Hydranencephaly with extensive periventricular necrosis and numerous ectopic glioneuronal nests.

The case reported here relates to a male infant with hydranencephaly who was born at 37 weeks of gestation and died immediately after birth. Post-mortem examination revealed that the cerebral hemispheres had been replaced by fluid-filled cavities within a normal-sized cranium. The membranous hemispheric wall was composed of gliosed tissue with multiple foci of necrosis and hemosiderin-laden macrophages. The ependyma was absent. Many necrotic foci containing hemosiderin were also found around the aqueduct and fourth ventricle. These findings suggest that hemorrhagic necrosis had occurred throughout the periventricular region, and more severely in the cerebral hemispheres. Moreover, numerous glioneuronal nests were found throughout the subarachnoid space and ventricles. Glioneuronal nests, if present, are usually minimal in hydranencephaly, whereas it is one of the pathological features of multicystic encephalopathy. The transition of multicystic encephalopathy to hydranencephaly has been demonstrated repeatedly. The former is a condition resulting from a severe circulatory disturbance, most often at the end of gestation or in the perinatal period. These lesions date later than hydranencephaly. Considering that numerous glioneuronal nests were found in the present case, it is likely that the encephaloclastic process developed toward the end of gestation.