[Failure of regain full function after surgery for otosclerosis: causes, diagnosis and treatment]

The aim of this study was to evaluate the causes, the diagnosis, the treatment and the results obtained by revision surgery, in cases of stapedectomy failures.

Retrospective study of 50 recent cases operated on between January 1997 and December 2001. DIAGNOSIS OF THE FAILURE: All reoperated patients had clinical and audiological assessment; CT scan with virtual endoscopy.

The mean time of onset of failure was 23 months. The mean preoperative air bone gap was 25.5 dB. Otoscopy revealed a retraction pocket caused by poor eustachian tube function in 9 cases. CT scan proved to be very effective at differentiating the cause of the failure.

In 11 cases the prosthesis was too short, in 8 cases the prosthesis had migrated out of the hole of stapedotomy and in 6 cases the piston was fixed in the stapedotomy hole. A partial or complete lysis of the long process of the incus was frequently associated, but in 9 cases it was the only cause of the failure. In all the cases when the piston was displaced, the stapedotomy was found to be covered by a thin mucous membrane, avoiding labyrinthine fistula. In 3 cases, the failure was due to recurrent otosclerosis. In 5 cases the failure was due to a local anomaly at the level of the oval window niche, 2 cases of failure were due to a malleus ankylosis. In 5 cases fibrous adhesion was found between the incus and the mucosa of the promontory. In one case a reparative granuloma was found at the level of the oval window.

In cases of partial lysis of the long process of the incus, a new prosthesis was placed in a 0.4 mm diameter stapedotomy, performed using a KTP laser. A 0.4 mm diameter piston was extended 0.2 mm below stapedotomy to avoid a new extrusion. Indeed some prosthesis extrusion could be due to increased movements of the ossicular chain in cases of eustachian tube dysfunction. In cases of complete lysis of the long process of the incus, or in cases of a very short long process of the incus, a piston was put in the stapedotomy and attached to the malleus manubrium. The results of revision stapedotomy were favorable in the absence of associated fibrous tissue adhesion or local malformation. The air bone gap was found to be less than 10 dB in 40 cases and between 10 and 20 dB in 8 cases. An impairment of the air bone gap was found in 2 cases. No case of bone conduction impairment was found in this series.