Microsurgical Outcomes in Medium-Sized Vestibular Schwannomas: A Multi-Institutional Study Comparing Retrosigmoid and Translabyrinthine Approaches

Background: Vestibular schwannomas (VS) between 1.5 and 2.5 cm (i.e., medium-sized) in cisternal diameter present a unique challenge. Recent evidence suggests with increasing cisternal diameter between 1.4 and 2.0 cm the facial nerve and hearing outcomes decline with microsurgery. In this size cohort the hearing preservation is ~10%; therefore, hearing is often not a significant factor in surgical decision making. Given this, the choice between retrosigmoid (RS) and translabyrinthine (TL) approach is contentious with each skull base team having their own preference. In this series, we combined the microsurgical data between two high-volume VS centers with opposing approach biases for medium-sized VS to assess the difference between the approaches in extent of resection (EOR) and long-term facial nerve outcomes.

Methods: This was a retrospective review of consecutive patients who underwent microsurgical resection of medium-sized VS between 2000 and 2020 with at least 12 months of clinical follow-up at two tertiary referral centers. Medium-sized was defined as maximal cisternal diameter between 1.5 and 2.5 cm, as measured according to the AAO-HNS guidelines. Facial nerve function was recorded preoperative, at discharge, and at one-year follow-up with a “good” outcome defined as House-Brackmann grade I or II. Extent of resection (EOR) was dichotomized into gross total resection (GTR) and subtotal resection (STR) as defined by the presence of visible tumor on 3-month MRI. Serviceable hearing was defined as AAO-HNS class A or B hearing.

Results: A total of 246 patients underwent microsurgical resection of medium-sized VS between the two institutions. There were 140 patients in the RS group and 106 in the TL group. There was no statistically significant difference in age, sex, and length of follow-up between the two surgical groups. The median length of follow-up was 49 months (range: 12–243 months), and 56.1% were female (n = 138). The mean tumor diameter was 2.03 and 2.08 cm in the RS and TL groups, (p > 0.05). The rate of GTR was 80% (n = 112) in RS and 80.1% (n = 85) in TL (p > 0.05). In the RS group, the rate of good facial nerve outcomes at discharge was 75%, which increased to 87.8% at 1-year follow-up. Compared with 66% at discharge and 81% at 1-year follow-up in the TL group (TL vs. RS at discharge and 12 months, p > 0.05). The local control rate for the RS group was 92.8 and 93.4% in the TL group (p > 0.05). In the RS cohort, serviceable hearing was preserved in 11.4%. There was no statistically significant difference between surgical groups in rate of CSF leak.

Conclusion: Medium-sized VS present a unique microsurgical challenge. There was no difference in facial nerve outcomes and EOR between patients who underwent RS and TL. Hearing can also be preserved at a non-negligible rate without sacrificing extent of resection. Therefore, we contend the choice of approach should be individualized to the patient based on tumor characteristics, serviceable hearing, and the preference of the skull-base surgical team.

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Artikel online veröffentlicht:
01. Februar 2023