Pathogenesis of congenital midline porencephaly.

A recent report in this journal described 5 children with holoprosencephaly, parietal scalp anomalies and midline intracranial cysts. The authors coined the term 'congenital midline porencephaly' for the clinical syndrome and described the cysts as diverticula of hydrocephalic lateral ventricles. This report describes 3 further children with the same syndrome. The author proposes that the midline cyst is simply a variant of the dorsal cyst reported in other cases of holoprosencephaly. It is further concluded that the cyst arises from primary dysgenesis of cerebral midline structures and is not the result of hydrocephalus. The monoventricle and cyst in these children have the CT scan appearance of the head of a primitive arrow. This 'arrowhead' sign may be helpful in the diagnosis of holoprosencephaly with congenital midline porencephaly.