This document summarizes key information about cerebrospinal fluid (CSF): - CSF is clear fluid that circulates in the brain and spinal cord cavities. It is produced by the choroid plexus and absorbed into veins. - CSF composition is 99% water with small amounts of proteins, sugars, and electrolytes. It acts as a buffer and regulates cranial pressure. - CSF flows from the ventricles through the brain and spinal cord, and is ultimately absorbed into veins by the arachnoid villi or spinal veins. Hydrocephalus occurs when CSF circulation is blocked.

1. Saddam Ansari
Tbilisi State Medical University

2. Introduction
• CSF is clear, colorless and transparent
• Circulates through cavity of the:
– Brain
– Subarachnoid space
– Central canal of spinal cord
• Part of Extracellular fluid (ECF)

3. Properties
• Volume : approximately 150 mL
• Rate of formation: approximately 0.3 mL/min
• Specific gravity : 1.005
• Reaction : Alkaline

4. Composition
Cerebrospinal Fluid
Water - 99.13% Solids - 0.87%
Inorganic substances
1.Sodium
2.Calcium
3.Potassium
4.Magnesium
5.Chlorides
6.Phosphate
7.Bicarbonates
8.Sulfates
Organic substances
1.Proteins
2.Amino acids
3.Sugar
4.Cholesterol
5.Urea
6.Uric acid
7.Creatinine
8.Lactic acid
Lymphocytes in CSF : 6/ cu mm

5. Continued…
• As CSF is part of ECF therefore it contain more
amount of Sodium than Potassium.
• Contains some lymphocytes.
• CSF secreted by ventricles does not contain
any cell.
• The lymphocytes are added when it flows in
the spinal cord.

6. Formation of CSF
• Site of formation
– Formed by the choroid plexus situated within the
ventricles.
– The choroid plexus are tuft of capillary projections present
inside ventricles and covered by:
• Pia mater
• Ependymal covering.

7. Continued...
Mechanism of formation
• Formed by process of secretion.
• Does not involve ultrafiltration or dialysis.
• Uses energy.
• Active transport mechanism is involved in secretion.

8. Continued…
Substances affecting the formation of
CSF
• Pilocarpine, ether and extracts of pituitary gland
stimulates the secretion of CSF by stimulating
choroid plexus.
• Injection of isotonic saline also stimulates CSF
formation.

9. Continued…
• Injection of hypotonic saline
– Causes greater rise in capillary pressure and
intracranial pressure,
– Fall in osmotic pressure leading to increase in CSF
formation.
• Hypertonic saline
– Decreases CSF formation
– Decreases CSF pressure

10. Circulation of CSF
Formation of CSF in lateral ventricles
Foramen of Monro
Third ventricle
Aqueductus Sylvius
Fourth ventricle
Foramen of magendie and foramen of
Luschka
Cisterna magna and Cisterna lateralis
Subarachnoid spaces
To cerebral hemispheres
To the spinal cord

12. Absorption of CSF
• Mostly absorbed by the Arachnoid villi into
Dural sinuses and Spinal veins.
• Small amount is absorbed along the
perineural spaces into cervical lymphatics and
in to the perivascular spaces.
• Normally, 500 mL of CSF is formed everyday
and equal amount is absorbed.

13. Mechanism of absorption of CSF
• By filtration due to pressure gradient between
hydrostatic pressure in the subarachnoid
space fluid
• And the pressure that exists in the Dural sinus
blood.
• The colloidal substances pass slowly and
crystalloids are absorbed rapidly.

14. Pressure exerted by CSF
• Varies in different position:
Lateral recumbent position = 10-18 cm of H2O
Lying position = 13 cm of H2O
Sitting position = 30 cm of H2O
Coughing and crying increases the pressure by
decreasing the absorption.
Compression of internal jugular vein also raises
the CSF pressure.

15. Function of CSF
• Protective Function:
– Acts as buffer
– Protects the brain from shock
• If brain receives severe blow , countercoup
injury may take place.

16. Continued…
• Regulation of Cranial Content Volume
– Is very essential because
– When substances are absorbed into the venous
sinuses, intracranial pressure is raised,
– Intracranial pressure in turn interferes with the
cerebral circulation causing Asphyxia.
• It is prevented by greater absorption of CSF to
give space for increasing cranial contents.

17. Continued…
• Medium of Exchange
• CSF is the medium through which substances
like :
– Nutritive substances
– Waste materials
are exchanged between blood and brain tissues.

18. Collection of CSF
• Collected by :
– Cisternal puncture or
– Lumbar puncture
• In Cisternal puncture
– CSF is collected by passing needle between
Occipital bone and Atlas, so it enters the cisterna
magna.

19. Continued…
• In Lumbar puncture
– The Lumbar puncture needle is introduced into
the subarachnoid space in the Lumbar region
, between the third and fourth Lumbar spines.
–Uses of Lumbar puncture
• Collecting CSF for diagnostic purpose.
• Injecting drugs for spinal anesthesia, analgesia and
chemotherapy.
• Measuring pressure exerted by CSF.

21. Blood–Cerebrospinal Fluid Barrier
• Barrier between the blood and cerebrospinal
fluid .
• Exists at the Choroid plexus.
• Similar to Blood-Brain Barrier(BBB)
• Allows the movement of only those
substances, which are allowed by BBB.

23. Substances which can pass through
Blood-Cerebrospinal Fluid Barrier
• Oxygen
• Carbon dioxide
• Water
• Glucose
• Amino acids
• Electrolytes
• Drugs such as L-dopa, 5-hydroxytryptamine
sulfonamides, tetracycline and other lipid soluble
drugs

24. Continued…
• Anesthetic gases such as ether, nitrous oxide
which are lipid soluble
• Other lipid soluble substances.

25. Substances which can’t pass through
Blood-Cerebrospinal Fluid Barrier
• Injurious chemical agents.
• Pathogens such as bacteria.
• Drugs such as Penicillin and the
Catecholamines.
• Dopamine also can’t pass therefore
Parkinsonism is treated with L-dopa instead of
dopamine.

26. Continued…
• Bile pigments
– However barrier is not well developed in infants.
– The bile pigments enter the brain tissues .
– During jaundice in infants, the bile pigments enter
the brain and causes damage of Basal ganglia
leading to Kernicterus.

27. CSF disorders
• Hydrocephalus
– Abnormal accumulation of CSF in the skull with
enlargement of head.
• 2 types of Hydrocephalus
1. non-communicating
2. communicating

28. Continued…
Non-communicating Hydrocephalus or
Internal Hydrocephalus
Due to the obstruction of any of the foramen through
which CSF escapes results in dilation of ventricular
cavity.
Communicating Hydrocephalus or External
Hydrocephalus
Due to blockage of Arachnoid villi.

29. Continued…
Symptoms of Hydrocephalus:
Headache
Vomiting
Atrophy of brain
Mental weakness
Convulsions

30. Continued…
• Normal pressure Hydrocephalus
– Same as Communicating Hydrocephalus but it is
due to decreased CSF absorption.
• Symptoms :
– Gait instabiltiy
– Urinary incontinence
– Dementia