18FDG-PET/CT in traumatic brain injury patients: the relative hypermetabolism of vermis cerebelli as a medium and long term predictor of outcome.

ABSTRACT

PURPOSE: Both, the constant presence of apparent hypermetabolism of the vermis cerebelli compared to the cerebellar hemispheres in traumatic brain injury, and the presence of a good relationship between the intensity of this sign and the severity of the clinical conditions have been addressed in previous studies. Aim of the present paper is to evaluate the possible correlation between the intensity of the finding and the medium and long term outcome in a group of patients. MATERIALS AND METHODS: A group of 105 patients consecutively admitted to the Brain Injury Rehabilitation Center of our Hospital between 2005 and 2012 was studied with a 18FDG-PET/CT study of the brain after head trauma; the metabolic activity of the cerebellar vermis was semiquantitatively assessed (vermis/cerebellum ratio, V/C). After that, all patients received systematic monitoring of their performance status via the timely administration of commonly used tests (DRS, LCF and GOS) during one whole year after the head trauma. The V/C parameter was compared with the evolution of performance abilities, as shown by the rating scales. RESULTS: Statistical analysis showed a significant direct association between the V/C ratio and the DRS score at each time point (3 months P<0.001; 6 months P<0.001; 12 months P<0.001) and significant inverse association with the LCF score (3 months P<0.001; 6 months P<0.001; 12 months P<0.001) and the GOS score (3 months P<0.001; 6 months P<0.001; 12 months P<0.001) at each time point. Moreover, patients with a V/C ratio ≥ 1 have a significantly greater probability to achieve a good functional outcome as defined by a DRS score ≥ 3 points, a LCF score ≥ 7 points and and a GOS score =5 points. CONCLUSIONS: In our group of patients, the V/C parameter has demonstrated to be a predictor of outcome. If validated by more extensive experiences, this approach could offer the possibility of performing a reliable prognostic evaluation in a notoriously "difficult" class of patients with an acceptable technique and economical effort.