ABSTRACT
Hydranencephaly is the total or virtually total absence of the cerebral hemispheres, which are reduced to a membranous sac of glial tissue, with no ependymal coating, in an intact skull. This is rare disorder (0.5 per thousand births). It is classified as a circulatory encephalopathy. Two opposing theories are generally advanced: the encephaloclastic or destructive theory and the theory of dysontogensis or malformation, due to early disruption of organogenesis. It has many causes (vascular, viral, parasitic, genetic, toxic, estrogenic...). It appears to be readily diagnosed by ultrasound, the neurological findings may be normal at birth, but transillumination of the skull remains a simple and reliable diagnostic test. Transfontanellar ultrasound, CT scanning and anatomical confirmation alone can establish the diagnosis. The prognosis is hopeless and there is no treatment.
