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Regional cerebral metabolism of glucose (rCMRglu) was evaluated in patients who were in a coma and vegetative state to determine the level of brain function during these conditions. rCMRglu was measured in 17 discrete brain regions with 2-18F-fluoro-2-deoxy-d-glucose (FDG) and positron emission tomography (PET) in 15 patients with brain pathology subsequent to cardiorespiratory arrest (CA), head trauma (HT), or brain ischemia (BI) resulting from cerebrovascular accident or brain surgery. Five comatose patients (Coma group, n = 5), and 10 vegetative state patients (VS, patients awake but not aware) were studied. The VS patients were subdivided, according to the length of their VS condition, into a VS group (n = 6, 3 months if CA or BI patients or >12 months if HT patients). Ten normal age-matched subjects served as control. Global CMRglu was 6.72 ± 0.93 (±SD) mg/100 g/min in control subjects. It was significantly (p ≤ 0.001) reduced to 3.70 ± 61 in coma, to 3.45 ± 0.78 in VS, and to 2.33 ± 0.34 mg/100 g/min in PVS patients. rCMRglu was significantly reduced (p ≤ 0.001) from control values in all the 17 structures surveyed in every patient. In the Coma and VS groups, there was an overlapping of rCMRglu in the majority of the brain structures. The only significant difference was in the occipital lobe, at level of the primary visual cortex, where a higher metabolic rate was found in VS patients (4.08 ± 0.89 vs. 3.79 ± 0.63 mg/100 g/min, p ≤ 0.001). rCMRglu was maximally reduced in PVS patients (range, 50–72%), and the reduction was significantly lower than that of the Coma (range, 36–54%) and VS (range, 34–54%) groups in all the structures (p ≤ 0.001). Global, as well as rCMRglu, did not correlate with clinical outcome, whereas younger age significantly correlated with recovery of consciousness.
Tommasino et al. (Sat,) studied this question.