Acute metabolic brain changes following traumatic brain injury and their relevance to clinical severity and outcome

Abstract

Conventional MRI can provide critical information for TBI patient care, but MRI abnormalities rarely correlate to clinical severity and outcome. Previous MR spectroscopy studies have reported clinically relevant brain metabolic changes in TBI. However, often these changes were assessed a few to several days after the trauma, with a consequent variation of the metabolic pattern due to temporal changes. We performed proton MR spectroscopic imaging (1H-MRSI) examinations in 10 TBI patients 48-72h after the trauma to obtain early measurements of central brain levels of N-acetylaspartate (NAA), choline (Cho), creatine (Cr) and lactate (La). Metabolite values were expressed as ratios to i) a metabolic pattern given the sum of the resonance intensities of all metabolites detected in the same voxel and ii) intravoxel Cr. We found that NAA ratios were significantly lower in TBI patients than in normal controls (NC). In contrast, Cho ratios were significantly higher in TBI patients than in NC. Increased La levels were found in 5/10 TBI patients. Both NAA and La values correlated closely with those of the Glasgow Coma Scale at presentation (r= 0.73 and -0.62 respectively; p<0.01 for both) and the Glasgow Outcome Scale at 3 months (r= -0.79 and 0.79, respectively; p<0.01 for both). Spectroscopic measures of neuro-axonal damage occurring soon after a brain trauma are clinically relevant. Significant increases of cerebral lactate also may be detected when 1H-MRSI is performed early after the trauma and, at this stage, can represent a reliable index of injury severity and disease outcome in TBI patients.