Patterns and predictive factors of hearing loss following microvascular decompression for hemifacial spasm: a systematic review.

Microvascular is a safe and effective therapeutic intervention for hemifacial spasm; however, its potential association with hearing impairment remains a concern. This study aimed to determine the prevalence, patterns, and risk factors of hearing loss following microvascular decompression in patients with hemifacial spasm. In accordance with PRISMA guidelines, a systematic literature search was conducted across PubMed, Cochrane Library, ScienceDirect, and Web of Science from inception to April 2025. Eligible studies included adult patients undergoing microvascular decompression for hemifacial spasm with preoperative and postoperative objective hearing assessments. Data on hearing outcomes and potential risk factors (e.g., brainstem auditory evoked response, cerebellar manipulation, and compressing vessels) were extracted. Meta-analysis was performed using a random-effects model, and meta-regression was used to explore potential moderators. Eleven studies (N = 4,014) met the inclusion criteria. The pooled prevalence of permanent postoperative hearing loss was 2.60% (95% confidence interval [CI]: 1.13%-5.87%), with high heterogeneity (I2 = 87.4%). Subgroup analysis revealed a higher prevalence in prospective studies (n = 4; 5.29%) compared to retrospective studies (n = 7; 1.97%), although the difference was not statistically significant. Most studies concluded that brainstem auditory evoked response monitoring, particularly changes in wave V latency or amplitude, consistently predicted hearing impairment. Excessive cerebellar retraction (greater depth, distance, and duration) was significantly associated with an increased risk of hearing loss. Study-level data regarding the type of compressing vessel were insufficient and inconsistently reported across the included studies, precluding reliable meta-regression analysis. Permanent postoperative hearing loss was estimated to occur in approximately 2.6% (range: 1.1%-5.9%) (95% confidence interval [CI]: 1.13%-5.87%) of patients undergoing microvascular decompression for hemifacial spasm, although the pooled estimate remained unstable because of substantial between-study heterogeneity (I2 = 87.4%), limiting the precision of this estimate. The risk is primarily influenced by intraoperative cerebellar manipulation and brainstem auditory evoked response changes. Meticulous surgical technique and intraoperative neuromonitoring can reduce the risk of this complication.