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Biomedical subjects

Fred H Linthicum

Publications and source records attributed to Fred H Linthicum.

At least 19 recordsLinked to original sources
PubMed2006

Presbycusic neuritic degeneration within the osseous spiral lamina.

OBJECTIVE: To describe a neglected anatomic variant occurring with presbycusis. STUDY DESIGN: Retrospective temporal bone histopathology study. METHODS: Quantitative analysis of peripheral hair cells, neurites, neurons, and the stria vascularis in temporal bones from individuals who had presbycusis. Fifty-three patients aged 65 years or older and with a down-sloping audiogram and clinical diagnosis of presbycusis were reviewed. Nine cases had normal hair and ganglion cell populations but reduced peripheral processes (neuritic presbycusis). These were compared with five normal-hearing controls on measurements of anterior middle and basal turn fiber bundle diameter and the ratio of basal to middle diameters. RESULTS: Thresholds at 4 and 8 kHz were significantly poorer in the neuritic presbycusis group than in the control group (p<or=0.004 and 0.05, respectively), as was speech discrimination score (p<or=0.028). The ratio of basal to middle turn diameters was significantly smaller in the neuritic presbycusis group (p<or=0.003). This effect was quite marked in that there was no overlap in ratios between the groups, with the maximum neuritic presbycusis group ratio smaller than the minimum control group ratio. There was a moderate negative correlation between ratio and threshold at 4 kHz (sigma=-0.49, p<or=0.075). CONCLUSION: Loss of peripheral neurites in the anterior basal cochlear segment is found in conjunction with presbycusis in temporal bones that have no other morphologic abnormalities. These cases can be identified by a gradual down-sloping audiogram in contrast to sensory (hair cell) presbycusis, which is characterized by a precipitous high tone loss.

Aged↗
PubMed2006

The effect of organ of corti loss on ganglion cell survival in humans.

HYPOTHESIS: Severe spiral ganglion cell loss does not necessarily follow loss of hair cells or supporting cells in humans. BACKGROUND: Despite some publications to the contrary, statements that loss of hair cells and/or supporting cells of the organ of Corti results in a severe loss of spiral ganglion cells in humans still appear in the literature, especially in respect to cochlear implants. This assumption is apparently based on studies in animals or cell culture and not from studies of human temporal bones. METHODS: Morphological analysis of archival temporal bones with microscopic and statistical analysis of ganglion cell, hair cell, and supporting cell populations was performed in 33 ears with total hearing losses of varying causes and durations of deafness. None of the ears had remaining hair cells. Six ears had had cochlear implants. RESULTS: Ganglion cell counts ranging from 2,889 to 34,299 and the corresponding percentage of remaining ganglion cells based on age-normative data were not significantly related to the duration of hearing loss (r = -0.13 and 0.02, respectively, p > 0.05) or to remaining supporting cell populations (r's from 0.15 to 0.27, p > 0.05). More than half of ears (51.5%) had ganglion cell counts within two standard deviations of age-normative means. Mean ganglion cell counts and percentage of remaining ganglion cells of ears with surviving peripheral processes (dendrites) did not differ significantly from those of ears with no peripheral processes. CONCLUSION: The loss of hair and supporting cells in the organ of Corti in humans does not necessarily result in as significant a loss of spiral ganglion cells as has been reported animals. In fact, our results suggest that ganglion cell loss may be a primary concomitant loss due to the disease process.

Adult↗
PubMed2006

Distribution of low-frequency nerve fibers in the auditory nerve: Temporal bone findings and clinical implications.

HYPOTHESIS: Low-frequency cochlear fibers are on the outer surface of the auditory nerve adjacent to the vestibular nerve in the distal part of the internal auditory canal. BACKGROUND: There is a misconception that low-frequency cochlear fibers are in the core of the cochlear nerve and are surrounded by high-frequency fibers. METHODS: We analyzed temporal bones with a loss of upper spiral ganglion cells caused by different etiologies (n = 6) and traced the corresponding fibers into the distal internal auditory canal. Spiral ganglion cells for each segment (I-IV) of the cochlea were counted, and we defined the location of nerve fibers from the various segments. RESULTS: There was total or near-total degeneration of the upper spiral ganglion cells in these bones. Corresponding low-frequency fibers were on the outer surface of the cochlear nerve adjacent to the vestibular nerve in the distal segment of the internal auditory canal. CONCLUSION: Low-frequency fibers seem to be located at the periphery of the cochlear nerve. These findings provide one possible explanation for the low-frequency sensorineural hearing loss found in 10% of patients with vestibular nerve schwannomas and may have clinical relevance in the diagnosis of these lesions.

Adult↗
PubMed2006

Human cochleae with three turns: an unreported malformation.

OBJECTIVE: The objective of this histologic study of archival temporal bone sections was to describe the morphology of human cochleae found with three turns, a previously unreported anomaly, found in three pairs of temporal bones. METHODS: The authors conducted histopathologic processing and measurement of basilar membrane length. Basilar membrane length was compared with that found in six normal control bones. RESULTS: Cochleae with three complete turns, rather than the usual two and a half turns, are described for the first time. All had longer than normal basilar membranes, with a mean length of 40.6 mm compared with a mean of 33.8 mm in the normal bones. CONCLUSIONS: Human cochleae with three turns exist as an unreported anomaly. This is a new category of anomaly, not likely based on interruption of development.

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PubMed2006

Multichannel cochlear implants: relation of histopathology to performance.

OBJECTIVES: To determine the relationship of surviving neural elements to auditory function in multichannel cochlear implant temporal bones. STUDY DESIGN: Case series of all 14 existing multichannel cochlear implants in our temporal bone collection. METHODS: Devices included Nucleus 22 (n = 11), Nucleus 24 (n = 1), Ineraid (n = 1), and Clarion (n = 1). Morphologic evaluation of structural elements including spiral ligament, stria vascularis, hair cells, peripheral processes, and spiral ganglion cells was performed. Clinical performance data were obtained from patient charts. For eight patients, nonimplanted contralateral temporal bones were available and paired comparisons were made. RESULTS: Despite frequent absence of hair cells and peripheral processes, all bones had at least some remaining spiral ganglion cells. Percent of normal remaining structures were unrelated to auditory performance with the implant for any of the structural elements. Ganglion cell count in segment III showed significant negative correlations to speech discrimination scores for words and sentences (Rhos = -.687 and -.661, P < or = .03 and .04) as did segment IV and total ganglion cell count with word score (Rhos = -.632 and -.638; P < or = .05). Spiral ganglion cell survival did not differ between implanted and nonimplanted ears, with the exception of segment I, which had fewer cells in the implanted ear (P < or = .028). CONCLUSIONS: Performance variability of cochlear implants cannot be explained on the basis of cochlear neuronal survival. Although hair cells and peripheral processes were frequently absent or greatly diminished from normal, all subjects had at least some spiral ganglion cells. And, in this series, there was an inverse relationship between survival of ganglion cells and performance.

Adult↗