Auditory Brainstem Response (ABR) was investigated in nine patients with multiple sclerosis. In this study, the fast and slow components of ABR were separated by using different filter bandwiths. The fast ABRs were recorded using 150-3, 000Hz filter bandwiths. The slow component was isolated using 5-150Hz filter bandwiths. In multiple sclerosis series, the fast components were prolonged and diminished in amplitude. The slow component, however, was not affected by the disease. These data support the hypothesis that the fast and the slow components of the ABR are generated by different mechanisms.
Ca2+ concentrations in perilymph and endolymph of the guinea pig were measured with the double-barreled Ca2+-selective microelectrodes, and the results showed 1.76±0.74×10-3M in perilymph and 2.20±0.19×10-5M in endolymph, respectively. The electrochemical potential gradient for Ca2+ between perilymph and endolymph was 23.2mV and the active transport mechanism from the former to the latter was thought to exist. The Ca2+ concentration in endolymph was abruptly increased in anoxic condition with simultaneous depression of endocochlear potential (EP), and was returned toward preanoxic value after reventilation. Intravenous administration of furosemide (60mg/kg) reduced EP and increased the Ca2+ concentration in endolymph, but the Ca2+ concentration did not show a tendency to recover to the initial value in spite of the recovery of EP. Although intravenous injection of furosemide (30mg/kg) or acetazolamide (100mg/kg) caused a slight to moderate depression of EP, the Ca2+ concentration in endolymph showed little change. These findings suggested that the increase of the Ca2+ concentration in endolymph in anoxia or furosemide (60mg/kg) administration was attributed to the influx of Ca2+ from perilymph due to the depression of EP.
For the study of noise induced hearing loss due to vibration, 68 patients with vibration syndrome (white wax disease) were examined by the audiometry, Békésy tracing, SISI test and impedance audiometry. They did not show C5 dip in audiogram but C4, C5, C6 down slope pattern, and their hearing loss reached to maximum level within the first 6 years of their works with vibrating machines. And it was revealed that their hearing loss progressed only at the same rate as physical change after their forth decade. Therefore, it seemed less likely that vibration causes their hearing worse after their retirement. Their hearing loss was severer than that of workers under chronic noise only, so it was believed that vibration makes noise induced hearing loss severer. And there were several differences between chain saw labours (22 ears) and coal miners (83 ears) on their audiograms, and the hearing loss of the former showed severer than that of the latter. We speculated that this was caused by the differences of their tools and their circumstances in temperature.
Inner ear pathophysiology and hearing prognosis of perilymphatic fistula were studied by the electrocochleography which derives from the external ear. We examined 10 cases of perilymphatic fistula who underwent exploratory tympanotomy. The results showed that 2 cases of dominant-S. P., 4 cases of existence of compound action potential (AP) and 4 cases of no response. Dominant-S. P. and A. P. indicated good prognosis of hearing, but no response poor prognosis. Electrocochleography is the useful technique for the diagnosis of inner ear change and prognosis of perilymphatic fistula as same as the other inner ear diseases. These findings suggested that endolmphatic hydrops existed in some cases of perilymphatic fistula.
The endolymphatic pH was measured with the double-barreled selective microelectrode and the endolymphatic HCO3- concentration was calculated from the values of the endolymphatic pH and venous Pco2 in guinea pigs. The normal value was 7.64±0.013 in pH and 41.9mM in the HCO3- concentration, respectively. Intravenous administration of acetazolamide (100mg/kg) caused the acidification and decreased the HCO3- concentration in endolymph. This result suggested that carbonic anhydrase induces HCO3- production in endolymph and acetazolamide decreased pH due to the inhibition of the activity of carbonic anhydrase. Anoxia showed the similar result as that of acetazolamide and is presumed to affect carbonic anhydrase via the Na+, K+-ATPase inhibition. Furosemide given intravenously had little change of HCO3- in endolymph. Furthermore, the change of HCO3- in endolymphunder anoxia or acetazolamide was confirmed by the direct measurement with double-barreled HCO3- selective microelectrode.
Three kinds of AER, auditory brainstem response (ABR), middle latency response (MLR) and slow vertex response (SVR), were recorded from 12 electrodes on the scalp of cats, and the topographic mapping with the scalp distribution of each AER was developed before and after the lesion experiments. The characteristics of the mapping were estimated by investigating the highest voltage area and lowest voltage area in the isovoltage maps of AER. In these experiments, the lesion was made by freezing the inferior colliculus on the contralateral side. The results were as follows; 1. The mappings revealed little differences even if the AER showed very clear changes before and after the experiments. On the other hand, the mapping differed greatly when the AER showed similar modality before and after the experiments. 2. We could not find certain tendency of the topographic mappings for the lesion. 3. MLR and SVR showed changes to some extent, after the lesion experiments. Conclusion: Unnegligible normal-variations on the topographic mappings of AERs have to be taken into consideration, when we apply them for the clinical usage as far as our data were concerned.