Send to

Choose Destination
J Alzheimers Dis. 2016;49(3):695-705. doi: 10.3233/JAD-150302.

Clinical Impact of a Second FDG-PET in Atypical/Unclear Dementia Syndromes.

Author information

Clinique Interdisciplinaire de Mémoire (CIME), CHU de Québec, PQ, Canada.
Département d'imagerie médicale, CHU de Québec, PQ, Canada.
Service de médecine nucléaire, Institut de Cardiologie et de Pneumologie de Québec (IUCPQ), PQ, Canada.
Département des Sciences Neurologiques, Université Laval, PQ, Canada.


Diagnosis of atypical/unclear dementia is often difficult and this delays treatment initiation. Several authors have shown that beyond standard dementia workup, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) reduces the number of unclear diagnoses, leads to earlier treatment, and has a beneficial impact on families. However, it is not uncommon that the FDG-PET findings are equivocal in this setting. For those cases, a repeat FDG-PET may clarify the diagnosis and prevent treatment delay. We retrospectively assessed the clinical impact of a repeat FDG-PET in 59 patients with atypical/unclear dementia syndromes and inconclusive initial FDG-PET. Changes in primary diagnosis, diagnostic confidence, and management following the second FDG-PET were examined. Conducting a second FDG-PET reduced the number of unclear diagnoses from 80% to 34% , led to diagnostic change in 24% of cases, and treatment modification in 22% of patients. Overall, the clinical impact was higher when initial diagnostic confidence was low and the second FDG-PET repeated ≥12 months after the first one. In tertiary care memory clinic settings, when diagnostic incertitude persists despite extensive evaluation and an equivocal FDG-PET, repeating the FDG-PET 12 months later can greatly clarify the diagnosis and improve management.


Atypical dementia; FDG-PET; brain imaging; differential diagnosis

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for IOS Press
Loading ...
Support Center