Conclusion: This study shows that by using the round window approach and deep insertion, it is possible to reduce electrode insertion trauma (EIT), as indicated by the results of the hearing preservation marker.
Objectives: In this prospective study EIT was evaluated in 42 subjects with low frequency hearing before surgery with 28 mm round window deep insertion.
Methods: The degree of hearing preservation was a marker of EIT. Pure tone audiometry, monosyllable testing was conducted preoperatively and then at 3, 6, and 13 months after surgery.
Results: Immediate hearing preservation (3 months postoperatively) was 92.9% (39/42). The surgery-related hearing preservation 13 months after surgery varied from 85% (34/40) to 90% (36/40). The ipsilateral implanted ear showed significant differences between preoperative and postoperative hearing thresholds (p < 0.005). Comparisons of thresholds for the control ear showed a significant difference between preoperative and postoperative thresholds tested 13 months after surgery (p < 0.05). When the subtraction factor of the mean contralateral hearing loss for each tested frequency for the same time interval was applied to the implanted ear, no significant hearing loss was found, showing that postoperative ipsilateral progressive hearing loss was caused by etiology rather than surgery.