Aqueductal stenosis | Figure 1

CincyKidsRad

Cincinnati Children's Radiology

Aqueductal stenosis

Axial (image 1) and sagittal (image 2) T2-weighted MRI shows massive hydrocephalus with enlargement of the lateral ventricles. The fourth ventricle (arrow) is normal in size on the sagittal image. The cerebellar tonsils are herniated through the foramen magnum. The combination of massive enlargement of the lateral ventricles and a normal fourth ventricle is characteristic of aqueductal stenosis. Aqueductal stenosis refers to a narrowing at the aqueduct of Sylvius. This narrowing or occlusion blocks the normal flow of cerebral spinal fluid.

Similar cases

Fetal MRI (image 1) shows massive enlargement of the lateral ventricles and stenosis (arrow on MRI) of the aqueduct of Sylvius. Aqueductal stenosis is one of the most common causes of fetal hydrocephalus. The narrowing of the aqueduct of Sylvius causes enlargement of the lateral and third ventricles. However, the fourth ventricle is normal in size as it is distal to the stenosis. Patients are treated with a ventriculoperitoneal shunt and may also undergo 3rd ventriculostomy.

Sagittal cut of the cerebelum allows us to study the structures of the fourth ventricle #Arborvitae

Sagittal T1-weighted (image 1) and coronal T2-weighted (image 2) MRI in an infant with aqueductal stenosis shows massive ventriculomegaly (arrow), an encephalocele (small arrow) arising from the posterior parietal convexity, and a large retrocerebellar cerebral spinal fluid space (dashed arrow) consistent with a Dandy-Walker malformation. Aqueductal stenosis refers to narrowing of the aqueduct of Sylvius. On imaging, the lateral and third ventricles are markedly dilated; mildly the fourth ventricle has a normal appearance. Associated ventricular rupture is uncommon. #NeuroWednesday

Axial (image 1) and sagittal (image 2) images from a fetal MRI show marked hydrocephalus. While there is a large volume of fluid in the posterior fossa, the fourth ventricle is not seen and the cerebral aqueduct is not visible. Aqueductal stenosis is the most common congenital cause of obstructive hydrocephalus. Acquired aqueductal stenosis can also occur in patients with brain tumors or intracranial hemorrhage.