Hydrocephalus with stenosis of the aqueduct of Sylvius

What it is

A congenital, X-linked, clinical subtype of L1 syndrome characterized by severe hydrocephalus often of prenatal onset, adducted thumbs, spasticity (mostly evidenced by brisk tendon reflexes and extensor plantar responses) and moderate to severe intellectual disability. This subtype represents the severe end of the L1 syndrome spectrum and is associated with poor prognosis.

Key facts

Prevalence

1-9 / 100 000

Age of onset

Antenatal, Neonatal

Inheritance

X-linked recessive

Classified as

Clinical subtype

Prevalence figures describe populations, not individuals, and are often estimates from a single study. Where the figure is an incidence or a birth prevalence, it says so.

Signs and symptoms

These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.

Gene

ICD-10 codes

ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.

Related health topics

Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.

Cross-references