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Saddam Ansari

Tbilisi State Medical University

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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)

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Properties

Volume : approximately 150 mL

Rate of formation: approximately 0.3 mL/min

Specific gravity : 1.005 Reaction : Alkaline

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Composition

Cerebrospinal FluidWater - 99.13% Solids - 0.87%

Inorganic substances

1.Sodium

2.Calcium

3.Potassium

4.Magnesium5.Chlorides

6.Phosphate

7.Bicarbonates

8.Sulfates

Organic substances

1.Proteins

2.Amino acids

3.Sugar

4.Cholesterol5.Urea

6.Uric acid

7.Creatinine

8.Lactic acid

Lymphocytes in CSF : 6/ cu mm

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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 inthe spinal cord.

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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.

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Continued...

Mechanism of formation Formed by process of secretion.

Does not involve ultrafiltration or dialysis.

Uses energy.

Active transport mechanism is involved in secretion.

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Continued

Substances affecting the formation of

CSF

Pilocarpine, ether and extracts of pituitary glandstimulates the secretion of CSF by stimulating

choroid plexus.

Injection of isotonic saline also stimulates CSF

formation.

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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

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Circulation of CSFFormation 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 hemispheresTo the spinal cord

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Absorption of CSF

Mostly absorbed by the Arachnoid villi intoDural sinuses and Spinal veins.

Small amount is absorbed along theperineural spaces into cervical lymphatics andin to the perivascular spaces.

Normally, 500 mL of CSF is formed everydayand equal amount is absorbed.

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Mechanism of absorption of CSF

By filtration due to pressure gradient betweenhydrostatic pressure in the subarachnoidspace fluid

And the pressure that exists in the Dural sinusblood.

The colloidal substances pass slowly andcrystalloids are absorbed rapidly.

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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.

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Function of CSF

Protective Function: Acts as buffer

Protects the brain from shock

If brain receives severe blow , countercoup

injury may take place.

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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 togive space for increasing cranial contents.

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Continued

Medium of Exchange

CSF is the medium through which substances

like : Nutritive substances

Waste materials

are exchanged between blood and brain tissues.

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Collection of CSF

Collected by :

Cisternal puncture or

Lumbar puncture

In Cisternal puncture

CSF is collected by passing needle betweenOccipital bone and Atlas, so it enters the cisterna

magna.

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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 andchemotherapy.

Measuring pressure exerted by CSF.

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BloodCerebrospinal Fluid Barrier

Barrier between the blood and cerebrospinalfluid .

Exists at the Choroid plexus.

Similar to Blood-Brain Barrier(BBB)

Allows the movement of only those substances,which are allowed by BBB.

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Substances which can pass through

Blood-Cerebrospinal Fluid Barrier

Oxygen

Carbon dioxide

Water

Glucose

Amino acids

Electrolytes

Drugs such as L-dopa, 5-hydroxytryptaminesulfonamides, tetracycline and other lipid solubledrugs

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Continued

Anesthetic gases such as ether, nitrous oxide

which are lipid soluble

Other lipid soluble substances.

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Substances which cant pass through

Blood-Cerebrospinal Fluid Barrier

Injurious chemical agents.

Pathogens such as bacteria.

Drugs such as Penicillin and theCatecholamines.

Dopamine also cant pass therefore

Parkinsonism is treated with L-dopa instead of

dopamine.

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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.

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CSF disorders

Hydrocephalus Abnormal accumulation of CSF in the skull with

enlargement of head.

2 types of Hydrocephalus

1. non-communicating

2. communicating

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Continued

Non-communicating Hydrocephalus orInternal HydrocephalusDue to the obstruction of any of the foramen throughwhich CSF escapes results in dilation of ventricular

cavity.

Communicating Hydrocephalus or ExternalHydrocephalusDue to blockage of Arachnoid villi.

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Continued

Symptoms of Hydrocephalus:

Headache

VomitingAtrophy of brain

Mental weakness

Convulsions

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Continued

Normal pressure Hydrocephalus Same as Communicating Hydrocephalus but it is

due to decreased CSF absorption.

Symptoms :

Gait instabiltiy Urinary incontinence

Dementia

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