Intraoperative Evaluation of Semiautomatic Localization of the Facial Nerve Using Diffusion Tensor Imaging in...

Facial nerve damage remains a significant risk during vestibular schwannoma (VS) resection, with reported incidences varying widely (3-46%). Damage risk increases with tumor size. Digital tractography enables nerve reconstruction but typically involves manual procedures, resulting in subjective evaluations that limit reproducibility and validation. We introduce a robust, semi-automatic tractography methodology with reproducible region-of-interest (ROI) generation and present an initial validation using a novel quantitative three-dimensional comparison approach in patients with a large VS.

To assess the accuracy of facial nerve reconstruction employing a semi-automatic ROI selection method in patients with VSs.

We included six patients with an average tumor size of 28 mm (95% CI: 17-40, 100% left) who underwent translabyrinthine VS surgery. Each VS patient was scanned with the regular neuronavigation magnetic resonance imaging (MRI) protocol and a custom diffusion-MRI protocol before surgery. The facial nerve trajectory was reconstructed with a diffusion tensor imaging-based tractography software package using semi-automatic ROI generation. We validated our reconstructions with the Brainlab neuronavigation system for intraoperative point annotation along the course of the facial nerve.

Tracts could be reconstructed in all included patients. The median distance and angle between the points and closest reconstruction were 5.1 mm (IQR: 3.5-7.6) and 38.5 degrees (IQR: 2.7-79.8), respectively.

We present a promising methodology for facial nerve reconstruction in patients with VSs. However, further optimization of the methodology is warranted before a proper clinical validation study can be performed.