Structural descriptions of neuronal networks are important for understanding brain dysfunctions; which dysfunctions, in particular?
Stam et al. have carried out a functional connectivity study in patients with Alzheimer's Disease. I don't know if that answers your question at all. Connectomics is just starting to kick off. It's far from certain that they it will end up being a key player in functional neuropathology in the coming decades, but it's one out of many promising new avenues of research.