A Review of FDG-PET in Progressive Supranuclear Palsy and Corticobasal Syndrome.

Although diagnostic criteria and research are constantly advancing, distinguishing between progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS) remains a significant challenge. This difficulty stems from their similar clinical symptoms and the lack of reliable biomarkers. In this work, we present a detailed review of fluorodeoxyglucose (FDG)-positron emission tomography (PET), exploring its potential role in differentiating PSP and CBS, drawing on their established utility in other neurodegenerative diseases. We searched the PubMed database from its inception for original research articles assessing the utility of FDG-PET for the diagnosis or differential diagnosis of PSP and CBS from other neurodegenerative conditions. A total of 91 studies were eligible. These 91 studies were categorized as follows: (a) 20 studies included only patients with PSP, (b) 15 studies included only patients with CBS, (c) 39 studies involved patients with Parkinson's disease and atypical Parkinsonian disorders, including subgroups of PSP and/or CBS, and (d) 17 studies compared patients with PSP and/or CBS to individuals with Alzheimer's disease, frontotemporal dementia, or other dementias. Most FDG-PET studies involving PSP and CBS were not specifically designed for these disorders. An additional obstacle lies in the methodological variability across studies. Despite several studies achieving high diagnostic accuracy for PSP and/or CBS with specificity exceeding 90% using FDG-PET, sensitivity remains considerably lower. CBS appears to have a distinct hypometabolic pattern compared to PSP, marked by asymmetry and predominant cortical involvement. CBS more often affects posterior cortical regions (parietal and posterior parts of the frontal cortex, and sometimes temporal and occipital parts) and the thalamus, whereas PSP appears to affect the striatum, frontal cortex, anterior cingulate, and subtentorial structures, typically in a more symmetrical manner. Large, multicenter studies are needed, utilizing standardized imaging and protocols.