Facial nerve regeneration surgery using fibroblast growth factor in Bell's palsy and Hunt syndrome

INTERVENTION: In intervention group: Facial nerve regenerating surgery with human recombinant bFGF (Fiblast spray, Kaken Pharmaceutical CO., Tokyo, Japan) via gelatin hydrogel. In control group: Transmastoid conventional facial nerve decompression surgery CONDITION: Bell's palsy and Hunt syndrome PRIMARY OUTCOME: Non‐recovery rate at 12 months after disease onset. Recovery is defined as an improvement of the House‐Brackmann facial grading score 1‐2. SECONDARY OUTCOME: Non‐recovery rate at 6 months after disease onset, incidence rate of sequelae at 12 months after disease onset. ; Postoperative bleeding which needs hemostasis in operating room and audiometric threshold elevation using air conduction pure tone audiometry at 250 Hz, 500 Hz, 1 kHz, 2 kHz, and 4 kHz test frequencies INCLUSION CRITERIA: Adult severe Bell's palsy and Hunt syndrome patients, who are older than 15 years, complete facial palsy(10 or less yanagihara score), degree of denervation exceeding 90% with ENoG and clinical follow unavailable for more than 12 month