The threshold shift at 500Hz bone conduction under positive and negative static pressure of 400mmH2O applied to the external auditory canal was examined in 20 patients of Meniere's disease with fluctuating low tone hearing loss21 patients of sensorineural hearing loss without fluctuating and 24 normal controls. In contrast to the 10 to 15dB threshold shift in the latter two groups (non-fluctuating group14.8±5.1dB at positive and 11.1±5.7dB at negative; normal controls13.6±5.4dB at positive and 9.3±5.3dB at negative)the former showed a significantly smaller shift (3.2±6.1dB at positive and 2.3±4.5dB at negative) while hearing was depressed. Howeverwhen the hearing was improvedthe pressure effect became greater even in the former group (11.3±5.3dB at positive and 9.1±4.8dB at negative). To understand further details of these phenomenawe performed electrophysiological animal experiments. Through a small hole made on the guinea pig's cochlear bony wall 300mmH2O pressure was applied to the scala tympani and the threshold of 500Hz CM was examined in both endolymphatic sac obliterated ears and non-obliterated ears. In 14 non-obliterated ears 21.1±5.1dB threshold shift was recordedwhereas it was only 1.6±2.6dB in 9 obliterated ears at 4-6th postoperative days. These results seem to reflect that the endolymphatic pressure is great during the early stage of hydrops. According to the present clinical and experimental studiesit may be safe to say that the fluctuation of hearing in Meniere's disease is the phenomenon accompanying with the fluctuation of the pressure in the scala medianamelyendolymphatic pressure may be greater when hearing was depressed.
- Gellé test
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