obsolete_L1 syndrome true L1 syndrome is a mild to severe congenital X-linked developmental disorder characterized by hydrocephalus of varying degrees of severity, intellectual deficit, spasticity of the legs, and adducted thumbs. The syndrome represents a spectrum of disorders including: X-linked hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS), MASA syndrome, X-linked complicated hereditary spastic paraplegia type 1, and X-linked complicated corpus callosum agenesis (see these terms). L1CAM syndrome http://purl.obolibrary.org/obo/MONDO_0017140 CRASH syndrome Corpus callosum hypoplasia-retardation-adducted thumbs-spasticity-hydrocephalus syndrome OMIM:304100 orphanet OMIM:307000 OMIM:303350 Replaced with Mondo term. 3.41.0 ICD10:Q04.8