Prognostication of Newborns with Hypoxic Ischemic Encephalopathy with EEG and Imaging Studies

INTRODUCTION: At the dawn of the third millennium, HIE remains the most common neurological disease of the perinatal period across all gestational ages. Many prospective and retrospective studies have been done attempting to link the various neurologic abnormalities to specific disorders of gestation or the perinatal period. Pathologic studies of the brain have produced careful descriptions of various cerebral abnormalities in patients with non progressive neurologic disorders and have led to attempts, often highly speculative, to formulate their causes. Early recognition of the severity of the condition is crucial in predicting the probable neurological outcome as well as for deciding the need for stimulation therapy for the physico-psycho-social development of the infant. In this study an attempt has been made to correlate electroencephalogram, CT and MRI brain done in early infancy with the neurological outcome of term asphyxiated newborns. AIMS AND OBJECTIVES OF THE STUDY: In a term newborn with hypoxic ischemic encephalopathy 1) To correlate the electroencephalogram and computed tomography of brain done in the newborn period with the neurological outcome 2) To correlate the magnetic resonance imaging of brain done at 3 months of age with the neurological outcome 3) To compare the usefulness of electroencephalogram, computed tomography and magnetic resonance imaging of brain in predicting the neurological outcome at one year. DISCUSSION: This study was done to correlate the neurological outcome of term newborns having hypoxic ischemic encephalopathy with findings of EEG and CT scan (done in the newborn period) and MRI Scan (done by three months). The secondary aim was to compare their relative usefulness in predicting neurodevelopment in these infants at one year of age. EEG AND ITS CORRELATION: Of the 31 cases, EEG was normal in 6(19.4%), while 4(12.9%) had isolated temporal spikes, 7(22.6%) had transient discontinuous activity and 14(45.2%) babies had suppression burst pattern. All babies who had shown suppression burst pattern either had Sarnat stage 2 or stage 3 hypoxic ischemic encephalopathy. All the 6 newborns with normal EEG were neurologically and developmentally normal at one year (p 0.017). 13 of the 14 babies with suppression burst pattern (one case lost to follow up) had an adverse outcome - death, neurological deficit or were suspect in the DDST 2 assessment (p <0.001) . In our study, EEG in the newborn period has a sensitivity of 100% and specificity of 40% in predicting neurological outcome at one year. It has a positive predictive value of 59.09%, a negative predictive value of 100% and accuracy of 67.86( Table 22) Ong L C et al have reported that EEG in asphyhxiated newborns has a PPV of 100%, NPV of 80.6%, sensitivity of 53% and specificity of 100% (16). In a study on 77 asphyxiated infants by Caravale et al, among those with a normal early EEG (within 7 days of life) 83% were normal at one year of age while the remaining17% had only mild neurodevelopment abnormality (69) . The negative predictive value of a normal EEG is emphasized by D M Murray et at (45) who concluded that a normal or mildly abnormal EEG within 6 hours of life is associated with normal neurodevelopment at 24 months. Our study has shown a 100% NPP for a normal EEG. A suppression burst pattern on EEG in the newborn period is associated with a very high likelihood of an unfavorable outcome (70,71,72,73,74,75,76). In a study by Grigg et al, out of 15 term infants with burst suppression on EEG, 14 had poor outcome (72). Results of our study are in agreement with this observation. CONCLUSION: In a term newborn with hypoxic ischemic encephalopathy 1) A normal EEG and/ or CT scan of brain during the acute phase of illness is associated with good neurological outcome (100% sensitivity and 100% negative predictive value) 2) Burst suppression pattern in the EEG during the acute phase of illness is associated with a poor neurological outcome (p <0.001) 3) Involvement of the basal ganglia or thalamus in the MRI at three months of age indicates a poor prognosis (p 0.002). 4) EEG combined with an MRI is most useful in predicting the neurological outcome(sensitivity 100%, negative predictive value 100%, accuracy 70%,positive predictive value 62.5% and p value 0.017)