Xu S, Zhuo J, Racz J, Shi D, Roys S, Fiskum G, Gullapalli REarly microstructural and metabolic changes following controlled cortical impact injury in rat: a Magnetic Resonance Imaging and Spectroscopy Study. J Neurotrauma 28:2091-2102

Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Journal of neurotrauma (Impact Factor: 3.71). 07/2011; 28(10):2091-102. DOI: 10.1089/neu.2010.1739
Source: PubMed


Understanding tissue alterations at an early stage following traumatic brain injury (TBI) is critical for injury management and limiting severe consequences from secondary injury. We investigated the early microstructural and metabolic profiles using in vivo diffusion tensor imaging (DTI) and proton magnetic resonance spectroscopy ((1)H MRS) at 2 and 4 h following a controlled cortical impact injury in the rat brain using a 7.0 Tesla animal MRI system and compared profiles to baseline. Significant decrease in mean diffusivity (MD) and increased fractional anisotropy (FA) was found near the impact site (hippocampus and bilateral thalamus; p<0.05) immediately following TBI, suggesting cytotoxic edema. Although the DTI parameters largely normalized on the contralateral side by 4 h, a large inter-individual variation was observed with a trend towards recovery of MD and FA in the ipsilateral hippocampus and a sustained elevation of FA in the ipsilateral thalamus (p<0.05). Significant reduction in metabolite to total creatine ratios of N-acetylaspartate (NAA, p=0.0002), glutamate (p=0.0006), myo-inositol (Ins, p=0.04), phosphocholine and glycerophosphocholine (PCh+GPC, p=0.03), and taurine (Tau, p=0.009) were observed ipsilateral to the injury as early as 2 h, while glutamine concentration increased marginally (p=0.07). These metabolic alterations remained sustained over 4 h after TBI. Significant reductions of Ins (p=0.024) and Tau (p=0.013) and marginal reduction of NAA (p=0.06) were also observed on the contralateral side at 4 h after TBI. Overall our findings suggest significant microstructural and metabolic alterations as early as 2 h following injury. The tendency towards normalization at 4 h from the DTI data and no further metabolic changes at 4 h from MRS suggest an optimal temporal window of about 3 h for interventions that might limit secondary damage to the brain. Results indicate that early assessment of TBI patients using DTI and MRS may provide valuable information on the available treatment window to limit secondary brain damage.

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    • "metabolites studied. In this study, values are reported relative to total creatine as is frequently done in 1 H-MRS studies (Mukonoweshuro et al. 2001; Kumar et al. 2003; Xu et al. 2011). The developmental profile of the data for our WT mice can be compared to the data from Kulak et al. (Kulak et al. 2010) (when their data are expressed as metabolite/tCr). "
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    • "e . , tCr ) is often assumed to remain relatively constant under physiological conditions , leading to its use as a reference for 1 H - MRS studies , our results add to ample evidence that tCr may be unstable in the context of brain injury ( Gasparovic et al , 2009 ; Schuhmann et al , 2003 ; Xu et al , 2011 ) . "
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