Frank R. Galey

Cochlear implants : histopathologic findings related to performance in 16 human temporal bones

This paper presents results of a histologic study of 16 temporal bones with cochlear implants from 13 subjects. Damage caused by electrode insertion in the basal turn of the cochlea was evaluated. Dendrite and spiral ganglion cell populations were compared to clinical performance scores to determine structures necessary for stimulation and the minimum number needed for electrical stimulation. Results show that damage from insertion of long electrodes was located mainly at the most anterior part of the basal turn; that despite total degeneration of dendrites in the area near the electrode, some spiral ganglion cells remained; and that spiral ganglion cells or possibly axons are the stimulated structures and that fewer of them than previously thought are necessary to achieve a hearing sensation from electrical stimulation.

Histologic evaluation of temporal bones with cochlear implants.

Ectopic bone in the scala tympani is characteristic of cochlear otosclerosis and meningitis, which are the two most frequent etiologies of deafness in cochlear implant patients. The ectopic bone in a multiple-electrode implanted bone is probably caused by disease (syphilis) rather than by the electrode or electrical stimulation. The sensory elements being stimulated by intracochlear electrodes probably are the ganglion cells.

A mixed carcinoid tumour of the middle ear.

Carcinoid tumours belong to the rarest neoplasms of the middle ear. Murphy et al. (1980) described an interesting carcinoid tumour of the middle ear displaying adenomatous features. The histological similarity of carcinoid tumours to adenomatous tumours of the middle ear has also been noted by Fayemi and Toker (1975). We describe a similar case which caused certain diagnostic difficulties. Light microscopy on frozen sections favoured the diagnosis of a low-grade adenocarcinoma but electron microscopy has revealed the presence of many intracellular membrane-bound neurosecretory granules and the diagnosis was revised to that of a mixed carcinoid tumour.

Computer-Aided Reconstruction of the Endolymphatic Sac

Computer-aided three-dimensional reconstruction techniques along with surface area and volume determinations have been applied to the intraosseous portion of Ihe human endolymphatic sac. Three-dimensional reconstruction has revealed that the lumen of the sac is a series of parallel tubules rather than folds. Surface-to-volume ratio determinations may reveal that the resorptive capacity of epithelium in this portion of the sac is significantly reduced in patients with Menieres disease.

Initial Observations of a Human Temporal Bone with a Multi-channel Implant

(1984). Initial Observations of a Human Temporal Bone with a Multi-channel Implant. Acta Oto-Laryngologica: Vol. 98, No. sup411, pp. 38-44.

Chorda Tympani Nerve Fibers in Man

Four normal human chorda tympani nerves were studied for quantitative data of nerve fibers. The average total number of nerve fibers was 5360 (range, 4941-6020). The average number of unmyelinated fibers was 1835 (range, 1518-2083), or 34% of the total. The diameters of myelinated fibers ranged from 1 to 7 microns, peaking at 2 microns. Most of the unmyelinated axons had a diameter between 0.5 and 2 microns. The importance of the quantitative evaluation of the chorda tympani nerve fibers is stressed in reporting structural changes.

Lermoyez's Syndrome: Histopathologic Report of a Case

This paper reports findings in a pair of temporal bones from a patient with clinical evidence of Lermoyezs syndrome, a rare variant of Menieres disease. Endolymphatic hydrops is limited to the basal turn of the cochlea and saccule in Lermoyezs syndrome, but more generalized in Menieres disease.

ELECTRON MICROSCOPY OF HYALIN BODIES IN THE HUMAN INTRAOSSEOUS ENDOLYMPHATIC SAC

Hyalin bodies are amorphous, eosinophilic masses protruding from the subepithelial connective tissue into the lumen of the intraosseous endolymphatic sac (ES). We studied hyalin bodies at the electron microscopic level. Celloidin- embedded temporal bone sections known to have hyalin bodies were re-embedded into plastic and cut into thin sections appropriate for electron microscopy. The results revealed that the hyalin bodies are composed predominantly of thick bundles of collagenous fibers arranged in various directions. Fibroblasts and disintegrated macrophages were occasionally observed among the collagen fibers. Concentric calcific structures found within the hyalin bodies were composed of multiple smaller, concentric, lamellar calcifications. The results of this study support the hypothesis that the hyalin bodies are a repository of membranous cellular debris phagocytized by the macrophages.