The role of high resolution ultrasound and MRI in the investigation of infants with macrocephaly.

External hydrocephalus was diagnosed using computed tomography in seven children presenting with macrocephaly. The value of different imaging techniques in distinguishing between subdural effusions and external hydrocephalus was investigated. High resolution ultrasonography combined with magnetic resonance imaging appeared to provide enough information to make a distinction between these two conditions. Radionuclide cisternography was still required to assess the flow pattern of the cerebrospinal fluid (CSF) which was important when placement of a lumboperitoneal shunt was considered.