Total of 438 patients with ISSNHL , including 76 with hearing loss in low-middle frequencies , 43 in middle-high frequencies , 162 in all frequencies and 157 in total deafness , were randomly divided into two groups , the systemic application group : dexamethasone ( DEX ) was applied by intravenous injection in dose of 10 mg3 d followed by 5 mg4 d , and the topical injection group : methylprednisolone sodium succinate of 40 mg was injected into cortical bone of mastoid region every three days .