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Thursday, May 7, 2009
Northwest Hall (Chicago Hilton)
12:00 PM
Background: Growing documentation of metabolic alterations in autism increases the need to characterize metabolism in brain tissue. Magnetic Resonance Spectroscopy (MRS) is constrained by the impossibility of performing whole brain acquisitions and the need to place localized voxels, as well as the impact of acquisition protocols on findings. Literature review can contribute to well-targeted choice of future research design.
Objectives: To consider the potentiality of MRS for measuring metabolites pertinent to emerging metabolic findings in ASD and from this vantage point to produce a systematic and critical overview of MRS investigations in ASD to date.
Methods: PubMed was searched for papers on MRS in ASD as well as brain metabolites. Relevant papers were reviewed and tabulated based upon regions of interest, absolute metabolite concentrations and/or ratios in each region studied, field strength, repetition time (TR) and time to echo (TE), subject characteristics (age, gender, diagnosis, use of sedation) and objectives (e.g. neurocognitive, pathophysiological or developmental).
Results: Regions chosen for investigation were scattered with many visited in only one study. For some regions studied multiple times the literature contains contradictory findings, possibly attributable to different acquisition protocols and/or subject and cohort heterogeneity.
Conclusions: The application of MRS is strongly hypothesis dependent given the need to place localized voxels, and also the impact of acquisition protocols on findings. Some of the most critical metabolites to measure from a metabolic standpoint (e.g. GABA, glutamate, glutathione, energy and membrane phosphates and phospholipids) as well as critical methods of acquisition (e.g. 31P, spectral editing techniques) have been underexplored, in part due to significant technical challenges. We hope that this systematic review will contribute to more effective and coordinated targeting of future investigations.
Objectives: To consider the potentiality of MRS for measuring metabolites pertinent to emerging metabolic findings in ASD and from this vantage point to produce a systematic and critical overview of MRS investigations in ASD to date.
Methods: PubMed was searched for papers on MRS in ASD as well as brain metabolites. Relevant papers were reviewed and tabulated based upon regions of interest, absolute metabolite concentrations and/or ratios in each region studied, field strength, repetition time (TR) and time to echo (TE), subject characteristics (age, gender, diagnosis, use of sedation) and objectives (e.g. neurocognitive, pathophysiological or developmental).
Results: Regions chosen for investigation were scattered with many visited in only one study. For some regions studied multiple times the literature contains contradictory findings, possibly attributable to different acquisition protocols and/or subject and cohort heterogeneity.
Conclusions: The application of MRS is strongly hypothesis dependent given the need to place localized voxels, and also the impact of acquisition protocols on findings. Some of the most critical metabolites to measure from a metabolic standpoint (e.g. GABA, glutamate, glutathione, energy and membrane phosphates and phospholipids) as well as critical methods of acquisition (e.g. 31P, spectral editing techniques) have been underexplored, in part due to significant technical challenges. We hope that this systematic review will contribute to more effective and coordinated targeting of future investigations.