"Isolated" hydrocephalus in families of spina bifida and anencephaly: a coincidence?

Hydrocephalus is a frequent complication of spina bifida. We wanted to find out if the risk of isolated hydrocephalus was greater in families with NTD (anencephaly and spina bifida) from 424 families studied between 1975 and 1984 in Brittany. The risk of recurrence of NTD is 1.8% in these families, the risk of hydrocephalus 0.3% which represents a risk three times greater than that of the population at large. This risk seems all the higher if the proband is a spina bifida of the male sex. However, no X-linked heredity can be reasonably assumed in these cases. We conclude that these families present a higher multifactorial risk of having another malformed child.