Facial Nerve Preservation Surgery for Koos Stage 3 and 4 Vestibular Schwannomas

Object: Large vestibular schwannomas pose a unique challenge of achieving surgical cure while maintaining normal facial nerve function. Facial nerve preservation surgery, defined as attempted maintenance of normal facial nerve function at the cost of residual tumor when adherent to the facial nerve or root entry zone, is a novel idea. We present our experience and evaluate functional outcomes and extent of resection.

Method: We performed a retrospective review of patients treated surgically by a single surgeon team (PVT, MP) for large (Koos 3 & 4) vestibular schwannomas between 2003–2012. We review the extent of resection, post-operative hearing and facial nerve function. We separated the patients into groups based on extent of resection (gross total, near-total and subtotal) and evaluated the tumor control rate and functional outcome.

Results: A total of 52 patients were included in the study. 18 patients underwent a retrosigmoid craniectomy and 34 underwent a translabyrinthine approach. Of the 18 patient who underwent a retrosigmoid approach, 7 (39%) had a gross total resection, 3 (17%) had a near-total resection and 8 (44%) had a subtotal resection. Of the 34 patients who underwent a translabyrinthine approach, 10 (29.5%) had a gross total resection, 9 (26.5%) and 15 (44%) had a subtotal resection. Hearing was preserved in 1 of 5 (20%) GTR patients, 0 of 2 NTR patients and 1 of 3 (33%) STR patients. Good facial nerve function (HBI & II) was achieved long term in 16 of 17 (94%) GTR patients, 11 of the 12 (92%) NTR patients and 21 of the 23 (91%) STR patients. Only the GTR group had HB IV or worse facial nerve function (1 patient). Long term tumor-control was 100% for GTR, 92% for NTR and 83% for STR. 9 STR patients and 1 NTR patient received postoperative radiation therapy. Average follow-up was 33 months.

Conclusion: Facial nerve preservation surgery is associated with good long term facial nerve outcome. In tumors with significant adhesions to the facial nerve, subtotal or near-total resection achieves similar facial nerve outcomes as gross-total resection of tumors without significant adhesions to the facial nerve. The rate of tumor progression following STR is 17%.