Cerebrospinal fluid

This is a good article. Click here for more information.
Source: Wikipedia, the free encyclopedia.

This article uses anatomical terminology.
Cerebrospinal fluid
subarachnoid space around the brain and spinal cord, and in the ventricles of the brain.
Image showing the location of CSF highlighting the brain's ventricular system
Details
Identifiers
Latinliquor cerebrospinalis
Acronym(s)CSF
MeSHD002555
TA98A14.1.01.203
TA25388
Anatomical terminology]

Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates.

CSF is produced by specialised

cerebral blood flow
.

CSF occupies the

subarachnoid space (between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord. It fills the ventricles of the brain, cisterns, and sulci, as well as the central canal of the spinal cord. There is also a connection from the subarachnoid space to the bony labyrinth of the inner ear via the perilymphatic duct where the perilymph is continuous with the cerebrospinal fluid. The ependymal cells of the choroid plexus have multiple motile cilia
on their apical surfaces that beat to move the CSF through the ventricles.

A sample of CSF can be taken from around the spinal cord via lumbar puncture. This can be used to test the intracranial pressure, as well as indicate diseases including infections of the brain or the surrounding meninges.

Although noted by Hippocrates, it was forgotten for centuries, though later was described in the 18th century by Emanuel Swedenborg. In 1914, Harvey Cushing demonstrated that CSF is secreted by the choroid plexus.

Structure

Circulation

MRI showing pulsation of CSF
Distribution of CSF

In humans, there is about 125–150 mL of CSF at any one time.

subarachnoid space through four openings – the central canal of the spinal cord, the median aperture, and the two lateral apertures.[1] CSF is present within the subarachnoid space, which covers the brain and spinal cord, and stretches below the end of the spinal cord to the sacrum.[1][2] There is a connection from the subarachnoid space to the bony labyrinth of the inner ear making the cerebrospinal fluid continuous with the perilymph in 93% of people.[3]

CSF moves in a single outward direction from the ventricles, but multidirectionally in the subarachnoid space.[3] Fluid movement is pulsatile, matching the pressure waves generated in blood vessels by the beating of the heart.[3] Some authors dispute this, posing that there is no unidirectional CSF circulation, but cardiac cycle-dependent bi-directional systolic-diastolic to-and-from cranio-spinal CSF movements.[4]

Contents

CSF is derived from blood plasma and is largely similar to it, except that CSF is nearly protein-free compared with plasma and has some different electrolyte levels. Due to the way it is produced, CSF has a lower chloride level than plasma, and a higher sodium level.[2][5]

CSF contains approximately 0.59% plasma proteins, or approximately 15 to 40 mg/dL, depending on sampling site.

venous system dilutes the concentration of larger, lipid-insoluble molecules penetrating the brain and CSF.[8] CSF is normally free of red blood cells and at most contains fewer than 5 white blood cells per mm3 (if the white cell count is higher than this it constitutes pleocytosis and can indicate inflammation or infection).[9]

Development

At around the fifth week of

neuropores of the neural tube close after the first month of development, and CSF pressure gradually increases.[3]

As the

rhombencephalon (hindbrain).[10] Subarachnoid spaces are first evident around the 32nd day of development near the rhombencephalon; circulation is visible from the 41st day.[3] At this time, the first choroid plexus can be seen, found in the fourth ventricle, although the time at which they first secrete CSF is not yet known.[3]

The developing forebrain surrounds the neural cord. As the forebrain develops, the neural cord within it becomes a ventricle, ultimately forming the lateral ventricles. Along the inner surface of both ventricles, the ventricular wall remains thin, and a choroid plexus develops, producing and releasing CSF.[10] CSF quickly fills the neural canal.[10] Arachnoid villi are formed around the 35th week of development, with arachnoid granulations noted around the 39th, and continuing developing until 18 months of age.[3]

The subcommissural organ secretes SCO-spondin, which forms Reissner's fiber within CSF assisting movement through the cerebral aqueduct. It is present in early intrauterine life but disappears during early development.[3]

Physiology

Function

CSF serves several purposes:

  1. Buoyancy: The actual mass of the human brain is about 1400–1500 grams, but its net weight suspended in CSF is equivalent to a mass of 25–50 g.[11][1] The brain therefore exists in neutral buoyancy, which allows the brain to maintain its density without being impaired by its own weight, which would cut off blood supply and kill neurons in the lower sections without CSF.[5]
  2. Protection: CSF protects the brain tissue from injury when jolted or hit, by providing a fluid buffer that acts as a shock absorber from some forms of mechanical injury.[1][5]
  3. Prevention of brain ischemia: The prevention of brain ischemia is aided by decreasing the amount of CSF in the limited space inside the skull. This decreases total intracranial pressure and facilitates blood perfusion.[1]
  4. Regulation: CSF allows for the
    neuroendocrine factors, to which slight changes can cause problems or damage to the nervous system. For example, high glycine concentration disrupts temperature and blood pressure control, and high CSF pH causes dizziness and fainting.[5]
  5. Clearing waste: CSF allows for the removal of waste products from the brain,
    motor neuron disease.[14][15]

Production

Comparison of serum and cerebrospinal fluid
Substance CSF Serum
Water content (% wt) 99 93
Protein (mg/dL) 35 7000
Glucose (mg/dL) 60 90
Osmolarity (mOsm/L) 295 295
Sodium (mEq/L) 138 138
Potassium (mEq/L) 2.8 4.5
Calcium (mEq/L) 2.1 4.8
Magnesium (mEq/L) 2.0–2.5[16] 1.7
Chloride (mEq/L) 119 102
pH 7.33 7.41
Further information: List of reference ranges
for cerebrospinal fluid

The brain produces roughly 500 mL of cerebrospinal fluid per day at a rate of about 20 mL an hour.

transcellular fluid is constantly reabsorbed, so that only 125–150 mL is present at any one time.[1]

CSF volume is higher on a mL per kg body weight basis in children compared to adults. Infants have a CSF volume of 4 mL/kg, children have a CSF volume of 3 mL/kg, and adults have a CSF volume of 1.5–2 mL/kg. A high CSF volume is why a larger dose of local anesthetic, on a mL/kg basis, is needed in infants.[18] Additionally, the larger CSF volume may be one reason as to why children have lower rates of postdural puncture headache.[19]

Most (about two-thirds to 80%) of CSF is produced by the

subarachnoid space; and a small amount directly from the tiny spaces surrounding blood vessels around the brain.[2]

CSF is produced by the choroid plexus in two steps. Firstly, a filtered form of

tight junctions between cells, which act to prevent most substances flowing freely into CSF.[21] Cilia on the apical surfaces of the ependymal cells beat to help transport the CSF.[22]

hydrogen ions. These are exchanged for sodium and chloride on the cell surface facing the interstitium.[3] Sodium, chloride, bicarbonate and potassium are then actively secreted into the ventricular lumen.[2][3] This creates osmotic pressure and draws water into CSF,[2] facilitated by aquaporins.[3] CSF contains many fewer protein anions than blood plasma. Protein in the blood is primarily composed of anions where each anion has many negative charges on it.[23]
As a result, to maintain
Na/K ATPase found on the surface of the choroid endothelium, appears to play a role in regulating CSF secretion and composition.[3][1]
It has been hypothesised that CSF is not primarily produced by the choroid plexus, but is being permanently produced inside the entire CSF system, as a consequence of water filtration through the capillary walls into the interstitial fluid of the surrounding brain tissue, regulated by
AQP-4.[4]

There are circadian variations in CSF secretion, with the mechanisms not fully understood, but potentially relating to differences in the activation of the autonomic nervous system over the course of the day.[3]

Choroid plexus of the lateral ventricle produces CSF from the arterial blood provided by the anterior choroidal artery.[25] In the fourth ventricle, CSF is produced from the arterial blood from the anterior inferior cerebellar artery (cerebellopontine angle and the adjacent part of the lateral recess), the posterior inferior cerebellar artery (roof and median opening), and the superior cerebellar artery.[26]

Reabsorption

CSF returns to the vascular system by entering the

neonate.[3] CSF turns over at a rate of three to four times a day.[2] CSF has also been seen to be reabsorbed through the sheathes of cranial and spinal nerve sheathes, and through the ependyma.[3]

Regulation

The composition and rate of CSF generation are influenced by hormones and the content and pressure of blood and CSF.

Na-K-Cl cotransporter) have the potential to impact membrane channels.[3]

Clinical significance

Pressure

Further information: Cerebral shunt

CSF pressure, as measured by

cmH2O (4.4–7.3 mmHg or 0.78–0.98 kPa). Most variations are due to coughing or internal compression of jugular veins in the neck. When lying down, the CSF pressure as estimated by lumbar puncture is similar to the intracranial pressure
.

ventriculo-peritoneal shunt, which diverts fluid to another part of the body.[29][30]

obese women.[29] Management may include ceasing any known causes, a carbonic anhydrase inhibitor such as acetazolamide, repeated drainage via lumbar puncture, or the insertion of a shunt such as a ventriculo-peritoneal shunt.[29]

CSF leak

Main article: Cerebrospinal fluid leak

CSF can leak from the

spinal surgery, or fibrin glue.[33]

Lumbar puncture

Vials containing human cerebrospinal fluid
Main article: Lumbar puncture

CSF can be tested for the diagnosis of a variety of

neurological diseases, usually obtained by a procedure called lumbar puncture.[34] Lumbar puncture is carried out under sterile conditions by inserting a needle into the subarachnoid space, usually between the third and fourth lumbar vertebrae. CSF is extracted through the needle, and tested.[32] About one third of people experience a headache after lumbar puncture,[32] and pain or discomfort at the needle entry site is common. Rarer complications may include bruising, meningitis or ongoing post lumbar-puncture leakage of CSF.[1]

Testing often includes observing the colour of the fluid, measuring CSF pressure, and counting and identifying

autoimmune conditions.[1] A lumbar puncture that drains CSF may also be used as part of treatment for some conditions, including idiopathic intracranial hypertension and normal pressure hydrocephalus.[1]

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 due to certain situations such as a tumour, because it can lead to fatal brain herniation.[32]

Anaesthesia and chemotherapy

See also:
Blood–cerebrospinal fluid barrier

Some

intrathecal space.[35]

Liquorpheresis is the process of filtering the CSF in order to clear it from endogen or exogen pathogens.

History

Various comments by ancient physicians have been read as referring to CSF. Hippocrates discussed "water" surrounding the brain when describing congenital hydrocephalus, and Galen referred to "excremental liquid" in the ventricles of the brain, which he believed was purged into the nose. But for some 16 intervening centuries of ongoing anatomical study, CSF remained unmentioned in the literature. This is perhaps because of the prevailing autopsy technique, which involved cutting off the head, thereby removing evidence of CSF before the brain was examined.[37]

The modern rediscovery of CSF is credited to Emanuel Swedenborg. In a manuscript written between 1741 and 1744, unpublished in his lifetime, Swedenborg referred to CSF as "spirituous lymph" secreted from the roof of the fourth ventricle down to the medulla oblongata and spinal cord. This manuscript was eventually published in translation in 1887.[37]

Albrecht von Haller, a Swiss physician and physiologist, made note in his 1747 book on physiology that the "water" in the brain was secreted into the ventricles and absorbed in the veins, and when secreted in excess, could lead to hydrocephalus.[37] François Magendie studied the properties of CSF by vivisection. He discovered the foramen Magendie, the opening in the roof of the fourth ventricle, but mistakenly believed that CSF was secreted by the pia mater.[37]

Thomas Willis (noted as the discoverer of the circle of Willis) made note of the fact that the consistency of CSF is altered in meningitis.[37] In 1869 Gustav Schwalbe proposed that CSF drainage could occur via lymphatic vessels.[1]

In 1891,

Harvey W. Cushing published conclusive evidence that CSF is secreted by the choroid plexus.[37]

Other animals

During

Teleostei fish, which do not have a subarachnoid space, is contained within the ventricles of their brains.[3] In mammals, where a subarachnoid space is present, CSF is present in it.[3] Absorption of CSF is seen in amniotes and more complex species, and as species become progressively more complex, the system of absorption becomes progressively more enhanced, and the role of spinal epidural veins in absorption plays a progressively smaller and smaller role.[3]

The amount of cerebrospinal fluid varies by size and species.[38] In humans and other mammals, cerebrospinal fluid turns over at a rate of 3–5 times a day.[38] Problems with CSF circulation, leading to hydrocephalus, can occur in other animals as well as humans.[38]

See also

References

  1. ^
    S2CID 2563483
    .
  2. ^
    ISBN 978-0-7216-0240-0
    .
  3. ^
    PMID 22100360
    .
  4. ^
    PMID 25089184
    .
  5. ^ a b c d e Saladin K (2012). Anatomy and Physiology (6th ed.). McGraw Hill. pp. 519–20.
  6. S2CID 19776406
    .
  7. PMID 6162199
    .
  8. S2CID 34773752
    .
  9. PMID 21250239
    .
  10. ^
    ISBN 978-0-443-06811-9.[page needed
    ]
  11. ISBN 978-1-58829-040-3
    .
  12. PMID 22896675
    .
  13. ^ Ropper, Allan H.; Brown, Robert H. (March 29, 2005). "Chapter 30". Adams and Victor's Principles of Neurology (8th ed.). McGraw-Hill Professional. p. 530.
  14. PMID 33094283
    .
  15. PMID 32819425
    .
  16. ISBN 9781416029083
    . Retrieved 14 April 2018 – via Google Books.
  17. ^
    PMID 37239132
    .
  18. ISSN 0003-2999
    .
  19. S2CID 20716137
    .
  20. ISBN 978-0-7817-5319-7
    .
  21. ISBN 978-1-4160-4574-8
    .
  22. PMID 22101065
    .
  23. PMID 12665532
    . Retrieved 18 August 2023.
  24. ^ Venturi S, Venturi M (2014). "Iodine, PUFAs and Iodolipids in Health and Disease: An Evolutionary Perspective". Human Evolution. 29 (1–3): 185–205.
  25. PMID 18828104
    .
  26. PMID 16228955
    .
  27. PMID 15624320
    .
  28. ^ Agamanolis D (May 2011). "Chapter 14 – Cerebrospinal Fluid :THE NORMAL CSF". Neuropathology. Northeast Ohio Medical University. Retrieved 2014-12-25.
  29. ^
    ISBN 978-0-7020-3084-0
    .
  30. ^ a b c d e "Hydrocephalus Fact Sheet". www.ninds.nih.gov. National Institute of Neurological Disorders and Stroke. Retrieved 19 May 2017.
  31. ^
    ISBN 978-0-07-180215-4
    .
  32. ^
    ISBN 978-0-7020-3084-0
    .
  33. ^
    PMID 15376362
    .
  34. ^
    PMID 14524396. Archived from the original
    on 2008-05-15. Retrieved 2009-03-05.
  35. ^
    PMID 15220175
    .
  36. ^ "Intrathecal Chemotherapy for Cancer Treatment | CTCA". CancerCenter.com. Archived from the original on 1 January 2018. Retrieved 22 May 2017.
  37. ^
    PMID 12956452
    .
  38. ^
    ISBN 978-1-118-68589-1
    .

External links

Wikimedia Commons has media related to Cerebrospinal fluid.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Cerebrospinal_fluid&oldid=1216493839"