[Obliterative otosclerosis]

In true (grade IV) obliterative otosclerosis, the limits of the oval windows are lost. The insertion of a prosthesis requires drilling and surgical ability. Thirty eight cases of the true obliterative otosclerosis operated in our Department between 1974 and 1992 have been reviewed. Only 6.2% of all the patients operated by us with the diagnosis of otosclerosis had true obliterative otosclerosis. The average preoperative gap in conversational frequencies was 39 dB. In general, the gap closure obtained (13 dB) was slightly lesser than that for otosclerosis. Reobliteration of the oval window may occur in this type of otosclerosis.