Cerebrospinal fluid (CSF) circulates through the brain, spinal cord, and subarachnoid space. It is produced by the choroid plexus in the ventricles and is absorbed by the arachnoid villi into the dural sinuses. CSF acts as a protective buffer and aids in nutrient exchange; its composition is similar to extracellular fluid with higher sodium than potassium levels. CSF pressure varies with body position and can be measured via lumbar puncture for diagnostic purposes.

1. Cerebrospinal Fluid(CSF)Saddam AnsariTbilisi State Medical University

2. IntroductionCSF is clear, colorless and transparentCirculates through cavity of the:BrainSubarachnoid spaceCentral canal of spinal cordPart of Extracellular fluid (ECF)

3. Properties Volume : approximately 150 mLRate of formation: approximately 0.3 mL/minSpecific gravity : 1.005Reaction : Alkaline

4. Composition

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 CSFSite of formationFormed 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 formationFormed 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 CSFPilocarpine, 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 salineCauses 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

12. Absorption of CSFMostly 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 CSFBy filtration due to pressure gradient between hydrostatic pressure in the subarachnoid space fluidAnd the pressure that exists in the Dural sinus blood.The colloidal substances pass slowly and crystalloids are absorbed rapidly.

14. Pressure exerted by CSFVaries 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 CSFProtective Function:Acts as buffer Protects the brain from shockIf brain receives severe blow , countercoup injury may take place.

16. Continued…Regulation of Cranial Content VolumeIs very essential becauseWhen 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 ExchangeCSF is the medium through which substances like :Nutritive substancesWaste materials are exchanged between blood and brain tissues.

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

19. Continued…In Lumbar punctureThe 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 BarrierBarrier 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 BarrierOxygenCarbon dioxideWater Glucose Amino acidsElectrolytes 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 solubleOther lipid soluble substances.

25. Substances which can’t pass through Blood-Cerebrospinal Fluid BarrierInjurious 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 pigmentsHowever 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 disordersHydrocephalusAbnormal 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 HydrocephalusSame as Communicating Hydrocephalus but it is due to decreased CSF absorption.Symptoms :Gait instabiltiyUrinary incontinenceDementia

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