Interchangeability of three different methods of calculating Pure Tone Average in patients with vestibular schwannoma to assess the risk of surgery-related hearing loss

Background: Patients with vestibular schwannoma (VS) most commonly present with hearing threshold reduction for high frequencies and a falling type of audiometric curve. However, it is doubtful whether all Pure Tone Averages described in the literature characterize patients with VS correctly, as the type of PTA which comprises higher frequencies may be more appropriate for hearing status assessment in those patients. Aim: The aim of this study was to analyze 3 common methods of calculating Pure Tone Averages (PTA1 – 500, 1000, 2000 and 3000 Hz; PTA2 – 500, 1000, 2000 and 4000 Hz; PTA3 – 500, 1000 and 2000 Hz) and to determine which of them is the most reliable for the assessment of VS patients. Material and Methods: The study group included 86 patients operated on due to vestibular schwannoma accessed via the middle cranial fossa. Results: Regarding the method of calculating Pure Tone Averages (PTA1, PTA2 and PTA3) identical or similar correlations were found between the preoperative values of Pure Tone Averages (PTA1, PTA2 and PTA3) and surgery-related hearing loss, as well as individual parameters of audiologic tests. Conclusions: Pure Tone Averages calculated according to 3 different methods (PTA1, PTA2, PTA3) may be used interchangeably in the assessment of hearing in VS patients