Longitudinal MR Spectroscopy Shows Altered Metabolism in Traumatic Brain Injury.

BACKGROUND AND PURPOSE: Brain trauma is known to result in heterogeneous patterns of tissue damage and altered neuronal and glial metabolism that evolve over time following injury; however, little is known on the longitudinal evolution of these changes. In this study, magnetic resonance spectroscopic imaging (MRSI) was used to map the distributions of altered metabolism in a single subject at five time points over a period of 28 months following injury. METHODS: Magnetic resonance imaging and volumetric MRSI data were acquired in a subject that had experienced a moderate traumatic brain injury (Glasgow Coma Scale 13) at five time points, from 7 weeks to 28 months after injury. Maps of N-acetylaspartate (NAA), total choline (Cho), and total creatine signal were generated and differences from normal control values identified using a z-score image analysis method. RESULTS: The z-score metabolite maps revealed areas of significantly reduced NAA and increased Cho, predominately located in frontal and parietal white matter, which evolved over the complete course of the study. A map of the ratio of Cho/NAA showed the greatest sensitivity to change, which indicated additional metabolic changes throughout white matter. The metabolic changes reduced over time following injury, though with abnormal values remaining in periventricular regions. CONCLUSIONS: The use of z-score image analysis for MRSI provides a method for visualizing diffuse changes of tissue metabolism in the brain. This image visualization method is of particularly effective for visualizing widespread and diffuse metabolic changes, such as that due to traumatic injury.

Distributions of Magnetic Resonance Diffusion and Spectroscopy Measures with Traumatic Brain Injury.

Magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) studies have demonstrated that measures of altered metabolism and axonal injury can be detected following traumatic brain injury. The aim of this study was to characterize and compare the distributions of altered image parameters obtained by these methods in subjects with a range of injury severity and to examine their relative sensitivity for diagnostic imaging in this group of subjects. DTI and volumetric magnetic resonance spectroscopic imaging data were acquired in 40 subjects that had experienced a closed-head traumatic brain injury, with a median of 36 d post-injury. Voxel-based analyses were performed to examine differences of group mean values relative to normal controls, and to map significant alterations of image parameters in individual subjects. The between-group analysis revealed widespread alteration of tissue metabolites that was most strongly characterized by increased choline throughout the cerebrum and cerebellum, reaching as much as 40% increase from control values for the group with the worse cognitive assessment score. In contrast, the between-group comparison of DTI measures revealed only minor differences; however, the Z-score image analysis of individual subject DTI parameters revealed regions of altered values relative to controls throughout the major white matter tracts, but with considerable heterogeneity between subjects and with a smaller extent than the findings for altered metabolite measures. The findings of this study illustrate the complimentary nature of these neuroimaging methods.

Vasopressin for cerebral perfusion pressure management in patients with severe traumatic brain injury: preliminary results of a randomized controlled trial.

BACKGROUND: After traumatic brain injury (TBI), catecholamines (CAs) may be needed to maintain adequate cerebral perfusion pressure (CPP), but there are no recommended alternative vasopressor therapies. This is an interim report of the first study to test the hypothesis that arginine vasopressin (AVP) is a safe and effective alternative to CAs for the management of CPP in patients with severe TBI. METHODS: Since 2008, all TBI patients requiring intracranial pressure monitoring at this Level 1 trauma center have been eligible for a randomized trial to receive either CA or AVP if vasopressors were required to maintain CPP greater than 60 mm Hg. RESULTS: To date, 96 patients have been consented and randomized. Demographics, vital signs, and laboratory values were similar. As treated, 60 required no vasopressors and were the least severely injured group with the best outcomes. Twenty-three patients received CA (70% levophed, 22% dopamine, 9% phenylephrine) and 12 patients received AVP. The two vasopressor groups had similar demographics, but Injury Severity Score (ISS) and fluid requirements on intensive care unit Day 1 were worse in the AVP versus the CA groups (all p < 0.05) before treatment. These differences indicate more severe injury with accompanying hemodynamic instability. Nevertheless, adverse events were not increased with AVP versus CA. Trends favored AVP versus CA, but no apparent differences were statistically significant at this interim point. There was no difference in mortality rates between CA and AVP. CONCLUSION: These preliminary results suggest that AVP is a safe and effective alternative to CA for the management of CPP after TBI and support the continued investigation and use of AVP when vasopressors are required for CPP management in TBI patients. LEVEL OF EVIDENCE: Therapeutic study, level II.

Whole-brain proton MR spectroscopic imaging of mild-to-moderate traumatic brain injury and correlation with neuropsychological deficits.

Changes in the distribution of the magnetic resonance (MR)-observable brain metabolites N-acetyl aspartate (NAA), total choline (Cho), and total creatine (Cre), following mild-to-moderate closed-head traumatic brain injury (mTBI) were evaluated using volumetric proton MR spectroscopic imaging (MRSI). Studies were carried out during the subacute time period following injury, and associations of metabolite indices with neuropsychological test (NPT) results were evaluated. Twenty-nine subjects with mTBI and Glasgow Coma Scale (GCS) scores of 10-15 were included. Differences in individual metabolite and metabolite ratio distributions relative to those of age-matched control subjects were evaluated, as well as analyses by hemispheric lobes and tissue types. Primary findings included a widespread decrease of NAA and NAA/Cre, and increases of Cho and Cho/NAA, within all lobes of the TBI subject group, and with the largest differences seen in white matter. Examination of the association between all of the metabolite measures and the NPT scores found the strongest negative correlations to occur in the frontal lobe and for Cho/NAA. No significant correlations were found between any of the MRSI or NPT measures and the GCS. These results demonstrate that significant and widespread alterations of brain metabolites occur as a result of mild-to-moderate TBI, and that these measures correlate with measures of cognitive performance.