[en] X-linked hydrocephaly (Li Syndrome) is a rare cause of hydrocephaly. It is, however, the most common genetic form of congenital hydrocephaly and consists of the association of hydrocephaly, mental retardation, leg spasticity and adducted thumbs. The phenotype is variable. A mutation of the LICAM gene is known to be the aetiology of the syndrome. We present an antenatal case managed in our department.