Proton Magnetic Resonance Spectroscopy of the Brain in Normal Preterm and Term Infants, and Early Changes after Perinatal Hypoxia-Ischemia

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Abstract
The aims of this study were 1) to define normal perinatal maturational changes in proton metabolite peak-area ratios in two regions of the neonatal brain, the thalamic and occipitoparietal regions, and2) to investigate abnormalities of these ratios after perinatal hypoxia-ischemia. Fifty-four infants were studied: 35 normal control infants at 31-42 wk of gestational plus postnatal age, and 19“asphyxiated” infants suspected of cerebral hypoxic-ischemic injury. Proton spectra were collected at 2.4 tesla from (2 cm)3 voxels using the point-resolved spectroscopy technique with a 270-ms echo time. Lactate was detected in all infants studied. In the normal infants, lactate relative to N-acetylaspartate (NAA), choline and creatine was significantly greater in the occipitoparietal region than in the thalamus, and fell with increasing maturity in both regions, whereas NAA/choline increased. The 19 asphyxiated infants were studied on a total of 34 occasions during the 1st wk of life (median age 1.8 d), at gestational plus postnatal ages of 27-41 wk. Maximum lactate/NAA was above 95% confidence limits for the control data in one or both regions in 11 of the 19 infants. Minimum NAA/choline was below 95% confidence limits in only one asphyxiated infant, who was later found to have congenital hypothyroidism. SD scores for lactate, relative to NAA, choline, and creatine, were higher in both regions in the asphyxiated infants compared with the normal infants, particularly in the thalamus. Early results of 1-y follow-up examinations indicate that raised lactate/NAA carries a poor long-term prognosis.