The 53-year-old woman presenting with cognitive decline and apraxia underwent positron emission tomography (PET) scan using 18F-fluorodeoxyglucose (FDG). The scans showed bilateral frontal and parietal hypometabolism, most prominent on the right side, with normal glucose metabolism in the basal ganglia (see figure).
Cerebrospinal fluid (CSF) analysis for 14-3-3 protein was negative. Total tau (t-tau) protein was 92.38 ng/mL and phosphorylated tau181 (p-tau) was 66.82 ng/mL. The CSF level of the 42–amino acid form of amyloid-β (αβ42) was 55.33 ng/mL, and the t-tau/αβ42 ratio was 1.67. Thus, with a low CSF αβ42 and elevated t-tau and p-tau, the patient was ultimately diagnosed as having a corticobasal syndrome (CBS) with underlying Alzheimer disease (AD) pathology.
Brain positron emission tomography scan with 18F-fluorodeoxyglucose (Z scale map) shows bilateral frontal and parietal hypometabolism, most prominently on the right side. Glucose metabolism is normal in the basal ganglia and the cerebellum. Courtesy of Jaime Toro, MD