Auditory brain stem response (ABR) evaluations were conducted on 50 patients with eighth nerve or low brain stem lesions. Indices of the ABR showed characteristic of “eighth nerve or low brain stem lesions” in all cases. Pathologies for the patients included eighth nerve tumors (19 patients), meningioma (6), intra-axial tumors (6), cerebellar tumors (3), vascular lesions (11), multiple sclerosis (2), neuro-Behçet's syndrome (2), vertebrobasilar dolichoectasia (2). Waeform paterns, response thresholds, interwave intervals, latency-intensity functions, and interaural latency differencies were evaluated for differentiation of these lesions. Compairing the eighth nerve tumor and the other lesions there was no significant difference of ABR waveform paterns. Response thresholds, interwave intervals, latency-intensity functions, and interaural latency differencies did not provide informations to distinguish the eighth nerve tumor from the other low brain stem lesions. Furthermore salient characteristic was not found in any index of the ABR for differentiation of lesions. This study showed that the differentiation of each disease from the other lesions was difficult because of similarity of ABR results.
A test battery consisted of the screening audiometry, tympanometry, tuning folk test and otoscopic test, was used as hearing assessment test in an elementary school. One hundred and fifty-two children received this test battery. And the children whose tympanogram showed type B or type C had the conventional pure tone audiometry. After these hearing test, it was concluded that the most important thing on the hearing health care of these elementary school children was the observation of detailed findings of the tympanic membrane.
Distortion product otoacoustic emissions (DP-OAE) were measured in normal and sensorineural hearing impaired patients with near 4kHz primary tones (f1=3.9875kHz, f2/f1=1.225). The power of the 4kHz DP-OAE was well correlated with 4kHz pure tone audiogram. This result indicated a clinical applicability of DP-OAE for assessing the cochlear function in high frequency area which is hard to examine with conventional e-OAE. The standard deviation of 4kHz DP-OAE powers of tinnitus sufferers were large, but there was no significant difference of powers between tinnitus sufferers and tinnitus free subjects. This result suggested the variabilities of origins of tinnitus.
Instantaneous time-varying spectral analysis of ABR was carried out. The conventional way of spectral analysis of ABR is a function of frequency (called time-invariant spectrum). The time-varying spectral analysis represents both the time and frequency characteristics of ABR at the same time. The time-varying spectrum of normal ABR showed its peaks at around the latency of each component of ABR. The dominant frequency ranges were at around 200-300Hz, 400-550Hz and 800-1000Hz. The prominent magnitudes of the highest frequency range of 800-1000Hz were concentrated into a part within range of 1.7-4.7msec in latency (wave I to wave III of ABR were within this range). Relative magnitudes of the frequency range of 400-550Hz and 200-300Hz did not decrease until latency became longer, compared to that of 800-1000Hz.
This study was aimed to know the change of the auditory evoked magnetic field response in tinnitus patients using the electrical promontory stimulation. The amplitude ratio of P2m and N1m of the auditory evoked magnetic field response in ipsilateral tinnitus patients was increased when tinnitus disappeared following the electrical promontory stimulation. The increase in the amplitude ratio resulted from the increased amplitude of P2m originated in the response of auditory cortex. In unilateral tinnitus patients whose ipsilateral tinnitus was not disappeared, neither N1m or P2m of the auditory evoked magnetic field response, however, was not changed. In bilateral tinnitus patients, even if ipsilateral tinnitus disappeared following the treatment, neither N1m or P2m of auditory evoked magnetic field response was not changed. A ratio of P2m; N1m is more than 0.5 in both bilateral and unilateral tinnitus patients in spite of promontory electrical stimulation.
The middle latency response (MLR) and the evoked potentials (EP) from the right and left auditory cortices were simultaneously recorded in awake cats. Before aspiration of the auditory cortices and/or inferior colliculi, the P1 latency of the EP, which is widely believed to originate from the auditory cortex, was similar to that of the negative A (NA) in the MLR which appears just after the auditory brainstem respose (ABR). After aspiration of the bilateral inferior colliculi, the amplitude of were 5 and all subsequent ABR waves were reduced. In addition, the NA latency and amplitude were both significantly reduced. The amplitude of both P1 and P2 fell below 60% of that before aspiration. There was a significant correlation between the reduction in amplitude of NA and that of P1. After aspiration of the bilateral auditory cortices, the NA amplitude was significantly reduced. After aspiration of the bilateral inferior colliculi and auditory cortices, wave 5 and all the subsequent ABR waves were reduced in amplitude. Also, the NA latency was shortened and its amplitude was reduced by up to 40% of that before aspiration. Therefore, it is likely that the NA was originated from the auditory cortex, while the MLR waves spared after aspiration probably arise from the nonspecific auditory pathways.
Subjective expressions of tinnitus nature using onomatopoeias and the results of pitch match test were analyzed in 41 cases of surgically proven unilateral acoustic neuroma (AN). The pitch match test was conducted at 11 frequencies between 125Hz and 8000Hz using pure-tone audiometer following to the method of Standardized Tinnitus Test in 1984 which was proposed by Tinnitus Study Group of Japan Audiological Society. The results obtained were as follows; 1) Sixteen kinds of onomatopoeia were used for the subjective expressions in 41 tinnitus ears. 2) When the incidence in use of each onomatopoeia was analyzed, the most frequently used onomatopoeia was “jie” (19.5%) followed by “sien”, “sah” and “pie” (9.8%). The incidence in use of “kien” was only 4.9%, which was the most frequently used onomatopoeia for the subjective expression in tinnitus ears without hearing loss or associated with cochlear deafness. 3) As far as the simulated tone of tinnitus was concerned, pure-tone was used in only 48.8%, band noise in 34.1% and white noise in 12.2%. Two tinnitus ears (4.9%) could not be simulated by either pure-tone, band noise or white noise. This result indicated that the incidence in pure-tone decreased and that in band noise and white noise increased in tinnitus ears of AN compared with that in tinnitus ears without hearing loss or associated with cochlear deafness. 4) The tinnitus pitch was distributed between 500Hz and 8000Hz and its incidence became to be higher as the frequency increased. 5) When the relationship between 16 kinds of onomatopoeia and simulated tones of tinnitus was analyzed, five onomatopoeias (31.3%) corresponded to only pure-tone (tonal onomatopoeia), five onomatopoeias (31.3%) to only band noise and white noise (noise onomatopoeia) and six onomatopoeias (37.5%) to both pure-tone and band noise or white noise (tonal-noise onomatopoeia). This result indicated that the incidence in tonal onomatopoeia decreased and that in noise onomatopoeia and tonal-noise onomatopoeia increased in tinnitus ears of AN compared with that in tinnitus ears without hearing loss or associated with cochlear deafness. 6) Based upon these results, it was concluded that the incidence in noise tinnitus is relatively high in tinnitus ears of AN which might be induced by the intricate pathophysiology of auditory dysfunction due to the coexistence of cochlear and retrocochlear impairments.
The long-term reproducibility of onomatopoetic expressions of tinnitus nature and the results in tinnitus pitch match test were investigated in 57 tinnitus ears associated with cochlear deafness. Their subjective impression on tinnitus nature and tinnitus pitch did not change for more than 6 months. The onomatopoetic expressions of tinnitus nature and the results in tinnitus pitch match test in individual tinnitus ears were compared among 3 consecutive tests which were conducted with an interval of about 6 months between each test sessions. The results obtained were as follows; 1) The onomatopoetic expressions of tinnitus nature corresponded in 93.0% of the subjects between the initial and the second test, in 94.3% between the second and the final test and in 87.7% between the initial and the final test. 2) The simulated tones in pure-tone audiometer corresponded in 90.9% of the subjects between the initial and the second test, in 97.6% between the second and the final test and in 90.7% between the initial and the final test. 3) The reproducibility of tinnitus pitch was lower than that of onomatopoetic expressions and simulated tones. The tinnitus pitch corresponded in 84.1% of the subjects between the initial and the second test, in 75.6% between the second and the final test and in only 67.4% between the initial and the final test. However, the pitch difference was within one octave in all tinnitus ears which showed the discrepancy of tinnitus pitch between two tests. 4) Based upon these results, it was concluded that the long-term reproducibility of onomatopoetic expressions of tinnitus nature and simulated tones in pure-tone audiometer was excellent, however, the tinnitus pitch could fluctuate within one octave in 20-30% of the subjects.