Sensory and Neural Degeneration with Aging, as Seen in Microdissections of the Human Inner Ear

Johnsson, Lars‐Göran; Hawkins, Joseph E.

doi:10.1177/000348947208100203

Cited by 266 publications

(99 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In humans, degeneration of hair cells in the basalmost cochlea due to unknown causes begins at a very early age (Johnsson and Hawkins 1972) and progresses with increasing age (Bredberg 1968). This suggests that the basal organ of Corti in humans may be damaged by relatively mild noise exposures, as is the mouse ear (Wang et al 2002).…”

Section: Implications Of the Findingsmentioning

confidence: 99%

Immunocytochemical Traits of Type IV Fibrocytes and Their Possible Relations to Cochlear Function and Pathology

Adams

2009

JARO

View full text Add to dashboard Cite

One of the more consistent and least understood changes in the aging human cochlea is the progressive loss of fibrocytes within the spiral ligament. This report presents an animal model for type IV fibrocyte loss, along with immunocytochemical evidence that noise-induced loss of these cells may account for previously unexplained hearing losses. The remarkably low threshold for noise-induced loss of type IV fibrocytes, approximately 24 dB less than the threshold for adjacent hair cell destruction, may account for the prevalence of missing fibrocytes in humans. In mice, changes in the spectrum of traumatizing noise had little effect upon the site of loss of the fibrocytes, suggesting that the primary site of damage that induced the loss was the basal-most cochlear turn, a site expected to be damaged by all three noise bands. Type IV fibrocytes were found to immunostain for connective tissue growth factor (CTGF) and for transforming growth factor beta receptor 3, a receptor that is known to activate CTGF expression. Type IV fibrocytes lack immunostaining for adenosine triphosphatase and connexins that are key players in potassium ion uptake and transmission, which suggests that they play little, if any, role in potassium recycling from perilymphatic space to the endolymphatic space. Consequently, their loss probably does not directly reduce this process. Immunostaining for a receptor for CTGF, low-density-lipoprotein-related protein 1, indicated that CTGF acts as an autocrine and a paracrine agent within the cochlea. The lack of CTGF paracrine effects following noise-induced loss of type IV fibrocytes may account for previously unexplained hearing losses.

show abstract

Section: Implications Of the Findingsmentioning

confidence: 99%

Immunocytochemical Traits of Type IV Fibrocytes and Their Possible Relations to Cochlear Function and Pathology

Adams

2009

JARO

View full text Add to dashboard Cite

show abstract

“…Schuknecht (Schuknecht, 1964) made one of the first attempts to classify the etiology of presbycusis, based on the changes in the temporal bones of aged humans and cats, dividing it roughly into four distinct types: (1) sensory, with hair cell loss and subsequent neural degeneration; (2) neural, with primary degeneration of cochlear neurons; (3) metabolic, with atrophy of the stria vascularis and a flat pure-tone audiogram; (4) mechanical, with changes in the basilar membrane affecting its properties and function. In sensory presbycusis, loss of outer hair cells begins in the basal region of the cochlea, leading to high-frequency hearing loss (Johnsson et al, 1967;Johnsson et al, 1972). Because of the intimate connection between loss of hair cells and their neurons, the term "sensorineural" presbycusis describes the high frequency hearing impairment resulting from loss of hair cells and degeneration of spiral ganglion cells without major changes in the function of the stria vascularis and other accessory structures of the inner ear.…”

Section: Introductionmentioning

confidence: 99%

Age-related auditory pathology in the CBA/J mouse

et al. 2008

View full text Add to dashboard Cite

Commercially obtained aged male CBA/J mice presented a complex pattern of hearing loss and morphological changes. A significant threshold shift in auditory brainstem responses (ABR) occurred at 3 months of age at 4 kHz without apparent loss of hair cells, rising slowly at later ages accompanied by loss of apical hair cells. A delayed high-frequency deficit started at 24 kHz around the age of 12 months. At 20 to 26 months, threshold shifts at 12 and 24 kHz and the accompanying hair cell loss at the base of the cochlea were highly variable with some animals appearing almost normal and others showing large deficits. Spiral ganglion cells degenerated by 18 months in all regions of the cochlea, with cell density reduced by approximately 25%. There was no degeneration of the stria vascularis and the endocochlear potential remained stable from 3 to 25 months of age regardless of whether the animals had normal or highly elevated ABR thresholds. The slow high frequency hearing loss combined with a modest reduction of ganglion cell density and an unchanged endocochlear potential suggest sensorineural presbycusis. The superimposed early hearing loss at low frequencies, which is not seen in animals bred in-house, may complicate the use of these animals as a presbycusis model.

show abstract

“…Studies on the vestibular system indicate a marked decline in the vestibular apparatus among older adults (i.e., reduction of hair cells of the cristae ampullares [semicircular canals] and of the macula of the utriculus and sacculus; Johnsson & Hawkins, 1972;Rosenhall & Rubin, 1975). The major contribution of the vestibular apparatus to posture is in maintaining the whole-body balance by perceiving the changes in direction as well as motion by adjusting the activity of the postural muscles (Inglis, Shupert, Hlavacka, & Horak, 1995;Keshner, Allum, & Pfaltz, 1987).…”

Section: Introductionmentioning

confidence: 99%

Effects of Aging on the Biomechanics of Slips and Falls

2005

View full text Add to dashboard Cite

Although much has been learned in recent decades about the deterioration of muscular strength, gait adaptations, and sensory degradation among older adults, little is known about how these intrinsic changes affect biomechanical parameters associated with slip-induced fall accidents. In general, the objective of this laboratory study was to investigate the process of initiation, detection, and recovery of inadvertent slips and falls. We examined the initiation of and recovery from foot slips among three age groups utilizing biomechanical parameters, muscle strength, and sensory measurements. Forty-two young, middle-age, and older participants walked around a walking track at a comfortable pace. Slippery floor surfaces were placed on the track over force platforms at random intervals without the participants' awareness. Results indicated that younger participants slipped as often as the older participants, suggesting that the likelihood of slip initiation is similar across all age groups; however, older individuals? recovery process was much slower and less effective. The ability to successfully recover from a slip (thus preventing a fall) is believed to be affected by lower extremity muscle strength and sensory degradation among older individuals. Results from this research can help pinpoint possible intervention strategies for improving dynamic equilibrium among older adults.

show abstract

Sensory and Neural Degeneration with Aging, as Seen in Microdissections of the Human Inner Ear

Cited by 266 publications

References 25 publications

Immunocytochemical Traits of Type IV Fibrocytes and Their Possible Relations to Cochlear Function and Pathology

Immunocytochemical Traits of Type IV Fibrocytes and Their Possible Relations to Cochlear Function and Pathology

Age-related auditory pathology in the CBA/J mouse

Effects of Aging on the Biomechanics of Slips and Falls

Contact Info

Product

Resources

About