The role of F-18 FDG PET/CT in the prognosis of patients with hypoxic/anoxic brain injury after cardio-circulatory arrest.

Background: Advances in resuscitation techniques have resulted in more patients surviving cardio-circulatory arrest (CA) and consequently developing hypoxic/anoxic brain damage. The aim of this study is to evaluate the role of PET/CT (Positron Emission Tomography/Computerized Tomography scan) with F-18 FDG (F-18 fluorodeoxyglucose) during the early rehabilitative hospitalization phase in determining the V/C (Vermis/Cerebellar) ratio as a prognostic index to predict patient outcome, as defined by clinical evaluation scales.
Methods: This is a single-center retrospective study of 37 consecutive adult patients admitted to the neurorehabilitation center between January 2011 and June 2019. Functional status was measured by the following clinical scales: FIM (Functional Indipendence Measure), LCFS (Levels of Cognitive Functioning Scale), GOS (Glasgow Outcome Scale) and CRS-R (Coma Recovery Scale-Revised). PET/CT with F-18 FDG as a functional imaging technique was used to calculate the V/C ratio as a ratio between the metabolism of the vermis and of the Cerebellar Hemisphere.
Results: A statistically significant correlation was observed between the V/C ratio and the delta values (difference between discharge and admission value) for each clinical evaluation scale (Delta FIM: P=0.0014; Delta LCFS P=0.0003). A statistically significant difference was observed between the V/C ratio of patients with LCFS ≥4 that showed an improved outcome (defined as an improvement of at least two points in LCFS), and that of patients with LCFS <4 that did not improve (P=0.0011). A V/C ratio cut-off of 1.5 corresponded with a positive predictive power of 80% and a negative predictive power of 82%; a value <1.5 predicted a better outcome.
Conclusions: Clinical evaluation scales when associated with F-18 FDG PET/CT measurement of metabolism, provide a more reliable prognosis. This allows for more focused rehabilitation treatment and better management of family members' expectation.