# Results of TcMEP guided vestibular schwannoma surgery; long term follow-up and progression free survival

## TL;DR

This study shows that using TcMEP during surgery for large vestibular schwannomas leads to good facial nerve outcomes and low recurrence rates, even with small tumor remnants.

## Contribution

The study provides long-term follow-up data on TcMEP-guided surgery for large vestibular schwannomas, showing its effectiveness and safety.

## Key findings

- 83% of patients had good facial nerve function (HB I–II) one year post-surgery.
- Median growth-free survival was 76 months after subtotal resection.
- Routine postoperative radiotherapy is not recommended due to low residual tumor growth within 8 years.

## Abstract

In patients with large vestibular schwannomas (VS), surgery is the primary treatment despite risks such as facial nerve dysfunction. Intra-operative monitoring with transcranial motor evoked potentials (TcMEP) helps predict facial nerve outcome but may lead to subtotal resections and later recurrence. This study compares TcMEP thresholds, facial nerve outcome, recurrence rate and progression-free survival in Koos grade 4 vestibular schwannomas. Fifty-five surgically treated patients with Koos grade 4 VS (2015–2024) were included in this retrospective study. All underwent facial nerve TcMEP monitoring. House-Brackmann (HB) scores were assessed postoperatively, and at 6 weeks, 6 months and 1 year. Progression-free survival was analyzed with Kaplan–Meier curves. Postoperatively, 58% showed a decline in facial nerve function. After one year, 83% had good function (HB I–II). A TcMEP threshold increase < 20 mA correlated with good outcomes. In 84% (47/55), a small residual tumor remained (mean 0.4 cc; range 0–7.9 cc). Median growth-free survival was 76 months after subtotal resection (STR) and not reached after near-total resection (NTR). We conclude that TcMEP-guided surgery for large vestibular schwannomas provides good facial nerve outcomes, small acceptable remnants and a low long-term recurrence risk. As fewer than half of residual tumors show growth within 8 years, routine postoperative radiotherapy is not recommended; a watchful-waiting strategy is preferred.