aqueductal stenosis

Newborn with

ventriculomegaly on prenatal ultrasound. Coronal (above) and sagittal (below) US of the brain show dilation of the lateral and third ventricles. The fourth ventricle is normal in size.The diagnosis was aqueductal stenosis.

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Newborn with

a large head. Coronal (left) and sagittal (right) US of the brain show dilation of the lateral and third ventricles. The fourth ventricle is normal in size.The diagnosis was aqueductal stenosis.

pediatricimaging.org • CC-by-nc-sa 4.0

Newborn with

ventriculomegaly on prenatal ultrasound. Axial (above left) and coronal (above right) T1 MRI without contrast of the brain show dilation of the lateral and third ventricles. Sagittal T2 MRI without contrast of the brain (below) shows narrowing at the aqueduct of Silvius with a decreased amount of CSF within it. The fourth ventricle is normal in size.The diagnosis was aqueductal stenosis.

pediatricimaging.org • CC-by-nc-sa 4.0

School ager

with long standing headaches who just had a VP shunt placed. AP and lateral radiographs of the skull (above) show throughout skull vault prominence of convolutional markings from gyral impressions on the inner table of the skull, which is also well demonstrated on the axial CT without contrast of the brain (below).The diagnosis was copper beaten skull caused by long-standing hydrocephalus in a patient with aqueductal stenosis.

pediatricimaging.org • CC-by-nc-sa 4.0

Radiopaedia • CC-by-nc-sa 3.0 • de

Aqueductal stenosis (AS) is the most common cause of congenital obstructive hydrocephalus, but can also be seen in adults as an acquired abnormality.

Epidemiology

Congenital aqueductal stenosis has an estimated incidence of ~1:5000 births although the reported range varies greatly (3.7:1,000,000 to 1:2000) . Rarely it may be inherited in an X-linked recessive manner (Bickers-Adams-Edwards syndrome) .

In adults, as an acquired abnormality, AS has different etiologies and thus different demographics related to them.

Clinical presentation

The clinical presentation depends on the severity and age of presentation as well as whether or not it is X-linked. In the infant enlarging head size, bulging fontanelles and gaping cranial sutures are seen. Setting sun phenomenon may also be present. In X-linked form (Bickers-Adams-Edwards syndrome) which is associated with profound intellectual disability, clinical assessment would reveal bilateral adducted thumbs.

The usual symptoms and signs of raised intracranial pressure and chronic hydrocephalus may also be present, including headache, vomiting, decreased conscious state .

Pathology

congenital
- aqueductal webs or diaphragms
- gliosis
acquired
- extrinsic compression
- intrinsic
  - infection: meningitis/ventriculitis
  - subarachnoid hemorrhage (SAH)

Radiographic features

Ultrasound

An antenatal exam can show features of fetal hydrocephalus with a near-normal posterior fossa. There can be secondary thinning of the cortical mantle as well as secondary macrocephaly.

MRI

Better delineates the extent of obstructive hydrocephalus, with an enlargement (often marked) of the lateral and third ventricles. The aqueduct may show funnelling superiorly. The 4 ventricle is not dilated. In cases of secondary obstruction, the underlying abnormality may also be evident (e.g. web, tumor).

sagittal T2: the absence of flow-void signal intensity at the aqueductal level has been suggested as a sign of aqueductal stenosis
sagittal CISS: best demonstrates obstructing web
CSF flow study: decreased aqueductal stroke volume and peak systolic velocity

Treatment and prognosis

Treatment is often either with a third ventriculostomy or VP shunting. There is a small recurrence risk (~4%) for congenital cases even when it is not X linked.