Cerebral Lactate and N-Acetyl-Aspartate/Choline Ratios in Asphyxiated Full-Term Neonates Demonstrated In Vivo Using Proton Magnetic Resonance Spectroscopy

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Abstract
The purpose of this study was to test the hypothesis that a high lactate signal and a low N-acetyl-aspartate/choline ratio in neonates with postasphyxial encephalopathy indicated a high chance of an adverse outcome in vivo when proton magnetic resonance spectroscopy was used. Twenty-one full-term asphyxiated neonates were examined at a mean postnatal age of 7.1 d. Five patients died, and five survivors had handicaps. Eleven of the 16 survivors (seven without handicaps and four with handicaps) had a second examination at 3 mo of age. After magnetic resonance imaging, spectra were obtained at 1.5 tesla. A 20-mm-thick slice was selected through the basal ganglia. After optimizing the B-0 field, we used a double spin-echo pulse sequence (90–180-180°) with a time to repeat of 2000 ms and a time to echo of 272 ms. Two-dimensional spectroscopic imaging was performed by 32 ± 32 phase encoding steps in two directions in a 225-mm field of view, resulting in 1-mL volumes, followed by computerized processing. Neuromotor development was examined at 6 wk, 3 mo, and every 3 mo thereafter. Lactate resonances were seen only in the five patients with grade 3 postasphyxial encephalopathy. Lactate was distributed diffusely (n = 4), or localized in areas of infarction (n = 1). N-acetyl-aspartate/choline ratios were significantly lower in the patients with an adverse outcome than in the survivors without handicaps, both neonatally (p < 0.005, Wilcoxon's rank sum test) and at 3 mo (p < 0.05). In conclusion, the presence of cerebral lactate and a low N-acetyl-aspartate/choline ratio demonstrated in vivo using proton magnetic resonance spectroscopy in full-term neonates with postasphyxial encephalopathy indicate a poor outcome.

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