<prompt> Cholesteatoma commonly perforates:Lat. Semicircular canalSup. semicircular canalPromontoryOval window  <response>: Ans. is a i.e. Lateral semicircular canal Cholesteatoma has the propey to destroy the bone by viue of the various enzymes released by it. Structures immediately at the risk of erosion are: - Long process of incus.deg - Fallopian canal containing facial nerve.deg - Horizontallateral semicircular canal.deg 