Modern Management of Large Vestibular Schwannoma

Objective Many factors influence the management of vestibular schwannomas (VSs); most important is the size of the tumor. We report our experience of large VSs over the last decade. A large-sized vestibular schwannoma is defined as 30 mm or more in the maximum tumor dimension. The maximum tumor dimension is the longest measurable distance on a single image; however, this is not always a good correlate with tumor volume which is the traditional limitation for primary or adjuvant GK SRS.

Methods We report our experience over the past 9 years with more than 400 new cases of VS treated with upfront or adjuvant GK SRS of which more than 35 were large VSs (volume > 10 cm³). We classified our resections as follows: total resection—complete macroscopic resection; near-total resection (NTR)—capsular remnants either on facial nerve or brainstem; radical subtotal resection (STR)—tumor remnant that is either less than 5 mm in maximum tumor dimension or 10% of initial tumor volume (either intra-canalicular or adherent to facial nerve or brainstem). Our strategy now aims for near-total resection or radical subtotal resection with SRS rather than total resection. Or increasingly GK-SRS as primary treatment in selected cases and we discuss this evolution in practice.

Results Recurrence is significantly and historically low in TR. Recurrence was 9% in NTR and 4% in SRT and FSR, which remains low and similar to recent publications of outcome of microsurgery. Better control is achieved with GK SRS either as an adjuvant to facial nerve sparing surgery or as primary treatment. Large VSs often demonstrate dramatic reduction in tumor volume post GK SRS and excellent functional outcome and long-term control.

Conclusion Previously total resection was the aim. In the modern era, near-total resection and radical subtotal resection with stereotactic radiosurgery achieve better VII nerve preservation and good tumor control. Preserving the facial nerve while leaving a tumor remnant that can be managed with adjuvant therapy or upfront GK SRS in selected cases has become the mainstay of our management strategy.