Abstract Details

To evaluate brain ¹⁸F-FDG-PET correlates of apathy in a series of patients with amyotrophic lateral sclerosis (ALS).

According to the recent Strong's classification of cognitive and behavioral impairment in ALS (2017) the diagnosis of ALS with behavioural impairment (ALSbi) requires the identification of apathy with or without other behavior changes. Therefore, the understanding of anatomo-functional substrates of apathy in ALS patients is important to better characterize the disease.

165 ALS patients underwent ¹⁸F-FDG-PET and were assessed  with the Frontal Systems Behaviour Scale (FrSBe) (Family version) to identify the presence of apathy ("after" score ≥65). We performed two multiple regression analyses in the whole sample (N=165): “after” apathy subscore and “before-after” gap were regressed against whole brain metabolism with SPM12. Focusing on patients with “after” apathy subscore ≥65 (N=84), we performed the following comparisons through the two-sample t-test model: patients with “before” apathy subscore ≥65 versus patients with “before” apathy subscore <65; patients with “before-after” gap <22 versus patients with “before-after” gap ≥22. For all the analyses FrSBe “after” disinhibition sub-score was included as covariate and the height threshold was set at p<0.005 (p<0.05 FWE-corrected).

In the whole sample, “after” apathy subscore correlated with hypometabolism in dorsolateral prefrontal (DLPFC), ventrolateral prefrontal (VLPFC), premotor (PMC), anterior cingulate cortices (ACC), and insula bilaterally. The “before-after” gap correlated with hypometabolism in right DLPFC, left VLPFC, left ACC, and bilateral PMC. In group comparisons, a significant difference was found only between patients with “before-after” gap <22 versus patients with “before-after” gap ≥22, namely a relative hypometabolism in DLPFC (right>left) and CAA bilaterally and in left PMC.

In this series of ALS patients assessed with ¹⁸F-FDG-PET, we found clusters of hypometabolism in several cortical regions previously related to apathy. The "before-after" gap in the apathy FrSBe score adequately identifies behavioural changes due to the neurodegenerative process.