Evaluation of inner ear damage by mastoid drilling with measurement of serum prestin (SLC26A5) levels

Objective: The objective of this study is to demonstrate any inner ear injury caused by drilling in mastoid surgery with prestin, outer hair cell motor protein specific to the cochlea. Methods: The patients with chronic otitis media requiring mastoidectomy (n = 21) and myringoplasty (n = 21) were included. Serum prestin level obtained from blood samples was measured before surgery and on postoperative days 0, 3, and 7 using Human Prestin (SLC26A5) ELISA Kit. All patients underwent the Pure Tone Audiometry (PTA) test before surgery and on the postoperative 7th day. The drilling time was also recorded for all patients who underwent mastoidectomy. Results: In both mastoidectomy and myringoplasty groups, the postoperative serum prestin levels increased on days 0 and 7 (pday-0 = 0.002, pday-7 = 0.001 and pday-0 = 0.005, pday-7 = 0.001, respectively). There was no significant difference in the serum prestin levels between the two groups, postoperatively. The PTA thresholds at day 7 did not change in either group. A significant decline at 2000 Hz of bone conduction hearing threshold in both groups and a decline at 4000 Hz in the myringoplasty group were found. There was no correlation between the drilling time and the increase of prestin levels in the postoperative day 0, 3, and 7. Conclusion: Our results showed that mastoid drilling is not related to a significant inner ear injury. Although the myringoplasty group was not exposed to drill trauma, there was a similar increase in serum prestin levels as the mastoidectomy group. Also, a significant decline at 2000 Hz of bone conduction hearing threshold in both groups and a decline at 4000 Hz in the myringoplasty group were found. These findings suggest that suction and ossicular manipulation trauma can lead to an increase in serum prestin levels and postoperative temporary or permanent SNHL at 2000 and 4000 Hz. Level of evidence: Level-4. (c) 2023 Associac,ao Brasileira de Otorrinolaringologia e Cirurgia Cervico-Facial. Published by Elsevier Espana, S.L.U. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).