Behavioral variant frontotemporal dementia (bvFTD) is a subtype of frontotemporal dementia, which has clinical symptoms of progressive personality and behavioral changes with deterioration of social cognition and executive functions. The pathology of bvFTD is known to be tauopathy or TDP-43 equally. We analyzed the ¹⁸F-THK5351 positron emission tomography (PET) scans, which were recently developed tau PET, in patients with clinically-diagnosed bvFTD.

Forty-eight participants, including participants with behavioral variant frontotemporal dementia (bvFTD, n =3), Alzheimer's disease (AD, n =21) and normal cognition (NC, n =24) who completed 3T magnetic resonance images, ¹⁸F-THK5351 PET scans, and detailed neuropsychological tests were included in the study. Voxel-wise statistical analysis and region of interest (ROI)-based analyses were performed to evaluate the retention of THK in bvFTD patients.

In the voxel-based and ROI-based analyses, patients with bvFTD showed greater THK retention in the prefrontal, medial frontal, orbitofrontal, anterior cingulate, insula, anterior inferior temporal and striatum regions compared to NC participants. Left-right asymmetry was noted in the bvFTD patients. A patient with extrapyramidal symptoms showed much greater THK retention in the brainstem.

The distribution of THK retention in the bvFTD patients was mainly in the frontal, insula, anterior temporal, and striatum regions which are known to be the brain regions corresponding to the clinical symptoms of bvFTD. Our study suggests that ¹⁸F-THK5351 PET imaging could be a supportive tool for diagnosis of bvFTD.