Hydrocephalus with stenosis of the aqueduct of Sylvius

Hydrocephalus with stenosis of the aqueduct of Sylvius (also known as aqueductal stenosis or X-linked hydrocephalus when caused by L1CAM mutations) is a congenital condition in which the cerebral aqueduct (aqueduct of Sylvius), a narrow channel connecting the third and fourth ventricles of the brain, is abnormally narrowed or blocked. This obstruction prevents the normal flow of cerebrospinal fluid (CSF), leading to its accumulation within the ventricles and resulting in hydrocephalus — an enlargement of the fluid-filled spaces in the brain. The condition primarily affects the central nervous system and can cause increased intracranial pressure, progressive enlargement of the head (macrocephaly), and damage to surrounding brain tissue. Key clinical features include macrocephaly, bulging fontanelles in infants, developmental delay, intellectual disability, spasticity (particularly of the lower limbs), and adducted (clasped) thumbs — the latter being especially characteristic of the X-linked form caused by mutations in the L1CAM gene (Xq28). This X-linked recessive form, also known as HSAS (Hydrocephalus due to Stenosis of the Aqueduct of Sylvius) or Bickers-Adams syndrome, predominantly affects males. However, aqueductal stenosis can also occur sporadically or as part of other genetic syndromes, and non-genetic causes such as infections or hemorrhage may also contribute. Treatment is primarily surgical and involves placement of a ventriculoperitoneal (VP) shunt to divert excess CSF from the brain ventricles to the abdominal cavity, thereby reducing intracranial pressure. Endoscopic third ventriculostomy (ETV) is an alternative surgical approach in selected patients. Early intervention is critical to minimize brain damage. Supportive therapies including physical therapy, occupational therapy, and developmental support are important components of long-term management. Despite treatment, many affected individuals experience some degree of intellectual disability and neurological impairment, and the prognosis varies depending on the severity and underlying cause.

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