ABSTRACT
Absence of the septum pellucidum may occur as an isolated malformation. Some of the common paediatric ultrasound and radiology textbooks mention this anomaly. However, only 12 case reports have been published so far. Absent septum pellucidum is also seen in combination with other cerebral malformations like septo-optic pituitary dysplasia (SOPD, de Morsier), agenesis of corpus callosum, holoprosencephaly etc. More often it is seen as a secondary injury due to an increasing internal hydrocephalus. Occurrence of this aplasia and its significance are often underestimated. At a paediatric centre in Germany the anomaly is expected to occur in 1: 1,000 to 1:3,000 cerebral ultrasound examinations. After a review of the literature four cases are presented. All of them were observed by ultrasound during the neonatal period. Using ultrasonography diagnosis of the isolated absence of septum pellucidum can be easily performed by the experienced physician, and will usually be of eminent relevance for the patient.
