Leonetti, John

OBJECTIVE Advancements in microsurgical technique and technology continue to improve outcomes in patients with skull base tumor. The primary cranial nerve eight monitoring systems used in hearing preservation surgery for vestibular schwannomas (VSs) are direct cranial nerve eight monitoring (DCNEM) and auditory brainstem response (ABR), although current guidelines are unable to definitively recommend one over the other due to limited literature on the topic. Thus, further research is needed to determine the utility of DCNEM and ABR. The authors performed a retrospective cohort study and created an interactive model that compares hearing preservation outcomes based on tumor size in patients receiving ABR+DCNEM and ABR-only monitoring. METHODS Twenty-eight patients received ABR+DCNEM and 72 patients received ABR-only monitoring during VS hearing preservation surgery at a single tertiary academic medical center between January 2008 and November 2022. Inclusion criteria consisted of adult patients with a preoperative American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) hearing classification of A or B. Tumor size was measured as the maximal medial to lateral length, including the internal auditory canal component. RESULTS Overall hearing preservation (word recognition score [WRS] > 0%) was achieved in 31 patients with ABR-only monitoring (43.1%) and in 18 patients with ABR+DCNEM (64.3%). Serviceable hearing preservation (AAO-HNS class A or B) was attained in 19 patients with ABR-only monitoring (26.4%) and in 11 patients with ABR+DCNEM (39.3%). There was no difference in overall hearing preservation between the two groups (p = 0.13). Change in tumor size was not associated with the odds of serviceable hearing preservation for the ABR-only group (p = 0.89); however, for ABR+DCNEM, there was some indication of an interaction between tumor size and the association of ABR+DCNEM versus ABR-only monitoring, with the odds of serviceable hearing preservation at p = 0.089. Furthermore, with ABR+DCNEM, every 0.5-cm increase in tumor size was associated with a decreased odds of serviceable hearing preservation on multivariable analysis (p = 0.05). For both overall and serviceable hearing preservation, a worse preoperative AAO-HNS classification was associated with a decreased odds of preservation (OR 0.43, 95% CI 0.19–0.97, p = 0.042; OR 0.17, 95% CI 0.053–0.55, p = 0.0031, respectively). CONCLUSIONS The result of this interactive model study proposes that there may be a higher chance of hearing preservation when using ABR+DCNEM rather than ABR alone for smaller tumors, with that relationship reversing as tumor size increases.

Iatrogenic facial paralysis occurs in less than 4% of major otologic procedures. The prevention of iatrogenic injuries involves study, training and experience. These concepts are carefully woven into residency training, fellowship and, ultimately, into peer review. The reasons for injury may be errors of omission, such as inadequate preparation for the procedure, or errors of commission, such as inadequate surgical exposure. Currently, there appear to be enough surgical cases for training programs and the core training of otolaryngology residents prepares them to handle most facial nerve problems. Included in this article is a more detailed description of the anatomy in and around the facial nerve, particularly in the mastoid, with suggestions on how to avoid problems and reduce injuries.