A clinical study on the SISI-test

Abstract

Since Dix at al. (1948) reported that loudness recruitment was characteristically present in endorgan (cochlear) hearing loss and characteristically absent in hearing loss associated with VIIIth nerve tumors, further studies have been made by many investigators concerning recruitment test.In 1959 Jerger et al. introduced the SISI-test, which they described simply as a test of differential intensity sensitivity, and SISI is not an indirect test for loudness recruitment but a way of telling whether the patient can hear very small changes in sound intensity. Evidence exists that the ability to bear these very small changes are unique to disorders of the cochlea. Yet the results of many workers have not reached agreement because of discrepancy in the testing procedures and its criteria.So in this study the SISI-test was given to 10 subjects with normal hearing, 72 patients with cochlear lesion, and three patients with VIIIth nerve tumor (Neurinoma) using from 500 to 8000Hz as the test frequencies.On the other hand, the results of the recruitment test by Bekesy audiometry were compared with that SISI-test on these subjects, and the following conclusions were drawn:1) The SISI scores of the subjects with normal hearing were 0 to 5 per cent with the test condition at sensation level of 10dB and intensity increment of one dB.As for the test condition, there is no significant difference in the SISI score between 10dB SL and 20dB SL, however, it is necessary to set the intensity increment at one dB in the SISI-test procedure.2) Under the test condition of sensation level of 10dB and intensity increment of one dB, the SISI scores of those with cochlear lesions were remarkably high, the majority showing 80 to 100 per cent. In these, sudden deafness and S.M. deafness showed 90 to 100 per cent of all cases, Meniere's disease and mixed deafness were 80 to 100 per cent scores in 92 to 96 per cent cases.3) The SISI scores of those with VIIIth nerve tumors were very low, being 0 to 5 per cent.4) As the criteria of the SISI score, the percentages above 80 were considered as “positive scores”.5) Those who were proved positive by the Bekesy test for the recruitment phenomenon showed scores of 80 to 100 per cent in the SISI-test and the both results were in good agreement.