摘要Background:Bilateral sudden sensorineural hearing loss (BSSHL) is rare and assumed to be a different clinical entity compared to unilateral SSHL (USSHL).This study examined the differences between the idiopathic BSSHL and USSHL.Methods:Forty-six sequential BSSHL patients (Se-BSSHL) and 68 simultaneous BSSHL (Si-BSSHL) were consecutively admitted between June 2008 and December 2015.Two sets of patients served as control groups:(1) USSHL patients with healthy contralateral ear and (2) USSHL patients with contralateral preexisting hearing loss (USSHLwCHL).We retrospectively analyzed differences among four cohorts using analysis of variance,Kruskal-Wallis test,Welch's t-test,and Chi-square test as appropriate before and after propensity score matching (PSM) based on age,gender,and body mass index (BMI).Results:The prevalence of idiopathic BSSHL was 8.6％ (114/1329) among the total SSHL patients.In the total cohort,USSHL patients tended to be younger,female,and tended to have lower BMI,renal parameters,and total cholesterol in addition to higher high-density lipoprotein compared to the other three groups.Most routine blood indicators,some coagulation markers,and immunoglobulin M (H =13.4,P =0.004) were significantly different among the study groups.After PSM,the major significant differences were found in audiometric characteristics.Si-BSSHL and Se-BSSHL patients demonstrated similar hearing thresholds as USSHL but were significantly better than the USSHLwCHL patients across most frequencies before and after treatment (H =30.0,P ＜ 0.001 for initial hearing and H =12.0,P =0.007 for final hearing).Moreover,the BSSHL patients showed different hearing loss distribution patterns (more descending type,x2 =33.8,P =0.001) with less hearing gain (H =17.5,P ＜ 0.001) compared to the USSHL patients.Conclusions:Idiopathic BSSHL is a relatively rare subtype of SSHL with a higher rate of descending audiogram type and inferior hearing outcome rather than being classified as a completely different disease entity compared to USSHL.