The effect of hypoglycemic seizures on cognitive function was evaluated in 16 children treated for insulin-dependent diabetes mellitus at the Hospital for Sick Children, Toronto, Canada. Mean age at diagnosis was 4.5 years (range 1-11 yrs), and 9 (53%) had suffered hypoglycemic seizures. Psychological evaluation at diagnosis and after 1, 3, and 7 years found significant deteriorations in verbal IQ vocabulary and digit span but not visuospatial skills over 7 years, primarily between 3 and 7 years. Full-scale IQ performance IQ, and achievement test scores were unaffected. These selective declines in cognitive function, targeting working memory, were associated with hypoglycemic seizures. Children having seizures had weaker perceptuomotor, attention, memory, and executive processing skills after 7 years treatment for diabetes. [1]

COMMENT. This long-term, prospective study demonstrates the risks of neurocognitive sequelae attending insulin control of diabetes mellitus and complicated by hypoglycemic seizures in young children. Intensive therapy and over-control of blood glucose should be avoided unless closely monitored to prevent hypoglycemic seizures.

Several articles on the effects of hypoglycemia on the developing brain are included in the April issue of Journal of Pediatrics.

Duvanel CB et al, Lausanne, Switzerland, investigate the long-term effects of neonatal hypoglycemia on brain growth and psychomotor development in small-for-gestational-age preterm infants [2]. Recurrent episodes of hypoglycemia are correlated with neurodevelopmental and physical growth deficits until 5 years of age. Without close screening of blood glucose, hypoglycemia in the neonate can be overlooked, since classical signs (apnea, seizures, jitteriness, lethargy, etc) may be absent. Rapid correction of even mild hypoglycemia in the neonate is recommended.

Hume R et al, University of Dundee, Scotland, report “Failure to detect preterm infants at risk of hypoglycemia before discharge.“ [3]. Fourteen (18%) of 79 consecutive preterm infants ready for discharge were found to be hypoglycemic (<47 mg/dL) but without classical symptoms. When a newborn is identified as susceptible to hypoglycemia, feeding regimens should be frequent and regular to avoid hypoglycemic episodes.

Cowett RM, Cleveland Clinic, reviewing neonatal hypoglycemia in an editorial [4], concludes that the study of neonatal glucose homeostasis is in its infancy. Further investigations should better define euglycemia relative to gestational age and the optimum timing and method of measurement of blood glucose in the neonate.

Becker DJ, Ryan CM, University of Pittsburgh, (Editorial), comment on “Intensive diabetes therapy in childhood: Is it achievable? Is it desirable? Is it safe?“ [5]. These authors advocate careful monitoring of diabetes control in young children, not only in those receiving intensive therapy but also for conventional diabetes control. Mild hypoglycemia (blood glucose level of 60-65 mg/dL) in a young child may induce a transient inattention and cognitive dysfunction (“hypoglycemic absence episode“), interfering with memory and the ability to learn. Further, episodes of mild hypoglycemia may obscure the warning symptoms of subsequent attacks, increasing the risk of severe hypoglycemia. The authors caution that chronic hyperglycemia with inadequate diabetes therapy may also have detrimental effects on brain function in children, and the emphasis on dangers of intensive therapy should not neglect the benefits of close control of blood glucose levels.