The clinical histories, results of auditory and vestibular examinations of 75 cases, mostly adults, with unilateral sensori-neural deafness of obscure etiology were discussed, and their clinical pictures were presented.
Fourty-six cases (61.3%) indicated sensory hearing loss and had many past histories as intrinsic or extrinsic factors such as hypertension, head injury, gastric ulcer, allergy, gynecological surgery, Streptomycin injection, and diabetes mellitus.
Five cases (6.7%) indicated sensory and retrocochlear hearing loss simultaneously, 11 cases (14.7%) indicated retrocochlear hearing loss, and 13 cases (17.3%) were unclassified.
Some cases with retrocochlear hearing loss of obscure etiology showed probabilities of cerebellopontine angle arachnitis and 46.7% of the patients complained of vertiginous symptoms, and 46.6% showed canal parasis in bithermal caloric examination.
Further investigations will be necessary about anatomical and morphological differences in the cases of obscure etiology.