Image processing commenced with baseline anatomical 3TMR images (A, axial section, midpontine level). Diffusion tensor images with overlaid colour-by-orientation fibers are shown in B. Reconstructed tracts of the trigeminal nerve onto colour-by-orientation images are shown in C. Panel D depicts the contour of the trigeminal nerve (blue) and location of the radiosurgical shot. Yellow circle denotes the 80% isodose line, representing the “target” of Gamma radiation to the nerve. Panel E shows focal area of post-gadolinium enhancement on the trigeminal nerve (yellow arrowhead), defining the “target” ROI. Panel F shows the location of the “proximal” ROI, proximal to the area of gadolinium enhancement (B, white arrow), and “unaffected” ROI, contralateral nerve.