csf

1. CEREBROSPINAL FLUID :
a) Formation and Circulation
b) Regulation, Flow and Absorption

2. • Definition
• Physical characteristics
• Composition
• Formation and Circulation
• Flow and Absorption
• Regulation
• Clinical importance
CSF- Discussion under the following
subheadings

3. HISTORY
• First report of existence of CSF – 17th century B.C.
• Hippocrates – 4th B.C.
• Galen discovered ventricular cavities – 2 A.D.
• Vesalius – watery humour – 16th A.D.
• Magendie performed first tap of CSF in 1825.

4. What is CSF ?
Cerebrospinal fluid is an ultra filtrate of plasma,
functioning as a hydraulic shock absorber. CSF is
found in the ventricles of the brain and also in the
subarachnoid space around brain and spinal cord.

5. FUNCTIONS
• Cushioning effect and protection
- As brain floats in CSF, it protects brain from minor
stress such as in jolting.
- No protection from major stress like head injury.
• Mechanical bouyancy and support
- CSF reduces the net weight of the brain from 1400g
to 25g
- This helps to increase the density of brain by not
increasing its weight and thus preserving blood
supply to lower zones of brain.

6. • Chemical protection – blood brain barrier.
• Nourishment and removal of metabolites

7. Because of its easy access, it has diagnostic and
therapeutic applications.
• Diagnostic - CSF analysis for detection of pathological
conditions.
• Therapeutic – Central neuraxial block.
Applications

8. Physical characteristics
Appearance – clear and colourless
Volume :120 -150ml
Specific gravity : 1.00010 – 1.00028
Rate of formation - ~ 550ml/day(0.35ml/min)
CSF turnover : 3-4 ( 3.7 ) times/day
CSF pressure : 60 – 150 mm H20 / 70 – 180 mm CSF

9. Volume of CSF:
Adults
Total - 120 to 150 ml
Ventricles - 65 to 75ml
Cisternal reservoir - 35 to 40ml
Spinal SA space - 25 to 30ml
Neonates – 10 to 60ml.(total CSF vol.)
80 to 100 mm H20

10. Specific gravity of CSF
- 1.00010 to 1.00028
- Relative to the CSF density, Local Anaesthetics are
classified as hypobaric, isobaric and hyperbaric solutions.

11. COMPOSITION
COMPOSITION CSF PLASMA RATIO
Protein(mg/dl) 15 - 45 6000 0.003
Glucose (mg/dl) 50 - 85 100 0.64
Chloride
(meq/kg h2o)
113 99 1.14
Na+(meq/kg h2o) 147 150 0.98
K+(meq/kg h2o) 2.9 4.6 0.62
HCO3 (meq/kgh2o) 25.1 24.8 1.01
PH 7.33 7.4
No. of cells 0-3 lymphocytes

12. FORMATION OF CSF
3 Sites:
• Choroid plexus ( 50 – 70 %)
• Ependymal surfaces of ventricles
• Perivascular spaces

14. Choroid plexus projects
into:
• temporal horn of
lateral ventricle
• post. Part of 3rd
ventricle
• roof of 4th ventricle

16. Choroid plexus
It is a cauliflower like growth
of blood vessels covered by a
thin layer of epithelial cells.
It is made of 3 layers:
• fenestrated capillary
endothelium
• extra cellular matrix
• epithelial cells

18. Mechanism of secretion
• Transport across any epithelial surface
2 mechanisms
transcellular transport paracellular transport
Choroid plexus

19. Transcellular transport

20. BLOOD CSF
Choroid plexus
epithelium
NET TRANSPORT
2K
3 Na
CO2
+ H2O
H2CO3
H+
HCO3
HCO3
Na
Cl Cl
Na Na
Cl
CA
1. Na+ –K+ ATPase
2. Na+ – H+ Exchange
3. Na+ – Cl- Cotransport
4. Carbonic Anhydrase
Furosemide
Acetazolamide
Glucose – Carrier
mediated transport.

21. VIRCHOW ROBIN SPACE
Virchow-Robin spaces, or enlarged
perivascular spaces(EPVS) are spaces
(often only potential) that surround blood
vessels for a short distance as they enter
the brain.
Their wall is formed by prolongations of
the pia mater.
Functions
• Secretion of proteins
• site of entry of lymphocytes and
macrophages in CSF

23. CIRCULATION OF CSF

25. Movement of CSF is by :
• Pulsating blood vessels – helps in flow of CSF through their
pulsations.
• Respiration – affects the central venous pressure –
indirectly affects sagittal venous pressure – CSF
absorption.
• Changes in posture – by indirectly affecting central venous
pressure.

26. CSF ABSORPTION
Bulk flow of CSF carries it
through the subarachnoid
space around and over the
brain into arachnoid
granulations

27. ARACHNOID GRANULATIONS
These are outpouchings of
arachnoid mater that
protrude into saggital
venous sinus.

28. Factors affecting CSF
ABSORPTION
• Site of absorption :
- 4/5th by cerebral arachnoid villi
- 1/5th by spinal arachnoid villi and
along nerve sheaths into lymphatics.
• CSF absorption is passive and is dependent on higher CSF
hydrostatic pressure than venous blood.
• Mean CSF pressure.(70 – 180mm CSF)

30. REGULATION
• Effect of CSF pressure on formation and absorption of
CSF.
0
0
0.4
0.8
1.2
1.4
FORMATION
68 100 112 200
OUTFLOW PRESSURE ( mm of csf )
FLOW
(ml/min)
Formation is independent of
CSF pressure
At 112 mm CSF – formation
is equal to absorption.
At 68 mm CSF - absorption is
zero.

31. Other Factors affecting CSF Synthesis
Rate of CSF formation is decreased by:
• Alkalosis
• Drugs - Acetazolamide – CA inhibitor
Furosemide – Na+ Cl- cotransport inhibitor
Cardiac glycosides – Na+ K+ ATPase inhibitor.
• Volatile anaesthetic agents – Enflurane and Desflurane
increase CSF formation as a result of vasodilation of
choroid plexus.

32. Clinical importance
Why to study CSF in Anaesthesia?
• Pathological states associated with CSF pathways
- Myeloceles , meningomyeloceles
- Hydrocephalus
• Centralneuraxial block
• Critical care setup – Head injuries
- infections – meningitis
• Neurosurgical procedures : Space occupying lesions, tumors,
etc – altered cerebral hemodynamics – affect CSF formation,
circulation and/ or absorption.

33. References
• Anatomy for Anaesthesiologists – Harold Ellis, Stanley
Feldman – 3rd edition
• Textbook of Clinical Anatomy – Richard S Snell – 8th edition
• Review of Medical Physiology- William F Ganong – 21st
edition.
• Textbook of Medical Physiology – Guyton and Hall – 11th
edition
• Textbook of Physiology (Excitable cells and Neurophysiology )
– Harry D Patton – 21st edition
• Physiology of Spinal Anaesthesia – Nicholas M Greene – 3rd
edition
• Textbook of Anaesthesia – Miller – 7th edition