The interaural discrimination test, in which was presented different speech sounds (digits) dichotically, was investigated for the differential diagnosis of retrocochlear deafness.
The results of this test in normal subjects and the battery of the test, had been reported in previous papers.
The present report concerns the results of the interaural discrimination test performed on 116 patients suspected of having the central disorders.
In normal subjects, the discrimination score obtained by each test was close to 100%. On the other hand, abnormal patterns were classified into three types. The normal pattern was called Type I. The cases in which the discrimination score of one ear was normal and that of the other ear was poor were classified as Type II, those in which the discrimination score of both ears decreased and that of one ear was significantly better than the other were classified as Type III, and those in which the discrimination score of both ears decreased similarly were classified as Type IV.
The results of the test were compared with clinical signs, comfirmed surgical findings and so on in each case.
In regard to Feldmann's suggestion, the authors concluded the following.
The pattern of Type II appears to be related to a localized lesion in either hemisphere.
In case of the pattern of Type III the lesion can be diffuse. The pattern of Type IV indicates the presence of a localized lesion such as a brain tumor being enlarged and affecting the other hemisphere.
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