However, this situation is sometimes referred to as dilated ventricles, and hydrocephalus is restricted for use only when intracranial pressure is increased. Congenital hydrocephalus occurs in .3 to .8 per 1,000 births. This defect occurs at approximately 6 to 10 weeks gestation, so it is conceivable to identify this defect before the foetus is viable. You can expect this variant to include absence of the interhemispheric fissure, a single primitive ventricle, fused thalami, and absent third ventricle, olfactory bulbs, and optic tracts. There can also be some facial anomalies consisting of aplasia or hypoplasia of midline structures are characteristic of holoprosencephaly.
Prognosis Depends on the type of holoprosencephaly and the presence of associated anomalies.
Chromosome abnormalities, especially trisomy 13 and 18, may be associated with holoprosencephaly. For this reason, if holoprosencephaly is identified, amniocentesis is recommended.