#1. Possible causes of blindness from hydrocephalus
#2. Which is true regarding X-linked hydrocephalus
Inherited hydrocephalus (HCP) with phenotypic expression in males, passed on through carrier mothers who are phenotypically normal. Classical phenotypic expression will skip single generations.
Incidence: 1/25,000 to 1/60,000.
Prevalence: ≈ 2 cases per 100 cases of hydrocephalus.
Gene located on Xq28.
L1CAM membrane-bound receptor plays a significant role in CNS development for axonal migration to appropriate target locations through Integrin cell adhesion molecules and MAP Kinase signal cascade.
Abnormal gene expression results in poor differentiation and maturation of cortical neurons, macroscopic anatomical abnormalities (bilateral absence of pyramidal tracts, see below). Cytoplasmic domain loss of function mutations result in severe L1 syndrome, whereas mutations retaining expression of some functional protein (component imbedded in cell membrane) leads to mild L1 syndrome.