Morphology Of The Vestibular Nerve: II. The Number Of Myelinated Vestibular Nerve Fibers In Man At Various Ages

This paper contains a study of the vestibular nerve and its branches in man at various ages. It has been done with the purpose of estimating the "normal" number of nerve fibers and to investigate whether any reduction occurs with increasing age. The vestibular nerves from 11 individuals of varying ages ranging from birth to 85 years were examined. There was no known history of vestibular disorders such as Menikre's disease or acoustic neuroma, or of treatment with ototoxic antibiotics or irradiation therapy to the head. Four persons in a "younger group", up to 35 years, had between, 16 040 and 20 212 (average of 18 346) myelinated vestibular nerve fibers. The number of nerve fibers in 5 old individuals, 75-85 years, ranged between 9 274 and 15 980 with an average value of 11 506. The study has thus shown a considerable reduction of the number of vestibular nerve fibers with increasing age. The reduction in number of nerve fibers in the old age group averages 37% and is statistically significant at better than the 1% level.