Frontal network syndrome testing: clinical tests and positron emission tomography brain imaging help distinguish the...

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

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

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.

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).

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