Implications of Tumor Size on Auditory Brainstem Implant Performance

Objectives To better understand the implications of tumor size on ABI Categories of Auditory Performance (CAP) score to facilitate more precise patient counselling Design Single centre retrospective chart review Setting Tertiary referral centre Participants Patients >18yo with NF2 that underwent ABI placement between the years 2009-2023 were included. Patients with prior surgical resection were excluded to reduce the potential of previous cochlear nucleus trauma confounding results. Main Outcome Measures Ipsilateral tumor volume was measured from the pre-operative MRI, and primary endpoint was one-year CAP score. Results Fourteen patients were included for analysis, with an average age of 35.3 years. The average pre-operative ipsilateral tumor volume was 22.8cm3 (stdev 22.4 cm3). The average post-operative CAP score was 2.7 (stdev 2). A negative association was found between ipsilateral tumor size prior to treatment and CAP score (slope = -0.058, p=0.010) utilizing a linear regression model. The model accounted for 43.7% of the variance in outcome (r2=0.437, adjusted R2=0.390), with a significant overall model fit (F(1,12)=9.31, p=0.010). Conclusions Increased tumor size has a negative correlation with ultimate ABI performance. There were patients in this study with larger tumor size that still benefited from ABI placement. While larger tumor size should not be a contraindication for ABI placement, understanding the role tumor size can have on performance variation can serve to improve tumor management strategies and pre-operative counselling.