SISI test and adaptation. III. Subjects with perceptive hearing defects

The effect of the adaptation of the ear on the SISI test was studied in 60 completely and 18 incompletely recuriting patients and in 5 patients with a verified acoustic neurinoma at 500 and 2000 Hz. The subjective suprathreshold adaptation to a 3 min tone of 20 dB (SL) ranged from 10 dB to over 20 dB, depending on the frequency and type of defect. The pre-adaptation mean SISI values in the recruiting groups ranged from 38 to 51% and the post-adaptation means from 38 to 49%. In retrocochlear lesions only one SISI value was questionable before and after adaptation, the others being 0%. The dispersion of the SISI scores was considerable, a fact that made statistical treatment difficult. Adaptation did not significantly affect the SISI value. It could be ascertained that high SISI values did not reliably distinguish between the hearing defect types, but if the SISI was low the possibility of a retrocochlear lesion should always be borne in mind.