Two structurally connected brain regions are more likely to interact, with the lengths of the structural bundles, their widths, myelination, and the topology of the structural connectome influencing the timing of the interactions. We introduce an in vivo approach, based on neuronal avalanches, for measuring functional delays across the whole brain in humans using magneto/electroencephalography and integrating them with the structural bundles. The resulting topochronic map of the functional delays/velocities shows that neuronal avalanches spread more quickly when they travel across larger (and likely more myelinated) white-matter bundles. Then, we estimated the topochronic map in multiple sclerosis patients, who have damaged myelin sheaths, and controls, demonstrating greater delays in patients across the network and that structurally lesioned tract were slowed down more than unaffected ones. In conclusion, we apply the framework of criticality to provide a novel framework for integrating tractography and magnetoencephalography, with the scope of estimating functional transmission delays in vivo at the single-subject and single-tract level.