[Study on treatment of absence of the oval window]

From March 1983 to June 1991 ten cases (twelve ears) underwent middle ear exploration for severe conductive hearing loss. Absence of oval window was found. Vestibulotomy and reconstruction of the ossicular chain were performed. Among patients with horizontal segments of the facial nerve displaced downward over the oval window region, or those after operation the inital gain of the hearing gradually reduced as a result of ablitecation of new fenestra, fenstration operation on the horizontal semicircular canal was performed. Vestibulotomy (10 ears) had resulted in elevated spech reception thresholds of 10-30 dB or more in 7 ears. Four of these patients had initial gain of the hearing reduced after 3 months. Fenestration in four cases resulted in elevated SRT of 20-45 dB. So fenestration is preferred. The authors have also presented their experience in the management of absence of the oval window.