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Eight Old World monkeys were exposed 8 h daily for 20 days to octave-band noise having center frequencies from 0.5--8 kHz at levels of 117--120 dB SPL. Two additional animals received exposures to wide-band, 120-dB SPL noise on the same schedule, and one animal was exposed to the 2-kHz octave band for 40 h continuously. Behavioral audiograms were measured throughout exposure and during a 1-month recovery period. Following recovery, the animals were sacrificed and their ears examined histologically. Monaural audiograms are presented showing initial and final TTS and PTS measured at the end of the recovery period. These are compared with complete cytocochleograms for each ear. Hair cell loss was generally restricted to the outer rows, and was reasonably well correlated with pattern of hearing loss. Some cell loss, including inner hair cells, was found in the extreme basal turn, usually without associated high-frequency hearing loss. The relationships between exposure frequency, hearing loss, and locus of cochlear pathology are discussed, as are changes in TTS during exposure.

In 24 temporal bones from patients with otosclerosis prepared by the method of microdissection and surface preparations, otosclerotic foci could be clearly seen during removal of the otic capsule. The state of activity of each focus was estimated on the basis of its consistency and vascularity. Small anterior foci constituted the most common form of involvement of the otic capsule. All were judged to be inactive, and none of them appeared to have caused obvious sensorineural degeneration. No cases of "pure cochlear otosclerosis" were seen. Sensorineural degeneration was associated with large anterior foci which reached the upper basal turn. One specimen displayed a circumscribed sensorineural degeneration in the upper basal turn, with an almost exact correspondence between the location and extent of the cochlear lesion and the site of invasion by the otosclerotic process in the bone and endosteum bordering on scala media and scala tympani. It is postulated that a toxic factor had diffused from the focus and acted directly on the organ of Corti. When multiple foci were present they were usually poorly defined. The otosclerotic process involved the round window, with new lamellar bone formation in the scala tympant of the lower half of the basal turn. The most extensive sensorineural degeneration in the entire material was seen in this group. One specimen also had severe cochlear hydrops. In three specimens large shunts were observed to connect the otosclerotic foci with the cochlear vasculature, which was severely dilated. Where otosclerosis involved the endosteum of the scala tympani, loss of vessels was observed. One specimum with extensive active capsular otosclerosis had severe sensorineural degeneration of the vestibular system. Vestibular pathology in fenestrated ears is also described. In a specimen from a patient with no caloric reaction, numerous hair cells were present in the macular organs.

Familial dysautonomia, or Riley-Day syndrome, is inherited in an autosomal recessive fashion and occurs almost exclusively in Jewish families. This disorder is characterized by a smooth tongue devoid of fungiform papillae and of taste buds, and is clinically associated with poor taste discrimination. An unsteady gait and dizziness on change in position are also common presenting symptoms. This study reports the histopathological findings of eight temporal bones from four patients with documented familial dysautonomia. For the control series, 13 normal temporal bones were also studied. The most striking finding in the dysautonomic patients was an extreme paucity of geniculate ganglion cells (P less than 0.001). A statistically significant reduction in the number of neurons was also found both in the superior and in the inferior divisions of the vestibular nerve (P less than 0.001). The paucity of the geniculate ganglion cells correlates well with the impairment of the taste in dysautonomic individuals, since the afferent fibers leaving taste buds of the anterior two-thirds of the tongue run via the chorda tympani and have their cell bodies in the geniculate ganglion. Furthermore, the reduction in the number of Scarpa's ganglion cells observed in the dysautonomic patients studied here could account for a poor response to caloric test, positional vertigo and an unsteady gait in this condition