Biomedical subjects
Publications and source records attributed to J A Vernon.
The relief of tinnitus has been effected in a cochlear-implant patient by presenting masking sounds to the microphone of the implant. Oddly enough, the presence of the masking sound improved the clarity of speech and music.
OBJECTIVE: To determine if the characteristics of tinnitus produced by head trauma are specific and exclusive when compared with other origins of tinnitus. DESIGN: Retrospective study using clinic test results and data from the Tinnitus Data Registry compiled from questionnaires, interviews, and testing. Tinnitus produced by head injury was compared with tinnitus of mixed origins, including no known origin. SETTING: A tinnitus referral clinic where all patients must see an otologist or an ear, nose, and throat physician prior to attending the clinic. PATIENTS: All patients had severe to moderately severe constant tinnitus and presented with tinnitus as the primary symptom. RESULTS: No exclusive characteristics were found to describe head injury-induced tinnitus. The tinnitus for the group with head injury was statistically significantly (P = .004) louder and occurred with greater incidence of continuing pain in the ears. The group with head injury also had more episodes of dizziness and a more severe form of tinnitus. However, no marked difference was noted in pitch of tinnitus, complexity (number of sounds) of tinnitus, or the minimum masking level. CONCLUSIONS: This retrospective study found that tinnitus induced by head injury was significantly (P = .004) louder than tinnitus induced from other causes but, interestingly, did not require higher levels of masking. The patients with head injury-induced tinnitus more frequently (P = .0003) displayed residual inhibition although the duration of residual inhibition was not different from that of the comparison group. Other symptoms associated with the tinnitus onset were more frequently mentioned by the group with head trauma-induced tinnitus, except for the condition of pressure sensation in the ears. Using a severity questionnaire, the group with head trauma-induced tinnitus rated their tinnitus as being more severe than did the comparison group. However, such things as pitch of the tinnitus, masking level, acceptance of wearable maskers, general hearing level, and complexity of the tinnitus did not distinguish the two groups.
Improved procedures have been developed for obtaining hearing thresholds, loudness matches, pitch matches, and masking curves of tinnitus. Computer programs enable all of these measures to be obtained in a single session. These measures have been obtained in tinnitus and nontinnitus subjects, with an external stimulus used to simulate tinnitus in nontinnitus subjects. These measures, obtained in repeated sessions, were used to determine the test-retest variability of each measure. The test-retest standard error of measurement, across-subjects, is reported, which enables changes in tinnitus to be determined. In nontinnitus subjects, the accuracy, as well as the reliability, is described.
The occurrence of hyperacusis is rare. In our Tinnitus Clinic, where more than 4,000 patients have been seen, hyperacusis has been seen only four times. Treatment of hyperacusis has been a combination of protection from external sounds along with desensitization to sound. Desensitization has been produced by very low intensity masking which is gradually increased every two to four weeks. The process of desensitization requires a great deal of time.
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Various electrical stimuli were tested for their ability to suppress or relieve severe tinnitus. Stimulation was applied transdermally by electrodes placed on the preauricular and postauricular regions and on the two mastoids. Of the 50 patients tested, only 14 (28%) obtained relief that met the criterion of a reduction in the tinnitus by 40% or more. When relief was obtained, it usually extended for several hours into the poststimulation period. There was only one positive response (2%) in the placebo trial, which was administered to all patients. It was concluded that transdermal electrical stimulation such as that used in this research is not a practical therapeutic procedure for the relief of tinnitus.
As one reviews the contents of this presentation, one finds there are no dramatic "breakthroughs" and there are frequent examples of neutral or negative findings. One should not let this state of affairs discourage continued research. It is often the case that many mistrials are encountered when investigating an area where very little is known. We expect research on tinnitus to proceed at a slow pace, but under no circumstances should the research effort in tinnitus be curtailed.
With care to provide properly chosen masking sounds, masking can help in 60-80% of clinically significant tinnitus cases. There is no universal masker; instead, an individual evaluation of each patient's tinnitus must be performed in order to match the masking sounds to the patient's audiogram and the spectral characteristics of the tinnitus. Successful long-term masking can usually be achieved in patients for whom (1) hearing impairment is not excessive. (2) the tinnitus frequency, FT, can be reliably located, and (3) the tinnitus can be completely masked by a band of noise at or near FT at a low sensation level. Such patients often experience residual inhibition (temporary suppression of tinnitus upon cessation of masking) which may accumulate with sustained use of masking, in some cases becoming permanent. Long-term masking is difficult or impossible for patients whose hearing is so impaired they cannot hear the masker, or those for whom the masking sounds must be presented at unacceptably loud levels to obtain adequate coverage of the tinnitus. There is a great need for additional work to determine what factors influence the effectiveness of masking, in order to improve our ability to provide appropriate masking stimuli even for the difficult cases.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Cochlear potentials measured in several species of lizard show a close correlation between maximum electrical output and number of hair cells, whereas there is no uniform relation to sensitivity. These results are interpreted as indicating structural differentiation and frequency discrimination in spatial terms in the more advanced lizard ears.
A follow-up study of two groups of tinnitus patients was conducted in an attempt to evaluate the tinnitus masking program. Results are discussed separately for a group of patients seen during the first three years of the program (1976 through 1978) and during the last year (1979). These results suggest an improvement in the management of the tinnitus patient and support this procedure as a viable technique in providing relief for selected tinnitus patients.
The possible beneficial effects of carbogen gas (95% O2/5% CO2) inhalation on noise-induced permanent cochlear impairment were investigated. Groups of guinea pigs were exposed to daily 3 1/2-hour presentations of 120 dB of broad-band noise in an atmosphere of either carbogen gas or normal air. Other groups received carbogen or normal air with a low intensity (50 dB) acoustic exposure. After a 30-day stabilization period each ear was examined electrophysiologically and histologically. Measures included a.c. cochlear potentials from 100 Hz through 20 kHz as well as counts of missing inner hair cells (IHCs) and outer hair cells (OHCs). Statistically significant improvement in the 1 microV isopotential function of the a.c. cochlear potential over all test frequencies and significant reduction in the number of missing IHCs and OHCs was found to result from inhalation of carbogen gas. Blood gas analysis demonstrated a rapid and marked elevation in arterial PCO2 and PO2 with a corresponding drop in pH to result from inhalation of carbogen. The vasodilating effects of increased arterial carbon dioxide tension are discussed in terms of current speculations regarding the role of vasoconstriction in noise-induced hearing loss.