Atypical FDG-PET Patterns Predict Higher Dementia Risk in Parkinson Disease

PET scan features of behavioral-variant frontotemporal dementia
PET scan features of behavioral-variant frontotemporal dementia
Investigators sought to determine whether brain pattern metabolic alterations in PD and FDG-PET SPM could predict dementia risk.

An atypical fluorodeoxyglucose positive emission tomography (FDG-PET) pattern is an early marker for identifying patients with Parkinson disease (PD) at higher risk for progression to dementia, according to the results of a study published in Neurology.

Andrea Pilotto, MD, of the neurology unit, department of clinical and experimental sciences, University of Brescia Parkinson’s Disease Rehabilitation Centre in Italy, and colleagues applied a single-subject statistical parametric mapping (SPM) procedure to FDG-PET data in a sample of 54 consecutive patients with a clinical diagnosis of PD and disease duration of at least 1 year.

Participants were recruited from the Neurology Unit of Spedali Civili Hospital, University of Brescia, Italy from January 2006 to December 2010.  Patients underwent extensive standardized motor and cognitive assessment at baseline and at 4-year follow-up.

Two experts evaluated the FDG-PET SPM and identified 29 patients with a typical PD pattern and 25 patients with atypical patterns, including 12 with dementia with Lewy bodies (DLB)-like patterns, 6 with Alzheimer disease (AD)-like patterns, 5 with corticobasal syndrome-like patterns, and 2 with frontotemporal-like patterns.  Investigators characterize typical patterns by limited brain hypometabolism confined to premotor and motor regions and atypical patterns by metabolic alterations involving the posterior parietal-occipital regions.

At 4-year follow-up, 13 patients with baseline atypical brain metabolic patterns had progressed to PD dementia.  DLB- and AD-like SPM patterns were the best predictors for PD dementia (P <.005, sensitivity 85%, specificity 88%), independently from demographics or cognitive baseline classification.

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The investigators noted that the study could not compare the single-subject FDG-PET predictive value with other newly proposed clinical predictors of dementia such as orthostatic hypotension or cerebrospinal fluid markers/amyloid imaging. They also felt that the study was limited by the lack of data about the exact time of conversion to dementia, which is important for calculating the value of single-subject FDG-PET patterns in predicting dementia in the short and medium term. 

The investigators called for these findings to be validated in prospective cohorts with confirmed neuropathology.


Pilotto A, Premi E, Caminiti SP, et al. Single-subject SPM FDG-PET patterns predict risk of dementia progression in Parkinson disease [published online February 16, 2018]. Neurology. 2018. doi:10/1212/WNL.0000000000005161.