Sudden onset, which can occur within minutes, hours or 3 days, unexplained sensorineural hearing loss with a hearing loss of at least 20 dB HL or more in at least two connected frequencies. Diagnosis based on: 1. It occurs suddenly and can be within minutes, hours or 3 days. 2. Non-fluctuating sensorineural hearing loss, which can be mild, moderate or severe, or even total deafness. Hearing loss of at least 20dB HL or more in two connected frequencies. Mostly unilateral, occasionally bilateral occurring simultaneously or sequentially. 3. The cause is unknown (no clear cause including systemic or local factors is found). 4.It may be accompanied by tinnitus and ear blockage. 5.It may be accompanied by vertigo, nausea and vomiting, but not repeatedly. 6.No other symptoms of cranial nerve damage except for the eighth cranial nerve. Principles of treatment: 1.Improve inner ear microcirculation drugs. 2.Neurotropic drugs. 3.Reducing blood viscosity and anticoagulant drugs. 4.Hormonal drugs. 5.Other treatment, such as mixed oxygen, hyperbaric oxygen and other treatment. Efficacy grading: 1.Cured: The hearing threshold of the damaged frequency returns to normal, or reaches the level of the healthy ear, or reaches the level before the disease. 1.Significant effect: The average hearing of the damaged frequency is improved by more than 30dB. 2.Effective: The average hearing of the damaged frequency is improved by 15-30dB. 4.Ineffective: The average hearing of the damaged frequency is improved by less than 15dB.