Sudden deafness, refers to the sudden onset of sensorineural hearing loss of unknown cause. Common causes include viral infections, vascular diseases, neoplastic diseases, drug toxicity, immune disorders, and ear diseases, etc. The etiology of about 1/3 of the patients is presumed or confirmed by long-term follow-up evaluation. 1.Viral infection. It can cause lesions of the cochlea, meninges, and nerves, resulting in hearing loss. Common viruses include parotid virus and cytomegalovirus. 2. Vascular diseases, such as spasm, thrombus, pressure in the blood vessels of the inner ear can cause insufficient blood supply to the inner ear, thus producing symptoms of deafness. 3. Tumor diseases, such as acoustic neuroma, can lead to damage to the auditory nerve, resulting in symptoms of deafness. 4. Drug toxicity, taking drugs with ototoxic side effects, such as chloramphenicol, gentamicin, cisplatin, quinine and so on. 5. Immune diseases, autoimmune diseases such as systemic lupus erythematosus, etc., can involve the inner ear may also appear sudden deafness. 6. Ear diseases, such as large vestibular aqueduct syndrome, Meniere’s disease, etc. Large vestibular aqueduct syndrome is mainly due to damage to the sensory hair cells. Meniere’s disease because of the accumulation of water in the membranous labyrinth. It is worth mentioning that if the etiology of the disease is clarified during the diagnosis and treatment, the diagnosis should be modified according to the etiology of the corresponding disease, such as acoustic neuroma, vestibular aqueduct syndrome, and so on.