6. CSF and Cerebral Blood Supply

What does CSF stand for?

Cerebrospinal fluid.

Where is CSF mostly secreted?

By choroid plexus epithelial cells in the lateral ventricles.

What is the CSF flow path?

Lateral ventricles → interventricular foramina → third ventricle → cerebral aqueduct → fourth ventricle → median/lateral apertures → cisterna magna/subarachnoid space → arachnoid villi/granulations → dural venous sinuses.

Where does CSF flow after the lateral ventricles?

Into the interventricular foramina.

Where does CSF flow after the interventricular foramina?

Into the third ventricle.

Where does CSF flow after the third ventricle?

Through the cerebral aqueduct/aqueduct of Sylvius.

Where is the cerebral aqueduct located?

In the midbrain.

Where does CSF flow after the cerebral aqueduct?

Into the fourth ventricle.

Where is the fourth ventricle located?

Between the pons/medulla and the cerebellum.

Where does CSF flow after the fourth ventricle?

Through the median aperture and lateral apertures.

Where does CSF flow after the median and lateral apertures?

Into the cisterna magna and subarachnoid space.

What space does CSF circulate through around the brain and spinal cord?

The subarachnoid space.

How does CSF return to venous blood?

Through arachnoid villi/granulations into dural venous sinuses.

Which dural venous sinus is especially important for CSF reabsorption?

The superior sagittal sinus.

What are the main functions of CSF?

CSF cushions the CNS, circulates metabolites, and helps maintain a protected chemical environment.

How does CSF protect the CNS mechanically?

It cushions the brain and spinal cord.

How does CSF help chemically?

It helps maintain a protected chemical environment around the CNS.

What is the blood-CSF barrier?

A barrier that limits what substances can enter CSF from the blood.

What does the blood-CSF barrier protect?

It protects the CSF and CNS environment from unwanted substances in blood.

What is the Circle of Willis?

An arterial connection at the base of the brain that links anterior and posterior cerebral circulation.

What are the main components of the Circle of Willis?

Internal carotid arteries, anterior cerebral arteries, anterior communicating artery, posterior communicating arteries, posterior cerebral arteries, and posterior contribution from the basilar artery.

Which arteries are part of the anterior circulation?

Internal carotid arteries and their branches, especially ACA and MCA.

What arteries do the internal carotid arteries give rise to?

The anterior cerebral artery and middle cerebral artery.

What does ACA stand for?

Anterior cerebral artery.

What does MCA stand for?

Middle cerebral artery.

What does PCA stand for?

Posterior cerebral artery.

What does the ACA supply?

Medial frontal/parietal cortex, especially leg and foot motor/sensory regions.

Which artery supplies the medial leg/foot motor and sensory cortex?

ACA.

What does the MCA supply?

Lateral cerebral cortex, including face/arm motor-sensory areas and many language areas.

Which artery supplies face and arm motor-sensory areas?

MCA.

Which artery supplies many language areas?

MCA.

Which arteries form the posterior circulation?

Vertebral arteries, basilar artery, and posterior cerebral arteries.

What do the vertebral arteries join to form?

The basilar artery.

What does the basilar artery supply?

Brainstem and cerebellar branches.

What does the basilar artery end as?

Posterior cerebral arteries.

What does the PCA supply?

Occipital lobe/visual cortex and inferior temporal areas important for memory.

Which artery supplies the visual cortex?

PCA.

Which artery supplies the occipital lobe?

PCA.

Which artery supplies inferior temporal areas important for memory?

PCA.

What does the anterior communicating artery connect?

The left and right anterior cerebral arteries.

What do the posterior communicating arteries connect?

The anterior circulation to the posterior circulation.

Why is the Circle of Willis clinically important?

It provides anatomic connections between major cerebral arteries, but these arteries often still act like functional end vessels in strokes.

Should major cerebral arteries be treated as functional end vessels in many strokes?

Yes, even though the Circle of Willis provides anatomic connections.

What is a watershed area?

A border zone between major arterial territories.

Where are common watershed areas in the brain?

Between ACA/MCA and MCA/PCA territories.

Why do watershed areas have lower blood flow?

They are at the distal ends of arterial branches.

Why are watershed areas vulnerable?

They have relatively low blood flow and oxygen delivery.

What conditions can injure watershed areas?

Hypoperfusion, anoxia, low blood pressure, shock, or severe vascular disease.

What is a watershed infarct?

A stroke in a border zone between major arterial territories.

What symptoms can watershed infarcts cause?

Mixed cortical signs depending on which border zone is affected.

Why are watershed areas clinically important in stroke?

They are vulnerable to low blood flow and can infarct during systemic hypoperfusion or vascular disease.