Frontal network syndrome testing: clinical tests and positron emission tomography brain imaging help distinguish the 3 most common dementia subtypes.

BACKGROUND

Dementia diagnosis and the various subtypes are challenging in the absence of biomarkers.

AIM: To examine available tests and neuroimaging procedures that may help distinguish these disorders.

METHODS

Alzheimer's disease (AD), cognitive vascular disorder (CVD), and Frontotemporal lobe disorders (FTLD) were tested with a hierarchical neuropsychological battery that included the Frontal Systems Behavior Scale, Mini-Mental State Examination, Montreal Cognitive Assessment Test, and subtests. All patients had multimodality magnetic resonance imaging and (18)F fluorodeoxyglucose-positron emission tomography (FDG-PET) brain scans.

RESULTS

Of the 161 patients evaluated for dysmemory and cognitive impairment, 31 satisfied the full protocol. The mean T scores for the 3 principal frontal system syndromes for the AD group were all abnormal save disinhibition. For the CVD and FTLD groups, all the 4 subcategory scores were abnormal. Disinhibition differed significantly between the AD and FTD group (analysis of variance [ANOVA], P = .02) and there was a strong association between the memory for 5 words test and a significant difference in the word list generation test score among the 3 groups (ANOVA, P = .0233). There was a strong association between the FDG-PET and the disease subtype (P < .0001).

CONCLUSION

Evaluation for disinhibition, word list generation, 5-word memory testing and PET brain imaging may help distinguish the 3 most common dementia subtypes.