Mapping brain morphological and functional conversion patterns in predementia late-onset bvFTD

Area of Science:

• Neuroscience
• Neurology
• Medical Imaging

Background:

• Diagnosing behavioral variant frontotemporal dementia (bvFTD) in its early, predementia stage is difficult due to subtle symptoms.
• Neuroimaging techniques like structural MRI and FDG PET are valuable for early bvFTD detection, but data is limited.

Purpose of the Study:

• To compare the diagnostic utility of structural MRI and FDG PET in identifying brain changes during the predementia stage of late-onset bvFTD.
• To investigate whether hypometabolism or grey matter (GM) density reduction is a more sensitive indicator of early bvFTD.

Main Methods:

• Retrospective analysis of 25 patients with late-onset probable bvFTD and 20 healthy controls.
• Structural MRI and FDG PET scans were acquired during the predementia stage (mean MMSE 27.1).
• SPM8 was used to compare imaging findings between bvFTD patients and controls, with bvFTD patients further categorized by symptom presentation (disinhibition vs. apathy).

Main Results:

• Hypometabolism was more extensive and statistically significant than GM density reduction in bvFTD patients.
• In the overall bvFTD group, hypometabolism affected frontal, temporal, parietal, and caudate regions, while GM reduction was more localized.
• Distinct patterns of hypometabolism and atrophy were observed between bvFTD subtypes with disinhibition and apathy.

Conclusions:

• Hypometabolism appears to precede or be more widespread than atrophy in the predementia stage of late-onset bvFTD.
• These findings highlight potential differences in brain involvement based on clinical presentation (disinhibition vs. apathy).
• The results suggest that FDG PET hypometabolism could serve as an early biomarker for bvFTD, aiding in patient selection for clinical trials.