Ventricular System

Question 1

Where is CSF located?

Answer 1

Within sub-arachnoid space, cisterns and ventricles.

Question 2

What is CSF?

Answer 2

Clear, colourless, odourless fluid constantly produced and circulated within the CNS

Question 3

What is the function of CSF?

Answer 3

Protection

Buoyancy

Nutrient supply

Waste removal

Hormone transport

Question 4

How much CSF is produced daily?

Answer 4

450 - 600 ml/day = 0.5ml/min

Question 5

Where is CSF produced?

Answer 5

Choroid plexus in ventricles.

Choroidal arteries make specialised capillary loops in pia.

Question 6

How is CSF made?

Answer 6

Filtration of blood.

Sodium is actively transported into the CSF. Chlorine follows due to passive electrochemical attraction.

Osmotic pressure in CSF increases and water is pulled into CSF and K+ is pumped back into the blood

Question 7

How does CSF circulate within the CNS?

Answer 7

Initial production occurs in choroid plexus of lateral ventricles -> Intraventricular foramena of monroe -> 3rd ventricle (more choroid plexus) -> cerebral aqueduct of sylvius -> 4th ventricle -> Central canal of spinal cord -> lower dilated dead end of spinal cord (terminal ventricle)

Question 8

How does CSF exit the CNS?

Answer 8

It exits at 4th ventricle to enter dilated cisterns in subarachnoid space via lateral foramen Lushka -> cerebellopontine cistern -> posterior foramen magendie -> cerebellomedullary cistern then travels either superiorly under surface of cerebral hemispheres to reach the top or inferiorly around the pons, medulla, cerebellum, and spinal cord.

Question 9

What powers CSF movement?

Answer 9

hydrostatic pressure.

Question 10

How does CSF return to venous circulation?

Answer 10

Arachnoid villi -> Superior sagittal sinus -> falx cerebri -> transverse sinus -> sigmoid sinus -> jugular foramen -> internal jugular

Question 11

Where are lumbar punctures taken?

Answer 11

At the lumbar cistern at the level of L4/5.

Question 12

When should lumbar punctures not be taken?

Answer 12

High intracranial pressure

Question 13

What is hydrocephalus and what kinds are there?

Answer 13

Build up of CSF. Can be communicating or non-communicating

Question 14

What is the difference between communicating and non-communicating hydrocephalus?

Answer 14

Non-communicating: CSF from ventricular system can’t communicate with subarachnoid space.

Question 15

What causes non-communicating hydrocephalus?

Answer 15

Overproduction of CSF (rare choroid plexus papilloma)

Blocked foramen of monroe

Blocked cerebral aqueduct

Blocked foramen of Magendie/Lushka

Question 16

What causes communicating hydrocephalus?

Answer 16

Impaired arachnoid granulations (reduced resorption)

Meninges infection (scar formation can block subarachnoid space)

Thrombosed superior sagittal sinus (CSF can’t be drained)

Subarachnoid haemorrhage.