All patients underwent a thorough clinical evaluation of VS-associated symptoms (i.e. hearing impairment, tinnitus, dizziness, balance problems, gait disturbance, headache, facial dysesthesia and/or palsy, swallowing difficulties, nausea, vomiting) by a semi-structured interview by experienced neurosurgeons. Finally, the presence of ipsilateral tinnitus symptoms was dichotomized for statistical analysis (0: no tinnitus, TN-; 1: tinnitus present, TN +). Hearing impairment was classified according to the Gardner & Robertson (GR) scale76 based on the results of the pure tone audiometry (PTA) and speech discrimination (SDS) resulting in five classes: GR 1 (good, PTA 0–30 dB and SDS 70–100%), GR 2 (serviceable, PTA 31–50 dB and SDS 50–69%), GR 3 (non-serviceable, PTA 51–90 dB and SDS 5–49%), GR 4 (poor, PTA 51–90 dB and SDS 1–4%), GR 5 (deaf, PTA 0 dB and SDS 0%). According to previous publication, the GR score was reclassified in (i) functional hearing (GR1 and GR2), (ii) non-functional hearing (GR3 and GR4) and (iii) no hearing (GR5)19,20,77. Additionally, hearing function was classified based on the presence or absence of waves I, III and V in the auditory brainstem response (ABR) examination performed before surgery: Group I (Waves I, III and V are present and the latency I-III is normal or slightly increased), Group II (Waves I, III and V are present and the latency I-III is pathologically increased > 2.66 ms), Group III (Wave III is lost but Waves I and V are present), Group IV (only wave I or wave 5 is present) and Group V (all waves are lost). VS tumor size was graded according to Koos classification78 into 4 classes: T1 (purely intrameatal), T2 (intra- and extrameatal), T3 (filling the cerebellopontine cistern), T4 (compressing the brain stem).