Diffusion MRI of the facial-vestibulocochlear nerve complex: a prospective clinical validation study

Jonathan Shapey*, Sjoerd B. Vos, Laura Mancini, Brett Sanders, John S. Thornton, Jacques Donald Tournier, Shakeel R. Saeed, Neil Kitchen, Sherif Khalil, Patrick Grover, Robert Bradford, Reuben Dorent, Rachel Sparks, Tom Vercauteren, Tarek Yousry, Sotirios Bisdas, Sebastien Ourselin

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Objectives: Surgical planning of vestibular schwannoma surgery would benefit greatly from a robust method of delineating the facial-vestibulocochlear nerve complex with respect to the tumour. This study aimed to optimise a multi-shell readout-segmented diffusion-weighted imaging (rs-DWI) protocol and develop a novel post-processing pipeline to delineate the facial-vestibulocochlear complex within the skull base region, evaluating its accuracy intraoperatively using neuronavigation and tracked electrophysiological recordings. Methods: In a prospective study of five healthy volunteers and five patients who underwent vestibular schwannoma surgery, rs-DWI was performed and colour tissue maps (CTM) and probabilistic tractography of the cranial nerves were generated. In patients, the average symmetric surface distance (ASSD) and 95% Hausdorff distance (HD-95) were calculated with reference to the neuroradiologist-approved facial nerve segmentation. The accuracy of patient results was assessed intraoperatively using neuronavigation and tracked electrophysiological recordings. Results: Using CTM alone, the facial-vestibulocochlear complex of healthy volunteer subjects was visualised on 9/10 sides. CTM were generated in all 5 patients with vestibular schwannoma enabling the facial nerve to be accurately identified preoperatively. The mean ASSD between the annotators’ two segmentations was 1.11 mm (SD 0.40) and the mean HD-95 was 4.62 mm (SD 1.78). The median distance from the nerve segmentation to a positive stimulation point was 1.21 mm (IQR 0.81–3.27 mm) and 2.03 mm (IQR 0.99–3.84 mm) for the two annotators, respectively. Conclusions: rs-DWI may be used to acquire dMRI data of the cranial nerves within the posterior fossa. Clinical relevance statement: Readout-segmented diffusion-weighted imaging and colour tissue mapping provide 1–2 mm spatially accurate imaging of the facial-vestibulocochlear nerve complex, enabling accurate preoperative localisation of the facial nerve. This study evaluated the technique in 5 healthy volunteers and 5 patients with vestibular schwannoma. Key Points: • Readout-segmented diffusion-weighted imaging (rs-DWI) with colour tissue mapping (CTM) visualised the facial-vestibulocochlear nerve complex on 9/10 sides in 5 healthy volunteer subjects. • Using rs-DWI and CTM, the facial nerve was visualised in all 5 patients with vestibular schwannoma and within 1.21–2.03 mm of the nerve’s true intraoperative location. • Reproducible results were obtained on different scanners.

Original languageEnglish
Pages (from-to)8067-8076
Number of pages10
JournalEuropean Radiology
Volume33
Issue number11
Early online date17 Jun 2023
DOIs
Publication statusPublished - Nov 2023

Keywords

  • Cranial nerves
  • Diffusion magnetic resonance imaging
  • Magnetic resonance imaging
  • Vestibular schwannoma

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