External hydrocephalus--diagnosis by ultrasound

We describe five infants with the appearance of external hydrocephalus diagnosed by real-time cranial ultrasound. The indication for scanning in all cases was a head circumference crossing the 90th centile. The interhemispheric fissure is widened with the falx usually visible and the cortical surface can be seen beneath the anterior fontanelle. There is minimal, if any, ventricular dilatation and none of the children went on to develop internal hydrocephalus. Two children had minor motor problems but there were no other neurodevelopmental sequelae.