Aqueductal stenosis

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Aqueductal stenosis

Nervous system

Autonomic nervous system disorders

Horner syndrome

Orthostatic hypotension


Aqueductal stenosis


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Aqueductal stenosis

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With aqueductal stenosis, aqueductal refers to a channel in the brain that allows fluid to flow through, and stenosis refers to a narrowing.

So aqueductal stenosis is a problem where a channel in the brain’s ventricular system gets narrowed, and that makes it hard for cerebrospinal fluid to flow through.

Let's start with some relevant anatomy.

The brain has four interconnected cavities in the brain called ventricles, and each one contains a structure called a choroid plexus.

The choroid plexus is made up of ependymal cells which produce cerebrospinal fluid - a fluid that helps provide buoyancy and protection, as well as metabolic fuel for the brain.

Highest up, are two C-shaped lateral ventricles that lie deep in each cerebral hemisphere.

The two lateral ventricles drain their cerebrospinal fluid into the third ventricle, which is a narrow, funnel-shaped, cavity at the center of the brain.

The third ventricle makes a bit more cerebrospinal fluid and then sends all of the cerebrospinal fluid to the fourth ventricle via the cerebral aqueduct.

The fourth ventricle is a tent-shaped cavity located between the brainstem and the cerebellum.

After the fourth ventricle, the cerebrospinal fluid enters the subarachnoid space, which is the space between the two inner linings of the brain - the arachnoid and pia mater.


The cerebral aqueduct, also referred to as the aqueduct of Sylvius, is a channel that carries cerebrospinal fluid (CSF) from the third to the fourth ventricle. Aqueductal stenosis means that this channel becomes narrow and does not allow CSF to properly flow through. This can lead to the accumulation of CSF in the brain, a condition known as hydrocephalus. As much CSF accumulates, it leads to brain compression and associated symptoms such as headache, vomiting, nausea, changes in mental status, and seizures. Children with hydrocephalus can present with head enlargement, intellectual disability, and developmental delay. The diagnosis is typically made with a CT scan or MRI.


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  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "The ventricular system of the brain: a comprehensive review of its history, anatomy, histology, embryology, and surgical considerations" Child's Nervous System (2013)
  6. "Hydrocephalus in aqueductal stenosis" Child's Nervous System (2011)
  7. "Endoscopic Third Ventriculostomy for Idiopathic Aqueductal Stenosis" World Neurosurgery (2013)

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