Pyocephalus in a case of encephalocele and Arnold-Chiari anomaly: interactions between malformations and inflammation.

This report deals with a 7-wk-old infant with an unusual tamponade empyema of the ventricular system associated with an occipital encephalocele and Arnold-Chiari anomaly. The infection extended from the ruptured encephalocele to the ventricular system. Arnold-Chiari malformation locked the infection within the ventricular system through herniation and occlusion of the ventricular foramina and prevented from spreading into subarachnoid space. The long survival of the infant allowed for the formation of pyocephalus. There was also an extensive coarctation of the ventricular walls and aqueductal occlusion which probably resulted from the infectious process in the early postnatal life.