CONGENITAL HYDROCEPHALUS - NOSOLOGY AND GUIDELINES FOR CLINICAL APPROACH AND GENETIC-COUNSELING

Congenital hydrocephalus is a serious condition that can arise from mu ltiple causes. It comprises a diverse group of conditions which result in impaired circulation and absorption of cerebrospinal fluid. Congen ital malformations of the central nervous system, infections, haemorrh age, trauma, teratogens and, occasionally, rumours can all give rise t o hydrocephalus. In this paper we focus on the genetic aspects of hydr ocephalus, excluding neural tube defects. The incidence is 0.4-0.8 per 1000 liveborns and stillbirths. X-linked hydrocephalus comprises appr oximately 5% of all cases. This condition is caused by mutations in th e gene at Xq28 encoding for L1, a neural cell adhesion molecule. Carri er detection and prenatal diagnosis can be offered to affected familie s by means of chorionic villus biopsy and linkage analysis or L1 mutat ion analysis. In general: recurrence risk for congenital hydrocephalus excluding X-linked hydrocephalus, is low; empiric risk figures found in various studies range from <1% to 4%. Unfortunately, prenatal diagn osis based on an early ultrasound scan is not always reliable as ventr iculomegaly usually starts after 20 weeks of gestation. We stress the importance of additional clinical investigations. Prognosis in the pre natally diagnosed patients depends on additional malformations but in general, is not very good. Conclusion Congenital hydrocephalus mag. be non-syndromic and syndromic. Prognosis depends primarily on the under lying cause and/or associated malformations, which have to be delineat ed on the basis of clinical cytogenetic and molecular analysis.