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Evaluation of spectrum of MRI ndings in children with Hypoxic Ischemic Encephalopathy and its comparison with transcranial sonography

Background: Hypoxic ischemic encephalopathy is a serious concern among asphyxiated newborns due to the associated long term sequelae like cognitive impairment and cerebral palsy. Though the incidence of hypoxic injury remains higher in preterm babies due to incomplete brain maturation, it can occur in term babies as well despite institutional deliveries due to an array of unavoidable fetal, maternal and placental causes. Aims: This study was conducted as an attempt to evaluate the risk factors, to study the correlation between the term of pregnancy with TCUS and MRI imaging findings in HIE and characterise patterns of CNS involvement. Materials and methods: It was a cross-sectional study carried on 50 neonates with clinically diagnosed HIE presenting to the Department of Radiodiagnosis, Rajindra Hospital Patiala who were subjected to transcranial sonography and MRI. Results and Conclusion: This study demonstrated term infants have significant involvement of basal ganglia thalamus type (central) pattern of involvement and preterm infants have periventricular leukomalacia type (white matter injury) of a pattern of involvement. The overall sensitivity and specificity of TCUS in detecting imaging findings in children with clinically diagnosed HIE compared to MRI was found to be 70.45% and 50% respectively, yielding the overall diagnostic accuracy of TCUS as 68% compared to MRI. TCUS can depict central and white matter abnormalities better than peripheral lesions. However MRI provides additional diagnostic information in many cases and can detect precisely the extent of brain injury.


Neonatal
Hypoxic-Ischemic Encephalopathy designates the clinical and neuropathologic findings following either intrapartum or neonatal asphyxia [1].
As per the American Academy of Paediatrics and the American College of Obstetrics and Gynaecologists Hypoxic Ischemic Encephalopathy (HIE) is clinically diagnosed according to the following essential criteria: Hypoxic-ischemic injury in full-term infants accounts for approximately 15%-20% of neonatal mortality, and 25% of those who survive to demonstrate significant neurological deficits. It occurs in 5% of preterm infants. Up to 19% of infants born before 28 weeks of gestation develop cerebral palsy [3] A widely used clinical classification of HIE devised by Sarnat and Sarnat (1976) classifies HIE into 3 stages.
Clinically diagnosed infants with signs and symptoms of hypoxic-ischemic insult can be imaged by Transcranial Ultrasound (TCUS), Computerized Tomography and Magnetic Resonance Imaging (MRI) during the neonatal period. Transcranial ultrasound is cheap, easily available, portable, bedside modality, especially useful in acute setting in critically ill infants in neonatal intensive care units. It is used as the first screening modality, is ideal for follow up of the evolution of changes within the brain parenchyma and monitor the response to treatment.
MR due to its high spatial resolution, excellent inherent soft tissue contrast, multiplanar imaging capability and lack of ionising radiations is an excellent modality in imaging of asphyxiated neonates. It has a higher detection rate and can precisely estimate the location and extent of lesions in HIE [5].
Despite advances in medical infrastructure and increasing institutional deliveries in developing countries, hypoxic-ischemic injury remains a common problem and major cause of neonatal mortality and long term adverse neurological outcome. This study aimed to evaluate the spectrum of MRI findings and to determine the sensitivity of transcranial ultrasound in comparison to MRI in children with clinically diagnosed hypoxicischemic injury.

Results
The present study consisted of 50 paediatric patients with clinically diagnosed HIE who were referred to the department of Radiodiagnosis, Rajindra Hospital Patiala.
The maximum number of children were in the <1 month age group (58%). The mean age of children in our study was 28.28 days.
Clinical staging: In this study out of a total of 50 children, on the initial clinical staging,11 (22%) had Stage I, 30 (60%) had stage II and 9 (18%) had stage III hypoxic-ischemic injury.
Clinical presentation: In this study of the total 50 children, the most common clinical presentation was respiratory distress seen in 35 (70%) newborns followed by convulsions in 24 (48%) and cyanosis in 13 (26%) newborns.

Risk factors:
Of the total newborns, the most common perinatal risk factor for asphyxia was found to be premature rupture of membranes in 7 (14%) neonates followed by Antepartum hemorrhage in 6 (12%). The other risk factors seen were Preeclampsic Toxemia in 5 (10%), maternal hyper tension in 4 (8%), oligohydramnios in 3 (6%) and maternal diabetes mellitus in 2 (4%) cases. No perinatal risk factor could be found in 23 (46%) cases.

Conclusion
The imaging spectrum of HIE is wide depending upon the time and severity of hypoxic insult, ranging from periventricular leukomalacia, germinal matrix hemorrhage to deep grey matter infarction in preterms and parasagittal cortical-subcortical injury to basal ganglia thalami injury in term neonates.

Limitations of the study
The only limitation of this study was a small sample size. A larger population cohort is desirable to achieve more accurate results.

Author contributions
Dr. Maonj Mathur, Dr. Ishita Gupta, Dr. Dimple Mittal all contributed equally in the conduct of the study and the preparation of the manuscript.