Brain magnetic resonance imaging review suggests unrecognised hypoglycaemia in childhood

There has been considerable debate over whether asymptomatic neonatal hypoglycaemia results in neurological damage. In a detailed multicentre study of 661 preterm infants hypoglycaemia was found to be common. Moderate hypoglycaemia (plasma glucose concentration less than 2.6 mmol/l) occurred in 433 of the infants and in 104 was found on three to 30 separate days. There was considerable variation among the centres, implying differences in decisions to intervene. The number of days on which moderate hypoglycaemia occurred was strongly related to reduced mental and motor development scores at 18 months (corrected age), even after adjustment for a wide range of factors known to influence development. When hypoglycaemia was recorded on five or more separate days adjusted mental and motor developmental scores at 18 months (corrected age) were significantly reduced by 14 and 13 points respectively, and the incidence of neurodevelopmental impairment (cerebral palsy or developmental delay) was increased by a factor of 3.5 (95% confidence interval 1.3 to 9.4). These data suggest that, contrary to general belief, moderate hypoglycaemia may have serious neurodevelopmental consequences, and reappraisal of current management is urgently required.

Symptomatic neonatal hypoglycemia may be associated with later neurodevelopmental impairment. Brain injury patterns identified on early MRI scans and their relationships to the nature of the hypoglycemic insult and neurodevelopmental outcomes are poorly defined. We studied 35 term infants with early brain MRI scans after symptomatic neonatal hypoglycemia (median glucose level: 1 mmol/L) without evidence of hypoxic-ischemic encephalopathy. Perinatal data were compared with equivalent data from 229 term, neurologically normal infants (control subjects), to identify risk factors for hypoglycemia. Neurodevelopmental outcomes were assessed at a minimum of 18 months. White matter abnormalities occurred in 94% of infants with hypoglycemia, being severe in 43%, with a predominantly posterior pattern in 29% of cases. Cortical abnormalities occurred in 51% of infants; 30% had white matter hemorrhage, 40% basal ganglia/thalamic lesions, and 11% an abnormal posterior limb of the internal capsule. Three infants had middle cerebral artery territory infarctions. Twenty-three infants (65%) demonstrated impairments at 18 months, which were related to the severity of white matter injury and involvement of the posterior limb of the internal capsule. Fourteen infants demonstrated growth restriction, 1 had macrosomia, and 2 had mothers with diabetes mellitus. Pregnancy-induced hypertension, a family history of seizures, emergency cesarean section, and the need for resuscitation were more common among case subjects than control subjects. Patterns of injury associated with symptomatic neonatal hypoglycemia were more varied than described previously. White matter injury was not confined to the posterior regions; hemorrhage, middle cerebral artery infarction, and basal ganglia/thalamic abnormalities were seen, and cortical involvement was common. Early MRI findings were more instructive than the severity or duration of hypoglycemia for predicting neurodevelopmental outcomes.

Lower blood glucose values are common in the healthy neonate immediately after birth as compared to older infants, children, and adults. These transiently lower glucose values improve and reach normal ranges within hours after birth. Such transitional hypoglycemia is common in the healthy newborn. A minority of neonates experience a more prolonged and severe hypoglycemia, usually associated with specific risk factors and possibly a congenital hypoglycemia syndrome. Despite the lack of a specific blood glucose value that defines hypoglycemia, concern for substantial neurologic morbidity in the neonatal population has led to the generation of guidelines by both the American Academy of Pediatrics (AAP) and the Pediatric Endocrine Society (PES). Similarities between the 2 guidelines include recognition that the transitional form of neonatal hypoglycemia likely resolves within 48 hours after birth and that hypoglycemia that persists beyond that duration may be pathologic. One major difference between the 2 sets of guidelines is the goal blood glucose value in the neonate. This article reviews transitional and pathologic hypoglycemia in the neonate and presents a framework for understanding the nuances of the AAP and PES guidelines for neonatal hypoglycemia.