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

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


1
CEREBROSPINAL FLUID a) Formation and
Circulation b) Regulation, Flow and Absorption
  • Dr Pooja Murthy

University College of Medical Sciences GTB
Hospital, Delhi
2

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

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
  • Serves as a pathway for pineal secretion to reach
    pineal gland.

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

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.
  • Density of CSF correlates with
  • Peak sensory level of block
  • Onset of block and duration of motor block
    indirectly.

11
COMPOSITION
12
FORMATION OF CSF
  • 3 Sites
  • Choroid plexus ( 50 70 )
  • Ependymal surfaces of ventricles
  • Perivascular spaces

13
  • Choroid plexus projects into
  • temporal horn of
  • lateral ventricle
  • post. Part of 3rd
  • ventricle
  • roof of 4th ventricle

14
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

15
Mechanism of secretion
  • Transport across any epithelial surface
  • 2 mechanisms
  • transcellular transport paracellular
    transport
  • Choroid plexus

16
Transcellular transport
17
Choroid plexus epithelium
  • Na K ATPase
  • Na H Exchange
  • Na Cl- Cotransport
  • Carbonic Anhydrase

BLOOD
CSF
NET TRANSPORT
H2O
CO2
2K
Acetazolamide
CA
3 Na
H2CO3
Na
H
HCO3
HCO3
Glucose Carrier mediated transport.
Cl
Cl
Cl
Na
Na
Furosemide
18
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

19
CIRCULATION OF CSF
20
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21
  • 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.

22
CSF ABSORPTION
Bulk flow of CSF carries it through the
subarachnoid space around and over the brain into
arachnoid granulations
23
ARACHNOID GRANULATIONS
These are outpouchings of arachnoid mater that
protrude into saggital venous sinus.
24
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)

25
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26
REGULATION
  • Effect of CSF pressure on formation and
    absorption of CSF.
  • Formation is independent of CSF pressure
  • At 112 mm CSF formation
  • is equal to absorption.
  • At 68 mm CSF - absorption is zero.

1.4
1.2
FLOW (ml/min)
0.8
ABSORPTION
0.4
FORMATION
0
0
68 100 112
200
OUTFLOW PRESSURE ( mm of csf )
27
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.

28
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.

29
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

30
THANK YOU
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