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{{BioPsy}}
 
{{BioPsy}}
'''Cerebrospinal fluid''' ('''CSF'''), ''Liquor cerebrospinalis'', is a clear [[bodily fluid]] that occupies the [[subarachnoid space]] in the [[brain]] (the space between the [[skull]] and the [[cerebral cortex]]—more specifically, between the [[arachnoid (brain)|arachnoid]] and [[pia mater|pia]] layers of the [[meninges]]). It is a very pure [[Saline (medicine)|saline]] solution with [[microglia]] and acts as a "cushion" or buffer for the cortex.
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'''Cerebrospinal fluid''' ('''CSF'''), ''Liquor cerebrospinalis'', is a clear [[bodily fluid]] that occupies the [[subarachnoid space]] and the [[ventricular system]] around and inside the [[brain]].
   
==Physiology==
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More specifically the CSF occupies the space between the [[arachnoid mater]] (the middle layer of the brain cover, [[meninges]]) and the [[pia mater]] (the layer of the meninges closest to the brain). Moreover it constitutes the content of all intra-cerebral (inside the brain, cerebrum) ventricles, cisterns and sulci (singular sulcus), as well as the [[central canal]] of the [[spinal cord]].
[[Image:CSFposter1p.jpg|thumb|300px|right|Cerebrospinal fluid (CSF) at glance.]]
 
Cerebrospinal fluid also occupies the [[ventricular system]] of the brain and the [[spinal cord]]. It is a prime example of the separation of brain function from the rest of the body, as all CSF is generated locally in the brain. It is produced by the [[choroid plexus]] which is formed by specialized ependymal cells. The [[choroid plexus]] enter the lateral ventricles through the choroid fissure, along the line of the fimbria/fornix, and the third and fourth ventricle through their roofs. The CSF formed by the choroid plexuses in the ventricles, circulates through the [[interventricular foramina]] ('''foramen of Monro''') into the [[third ventricle]] and then via the [[mesencephalic duct]] (cerebral aqueduct) into the [[fourth ventricle]], whence it exits through two lateral apertures ([[foramina of Luschka]]) and one median aperture ([[foramen of Magendie]]). It then flows through the cerebromedullary cistern down the spinal cord and over the cerebral hemispheres.
 
   
CSF returns to the vascular system primarily along the olfactory tracts and into the lymphatic channels of the nasal mucosa. CSF also drains along cranial and spinal nerve roots. At high intercranial pressures CSF flows into the [[venous system]] by the [[arachnoid granulations]]. <ref>A. Zakharov et al. "Lymphatic cerebrospinal fluid absorption pathways in neonatal sheep revealed by subarachnoid injection of Microfil". Neuropathology and Applied Neurobiology (29):563-573 </ref>
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It is an approximately [[isotonic]] solution and acts as a "cushion" or buffer for the cortex, providing also a basic mechanical and [[immunological]] protection to the brain inside the [[skull]].
   
The cerebrospinal fluid is produced by the ventricles (mostly the lateral ventricles) at a rate of 500 ml/day. Since the volume that may be contained by the brain is of 150 ml, it is frequently replaced (3-4 times per day turnover), exceeding amounts getting into the blood. This continuous flow through the ventricular system into the subarachnoid space and finally exiting into the venous system provides somewhat of a "sink" that reduces the concentration of larger, lipoinsoluble molecules penetrating into the brain and CSF. (Saunders et al., 1999)
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[[Image:CSFposter1p.png|thumb|300px|right|Cerebrospinal fluid (CSF) at glance.]]
   
The CSF contains approximately 0.3% plasma proteins, also being 15 to 40 mg/dL, depending on sampling site. (Felgenhauer, 1974)
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==Circulation==
  +
It is produced in the brain by modified [[ependymal cells]] in the [[choroid plexus]]. It circulates from the choroid plexus through the [[interventricular foramina]] ('''foramen of Monro''') into the [[third ventricle]], and then through the [[mesencephalic duct]] (cerebral aqueduct) into the [[fourth ventricle]], where it exits through two lateral apertures ([[foramina of Luschka]]) and one median aperture ([[foramen of Magendie]]). It then flows through the cerebromedullary cistern down the spinal cord and over the cerebral hemispheres.
   
==Pathology==
+
Traditionally, it has been thought that CSF returns to the vascular system by entering the [[dural venous sinuses]] via the [[arachnoid granulations]]. However, some<ref name="pmid14636163">{{cite journal |author=Zakharov A, Papaiconomou C, Djenic J, Midha R, Johnston M |title=Lymphatic cerebrospinal fluid absorption pathways in neonatal sheep revealed by subarachnoid injection of Microfil |journal=Neuropathol. Appl. Neurobiol. |volume=29 |issue=6 |pages=563-73 |year=2003 |pmid=14636163 |doi=}} </ref> have suggested that CSF flow along the [[cranial nerves]] and spinal nerve roots allow it into the lymphatic channels; this flow may play a substantial role in CSF reabsorbtion, particularly in the [[neonate]], in which arachnoid granulations are sparsely distributed.
   
The cerebrospinal fluid has many putative roles including mechanical protection of the brain, distribution of [[neuroendocrine]] factors, and facilitation of pulsatile [[cerebral blood flow]]. Understanding cardiovascular dynamics is valuable as the flow pattern of arterial blood must be tightly regulated within the brain in order to ensure consistent brain [[oxygenation]]. CSF movement allows arterial expansion and contraction by acting like a spring, which prevents wide changes in intracranial blood flow. When disorders of CSF flow occur, they may therefore impact not only CSF movement, but also the intracranial blood flow, with subsequent neuronal and glial vulnerabilities. The venous system is also important in this equation. Infants and patients shunted as small children may have particularly unexpected relationships between pressure and ventricular size, possibly due in part to venous pressure dynamics. This may have significant treatment implications but the underlying pathophysiology needs to be further explored.
+
==Amount and constitution==
  +
The cerebrospinal fluid is produced at a rate of 500 ml/day. Since the brain can only contain from 135-150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the [[superior_sagittal_sinus|superior sagittal sinus]]. This continuous flow into the venous system dilutes the concentration of larger, lipoinsoluble molecules penetrating the brain and CSF. <ref name="pmid10027064">{{cite journal |author=Saunders NR, Habgood MD, Dziegielewska KM |title=Barrier mechanisms in the brain, I. Adult brain |journal=Clin. Exp. Pharmacol. Physiol. |volume=26 |issue=1 |pages=11-9 |year=1999 |pmid=10027064 |doi=}}</ref>
  +
  +
The CSF contains approximately 0.3% plasma proteins, or 15 to 40 mg/dL, depending on sampling site. <ref name="pmid4456012">{{cite journal |author=Felgenhauer K |title=Protein size and cerebrospinal fluid composition |journal=Klin. Wochenschr. |volume=52 |issue=24 |pages=1158-64 |year=1974 |pmid=4456012 |doi=}}</ref>
  +
CSF pressure ranges from 60 - 100 mmH2O or 4.4 - 7.3 mmHg, with most variations due to coughing or internal compression of jugular veins in the neck.
  +
  +
==Function==
  +
The cerebrospinal fluid has many putative roles including mechanical protection of the brain, distribution of [[neuroendocrine]] factors and prevention of brain [[ischemia]]. The prevention of brain ischemia is made by decreasing the amount of cerebrospinal fluid in the limited space inside the [[skull]]. This decreases total intracranial pressure and facilitates for blood perfusion.
  +
  +
==Pathology==
  +
When CSF pressure is elevated, [[cerebral blood flow]] may be constricted. When disorders of CSF flow occur, they may therefore affect not only CSF movement, but also the intracranial blood flow, with subsequent neuronal and glial vulnerabilities. The venous system is also important in this equation. Infants and patients shunted as small children may have particularly unexpected relationships between pressure and ventricular size, possibly due in part to venous pressure dynamics. This may have significant treatment implications but the underlying pathophysiology needs to be further explored.
   
 
CSF connections with the [[lymphatic system]] have been demonstrated in several [[mammal]]ian systems. Preliminary data suggest that these CSF-lymph connections form around the time that the CSF secretory capacity of the [[choroid plexus]] is developing (in [[uterus|utero]]). There may be some relationship between CSF disorders, including [[hydrocephalus]] and impaired CSF lymphatic transport.
 
CSF connections with the [[lymphatic system]] have been demonstrated in several [[mammal]]ian systems. Preliminary data suggest that these CSF-lymph connections form around the time that the CSF secretory capacity of the [[choroid plexus]] is developing (in [[uterus|utero]]). There may be some relationship between CSF disorders, including [[hydrocephalus]] and impaired CSF lymphatic transport.
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Cerebrospinal fluid can be tested for the diagnosis of a variety of [[neurological disease]]s. It is usually obtained by a procedure called [[lumbar puncture]] in an attempt to count the cells in the fluid and to detect the levels of protein and glucose. These parameters alone may be extremely beneficial in the diagnosis of [[subarachnoid hemorrhage]] and [[central nervous system]] infections (such as [[meningitis]]). Moreover, a cerebrospinal fluid [[Microbiological culture|culture]] examination may yield the [[microorganism]] that has caused the infection. By using more sophisticated methods, such as the detection of the [[oligoclonal bands]], an ongoing inflammatory condition (for example, [[multiple sclerosis]]) can be recognized. A [[beta-2 transferrin]] assay is highly specific and sensitive for the detection for e.g. cerebrospinal fluid leakage.
 
Cerebrospinal fluid can be tested for the diagnosis of a variety of [[neurological disease]]s. It is usually obtained by a procedure called [[lumbar puncture]] in an attempt to count the cells in the fluid and to detect the levels of protein and glucose. These parameters alone may be extremely beneficial in the diagnosis of [[subarachnoid hemorrhage]] and [[central nervous system]] infections (such as [[meningitis]]). Moreover, a cerebrospinal fluid [[Microbiological culture|culture]] examination may yield the [[microorganism]] that has caused the infection. By using more sophisticated methods, such as the detection of the [[oligoclonal bands]], an ongoing inflammatory condition (for example, [[multiple sclerosis]]) can be recognized. A [[beta-2 transferrin]] assay is highly specific and sensitive for the detection for e.g. cerebrospinal fluid leakage.
   
Lumbar puncture can also be performed to measure the [[intracranial pressure]], which might be increased in certain types of [[hydrocephalus]].
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Lumbar puncture can also be performed to measure the [[intracranial pressure]], which might be increased in certain types of [[hydrocephalus]]. However a lumbar puncture should never be performed if increased intracranial pressure is suspected because it could lead to [[brain herniation]].
   
This fluid has an importance in anethesology. [[Baricity]] refers to the density of a substance compared to the density of human cerebral spinal fluid. Baricity is used in [[anesthesia]] to determine the manner in which a particular drug will spread in the [[intrathecal]] space.
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This fluid has an importance in anethesiology. [[Baricity]] refers to the density of a substance compared to the density of human cerebral spinal fluid. Baricity is used in [[anesthesia]] to determine the manner in which a particular drug will spread in the [[intrathecal]] space.
   
  +
==See also==
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*[[Blood brian barrier]]
   
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== References ==
== Notes ==
 
 
<references/>
 
<references/>
   
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[[Category:Central nervous system]]
 
[[Category:Central nervous system]]
 
[[Category:Neurology]]
 
[[Category:Neurology]]
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[[he:נוזל מוחי שדרתי]]
 
[[he:נוזל מוחי שדרתי]]
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[[hu:Agy-gerincvelői folyadék]]
 
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[[ja:脳脊髄液]]

Revision as of 22:41, January 21, 2008

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Cerebrospinal fluid (CSF), Liquor cerebrospinalis, is a clear bodily fluid that occupies the subarachnoid space and the ventricular system around and inside the brain.

More specifically the CSF occupies the space between the arachnoid mater (the middle layer of the brain cover, meninges) and the pia mater (the layer of the meninges closest to the brain). Moreover it constitutes the content of all intra-cerebral (inside the brain, cerebrum) ventricles, cisterns and sulci (singular sulcus), as well as the central canal of the spinal cord.

It is an approximately isotonic solution and acts as a "cushion" or buffer for the cortex, providing also a basic mechanical and immunological protection to the brain inside the skull.

File:CSFposter1p.png

Circulation

It is produced in the brain by modified ependymal cells in the choroid plexus. It circulates from the choroid plexus through the interventricular foramina (foramen of Monro) into the third ventricle, and then through the mesencephalic duct (cerebral aqueduct) into the fourth ventricle, where it exits through two lateral apertures (foramina of Luschka) and one median aperture (foramen of Magendie). It then flows through the cerebromedullary cistern down the spinal cord and over the cerebral hemispheres.

Traditionally, it has been thought that CSF returns to the vascular system by entering the dural venous sinuses via the arachnoid granulations. However, some[1] have suggested that CSF flow along the cranial nerves and spinal nerve roots allow it into the lymphatic channels; this flow may play a substantial role in CSF reabsorbtion, particularly in the neonate, in which arachnoid granulations are sparsely distributed.

Amount and constitution

The cerebrospinal fluid is produced at a rate of 500 ml/day. Since the brain can only contain from 135-150 ml, large amounts are drained primarily into the blood through arachnoid granulations in the superior sagittal sinus. This continuous flow into the venous system dilutes the concentration of larger, lipoinsoluble molecules penetrating the brain and CSF. [2]

The CSF contains approximately 0.3% plasma proteins, or 15 to 40 mg/dL, depending on sampling site. [3] CSF pressure ranges from 60 - 100 mmH2O or 4.4 - 7.3 mmHg, with most variations due to coughing or internal compression of jugular veins in the neck.

Function

The cerebrospinal fluid has many putative roles including mechanical protection of the brain, distribution of neuroendocrine factors and prevention of brain ischemia. The prevention of brain ischemia is made by decreasing the amount of cerebrospinal fluid in the limited space inside the skull. This decreases total intracranial pressure and facilitates for blood perfusion.

Pathology

When CSF pressure is elevated, cerebral blood flow may be constricted. When disorders of CSF flow occur, they may therefore affect not only CSF movement, but also the intracranial blood flow, with subsequent neuronal and glial vulnerabilities. The venous system is also important in this equation. Infants and patients shunted as small children may have particularly unexpected relationships between pressure and ventricular size, possibly due in part to venous pressure dynamics. This may have significant treatment implications but the underlying pathophysiology needs to be further explored.

CSF connections with the lymphatic system have been demonstrated in several mammalian systems. Preliminary data suggest that these CSF-lymph connections form around the time that the CSF secretory capacity of the choroid plexus is developing (in utero). There may be some relationship between CSF disorders, including hydrocephalus and impaired CSF lymphatic transport.

Diagnosis and therapy

Cerebrospinal fluid can be tested for the diagnosis of a variety of neurological diseases. It is usually obtained by a procedure called lumbar puncture in an attempt to count the cells in the fluid and to detect the levels of protein and glucose. These parameters alone may be extremely beneficial in the diagnosis of subarachnoid hemorrhage and central nervous system infections (such as meningitis). Moreover, a cerebrospinal fluid culture examination may yield the microorganism that has caused the infection. By using more sophisticated methods, such as the detection of the oligoclonal bands, an ongoing inflammatory condition (for example, multiple sclerosis) can be recognized. A beta-2 transferrin assay is highly specific and sensitive for the detection for e.g. cerebrospinal fluid leakage.

Lumbar puncture can also be performed to measure the intracranial pressure, which might be increased in certain types of hydrocephalus. However a lumbar puncture should never be performed if increased intracranial pressure is suspected because it could lead to brain herniation.

This fluid has an importance in anethesiology. Baricity refers to the density of a substance compared to the density of human cerebral spinal fluid. Baricity is used in anesthesia to determine the manner in which a particular drug will spread in the intrathecal space.

See also

References

  1. Zakharov A, Papaiconomou C, Djenic J, Midha R, Johnston M (2003). Lymphatic cerebrospinal fluid absorption pathways in neonatal sheep revealed by subarachnoid injection of Microfil. Neuropathol. Appl. Neurobiol. 29 (6): 563-73.
  2. Saunders NR, Habgood MD, Dziegielewska KM (1999). Barrier mechanisms in the brain, I. Adult brain. Clin. Exp. Pharmacol. Physiol. 26 (1): 11-9.
  3. Felgenhauer K (1974). Protein size and cerebrospinal fluid composition. Klin. Wochenschr. 52 (24): 1158-64.


Meninges of the brain and medulla spinalis

Dura mater - Falx cerebri - Tentorium cerebelli - Falx cerebelli - Arachnoid mater - Subarachnoid space - Cistern - Cisterna magna - Median aperture - Cerebrospinal fluid - Arachnoid granulation - Pia mater



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