Shawky et al. (2000) studied 44 children with hydrocephalus to identify the genetic factors involved.  The most frequent etiology was congenital aqueductal stenosis followed by other causes such as Arnold Chiari malformation and congenital toxoplasmosis. First born children were found to be significantly more affected by congenital hydrocephalus than thier siblings. Also, male to female ratio of affected children were higher, indicating X-linked recessive mode of inheritence.

[Shawky RM, Mokhtar GM, Abdel Hay A, Agaiby E. Some genetic aspects of congenital hydrocephalus. Egyptian J Med Hum Genet. 2000; 1(1):197-205.]

Teebi et al. (1989) described an Arab child of consanguineous parents with the characteristic 'inverted' facial expression, i.e., when smiling or laughing, he appeared to be crying. Investigations at age 6 showed minor changes, indicating the probable importance of detecting the abnormality through the facial expression at an early age. In 1991, Teebi and Hassoon indicated that at age 8 the child still showed the inverted facial expression upon laughing, but also had renal changes as a consequence of a neurogenic bladder in addition to hydrocephalus due to stenosis of the aqueduct of Sylvius. Teebi and Hassoon (1991) suggested that the association is not fortuitous and probably widens the spectrum of urofacial syndrome or represents a distinct entity mimicking the urofacial syndrome.

In a retrospective study conducted by Rajab et al. (1998), incidence of congenital hydrocephalus was found to be 0.53/1000 births and incidence of congenital hydrocephalus with associated spina bifida was 0.44/1000. Among those affected the male to female ratio of 1.5:1 indicated X-linked hydrocephalus.

Addar and Babay (2005) reported for the first time in the literature two families with recurrent congenital hydrocephalus each for the fourth time. The first showed evidence of X-linked recessive form, while the second was an autosomal recessive form.