Behavioural variant Frontotemporal Dementia: Not all it seems?

Abstract

Background: The diagnosis of the behavioural variant of frontotemporal dementia (bvFTD) can be challenging. At present there is a paucity of prospective work addressing the specificity of current diagnostic criteria for bvFTD with respect to long-term outcome (i.e., false positives versus true positives).

Methods: Here we report two individuals who met current clinical criteria for bvFTD and who underwent detailed long-term clinical and neuropsychological follow-up. In addition, both had serial volumetric MRI and functional metabolic (FDG-PET) imaging separated by 5 years.

Results: One case had a slow clinical decline as well as both progressive atrophy and hypometabolism in a frontotemporal distribution, consistent with a neurodegenerative FTD syndrome. However, the second developed neither atrophy nor hypometabolism and remained clinically stable, a decade from symptom onset.

Conclusion: We propose that these cases illustrate that while there may be a slow evolution in bvFTD, it is possible that some cases who meet current criteria may not have a neurodegenerative syndrome. If correct, this hypothesis has important implications for the current diagnostic criteria. A potential hierarchy for diagnostic certainty in bvFTD is suggested.

Keywords:

• Frontotemporal dementia
• longitudinal progression
• MRI
• positron emission tomography
• phenocopy

Acknowledgments

Dr C. M. Kipps is supported by the Wellcome Trust (Grant No: 073850), Dr Nestor and Professor Hodges are supported by the Medical Research Council (MRC-UK).