Frontal Hypometabolism in Neurocognitive Disorder with Behavioral Disturbance

Criteria for the behavioral variant of frontotemporal dementia (bvFTD) include decreased frontal metabolism. F-18-FDG PETwas used to investigate whether patients with the behavioral variant of neurocognitive disorder (bvNCD) who did not fulfill 3 bvFTD criteria had the characteristic brain metabolic pattern. Methods: Patients were referred from the memory clinic to the nuclear medicine department for differential diagnosis of neurocognitive disorder with dysexecutive syndrome and predominant mild frontal atrophy. When only 2 bvFTD criteria were met, patients were classified into 2 groups before F-18-FDG PET: probable bvFTD (n = 25) or bvNCD (n = 27). Results: Voxel-based and multivariate partial least-squares analyses of F-18-FDG PET did not show significant between-group difference at inclusion. After 4.8 y of follow-up, most patients with probable bvFTD received the same diagnosis, 3 remained stable, and 1 participant was given a psychiatric diagnosis. Five patients with bvNCD fulfilled the criteria for probable bvFTD at a 4.4-y mean follow-up, whereas 2 participants remained stable and 3 received alternative neurologic or psychiatric diagnoses. When initial F-18-FDG PET findings were compared between groups stratified at follow-up (26 bvFTD vs. 17 bvNCD), there was a trend (P < 0.001, uncorrected) for lower prefrontal metabolism with relatively preserved premotor metabolism in bvFTD than in bvNCD. Twelve bvNCD participants had neuropsychologic testing before inclusion. They all presented executive dysfunction and normal visuospatial performance, and most (n = 9) had memory-encoding impairment. Conclusion: Frontal hypometabolism was observed in a dysexecutive presentation of frontal neurodegenerative disorder (bvNCD) that did not fulfill all clinical criteria for bvFTD.

Automated summary

The study investigated whether patients with behavioral variant of neurocognitive disorder (bvNCD) who did not meet all criteria for bvFTD exhibited characteristic brain metabolic patterns using F-18-FDG PET. Results showed no significant differences between the two groups initially, but after 4.8 years of follow-up, most probable bvFTD patients maintained their diagnosis while some bvNCD patients showed progression towards bvFTD criteria, indicating frontal hypometabolism in bvNCD that did not meet all clinical criteria for bvFTD.