L1CAM and Hydrocephalus: For example, a few hundred variants in L1CAM have been described in individuals with CC hypoplasia, retardation, adducted thumbs, apasticity and hydrocephalus (CRASH) syndrome (Rosenthal et al., 1992; Jouet et al., 1994; Weller and Gärtner, 2001; Vos et al., 2010).