MR imaging and in vivo proton spectroscopy of the brain in neonates with hypoxic ischemic encephalopathy

Abstract 

Introduction: A number of studies have suggested the potential utility of in vivo proton MR spectroscopy for the evaluation of brain injury in the asphyxiated neonates. We present our initial experience with in vivo proton MR spectroscopy in neonates who were diagnosed as having hypoxic injury on clinical examination and the severity of the insult was graded using Sarnat staging. Methods and material: MR imaging and in vivo proton MR spectroscopy was performed in 16 neonates with hypoxic ischemic encephalopathy (HIE) to correlate the imaging and metabolite abnormality with clinical severity of the condition at the time of insult and with outcome at 2 months of age. The ratios of different metabolites were calculated as observed on MR spectroscopy from an 8 ml voxel that included thalami, basal ganglia and part of the ventricular system using spin echo technique with an echo time of 135 ms. Results and discussion: The results of the spectroscopy were compared with imaging abnormalities and Sarnat's clinical staging of HIE. MR Imaging abnormalities included basal ganglia, thalamic and periventricular hemorrhage and periventricular hyperintensities and were noticed in 8/16 neonates with different stages of HIE. Maximum imaging abnormalities were noted in stage II (6/9) followed by stage III (1/2) and stage I (1/5), respectively. The α-Glx resonance at 3.76 ppm was seen in14/16, Glycine at 3.56 ppm (Gly) was seen in 10/16 and Lactate (L) at 1.33 ppm was observed in 4/16 neonates with HIE. Conclusion: MR spectroscopy was more sensitive than imaging in detecting the insult due to HIE and increased concentration of α-Glx/Cr and Gly/Cr correlated better with severity of the HIE. The demonstration of L was associated with poor outcome.

Keywords:  Neonatal brain, Magnetic resonance, MR spectroscopy, Hypoxic ischemic encephalopathy