Microsurgical Resection of Large and Giant Acoustic Neuromas: A Focus on Facial Nerve Outcomes and Complications

Background Large (2.5–3.99 cm) and giant (≥4 cm) acoustic neuromas provide a challenge for successful microsurgical resection. An association between tumor size and facial nerve outcomes has been identified in several studies, yet this finding remains inconsistent. In this study, we analyzed a one neurosurgeon/three neuro-otologists series to specifically assess facial nerve outcomes in this challenging group.

Methods A retrospective chart review of 220 recent consecutive cases of microsurgical resection of acoustic neuromas, under the care of one neurosurgeon (JJM), was performed. We included patients with tumor diameters >2.5 cm. Facial nerve function was assessed pre-/postoperatively and at final follow-up, with outcomes dichotomized as good (House-Brackmann [HB] I–II) or poor (HB III–VI). Complication rates and tumor control were also analyzed.

Results In this series, 124 patients qualified (92 large and 32 giant tumors). Mean follow-up was 32 months. There were no mortalities. Nine patients had prior radiation; five patients had prior craniotomy. There was minor female prevalence (51.6%) and significant right-sidedness (75%). The mean tumor diameter was 3.4 ± 0.9 cm. Gross total (100% resection) or near-total resection (95–99% resection) was achieved in most cases (45 and 40% of patients, respectively). Two patients had poor facial nerve function preoperatively and were excluded from our analysis of postoperative CNVII function. Of those with good baseline facial function, 27% developed facial weakness immediately postoperatively, improving to 12% at final follow-up. The surgical approach (retrosigmoid 60%, translabyrinthine 40%) was not associated with either initial or final CNVII function. Facial nerve outcomes did not differ between giant tumors and large tumors at any time point postoperatively. Patients with giant tumors suffered more medical complications than patients with large tumors (12.9 vs. 2.2%, p = 0.0359, OR = 6.59), and also had an increased length of stay (mean: 8.0 vs. 4.7 days, p = 0.0003). There were no differences in requirement for VP shunting, CNVI palsy, wound complications, meningitis, or CSF leak between large and giant tumors. Surgical approach was not associated with differences in any of these complications in these two groups. Extent of resection (EOR) by surgeon impression was greater in large tumors than giant tumors (mean 97.1 vs. 92.2%, p = 0.0048). There was no statistical association between EOR and facial nerve outcome. We will discuss MRI-based volumetric analysis of EOR during the presentation.

Conclusion Our series demonstrates that excellent facial nerve outcomes can be achieved even in tumors of significant size with 88% of patients with good facial nerve function (HB I–II). These tumors can be resected safely with no mortalities and low surgical morbidity as long as the intent remains gross total or at least near total surgical resection. Patients with giant tumors are more likely to suffer medical complications (UTI, PNA, DVT/PE) than patients with large tumors, correlating with the increased length of stay in these patients. These results highlight the need for diligent efforts at directed prophylaxis in these susceptible patients.