No abstract

Prominence of the extraaxial space occasionally is encountered in infants referred for ultrasonography to exclude hydrocephalus. The interpretation of this finding can be problematic. We examined the width of the extraaxial compartment in 82 normal newborn infants. Scanning technique was optimized for viewing the near field, and the extraaxial space was measured over the cerebral convexities. Correlation was made with demographic variables. Measurements varied from 0 to 3.3 mm (mean, 1.6 mm), with slight negative linear relationship to gestational age. We conclude that small amounts of extraaxial fluid, up to 3.3 mm in width on scans, are common and normal in newborn infants.

The goal of this study was to examine sonographically the extraaxial space in neurologically normal infants with occipital frontal circumference greater than or equal to the 95th percentile for age and correlate these dimensions with neurologic follow-up findings to determine a range of normal values. We thus hope to obviate unnecessary workup of these patients, including additional imaging or intervention. Our results demonstrate that for infants with a craniocortical width or sinocortical width less than 10 mm, the negative predictive value and specificity for developing a neurologic abnormality during the 55 week follow-up period were 94 to 100%. Thus, for neurologically normal infants with occipital frontal circumference greater than or equal to the 95th percentile for age and a head ultrasonogram that is otherwise normal, a craniocortical or sinocortical width of up to 10 mm can be considered within normal limits. Clinical follow-up evaluation is prudent, but additional imaging of these infants is not required.