Severe neonatal hypernatraemia is a life-threatening electrolyte disorder because of its neurological complications. These are brain oedema, intracranial haemorrhage, haemorrhagic infarcts and thromboses. There are few reports concerning the radiological findings in the central nervous system in severe neonatal hypernatraemia. Cranial MRI findings in hypernatraemia have been reported in an older child, but have not been described in newborn infants. We report the cranial MRI findings in a newborn infant with acute renal failure and severe hypernatraemia.