A 28-year-old woman presents with a 4-year history of recurrent ear discharge and progressive hearing loss in the right ear. She reports a history of severe ear infection at age 6 following a head trauma with tympanic membrane perforation. On otoscopy, there is a retraction pocket in the posterosuperior quadrant with no visible perforation. Audiometry shows a 40 dB air-bone gap. High-resolution CT temporal bone demonstrates erosion of the lateral semicircular canal and the stapes footplate. What is the most appropriate next step in management?