Surgical protocol
All patients were placed under general anesthesia, and facial nerve monitoring electrodes were put in place. A standard mastoidectomy was performed through a postauricular incision, with decompression of the sigmoid sinus. The facial nerve and three semicircular canals were identified and skeletonized, after which the endolymphatic sac was identified posterior to the posterior semicircular canal, along the posterior fossa plate, below Donaldson’s line. The bone over the sac was widely removed for decompression. A fenestration was made at a spot on the posterior canal as far as possible away from the ampulla, keeping the membranous labyrinth intact. Next, a small piece of soft tissue was filled into the fenestration to tightly block the membranous labyrinth over a short segment, after which, the fenestration was finally sealed with bone wax to further safeguard against perilymph leakage. Thereafter, the superior and horizontal semicircular canals were blocked using the same method.