Hypoxic ischemic encephalopathy-MRI

History : 4 day old neonate was delivered by LSCS after clinical fetal destress on account of meconium staining of the liquor. Apgar at birth reported normal with normal sugar levels presently, with history of seizures.MRI Brain shows two well defined dots of restricted diffusion seen in the parasagittal location of posterior parietal region predominantly involving the white matter, with not reaching upto the cortex, no significant basal ganglia or thalamic involvement, or cortical highlighting or diffuse white matter hyperintensity or gross structural abnormalities.

Hypoxic ischemic encephalopathy is now appropriatly reffered to as neonatal encephalopathy to encompase all the variants:

a) Commonest presentation for an acute hypoxia in term children usually leads to severe basal ganglia thalamic lesions ( BGT), predominantly an initially involving posterolateral lentiform nucleus and ventrolateral thalami. These are usually severe and lead to high mortality. The additional features amongst them diffuse cerebral edema, slit like ventricles and reduced extra-cerebral spaces.

b) The other uncommon variant is reffered to as parasagittal infarction which involves the deep white matter only at border zones of major arterial territories ( water shed ) some of these may present with full blown HIE as well. These occur usually in the presence of severe hypoglycemia and lead to microcephaly all though the neurodevelopmental outcome surprisingly good particularly for motor function because there is minimal or no involvement of BGT. These infants may also show more profound metabolic abnormalities such as prolonged conjugated hyperbilirubinemia, and recurrent hypoglysemia and developed marked cognitive and motor impairement.

c) Multifocal areas of infarction that do not appear to be in parasagittal distribution may be secondary to infections like herpes, varicella, and listeria, in which case contrast study would help. The CMV lesions may persist for years in white matter and not show atrophy, the key lies in the presence of subependymal cysts.

Case by Dr MGK Murthy, Sr Consultant Radiologist
Teleradiology Providers, Unit of Prime Telerad Providers (P) Ltd