Presbycusic neuritic degeneration within the osseous spiral lamina.
OBJECTIVE
To describe a neglected anatomic variant occurring with presbycusis.


METHODS
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).


CONCLUSIONS
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.
Chen
Margaret A
MA
Division of Head and Neck Surgery, Department of Surgery, University of California, San Diego, and Department of Electron Microscopy, House Ear Institute, Los Angeles, California 90057, USA.
Webster
Paul
P
Yang
Eric
E
Linthicum
Fred H
FH
D000368:Aged; D000369:Aged, 80 and over; D001301:Audiometry, Pure-Tone; D016022:Case-Control Studies; D003053:Cochlear Duct / Q000473:pathology*; D005260:Female; D006198:Hair Cells, Auditory / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016501:Neurites / Q000473:pathology*; D011304:Presbycusis / Q000150:complications / Q000473:pathology* / Q000503:physiopathology*; D012189:Retrospective Studies