Benign subdural collections of infancy

Benign subdural collections (or effusions) of infancy, are perhaps better characterized by the term benign extra-axial fluid collections of infancy since it is difficult to distinguish whether they are subdural or subarachnoid.

They appear on CT as peripheral hypodensities over the frontal lobes in infants. Imaging may also show dilatation of the interhemispheric fissure, cortical sulci, and Sylvian fissure. Ventricles are usually normal or slightly enlarged, with no evidence of transependymal absorption. Brain size is normal. Transillumination is increased over both frontal regions. The fluid is usually clear yellow (xanthochromic) with high protein content. The etiology of these is unclear; some cases may be due to perinatal trauma. They are more common in term infants than preemies. Must be differentiated from external hydrocephalus