PubMed Health⌕ Search

Biomedical subjects

F H Linthicum

Publications and source records attributed to F H Linthicum.

At least 19 recordsLinked to original sources
PubMed2001

Cholesteatoma behind an intact tympanic membrane: histopathologic evidence for a tympanic membrane origin.

BACKGROUND: Several theories have been proposed with respect to the origin and pathogenesis of cholesteatoma behind an intact tympanic membrane. CASE REPORT: The authors describe a case of cholesteatoma behind an intact tympanic membrane in a 71-year-old man with a history of tympanic membrane retraction fixed to the incus without evidence of a perforation. The membrane eventually became detached, and remnants of keratinizing squamous epithelium were found on the incus. DISCUSSION: Mechanisms such as metaplasia, ectopic epidermis rests, or ingrowth of meatal epidermis have been proposed to explain the pathogenesis of cholesteatoma behind an intact tympanic membrane. These findings, based on temporal bone histopathology, support the role of an acquired epidermal rest. CONCLUSIONS: This case report provides evidence that cholesteatoma behind an intact tympanic membrane can be established from a resolved retraction of the pars tensa of the tympanic membrane.

Aged↗
PubMed2001

Myelination of the human auditory nerve: different time courses for Schwann cell and glial myelin.

The goal of this study was to trace the development of myelin in the human auditory nerve. To do this, we used the Woelcke iron-hematoxylin technique to stain myelin sheaths in sections from fetal temporal bones and brain stems. In the cochlea, aggregations of Schwann cells are seen in the modiolus and along the spiral lamina by the 15th fetal week. By the 22nd fetal week, dense arrays of stained Schwann cells are present on auditory nerve axons within the temporal bone. By the 24th fetal week, light myelin sheaths extend up to, but not beyond, the glial junction. Myelin sheaths are not present in the auditory nerve central to the glial junction until the 26th fetal week or later. These results demonstrate a gap of several weeks between the onset of Schwann cell myelination distally and glial myelination proximally. The period between these two events may represent the time of final maturation of the organ of Corti.

Brain Stem↗
PubMed2000

The Clarion electrode positioner: temporal bone studies.

OBJECTIVE: To study the relationship of the Clarion electrode to the modiolus when using an intracochlear positioner. BACKGROUND: There are theoretical advantages to positioning a cochlear implant electrode in close proximity to the modiolus. This may allow more focused, discrete fields of electrical current, reducing both requirements to achieve threshold and the channel interactions associated with the simultaneous and nonsimultaneous stimulation of closely spaced electrodes. METHODS: Ten fresh temporal bones were used to assess the position of the electrode in the scala tympani with the positioner in place. The bones were X-rayed after implantation. The relationship of the electrode to the modiolus was studied by calculating a ratio between the curve assumed by the electrode in relationship to the outer wall of the cochlea. The depth of insertion was evaluated in degrees or number of turns around the modiolus. RESULTS: The electrode was brought closer to the modiolus and a greater depth of insertion was achieved in all cases with the positioner. CONCLUSION: The intracochlear positioner is capable of bringing the electrode consistently closer to the neural elements within the modiolus.

Cochlear Implantation↗
PubMed2000

Auditory perception in vestibular neurectomy subjects.

The auditory efferent nerve is a feedback pathway that originates in the brainstem and projects to the inner ear. Although the anatomy and physiology of efferents have been rather thoroughly described, their functional roles in auditory perception are still not clear. Here, we report data in six human subjects who had undergone vestibular neurectomy, during which their efferent nerves were also presumably severed. The surgery had alleviated these subjects' vertigo but also resulted in mild to moderate hearing loss. We designed our experiments with a focus on the possible role of efferents in anti-masking. Consistent with previous studies, we found little effects of vestibular neurectomy on pure-tone detection and discrimination in quiet. However, we noted several new findings in all subjects tested. Efferent section increased loudness sensation (one subject), reduced overshoot effect (five subjects), accentuated 'the midlevel hump' in forward masking (two subjects), and worsened intensity discrimination in noise (four subjects). Poorer speech in noise recognition was also observed in the surgery ear than the non-surgery ear in three out of four subjects tested, but this finding was confounded by hearing loss. The present results suggest an active role of efferents in auditory perception in noise.

Adult↗
PubMed2000

Extraneous round window membranes and plugs: possible effect on intratympanic therapy.

Recently there has been increasing interest in the possibility of treating inner ear disorders by application of medication into the middle ear on the premise that it will diffuse through the round window membrane into the inner ear. We examined 202 temporal bones from 117 patients to determine the frequency of round window niche obstruction. Patients ranged in age at the time of death from 31 to 97 years. Eleven percent of the ears were found to have fibrous tissue or a fat plug, and 21% had an extraneous (false) round window membrane. Of the 85 patients from whom both temporal bones were examined, 56% had no obstruction in either ear, while 22% had obstruction in both ears. We conclude that anatomic variations of the round window niche may explain the wide variations found in dosage of medication required to produce a clinical result.

Adipose Tissue↗
PubMed2000

Idiopathic sudden sensorineural hearing loss: temporal bone histopathologic study.

We microscopically examined the temporal bones of 12 ears with idiopathic sudden sensorineural hearing loss (iSSNHL), 10 ears with presbycusis, 11 ears with normal hearing, and 8 unaffected contralateral ears of patients with iSSNHL. The degeneration of the spiral ligament, vascular stria, hair cells, dendrites, and apical spiral ganglion cells was greater in ears with iSSNHL than in the other groups. The apical ganglion cells were significantly more affected than the basal ganglion cells, and the spiral ganglion cell loss increased as a function of duration of iSSNHL. Cochlear ossification was found in 1 ear with iSSNHL, and hydrops in 2. These findings suggest a viral rather than a vascular or ruptured inner ear membrane origin for iSSNHL.

Adult↗
PubMed1999

Meniere's disease and endolymphatic hydrops without Meniere's symptoms: temporal bone histopathology.

We studied temporal bone histopathology in 21 ears with Meniere's disease and 24 ears with endolymphatic hydrops without Meniere's symptoms and compared the findings to those in 10 ears with presbycusis and 11 ears with normal hearing. Normal hearing ears showed less degeneration of cochlear structures than the other ears. In ears with endolymphatic hydrops without Meniere's symptoms, the degeneration of spiral ligament, hair cells, dendrites (peripheral processes) and apical spiral ganglion cells was more severe than in the other three groups. In ears with Meniere's disease and endolymphatic hydrops without Meniere's symptoms, the hair cells and dendrites were more affected than ganglion cells and there was no correlation between hair cell and ganglion cell degeneration. These findings suggest that a permanent threshold shift in late stage endolymphatic hydrops is not related to ganglion cell loss but rather to degeneration of sensory elements.

Aged↗
PubMed1999

Application of labeling techniques to archival temporal bone sections.

Pathology of the human inner ear has traditionally been studied in celloidin-embedded, hematoxylin and eosin-stained sections of the temporal bone. Although the traditional histologic approach has yielded valuable information, it is now possible to extend these studies to include analysis of molecules using immunohistochemical and histochemical staining techniques. Fourteen antibodies and 6 lectins have been applied to 420 archival, celloidin-embedded human temporal bone sections. Tissues had been fixed in 10% formalin, embedded in celloidin, sectioned, and stored for as many as 40 years. The staining intensities varied among sections, so they were ranked from 'no label" to "dense label." To investigate the relationships between the extent of postmortem changes (PMCs), storage time, and staining intensity for each antibody, the sections were graded according to their PMCs, which ranged from good preservation of the temporal bone histologic structure to severe postmortem autolysis. Although statistical analysis indicated that both extent of PMCs and storage time in general decrease the staining intensity, both poorly fixed tissue and sections stored for a long time can yield good immunostaining results with some antibodies.

Antibodies↗
PubMed1999

Coexpression of neurotrophic growth factors and their receptors in human facial motor neurons.

Neuronal development and maintenance of facial motor neurons is believed to be regulated by neurotrophic growth factors. Using celloidin-embedded sections, we evaluated immunoreactivity of 11 neurotrophic factors and their receptors in facial nuclei of human brain stems (4 normal cases, and 1 from a patient with facial palsy and synkinesis). In the normal subjects, positive immunoreactivity of the growth factor neurotrophin-4 and acidic fibroblast growth factor (aFGF) was observed in facial motor neurons, as was positive immunoreactivity against ret, the receptor shared by glial cell line-derived neurotrophic factor and neurturin. Immunoreactivity was moderate for the receptor trkB and strong for trkC. In the case of partial facial palsy, surviving cells failed to show immunoreactivity against neurotrophins. However, immunoreactivity of aFGF was up-regulated in both neuronal and non-neuronal cells in this patient. Results suggest that these trophic growth factors and their receptors may protect facial neurons from secondary degeneration and promote regrowth of the facial nerve after axotomy or injury.

Adolescent↗
PubMed1999

Tympanosclerosis.

Explore the source record for details and available documents.

Autoimmune Diseases↗
PubMed1998

Mutations in a novel cochlear gene cause DFNA9, a human nonsyndromic deafness with vestibular dysfunction.

DFNA9 is an autosomal dominant, nonsyndromic, progressive sensorineural hearing loss with vestibular pathology. Here we report three missense mutations in human COCH (previously described as Coch5b2), a novel cochlear gene, in three unrelated kindreds with DFNA9. All three residues mutated in DFNA9 are conserved in mouse and chicken Coch, and are found in a region containing four conserved cysteines with homology to a domain in factor C, a lipopolysaccharide-binding coagulation factor in Limulus polyphemus. COCH message, found at high levels in human cochlear and vestibular organs, occurs in the chicken inner ear in the regions of the auditory and vestibular nerve fibres, the neural and abneural limbs adjacent to the cochlear sensory epithelium and the stroma of the crista ampullaris of the vestibular labyrinth. These areas correspond to human inner ear structures which show histopathological findings of acidophilic ground substance in DFNA9 patients.

Amino Acid Sequence↗