The document discusses the cerebrospinal fluid (CSF) and its role in protecting the brain. CSF is produced in the ventricles of the brain by the choroid plexus, circulates through the brain and spinal cord, and is absorbed by the arachnoid villi into venous sinuses. It provides buoyancy and cushioning to the brain, maintains homeostasis, and acts as a conduit for waste removal. CSF has similar constituents as plasma but lower protein and glucose levels. It is circulated through the brain by pulsating blood vessels, respiration, and changes in posture.

1. CSF and Blood Brain BarrierCSF and Blood Brain Barrier

2. Protection
• Bone
– Cranial bones & vertebral arches
• Meninges
– Dura mater
– Arachnoid mater
– Pia mater
• Cerebrospinal fluid (CSF)
2

3. 3

5. Protective Function
The most critical role for CSF (and the meninges) is to
protect the brain. The dura is attached firmly to bone.
Normally, there is no "subdural space," with the arachnoid
being held to the dura by the surface tension of the thin
layer of fluid between the two membranes
the brain itself is supported within the arachnoid by the blood
vessels and nerve roots and by the multiple fine fibrous
arachnoid trabeculae. The brain weighs about 1400 g in air, but
in its "water bath" of CSF it has a net weight of only 50 g.
the brain itself is supported within the arachnoid by the blood
vessels and nerve roots and by the multiple fine fibrous
arachnoid trabeculae. The brain weighs about 1400 g in air, but
in its "water bath" of CSF it has a net weight of only 50 g.

7. Function of CSF
• Maintenance of a constant external
environment for neurons and glia
• Mechanical cushion to protect the brain
and buoyant to the heavy brain (1400 g)
• Serve as a lymphatic system and a conduit
for neuropeptides
• pH of CSF regulates pulmonary ventilation
and CBF

8. Cerebrospinal fluid (CSF)
• Supports (buoys) mass
• Cushions CNS - like
waterbed
• Nourishes brain tissue
• Contains proper
electrolytes for CNS
8

9. Cerebrospinal fluid (CSF)
 Filtered from blood
plasma in choroid
plexuses
 Circulates in through
ventricles, canals, &
between meninges
 Returned to blood at
superior sagittal sinus
9

10. Cerebro spinal Fluid
• The entire cerebral cavity enclosing the
brain and spinal cord has a capacity of
about 1600 to 1700 milliliters;
• about 150 milliliters of this capacity is
occupied by cerebrospinal fluid and the
remainder by the brain and cord.

11. • This fluid, is present in the ventricles
• of the brain, in the cisterns around the
outside of the brain, and in the subarachnoid
space around both the brain and the spinal
cord.
• All these chambers are connected with one
another, and the pressure of the fluid
• is maintained at a surprisingly constant level.

12. 12
From: Laterra J et al., in Basic Neurochemistry
Cerebrospinal fluid (CSF)

13. Cerebro spinal fluid production & Circulation
Clear, colourless, alkaline fluid is found in
 Ventricles of brain
 Cisterns around brain
 Subarachnoid space around
brain and spinal cord

14. Ventricular System
• Within the brain is a communicating system of
cavities that are lined with ependyma cells and
filled with cerebrospinal fluid (CSF)
• There are:
– two lateral ventricles,
– the third ventricle,
– the cerebral aqueduct,
– and the fourth ventricle within the brain stem.

15. Ventricles of the Brain
 2 Lateral ventricles (1, 2) in cerebral hemispheres
 Third ventricle (3) between hemispheres
 Fourth ventricle (4) in midbrain and medulla
15

16. Ventricles and Location of the Cerebrospinal
Fluid
Slide
Figure 7.17a

17. Choroid Plexus :
Temporal horn of each lateral ventricle
Choroid plexus
present in Posterior portion of III ventricle
Roof of IV ventricle
 Vascular fringes of piamater break up into complex
capillary network covered by cuboidal epithelial
cells,
 Cells contain mitochondria, granules, vesicles indicating
involvement in active metabolic process (secretory)

18. Choroid
Plexus
18

19. Arachnoid villi
 Microscopic finger like projections of arachnoid
membrane into walls of venous sinuses.
 Lined by endothelial cells
 Large conglomerates of villi called arachnoid
granulations / pachionian bodies
 Electron microscopic study shows transcellular
channels / pores in lining endothelium which allows
free absorption of CSF, proteins.
Arachnoid villi
 Microscopic finger like projections of arachnoid
membrane into walls of venous sinuses.
 Lined by endothelial cells
 Large conglomerates of villi called arachnoid
granulations / pachionian bodies
 Electron microscopic study shows transcellular
channels / pores in lining endothelium which allows
free absorption of CSF, proteins.

20. 20

21. Perivascular space :
Blood vessel entering brain substance will carry
with it sleeve of arachnoid immediately surrounding the
vessel and sleeve of pia more externally. Extension of
SAS around the vessel known as PV space / virchow robin
space.
Products of metabolism, inflammatory exudates
pass from brain substance into perivascular space, to enter
CSF in subarachnoid space.

23. Formation of CSF
 Active secretion by choroid plexus
 Trans ependymal diffusion of brains
interstitial fluid into ventricles (minimal)

24. Secretion :
Na+
K+
ATPase, carbonic anhydrase takes part in
Active transport of Na+ occurs through epithelial cells
lining choroid plexus
Na+
will carry Cl
-
with it.
Na+
& Cl-
increase the quantitiy of osmoticaly active
substances in CSF, which cause immediate osmosis of
water through the membrane.
Less important transport process move small amount of
glucose into CSF, K+
& HCO3- out of CSF

25. 25
Net transport of Na+
and Cl-
across
the epithelium results in the
secretion of CSF.
Cl-
efflux from the epithelium to
CSF is mediated by a cotransporter.
The generation of H+
and HCO3 by
carbonic anhydrase is important in
the secretion of CSF.
From: Laterra J et al., in Basic Neurochemistry
Production of CSF

27. Resulting characteristics of CSF :
Osmotic pressure & Na+
equal to plasma
Cl-
15% greater than plasma
K+
40% less than plasma
Glucose 30% less than plasma
Resulting characteristics of CSF :
Osmotic pressure & Na+
equal to plasma
Cl-
15% greater than plasma
K+
40% less than plasma
Glucose 30% less than plasma

28. CSF formationCSF formation
• 50% by choroid plexuses in the ventricles
• 40% by meningeal blood vessels and
ependymal lining of ventricles
• 10% by brain and spinal cord blood vessels
• Absorption
• 80% by arachinoid villi into venous sinuses
and spinal veins
• 20% by cervical lymphatics and perivascular
spaces
• 50% by choroid plexuses in the ventricles
• 40% by meningeal blood vessels and
ependymal lining of ventricles
• 10% by brain and spinal cord blood vessels
• Absorption
• 80% by arachinoid villi into venous sinuses
and spinal veins
• 20% by cervical lymphatics and perivascular
spaces

29. CSFCSF
• CSF is a clear colorless, isotonic alkaline
fluid, almost protein and cell free and contains
less glucose and k+ than plasma.
• Volume- 130-150ml
• Daily secretion-500-550ml
• Rate of formation-0.2-0.3ml/min
• Pressure-130mm of water
• CSF is a clear colorless, isotonic alkaline
fluid, almost protein and cell free and contains
less glucose and k+ than plasma.
• Volume- 130-150ml
• Daily secretion-500-550ml
• Rate of formation-0.2-0.3ml/min
• Pressure-130mm of water

31. Circulation :
From lateral ventricles through foramen of monro / inter
ventricular foramen to III ventricle
From III ventricle through cerebral aqueduct of sylvius
to IV ventricle
From IV ventricle leaves via median and lateral foramen
of magendie and luschka to reach SAS covering cerebrum
and spinal cord
After bathing surface of spinal cord and base of brain
CSF passes upward over convexity of hemispheres to be
absorbed in intracranial venous sinuses.

33. Circulation of cerebrospinal fluid
CSF drains from lateral ventricle interventricular foramina third ventricle
mesencephalic aqueduct
fourth ventricle median and two lateral apertures
subarachnoid space arachnoid granulations superior sagittal sinus vein

34. 34

36. Subarachnoid
space
Subaracnoid
granulations
Superior
sagital sinus

37. Absorption :
4/5th
of CSF absorbed via cerebral arachnoid villi
1/5th
spinal arachnoid villi
Hydrostatic pressure in sub arachnoid space is higher than
in dural sinuses facilitates fluid movement
Small amount pass into perivascular space, sheath of cranial
nerves
Characteristics of CSF
pH 7.31 – 7.34
Specific gravity - 1005
Osmolarity 290 – 295 mosm /l
Volume 70-120 ml (25ml ventricles 25 ml spinal theca)

38. Force of circulationForce of circulation
• Movement of the CSF is by pulsating blood
vessels, respiration and changes of posture
• CSF is secreted continuously at a rate of
about 0.5ml per minute i.e. 720 ml per day
• Total CSF in the brain 120 ml
• CSF pressure can be measured by attaching
a vertical tube to the lumbar puncture
needle – 10 cm water
• Movement of the CSF is by pulsating blood
vessels, respiration and changes of posture
• CSF is secreted continuously at a rate of
about 0.5ml per minute i.e. 720 ml per day
• Total CSF in the brain 120 ml
• CSF pressure can be measured by attaching
a vertical tube to the lumbar puncture
needle – 10 cm water
38

40. Rate of formation : 0.35 ml / min
500 ml / day
Rate of formation : 0.35 ml / min
500 ml / day
ConstituentsConstituents mg / dlmg / dl PlasmaPlasma CSFCSF
ProteinProtein 7000-80007000-8000 20-4020-40
GlucoseGlucose 70-11070-110 40-7040-70
NaclNacl 560-630560-630 720-750720-750
CholestrolCholestrol 130-230130-230 NilNil
UreaUrea 20-4020-40 10-3010-30
CreatinineCreatinine 0.6 – 1.50.6 – 1.5 0.5 – 1.90.5 – 1.9
Uric acidUric acid 2 – 82 – 8 0.5 – 2.50.5 – 2.5
PhosphatesPhosphates 2- 42- 4 1.2 – 2.01.2 – 2.0

41. Constituent osmol / litreConstituent osmol / litre PlasmaPlasma CSFCSF
Na+Na+ 136 – 145136 – 145 137-145137-145
K+K+ 3.5 – 5.03.5 – 5.0 2.7 – 3.92.7 – 3.9
Ca2+Ca2+ 4.5 – 5.54.5 – 5.5 2.1 – 3.02.1 – 3.0
Mg 2+Mg 2+ 1.3 – 2.11.3 – 2.1 2.0 – 2.52.0 – 2.5
Cl-Cl- 98 – 10698 – 106 116-122116-122
HCO3-HCO3- 21-2721-27 20-2420-24
pH unitspH units 7.36 – 7.447.36 – 7.44 7.31 – 7.347.31 – 7.34
OsmolarityOsmolarity 290 – 295290 – 295 285-295285-295
CSF Pressure :
Lateral recumbent - 60 – 180 mm H2O
Shifting - 300 mm H2O
CSF Pressure :
Lateral recumbent - 60 – 180 mm H2O
Shifting - 300 mm H2O

45. Optic Disc Edema
• Papilledema/Choked Disk
– non-inflammatory congestion of optic disk
associated with increased ICP (due to cerebral
tumors, abscesses, subdural hematoma,
hydrocephalous, malignant hypertension)
– Mechanism: obstruction of venous flow caused
by pressure on the Central Retinal Vein where
it leaves the optic nerve
• Papilledema/Choked Disk
– non-inflammatory congestion of optic disk
associated with increased ICP (due to cerebral
tumors, abscesses, subdural hematoma,
hydrocephalous, malignant hypertension)
– Mechanism: obstruction of venous flow caused
by pressure on the Central Retinal Vein where
it leaves the optic nerve

46. Clinical Findings
• enlarged blind spot
• normal VA and normal
VF
• Fundus Findings:
hyperemia of the disk,
blurring of the margins,
distention of retinal
veins, absence of
pulsation of CRV, disk
swelling to 6-10 D,
hemorrhages
• enlarged blind spot
• normal VA and normal
VF
• Fundus Findings:
hyperemia of the disk,
blurring of the margins,
distention of retinal
veins, absence of
pulsation of CRV, disk
swelling to 6-10 D,
hemorrhages

47. HYDROCEPHALUS

48. “Hydrocephalus” means excess water in the cranial
vault.
This condition is frequently divided into communicating
hydrocephalus and noncommunicating hydrocephalus.
In communicating hydrocephalus fluid flows
readily from the ventricular system into the subarachnoid
space, whereas in noncommunicating hydrocephalus
fluid flow out of one or more of the ventricles
is blocked.
“Hydrocephalus” means excess water in the cranial
vault.
This condition is frequently divided into communicating
hydrocephalus and noncommunicating hydrocephalus.
In communicating hydrocephalus fluid flows
readily from the ventricular system into the subarachnoid
space, whereas in noncommunicating hydrocephalus
fluid flow out of one or more of the ventricles
is blocked.

49. Hydrocephalus
• Large amounts of fluid accumulate
when the capacity for CSF
reabsorption is decreased
• (external hydrocephalus,
communicating hydrocephalus).

50. Hydrocephalus
• Fluid accumulates proximal to the
block and distends the ventricles when
the foramens of Luschka and Magendie
are blocked or there is obstruction
within the ventricular system (internal
hydrocephalus, noncommunicating
hydrocephalus).

51. HydrocephalusHydrocephalus
• Obstructive hydrocephalus/internal/
• noncomunicating
– Congenital malformations
– After inflammation or hemorrhage
– Mass lesions
• Communicating hydrocephalus(external)
– Overproduction of CSF
– Defective absorption of CSF
– Venous drainage insufficiency
• Obstructive hydrocephalus/internal/
• noncomunicating
– Congenital malformations
– After inflammation or hemorrhage
– Mass lesions
• Communicating hydrocephalus(external)
– Overproduction of CSF
– Defective absorption of CSF
– Venous drainage insufficiency

52. Usually the noncommunicating type of hydrocephalus
is caused by a block in the aqueduct of Sylvius,
resulting from atresia (closure) before birth in many
babies or from blockage by a brain tumor at any age.
As fluid is formed by the choroid plexuses in the two
lateral and the third ventricles, the volumes of these
three ventricles increase greatly.
This flattens the brain into a thin shell against the
skull.

53. In neonates, the increased pressure also causes the whole
head to swell because the skull bones have not yet fused.

55. The communicating type of hydrocephalus is usually
caused by blockage of fluid flow in the subarachnoid
spaces around the basal regions of the brain or by blockage
of the arachnoidal villi where the fluid is normally
absorbed into the venous sinuses. Fluid therefore collects
both on the outside of the brain and to a lesser
extent inside the ventricles.This will also cause the head
to swell tremendously if it occurs in infancy when the
skull is still pliable and can be stretched, and it can
damage the brain at any age.

56. Treatment
• A therapy for many types of hydrocephalus
is surgical placement of a silicone tube
shunt all the way from one of the brain
ventricles to the peritoneal cavity where the
excess fluid can be absorbed into the blood.

57. Normal Brain
57

58. Normal Ventricles
58

59. Hydrocephalus
59

60. Hydrocephalus
60

61. Normal ventricles and hydrocephalus
61

64. Cerebral EdemaCerebral Edema
• Vasogenic edema: A state of increased
extracellular fluid volume; Brain tumor, abscess, infarct,
hemorrhage; glucocorticoids, hypertonic solutions
• Cytotoxic edema: The swelling of cellular
elements; Hypoxia/asphyxia, water intoxication, meningitis,
encephalitis, Reye’s syndrome
• Interstitial edema: Attributed to increased
water and sodium in periventricular white
matter; Obstructive hydrocephalus; Surgical shunting, acetazolamide

66. 66

67. CSF samplingCSF sampling
• Contraindication or precaution in ↑ICP
• Pressure from lumbar puncture: 65-195 mm CSF (H2O), or
5 – 15 mmHg
• Cells: 0; ↑ by inflammation, tumor, or other cerebral
damage
• Protein: < 35 mg/dl; ↑ in blockage or increased BBB
permeability.
• Glucose: > 40 mg/dl; ↓ in meningeal tumor, fungal or TB
infection, sarcoidosis
• Appearance: not cloudy or xanthochromic
• Contraindication or precaution in ↑ICP
• Pressure from lumbar puncture: 65-195 mm CSF (H2O), or
5 – 15 mmHg
• Cells: 0; ↑ by inflammation, tumor, or other cerebral
damage
• Protein: < 35 mg/dl; ↑ in blockage or increased BBB
permeability.
• Glucose: > 40 mg/dl; ↓ in meningeal tumor, fungal or TB
infection, sarcoidosis
• Appearance: not cloudy or xanthochromic

69. barriers, called the blood cerebrospinal
fluid barrier and the blood-brain barrier,
exist between the blood and the
cerebrospinal fluid and brain fluid,
respectively.

70. Barriers exist both at the choroid plexus and at
the tissue capillary membranes in essentially all
areas of the brain parenchyma except in some
areas of the hypothalamus, pineal gland, and
area postrema, where substances diffuse with
greater ease into the tissue spaces.

73. In general, the blood–cerebrospinal fluid and blood
brain barriers are highly permeable to water, carbon
dioxide, oxygen, and most lipid-soluble substances
such as alcohol and anesthetics;
slightly permeable to electrolytes such as sodium,
chloride, and potassium;
almost totally impermeable to plasma proteins and
most non–lipid-soluble large organic molecules.

74. The cause of the low permeability of the blood–
cerebrospinal fluid and blood-brain barriers is the
manner in which the endothelial cells of the brain
tissue capillaries are joined to one another.They are
joined by so-called tight junctions. That is, the
membranes of the adjacent endothelial cells are tightly
fused rather than having large slit-pores between
them, as is the case for most other capillaries of the
body.

76. Function of CSF
• Maintenance of a constant external
environment for neurons and glia
• Mechanical cushion to protect the brain and
provide buoyancy to the heavy brain (1400
g)
• Serves as a lymphatic system and a conduit
for neuropeptides
• pH of CSF regulates pulmonary ventilation
and CBF

77. Function of CSF
• Maintenance of a constant external
environment for neurons and glia
• Mechanical cushion to protect the brain and
provide buoyancy to the heavy brain (1400
g)
• Serves as a lymphatic system and a conduit
for neuropeptides
• pH of CSF regulates pulmonary ventilation
and CBF

78. Functions and Properties of the BBBFunctions and Properties of the BBB
• General Properties of the BBB
1. Large molecules do not pass through the BBB easily.
2. Low lipid (fat) soluble molecules do not penetrate into the brain.
However, lipid soluble molecules rapidly cross the BBB into the
brain.
3. Molecules that have a high electrical charge to them are slowed.
• Therefore:
– The BBB is selectively permeable to :Oxygen, Carbon dioxide and
glucose
– The BBB is not permeable to
hydrogen ions
• General Properties of the BBB
1. Large molecules do not pass through the BBB easily.
2. Low lipid (fat) soluble molecules do not penetrate into the brain.
However, lipid soluble molecules rapidly cross the BBB into the
brain.
3. Molecules that have a high electrical charge to them are slowed.
• Therefore:
– The BBB is selectively permeable to :Oxygen, Carbon dioxide and
glucose
– The BBB is not permeable to
hydrogen ions

80. Function of CSF
• Maintenance of a constant external
environment for neurons and glia
• Mechanical cushion to protect the brain and
provide buoyancy to the heavy brain (1400
g)
• Serves as a lymphatic system and a conduit
for neuropeptides
• pH of CSF regulates pulmonary ventilation
and CBF

83. Pineal
Area Postrema
organum
vasculosum of the
lamina terminalis
Posterior Pituitory
Subfornical organs
subcommissural organ

87. 87