Congenital midline porencephaly: a new brain malformation associated with scalp anomaly.

5 cases of dysgenetic hydrocephaly associated with scalp anomalies are described. This brain-scalp anomaly complex is characterized by congenital hydrocephalus, alopecia or cephalocele in the parietal midline and symmetrical defect of the bilateral posterior cerebral mantle along the midline. Midline septal structures of the cranial cavity and tentorium cerebelli were also defective and replaced by a huge dorsal CSF cavity. Histological features of the covering membrane of the dorsal cyst indicate that this new brain anomaly is the consequence of a porencephalic process and we postulate the 'midline porencephaly'. Cerebral angiography is the most valuable method for the diagnosis of this anomaly and its venous phase reveals dysgenesis of the galenic drainage as well as of the dural sinuses.