Brain Metabolic Correlates of Apathy in Amyotrophic Lateral Sclerosis: a 18F-FDG-PET study

Background and purpose: The aim of this study was to evaluate brain metabolic correlates of apathy in amyotrophic lateral sclerosis (ALS). Methods: A total of 165 ALS patients underwent 18F-2-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET) and Frontal Systems Behaviour Scale (FrSBe) evaluation. FrSBe provides "before" and "after" apathy subscores, referring to premorbid and morbid conditions. "After" apathy subscore and "before-after" gap, i.e. the difference between "before" and "after" subscores, were regressed against whole-brain metabolism. Among patients with a pathological "after" apathy subscore (i.e., >=65), we compared patients with "before" apathy subscores >=65 and =22. Results: In the whole sample, the "after" apathy subscore negatively correlated with metabolism in the dorsolateral prefrontal cortex (DLPFC), dorsomedial prefrontal cortex (DMPFC), ventrolateral prefrontal cortex (VLPFC), premotor cortex (PMC) and anterior cingulate cortex (ACC), and insula bilaterally. A positive correlation was found in the cerebellum and pons. The "before-after" gap negatively correlated with metabolism in bilateral DLPFC, DMPFC and PMC, and left VLPFC and ACC, and positively correlated with cerebellar and pontine clusters. Among patients with an "after" apathy subscore >=65, we found no difference between those with "before" apathy subscores >=65 and =22, compared to patients with a gap