Ebihara H
Department of Otolaryngology, School of Medicine, Tokyo Medical and Dental University.
Nihon Jibiinkoka Gakkai Kaiho. 1995 Dec;98(12):1887-93. doi: 10.3950/jibiinkoka.98.1887.
The middle ear is a cavity surrounded by solid bone, lined with mucosa with a lumen filled with gas. To examine this unique ventilation system under atmospheric pressure, the middle ear pressure of 50 normal ears was previously examined. Positional tympanometry, whereby the middle ear pressure is increased as the subject assumes the lateral position under atmospheric pressure was used. As a result, (1) The middle ear pressure was elevated by the change from the sitting position to the lateral position. Venous pressure was regarded as causative factor of this pressure elevation. (2) The elevation of the middle ear pressure in the lateral position suggested gas production from the mastoid cells of the middle ear. In this study, a proportion of the mastoid cells were removed to resect a tumor of the internal acoustic meatus in conjunction with resection of an acoustic tumor. After resection the area was filled with fascia and fatty tissue. The middle ear pressure of each subject was monitored to determine the effect of a decrease in the mastoid cell volume on middle ear pressure. The results were continuously recorded every 12 seconds for the lower ear when the subjects were in the lateral position. The following results were obtained. (1) The elevation of the middle ear pressure due to positional change among subjects which had had acoustic tumors resected was noticeably greater than the elevation in normal ears. This is thought to have been the result of an elevation in cerebrospinal fluid pressure attributable to positional change, along with an elevation in intravenous pressure. (2) We made comparisons of increases in middle ear pressure 10 minutes after assuming the lateral position in 14 ears after acoustic tumor resection and in 21 normal ears. No noticeable differences were found in the middle ear pressure increases between the two groups despite the fact that the volume of the mastoid cells in the group that had tumors resected had been greatly reduced.
中耳是一个由坚固骨质包围的腔隙，内衬黏膜，腔内充满气体。为了在大气压下检查这个独特的通气系统，之前对50只正常耳朵的中耳压力进行了检测。采用体位鼓室图法，即在大气压下受试者采取侧卧位时中耳压力会升高。结果显示：（1）从中卧位变为侧卧位时中耳压力升高。静脉压被认为是导致这种压力升高的因素。（2）侧卧位时中耳压力升高提示中耳乳突气房产气。在本研究中，为切除内耳道肿瘤并同时切除听神经瘤，部分乳突气房被切除。切除后该区域用筋膜和脂肪组织填充。监测每个受试者的中耳压力，以确定乳突气房体积减小对中耳压力的影响。当受试者处于侧卧位时，每隔12秒持续记录下侧耳的结果。获得了以下结果：（1）切除听神经瘤的受试者因体位改变导致的中耳压力升高明显大于正常耳朵。这被认为是由于体位改变导致脑脊液压力升高以及静脉压升高的结果。（2）我们比较了14只切除听神经瘤后的耳朵和21只正常耳朵在采取侧卧位10分钟后中耳压力的升高情况。尽管切除肿瘤组的乳突气房体积大幅减小，但两组之间中耳压力升高未见明显差异。
