APATHY AND CORTICAL THICKNESS IN THE ALZHEIMER'S DISEASE SPECTRUM: THE ARGENTINA-ADNI EXPERIENCE

Apathy is a predominant behavioral symptom in Alzheimer’s Disease with severe consequences in every day function. Physicopathological aspects, clinical features, and differential diagnosis in depression still remain controversial. The finding of biological markers of apathy could be a useful diagnostic tool, and atrophy identification trough MRI could represent this option. Our aim is to study possible correlation between neuropsychiatric behavior focused in apathy and localized cortical atrophy in AD spectrum. 22 patients (dementia=8 and mild cognitive impairment=13) from the Argentina-ADNI cohort with a positive amyloid biomarker (Ab42 in CSF or PiB-PET) were selected. Apathy and depression were measured with Neuropsychiatric Inventory apathy sub score (NPI-AS) and Geriatric Depression Scale (GDS) respectively. Patient underwent a 3T MRI scanning and the cortical images were analyzed using Freesurfer. Two statistical analysis were performed, a multiple lineal regression using SPSS and a voxel-based surface group analysis using Qdec tool of freesurfer. An age related lineal regression model showed correlation between cortical thickness with apathy (aR2=0.70, p<0.01). A decrease in 1mm in left anterior-medial region of cingulum gyrus explained 6 points increase in NPI-AS(p<0.001), in left occipitotemporal lateral fusiform gyrus 3 points increase in NPI-AS (p<0.05) and in right frontal superior gyrus 3.8 points decrease in the NPI-AS (p<0.05). White matter lesions showed no-significant impact in the model and there was not founded correlation between GDS and cortical atrophy. In parallel surface group analysis show similar regional differences between apathetic and non-apathetic patients and could show more specific boundaries of the related local atrophy. The compromise of cortical structures such as cingular cortex and its high correlation with apathy confirm his role in motivation circuits in AD spectrum. White matter lesions don't correlate in this AD-apathy model, maybe their relevance has to be confine to another neurological diseases. The relevance of right superior frontal gyrus in this model suggest new queries about the complexity of the motivation network involved in AD, further research could be perform to accurate his role.