Physiology 1 - CSF production and papilloedema

Question 1

Describe the composition of CSF

Answer 1

Normal CSF is clear and colorless, contains little protein (15-45mg/dl), little immunoglobulins and only 1-5 cells/ml

Question 2

What are the 3 major functions of CSF?

Answer 2

• Mechanical protection: shock-absorbing medium that protects brain tissue. Brain “floats” inside the cranial cavity
• Homeostatic function: pH of CSF affects pulmonary ventilation and cerebral blood flow. Transports hormones.
• Circulation: medium for minor exchange of nutrients and waste products between blood and brain tissue

Question 3

What test is done to analyse CSF?

Answer 3

Lumbar puncture

Question 4

Where is CSF produced ?

Answer 4

By secretory epithelium (chorocoid cells) of the choroid plexus in the ventricules

Question 5

Describe the development of the choroid plexus in the ventricles

Answer 5

• Arteries invaginate the roof of the ventricle to form the choroid fissure
• The involuted ependymal cells along with the vessels enlarge into villi and form the choroid plexus

Question 6

Which ventricles is the choroid plexus found in ?

Answer 6

3rd and 4th and lateral ventricles

Question 7

What does CSF secretion involve in terms of ion movements causing it ?

Answer 7

The transport of ions ( Na+, Cl¯ and HCO3¯) across the epithelium from blood to CSF

Question 8

Describe the route/circulation of CSF production

Answer 8

1. CSF is produced in the lateral ventricles flows through interventricular foramen into the 3rd ventricles
2. More CSF added from the 3rd ventricles
3. Then flows through aqueduct of midbrain (cerebral aqueduct) into 4th ventricle
4. 4th ventricle adds more CSF
5. CSF then enters the subarachnoid space through the single and 2 lateral apertures
6. CSF then circulates in the central canal of the spinal cord

Question 9

What is hydrocephalus ?

Answer 9

• Accumulation of CSF in the ventricular system or around the brain (either due to obstruction or overproduction)
• Resulting in subsequent enlargement of one or more ventricles and increase in CSF pressure

Question 10

What would the imaging of hydrocephalus look like ?

Answer 10

Would show enlargement of the ventricles

Question 11

What is papilloedema ?

Answer 11

Optic disc swelling due to increased intracranial pressure transmitted to the subarachnoid space surrounding the optic nerve

Question 12

On fundoscopy what would you see in papilloedema ?

Answer 12

Bluging of the optic disc

Question 13

What is Idiopathic intracranial hypertension / pseudotumor cerebri?

Answer 13

• Increased CSF pressure but no signs of ventricular enlargement
• Symptoms include headache and visual disturbances (visual field disturbances to blindness) due to papilloaedema

Question 14

What are some of the visual symptoms that can be due to papilloedema ?

Answer 14

Enlarged blind spot, blurring of vision, visual obscurations and loss of vision