The effect of VLBW ( < 1.5 kg) and subnormal head size at 8 months of age (corrected for prematurity) on neurocognitive abilities at school age was investigated by a longitudinal follow up of 249 children born between 1977 to 1979 and admitted to the neonatal intensive care unit at Rainbow Babies and Children’s Hospital, Cleveland, OH. Head size was subnormal at birth in 12%, at term 23%, and at 8 months 13%. As compared with 216 children with normal head sizes, the 33 children with subnormal head sizes at the age of 8 months had significantly lower mean birth weights and higher neonatal risk scores and at 8 years of age had a higher incidence of neurologic impairment and lower IQ scores. A subnormal head size at 8 months of age was predictive of poor verbal and performance IQ scores at 8 years of age; lower scores for receptive language, speech, reading, mathematics and spelling; and a higher incidence of hyperactivity. [1]

COMMENT. A relation between subnormal head circumference and cognitive functioning has been reported in many different studies, including children with learning disabilities. Improvements in neonatal growth and development may depend on nutrition of chronically ill neonates and environmental enrichment after discharge from hospital. This study shows that the determination of the head circumference at 8 months of age is a useful means of predicting subsequent cognitive deficits and difficulties in school. Volpe JJ, in an editorial [2], stresses the need for a better method of detection of brain injury in VLBW infants since 77% of those with normal head circumference at 8 months had IQs below 85 and an academic skill index below 80 in the study by Hack et al. Those infants with a small head circumference at 8 months of age made up only a minority of infants who subsequently had cognitive deficits. Cranial ultrasonography detects overt brain lesions but not the subtle lesions in the periventricular white matter. MRI may detect periventricular injury missed by ultrasound and CT scanning; it is also used to measure the progress and degree of myelination in the human infant in the first months of life. A decreased rate of brain growth in the first months of life might identify a larger proportion of at risk infants and justify further study with the MRI in selected patients.

Collin MF and associates from the Department of Pediatrics, Loyola University Medical Center, Maywood, IL report that normal infant development is poorly predictive of continued normal development in the extremely low birth weight infant [3]. Only 11 (31%) of 36 children had normal development upon reassessment in early childhood. With or without major complications, extremely low birth weight places children at risk for emerging development problems with age. Head circumference was not addressed in this study.