# Machine Learning Method for Prediction of Hearing Improvement After Stapedotomy
## 4 Discussion
In all four analyzed examples, the preoperative hearing at the same frequency as the target was the most important feature. Nevertheless, the main difference in predicting the AC hearing at 2000 and 8000 Hz was the conduction type of the most significant hearing intensity feature. At 2000 Hz, the preoperative BC was most impactful, whereas at 8000 Hz, the preoperative AC was the most valuable. This finding indicates that preoperative BC values are significant mainly for the prediction of AC between 500 Hzand 4000 Hz, serving as a limit in the ABG reduction. The SHAP analysis revealed that the lower preoperative hearing intensity values resulted in lower hearing intensity predictions. Young age was generally associated with better postoperative hearing. Feature importance can be compared to other hearing recovery prediction approaches. It should be noted that the significance of features for hearing recovery may vary depending on the surgical procedure or underlying medical condition. The importance of hearing intensity features has been widely reported; however, some authors aggregate these features (for example, as PTA). The significance of preoperative high frequency hearing at 8000 Hz was recognized also in the case of ISSHL hearing recovery [5; 6; 7]. Furthermore, the importance of BC frequencies was observed in mastoidectomy hearing recovery prediction [9]. While age and ABG had a considerable influence on the prediction in our case, they were not among the most important factors, as they were in some previous studies [8; 9]. In our case, the ABG influence may have been diminished by the effect of other hearing intensity features. In our approach, the analysis of the influence of features for single hearing intensity prediction was enabled, in contrast to previous work. Our method is applicable as a decision support for stapedotomy surgery or potentially in any setting where audiogram estimation is required. In its current state, this system can be adapted and trained on isolated surgical data from a single surgeon. The drawback of focusing on a single surgeon is that the operating surgeon must perform a large number of operations with consistent results and comparable surgery settings to collect enough data. Only then is the model able to learn valuable insights, since inconsistent surgery performance or settings could lead to data of inadequate quality. Future studies could incorporate multi-surgeon and multi-center data to enhance the external validity and improve generalizability. Nevertheless, to create a more general machine learning system, other factors such as device type, surgical technique, etc., would need to be considered. Limitations of this study include the small number of patients and features. Although preoperative hearing intensities are consistently among the most significant features for hearing recovery prediction [4; 5; 6; 7; 8; 9], other factors influence the outcome in stapedotomy--primarily, the anatomical conditions in the middle ear (location of the long process of the incus ossicle, a dehiscent facial nerve, which narrows the oval window niche and thickness of the stapedial footplate). The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app142411882/s1](https://www.mdpi.com/article/10.3390/app142411882/s1)]([https://www.mdpi.com/article/10.3390/app142411882/s1](https://www.mdpi.com/article/10.3390/app142411882/s1)). [PERSON] planned the study, conducted the literature review and data acquisition, provided supervision, and contributed to writing the manuscript. [PERSON] implemented the algorithms, performed data analysis, obtained the results, and prepared the first draft of the manuscript. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The study received approval from the ethical committee in our institution (UKC-MB-KME-83/14, approval date 23 October 2014). Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.