Clinico-statistical study on acoustic tumors with sudden hearing loss

Acoustic tumors associated with sudden hearing loss were studied clinico-statistically to clarify the differential diagnosis between so-called sudden deafness and acoustic tumor of this type. A significant difference was found in the frequency of such abnormalities as gaze nystagmus, canal paresis in the caloric (nystagmus) test, inhibition of optokinetic nystagmus, dilatation of the internal auditory canal, and cranial nerve signs. However, there was no significant difference in such symptoms as preceding upper respiratory tract infection and rotatory vertigo at the onset of sudden deafness. In this study, most of the patients with sudden deafness had tumors of 2 cm or larger in diameter. Apart from the atypical feature of sudden onset, the acoustic tumors of this type have several characteristics. Therefore, the differential diagnosis of two diseases is not difficult if the possibility of acoustic tumor is taken into consideration and the above tests are performed for equivocal cases. The CT scan provides the most useful information for making a definite diagnosis of acoustic tumors in cases of this type.