in AD. A larger sample of AD patients is necessary to clarify the peripheral auditory system findings in the present study.

Aged↗
PubMed1995

Constituents of the endolymphatic tubules as demonstrated by three-dimensional morphometry.

The various constituents of the tubules of the human adult intraosseous endolymphatic sac were stained with lectins and Millon reaction to reveal some of the carbohydrate and protein-containing substances in the endolymph. The amount of each substance was determined by digitizing sequential temporal bone sections. Differing amounts of the various identified substances were found in sacs from patients with Meniere's disease, patients with labyrinthine fibrosis, and controls.

Ear, Inner↗
PubMed1994

Juxtaposition lipoma to the mastoid seventh nerve.

The precise embryological source for fat in juxtaposition to the vertical portion of the seventh nerve in the mastoid is unknown. Seventeen percent of 240 temporal bones disclosed various amounts of fat adjacent to this portion of the nerve. Shiny areas of fat granules are occasionally seen around, and perhaps at first glance mistaken for, the seventh nerve during mastoid surgery. The radiographic appearance of fat in this area has not been described. Bilateral 1-cm ovoid images were interpreted in a 16-year-old girl as seventh nerve neuromas or perhaps hemangiomas, but were surgically proven to be a lipoma in the only ear operated on. Lipoma should be considered in the differential diagnosis for a mass in this location which demonstrates increased T1 signal, progressive decreased signal on T2-weighted images, and has signal intensity isodense with that of fat.

Adipose Tissue↗
PubMed1994

Identification of substances in the endolymphatic sac.

The composition of the contents of the endolymphatic sac (ES) has yet to be fully defined. Carbohydrates have been found in the ES of human fetuses and animals but not identified in the adult human ES. In the present study, celloidin was removed from previously prepared human temporal bone sections and a histochemical method was used to detect carbohydrates and protein in the ES. Six biotinylated lectins were used to identify specific carbohydrates in 15 ears: beta-D-N-acetylglucosamine, beta-D-galactose, D-galactose, alpha-D-mannose, D-N-acetylgalactosamine and alpha-L-fucose. The intensity of staining was graded qualitatively. A substance in the ES tubules that did not stain with any lectin was identified by the Millon reaction as containing protein. The carbohydrates and protein may exist in the different tubules or in the same tubule without mixing. This finding seems to support the idea that at least some of these substances are produced locally in the ES. Our observations support the hypothesis of the existence of a secretion and degradation system in the endolymphatic sac.

Carbohydrates↗
PubMed1994

Effect of profound hearing loss on a central auditory nucleus.

The present study was designed to investigate the type and extent of degeneration occurring in the human central auditory system subsequent to profound hearing loss. The authors have examined the size of one population of neurons in the ventral cochlear nucleus in seven subjects with profound hearing loss (audiometric responses poorer than 90-100 dB HL). Six normal subjects, ages 35-78, were used as controls. Cell size in the hearing-impaired subjects ranged from normal to reduced by more than 50 percent. Two factors appear to contribute to the variability in cell size reduction. The correlation coefficient (Spearman rs) of cell size with duration of profound deafness was -0.48, indicating a moderate tendency for neurons to become smaller with longer periods of deafness. The correlation coefficient of cell size with number of surviving cochlear ganglion cells was 0.73, indicating a stronger tendency for neurons to be larger with greater eighth nerve innervation of the cochlear nucleus. Two cases of Scheibe degeneration showed the most severe degenerative change in the central auditory system.

Adult↗
PubMed1994

Mixed hearing loss in otosclerosis: indication for long-term follow-up.

This retrospective study of 146 ears with long-term follow-up after otosclerosis surgery evaluated the stability of hearing results, the incidence of sensorineural hearing loss, and the effect of fluoride treatment. Follow-up was at least 15 years (mean, 25.2 yr; range, 15-44 yr). There were 97 large fenestra stapedectomy operations, 23 lateral canal fenestrations, 7 mobilizations, and 19 revision stapes operations. The level of air-bone gap achieved at surgery remained stable over time; the mean deterioration rate was only 0.2 dB per year. Profound sensorineural hearing loss ( > or = 65 dB bone conduction average) at the most recent follow-up occurred in 13 ears (8.9%). Such hearing loss occurred in all operative groups. Mean bone conduction average immediately postoperatively was significantly higher in these ears than in others in the study. This finding indicates that a mixed hearing loss at surgery is a factor that increases the risk of later profound cochlear loss. Only 3 percent of ears with pure conductive hearing loss, but 28 percent of patients with mixed hearing loss at surgery eventually suffered profound cochlear loss. Sodium fluoride was used to treat 11 ears with progressive cochlear loss. The rate of bone conduction hearing deterioration decreased in all ears after treatment, and none developed profound hearing loss. Follow-up after the first postoperative year is not necessary if pure conductive hearing loss is present at surgery. Annual follow-up with audiograms is recommended if a mixed hearing loss is present. Fluoride treatment is recommended if inner ear hearing loss progresses.

Adult↗
PubMed1993

Arterial supply of the human endolymphatic duct and sac.

The arterial anatomy of the endolymphatic duct and sac was studied in vascular casts of methyl methacrylate of six human heads. The chief source of arterial blood supply to the endolymphatic duct and sac appeared to be the occipital artery. Arterioles entered the bone of the mastoid process. Arterioles in bone, the walls of the sigmoid sinus, and the posterior fossa dura coursed medially to supply the endolymphatic sac. The orientation of arterioles tended to be along the long axis of the endolymphatic duct and sac, whereas venules were more likely to be circumferentially oriented. Arterioles arising from dural vessels divided into deeper branches, which supplied periductal connective tissue, and superficial branches, which entered canaliculi of the vestibular aqueduct. Gross anatomic findings were confirmed by histologic examination of temporal bones.

Arteries↗