Tinnitus Facts, Theories, and Treatments (1982) / Chapter Skim
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2 Facts, Theories, and Issues
2 Facts, Theories, and Issues
Pages 10-31
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From page 10... ...
And it sounds reasonable that emotional changes might produce changes in the composition of the inner-ear fluids and/or changes in the cochlear blood supply that might in turn produce differential neural activity that would produce auditory sensations. But while these and dozens of other equally attractive proposals may be partially or entirely correct, there is little evidence to support any of them.
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From page 11... ...
disappearance of the tinnitus following removal or treatment of the cause. As might be expected, many of these unequivocal sources of tinnitus involve gross causes.
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From page 12... ...
believes that the wax is serving to simply attenuate external sounds, thereby allowing a preexisting tinnitus to be revealed, an effect that can sometimes also be observed by inserting plugs into the ear canal. It has been asserted that the tinnitus that accompanies otosclerosis is typically present only as long as the hearing loss is less than 50-60 dB (Lempert, 1946; Saltzman, 1949; J
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From page 13... ...
even successful surgery to remove the tumor rarely eliminates the tinnitus. m e clinician should remain alert to the possibility of an eighth-nerve tumor when unilateral tinnitus and hearing loss combine with vertigo, but it is far from inevitable that a tumor will prove to be the cause.
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From page 14... ...
that in order for a person to have an experience of a spectrally distinct sound for which there is no acoustical concomitant, something about the neural activity in that person's auditory pathway must be misleading higher auditory centers into the erroneous experience. m at "something n might be a mechanical force -- for example, a tumor or a blood clot causing a local compression of neural tissue-or a biochemical or biomechanical upset affecting a subset of neurons at some level in the auditory nervous system.
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From page 15... ...
In order to examine the evidence pertaining to this proposal, it is necessary to briefly review the facts of spontaneous firings in normal primary fibers. The range of spontaneous firing rates is 0-100 action potentials per second in what are believed to be normal primary auditory fibers, but the distribution of rates is bimodal, not rectangular.
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From page 16... ...
studied the spontaneous firing rates of primary auditory fibers in cats that had been exposed to intense noise bands for an hour or two. The effects differed in the different spectral regions surrounding the exposure, but in those regions where responsivity to sound was greatly reduced, the spontaneous rates were significantly depressed.
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From page 17... ...
A curious aspect of this latter outcome is that the cells with increased spontaneous rates had low characteristic frequencies; tinnitus following noise exposure is typically high in frequency. In contrast wicn Kiang et al.
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From page 18... ...
has argued that any ciliary change that alters the degree of coupling between the stereocilia and the Rectorial membrane will alter the inherent noise level at that interface. Specifically, loss of stereociliary stiffness would lead to a partial decoupling at the hair-cell/tectorial membrane interface and a consequent increase in the inherent noise level.
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From page 19... ...
First, there are perceptions of sounds that have no (as yet detected) objective counterpart and that are presumably caused by abnormal activity at some place or places in the auditory nervous system (classical subjective tinnitus)
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From page 20... ...
Most of these people had apparently responded to a newspaper ad soliciting tinnitus sufferers, but it appears that none was afflicted with a particularly severe form. The 4 People having an OAK corresponding to a conscious exper i _ ence may not have been actual surrerers -- so muon an n"-urally careful introspectors, and perhaps with practice others might also come to hear their normally unheard OAEs.
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From page 21... ...
. mese echoes are acoustic energy detectable (using a microphone sealed in the outer-ear canal)
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From page 22... ...
. mese peaks and troughs have been discussed as being normal consequences of the same mechanisms responsible for OAEs and cochlear echoes.
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From page 23... ...
than in the past, it appears that OAEs will not prove to be responsible for many instances of severe, problem tinnitus. Students of hearing interested in the general topic of otoacoustic emissions are referred to the visionary paper by Gold (1947/1948)
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From page 24... ...
. POSSIBLE EXPERIMENTAL MODELS OF TINNITUS A well-established research strategy in the medical sciences is to develop procedures for inducing the malady of interest in weakened or reversible form in otherwise healthy humans or in species other than man.
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From page 25... ...
-- ~ Following exposure to octave-band noise, the tinnitus frequency was well below the maximum TTS frequency; with one-third octave bands, the tinnitus frequency continued to be lower than the maximum TTS frequency, but the difference was smaller than with octave bands; and with tonal exposure stimuli, the tinnitus frequency was higher than the maximum TTS frequency. From personal experience it is clear that monaural exposure to an intense sound can produce tinnitus in both ears.
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From page 26... ...
(1981) monitored a spontaneous OAK in a guinea pig while performing various psychophysical and physiological manipulations.
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From page 27... ...
indicates that the disorder is more common in whites than in blacks (also see CIBA Foundation, 1981:28) , is associated with industrialization and urbanization, and is believed to be absent in species other than humans.
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From page 28... ...
Surgical treatments have ranged from the extremes of labyrinthectomy and vestibular neurectomy to more selective (and less destructive) procedures aimed at the endolymphatic sac.
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From page 29... ...
He believed in blocking the stellate ganglion (located along the sympathetic trunk at the level of the seventh cervical vertebrae) with an injection of procaine hydrochloride as early in a Meniere's episode as possible, and, if there were several recurrences, he felt that a partial dorsal sympathectomy was advised.
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From page 30... ...
Exactly which consequence of the fluid accumulation and distension is responsible for the hearing loss and tinnitus produced by Meniere's Disease has been the object of some attention. An excess of fluid pressure could produce changes in the mechanics and micromechanics of the cochlear duct as well as possibly cause some compression of certain critical structures -- such as the Rectorial membrane, the hair cells, or the nerve fibers themselves-thus causing stimulation in the acoustic chain.
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From page 31... ...
31 was either not, or was only indirectly, related to the Meniere's Disease. As it turns out, the tinnitus complained about was easily masked, and a hearing aid or tinnitus masker/instrument typically provided acceptable relief.
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