[Preliminary evaluation of the protective effects of semicircular canal occlusion under continuous irrigating mode of endoscopic ear surgery on hearing function].

Abstract

Objective: To introduce a new technique of precise exposure and preservation of membranous semicircular canal under endoscope, and to evaluate the protective effect of this method on hearing preservation of semicircular canal occlusion. Methods: The study included three patients with unilateral refractory Meniere's disease, including 1 male and 2 females, with hearing stage 4 in 2 cases and stage 3 in 1 case, the average hearing thresholds were 72.5, 82.5 and 48.8 dBHL, respectively. All of them were treated with triple semicircular canal occlusion under continuous irrigating mode of endoscopic ear surgery (CIM-EES) in RenMin Hospital of WuHan University. The surgical procedure involved the following key steps: the bony walls of the three semicircular canals near the ampullae were gradually thinned to expose the blue line. The endoscope was positioned as close as possible to the operating area to obtain a clear, magnified view. A micro hook needle was used to create a window on the bony semicircular canals. The hook needle progressively removed the bony material while preserving the membranous canals, which were clearly visible during the procedure. The bone dust was removed out of the surgical area by the continuous exchanged insuline without the help of suction that can avoid the damage of the membranous semicircular canals caused by aspiration and the open bony canals were precisely filled with bone wax and covered with bone powder to ensure complete occlusion of the three semicircular canals. Postoperative follow-up included regular assessments of vertigo control and hearing preservation. Results: All the 3 patients obtained complete hearing preservation at 6 months after surgery, and the hearing preservation rate was 100%. The average hearing thresholds at 6 months postoperatively were 66.3, 81.3, and 50.0 dBHL, respectively. Postoperatively, all patients experienced horizontal spontaneous nystagmus toward the healthy side on the day of surgery and the first day after surgery. One patient reported complete disappearance of tinnitus, while the other two patients showed no change in tinnitus severity. Postoperative MRI revealed complete occlusion of the three semicircular canals with normal vestibular imaging. At 6 months postoperatively, none of the patients experienced any vertigo attacks, suggesting effective control of vertigo symptoms. Conclusions: Precise Semicircular canal occlusion under CIM-EES is a promising technique for the treatment of intractable vertigo in patients with refractory Meniere's disease. This method provides clear visualization of the membranous canals, reducing the risk of inner ear damage and preserving hearing function of the patients.