Hypometabolic and hypermetabolic brain regions in patients with ALS-FTD show distinct patterns of grey and white matter degeneration: A pilot multimodal neuroimaging study

•MRI-PET shows contrasting pathophysiology between hypo- and hypermetabolic brain regions in patients with ALS-FTD.•Differential amounts of WM degeneration underly areas of hypo- vs hypermetabolism.•Frontal lobes of ALS-FTD patients show more hypometabolism associated with severe WM degeneration.•Temporal lobes of ALS-FTD patients show more hypermetabolism associated with less severe WM degeneration.