Otology is a division of medicine which studies normal and pathological anatomy and physiology of the ear (hearing and vestibular sensory systems and associated structures and functions) as well as their diseases, diagnosis and treatment. Otologic surgery usually refers to surgery of the middle ear and mastoid connected to chronic otitis media, such as tympanoplasty, or ear drum surgery, ossiculoplasty, or surgery of the hearing bones, and mastoidectomy. Otology also contains surgical treatment of conductive hearing loss, such as stapedectomy surgery for otosclerosis. Neurotology, a interrelated field of medicine and subspecialty of Otolaryngology, is the study of diseases of the inner ear, which can leading to hearing and balance disorders. Neurotologic surgery generally refers to surgery of the inside ear or surgery that implicates entering the inner ear with risk to the hearing and balance organs, including labyrinthectomy, cochlear implant surgery, and surgery for lumps of the temporal bone, such as intracanlicular acoustic neuromas.