Figure 3 Patient No 1. Fibre‐tracking of the pyramidal tracts was disrupted in a 67‐year‐old man with a left fronto‐parietal glioblastoma multiforme. Upper: preoperative T2 weighted MRI identified a focus of hyperintensity in the left perirolandic region with gadolinium enhancement of the rostral precentral cortex. Stimulation of the left cortex rarely elicited weak motor evoked potential (MEP) responses on the right abductor pollicis brevis muscle. Subcortical stimuli, even on the approximated posterior bank of the precentral gyrus on neuronavigation (intersection of the yellow lines in the intraoperative navigation image), did not elicit MEPs. Middle: a relative anisotropy map indicated the principal eigenvector (green, anterior–posterior; red, right–left; and blue, inferior–superior). Fibre‐tracking of the left pyramidal tracts (red lines) near the tumour was disrupted during its course to the cortex. Lower: postoperative MRI with gadolinium enhancement.