Thank you for reporting. This is due to an error that was made when VMTK toolkit was updated to work with most recent version of VTK. You can track resolution of the error here:
Hi,
I’m also interested in segmenting the facial nerve on MRI.
What was eventually your method and result?
Manual segmentation is quite straightforward, but it may take several minutes.
If you want fully automatic segmentation then you can train a deep learning segmentation model, similarly to how @cpinter’s group did at the last Slicer project week (see their project page).