Sudden deafness is defined as: 1, sudden onset of sensorineural hearing loss of at least two frequencies greater than or equal to 20 dbhl within 72 hours, mostly unilateral, but a few can occur bilaterally or sequentially. 2.No clear cause is found. 3.It may be accompanied by tinnitus, ear stuffiness and swelling, abnormal skin sensation around the ear, etc. 4.It may be accompanied by vertigo, nausea and vomiting.