Abstract
For evaluation of recruitment by ECochG-CM, electrocochleography was performed in 10 ears with recruitment which was found by ABLB test and self-recording audiometry, in 6 Meniere's disease patients and 4 acoustic neuroma patients. 10 ears with normal hearing were used for control. Short tone bursts with frequency of 1, 2, 4kHz were employed as acoustic stimuli to evoked ECochG-CMs and clicks were used to measure ECochG-AP. The results were as follows.
1. Elevation of CM detection thresholds was seen in all cases with recruitment. It is considered that the presence of recruitment implies cochlear deafness. But one case with acoustic neuroma revealed lower CM detection thresholds than audiometric thresholds. This means that the existence of retrocochlear deafness is not proven from psychological audiometric test.
2. At higher stimulus levels, the input-output curves of 1kHz-CM in cases showing recruitment were similar to the curves obtained from normal control. It is supposed that this finding has relevance to the recruitment on ECochG-CM. On the other hand, the AP input-output curves in cases with Meniere's disease indicate no recruitment. For assessment of recruitment input-output curves of both CM and AP are thought to be necessary.
