Phase audiometry--a rapid method for detecting cerebello-pontine angle tumours?

Four groups of subjects have been investigated, using a manual phase audiometer. Group 1 consisted of 20 normal-hearing subjects. Group 2 of 22 subjects with unilateral or asymmetric cochlear hearing loss. Group 3 of 14 subjects with surgically verified CPA tumours, and Group 4 of 15 subjects with unilateral conductive impairment. In this report we suggest an upper borderline value for detecting interaural time differences of 120 microseconds. If the subject is able to detect only a value exceeding 120 microseconds, there is likely to be a retrocochlear lesion.