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You are watching: Which of the following is not a function of cerebrospinal fluid (csf)?

StatPearls . Treasure Island (FL): StatPearls Publishing; 2021 Jan-.


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Introduction

Cerebrospinal liquid (CSF) is an ultrafiltrate the plasma consisted of within the ventricles that the mind and the subarachnoid spaces that the cranium and also spine.<1> It performs an essential functions, including offering nourishment, waste removal, and protection come the brain.<2> Adult CSF volume is approximated to it is in 150 ml, v a distribution of 125 ml within the subarachnoid spaces and 25 ml in ~ the ventricles. CSF is primarily secreted through the choroid plexus with other sources playing a an ext poorly defined role. In the adult population, its cheap varies in between individuals, usually varying from 400 to 600 ml every day. The continuous secretion that CSF contributes to finish CSF renewal 4 to five times every 24-hour period in the mean young adult. The palliation of CSF turnover may add to the buildup of metabolites seen in aging and neurodegenerative diseases. The composition of CSF is strictly regulated, and also any variation have the right to be valuable for diagnostic purposes.<1>


Cellular

Seventy to eighty percent of CSF production is via a network of modified ependymal cells recognized as the choroid plexus (CP).<1> The CP is a very specialized, simple, cuboidal epithelium constant with ependymal cell lining the ventricles of the brain. This an easy cuboidal epithelium surrounds clusters of fenestrated capillaries enabling for the filtration that plasma.<3> CP cell have dense microvilli present on their apical surface. They space interconnected via tight junctions, creating a blood-CSF obstacle that helps control the composition of CSF.<1>

As there is no appreciable barrier between the CSF and also the extracellular room of the brain (ECSB), the blood-CSF barrier additionally serves to control the environment of the brain.<2> Larger building materials such together cells, protein, and glucose are not allowed passage, whereas ion and little molecules such as vitamins and nutrients deserve to pass right into the CSF reasonably easily.<4> Water is enabled passage v the CP epithelium via epithelial AQP1 channels. Building material that might not pass v the blood-CSF barrier, however are required by the brain can be proactively synthesized through or proactively transported v the CP epithelial cells into the CSF. A 5-mV lumen confident voltage potential is present throughout CP epithelial cell membranes. This electric potential difference pulls sodium, chloride, and bicarbonate ions from the plasma right into the CSF, creating an osmotic gradient which climate drives the movement of water into the CSF.<3> 

When contrasted to plasma, CSF has actually a higher concentration the sodium, chloride, and also magnesium, however a lower concentration of potassium and calcium.<1> Unlike plasma, CSF has only trace quantities of cells, protein, and also immunoglobulins.<2> No cells can pass with the blood-CSF barrier, although small numbers that white blood cells are usually presented to the CSF indirectly. The normal cell counting of CSF is normally lower than 5 cells/ml.<1> Despite alters in blood composition and also flow, the composition of CSF is preserved constant, which offers a secure intraventricular environment, critical for maintaining normal neuronal function.<3>


Function

CSF assists the mind by providing protection, nourishment, and waste removal. CSF provides hydromechanical defense of the neuroaxis through two mechanisms. First, CSF acts together a shock absorber, cushioning the mind against the skull. Second, CSF allows the brain and spinal cord to end up being buoyant, reducing the efficient weight that the mind from its common 1,500 grams to a lot lesser 50 grams. The reduction in load lessens the force used to the brain parenchyma and also cerebral vessels throughout mechanical injury. Another function of CSF is to keep homeostasis the the interstitial liquid of the brain. A stable atmosphere for brain parenchyma is command for maintaining normal neuronal function. 

The significant conduit the nutrient supply to the mind is the CP-CSF-ECSB nexus. Substrates essential by the mind are transported native the blood, v the CP, into the CSF, and then diffuse right into the ECSB for transportation to your sites of activity within the brain. CSF additionally assists in the removal of mind metabolism rubbish products, such as peroxidation products, glycosylated proteins, excess neurotransmitters, debris from the lining that the ventricles, bacteria, viruses, and otherwise unnecessary molecules. Accumulation of together unnecessary molecules, watched in aging and also some neurodegenerative diseases, interferes through neuronal work of the brain. The disruption of cerebral physiology competent with the disruption of the hydrodynamics or ingredient of CSF suggests the importance of CSF functioning.<1><2><3>


Mechanism

CSF is repetitively secreted through an unchanging composition, to work to preserve a stable setting within the brain.<3> CSF is moved along the neuroaxis indigenous the site of secretion to the website of absorption, mainly by the rhythmic systolic pulse wave within the choroidal arteries. Lesser components of CSF circulation are frequency the respiration, posture, venous press of the jugular vein, the physical effort of the individual, and also time that day.<2>

CSF is secreted by the CPs located within the ventricles that the brain, v the two lateral ventricles being the primary producers. CSF operation throughout the ventricular device unidirectionally in a rostral to caudal manner. CSF produced in the lateral ventricles travel v the interventricular foramina come the 3rd ventricle, with the cerebral aqueduct to the 4th ventricle, and also then through the mean aperture (also well-known as the foramen that Magendie) right into the subarachnoid an are at the basic of the brain. Once in the subarachnoid space, the CSF starts to have a gentle multidirectional circulation that creates an equalization that composition transparent the CSF. The CSF flows end the surface ar of the brain and under the size of the spinal cord while in the subarachnoid space. It leaves the subarachnoid an are through arachnoid villi uncovered along the premium sagittal venous sinus, intracranial venous sinuses, and around the roots of spinal nerves.

Arachnoid villi space protrusions that arachnoid mater v the dura mater into the lumen the a venous sinus. A 3 to 5 mmHg press gradient in between the subarachnoid an are and venous sinus pulls CSF into the venous outflow system through the arachnoid villi that help in its absorption. CSF may additionally enter right into the lymphatic mechanism via the nasal cribriform plate or spinal nerve roots. The clearance of CSF is dependent ~ above the attitude of the individual, push differentials, and pathophysiology.<1><2>


Related Testing

Lumbar puncture (LP), likewise known together a spinal tap, is a frequently performed invasive procedure in i m sorry CSF is removed from the subarachnoid space. LP is supplied in the measure of intracranial pressure and the sampling of CSF. It is generally indicated in the testimonial of acute headaches and also infections of the central nervous system. During one LP, the patience is inserted in the lateral recumbent position. A sterile spinal needle is then slowly inserted between vertebrae, generally at the level of L3/4 or L4/5, right into the subarachnoid space. Needle insertion may be guided through fluoroscopy or ultrasound to improve success rates and reduce the incidence of trauma. 

Once CSF starts to flow through the needle, the is collected serially into 4 sterile tubes. As soon as collected, CSF deserve to be analyzed for abnormally present or elevated CSF components, aiding in diagnosis. Because that example, the visibility of xanthochromia, a yellow-orange discoloration the CSF caused by red blood cabinet degeneration, indicates the opportunity of a subarachnoid hemorrhage. Elevation in concentrations of immunoglobulins, termed oligoclonal bands, may show the existence of a systemic infection or an autoimmune disease.

Contraindications of LP incorporate raised intracranial pressure, bleeding disorders, and also local skin infection. The procedure is fairly safe with hardly ever serious complications. Complications that LP incorporate infection, bleeding, radicular pain, or cerebral herniation. The most usual complication is a post-LP headache v symptoms start within 24 hours of the procedure and also often solving by work 10.<5><6>


Clinical Significance

Hydrocephalus is a pathological problem in i m sorry CSF abnormally accumulates due to increased CSF production, blockage that flow, or lessened absorption. The ventricles distend to accommodate elevated CSF volumes, perhaps causing damages to the brain by pushing its tissue versus the boney skull. Hydrocephalus might be congenital or acquired. Blocked CSF circulation throughout the ventricles is classified as non-communicating, or obstructive, hydrocephalus. The blockage is frequently a fixed such as a tumor or one abscess situated within a foramen. Because CSF secretion is constant, obstruction of circulation will bring about CSF build up in former of the blockage. For example, stenosis of the cerebral aqueduct, among the most common causes of obstructive hydrocephalus, leader to enlargement the both lateral ventricles and the third ventricle. If the flow of CSF i do not care obstructed exterior the ventricles, in either the subarachnoid an are or website of absorption, the classifies together communicating, or non-obstructive, hydrocephalus. 

Hydrocephalus have the right to be brought about by hereditary defects, infections, bleeding in the brain, trauma, or CNS tumors. Symptoms incorporate headaches, convulsions, nausea, vomiting, disturbances the vision, and mental deterioration. The diagnosis is established through imaging approaches such together ultrasound, computed tomogram (CT), or magnetic resonance imaging (MRI) scans. The most typical treatment is shunt insertion, which diverts CSF away from the ventricles come an area the the body whereby it have the right to be soaked up into circulation. Endoscopic third ventriculostomy, a procedure in which a feet is created in the floor that the third ventricle allowing CSF to bypass one obstruction, and cauterization of CP sections which decreases CSF production are various other treatment options.  If left untreated, hydrocephalus returns a risk of cognitive disturbances, physical disturbances, and also death.<7><8>

CSF Leak is a problem in which CSF is able to escape indigenous the subarachnoid room through a feet in the neighboring dura. The volume that CSF lost in a leak varies, ranging from minute to very substantial amounts. If the ns of CSF is good enough, voluntarily intracranial hypotension (SIH) may occur. SIH most frequently presents with a positional headache resulted in by downward displacement that the brain due come loss the buoyancy previously listed by the CSF. Posterior neck stiffness, nausea, and also vomiting are additionally common symptoms. The incidence that SIH is estimated to it is in 5/100,000 annually. Women are twice as likely to be affected and have a peak period at roughly 40 years.

Diagnosis is aided by typical MRI findings, such as an increase of intracranial venous volume, pituitary hyperemia, enhanced pachymeninges, and also descent that the brain. Many instances of SIH resolve without treatment. Conservative ideologies such as bed rest, hydration, and also increased caffeine input may additionally be effective; however, more drastic measures might be necessary. One epidural blood patch, wherein blood is injected into the spinal epidural space, might relieve CSF hypovolemic symptoms by replacing shed CSF volume with blood volume. Surgical repair of the CSF leak via a suture or metal aneurysm clip is relatively safe and also effective in giving relief.<9>

Meningitis is a condition in i m sorry the coverings the the brain become inflamed. There are two divide of meningitis: aseptic and also bacterial. Aseptic meningitis can an outcome from agents such as fungi, medications, and cancer metastasis, but viruses reason the bulk of aseptic meningitis cases. Fever, nuchal rigidity, and also photophobia room classically presenting symptoms. Diagnosis is via an analysis of CSF acquired through LP. Famous PCR analysis of CSF is advantageous in diagnosing famous meningitis. Therapy is regularly supportive, managing fever and pain. Bacter meningitis has actually a much lower incidence 보다 aseptic meningitis, but is more serious. However, the incidence of bacterial meningitis has actually substantially dropped due to routine vaccination.

Symptoms are comparable to aseptic meningitis, but clinical presentation is much more severe. Additional symptoms include altered mental status, seizures, and focal neurologic signs. Diagnosis is also possible via LP. CSF is usually cloudy in appearance with a short glucose level and potential positive gram stain and culture. Patients presumed to have actually bacterial meningitis should instantly receive broad-spectrum antibiotics to stop clinical deterioration. After society results return, the clinician can make adjustments to the antibiotics. Patients should furthermore be admitted to the intensive care unit for close monitoring. Most patients with bacterial meningitis that receive proper treatment recoup without complications.<10>

Subarachnoid Hemorrhage (SAH) is the leakage the blood right into the subarachnoid an are where it mixes v CSF. Trauma is the many common reason of SAH through 80% that nontraumatic SAHs resulting from aneurysm rupture. Various other nontraumatic reasons of SAH encompass arteriovenous malformations and vasculitis. Spontaneous SAH has actually a low incidence, with just 30,000 cases an international annually. Ninety-seven percent that patients with SAH present with a sudden onset headache, explained as a thunderclap headache or the worst headache that the patient"s life. Various other symptoms include vomiting, seizures, lose of consciousness, and also death. Non-contrast head CT is helpful in diagnosis. CT has actually high sensitivity after hemorrhage, but sensitivity decreases as time passes. After ~ a an unfavorable CT, one LP have to follow to preeminence out SAH. An LP is positive as soon as erythrocytes are present in tubes 1 and 4, or xanthochromia is visible. Management of SAH consists of reducing dangers of re-bleeding and avoiding any kind of secondary brain injuries.<11> 

Pseudotumor Cerebri Syndrome (PTCS) is a rare medical problem in i m sorry intracranial press is raised without the incident of ventriculomegaly or intracranial masses. The pathogenesis is no well understood. The most widely embraced theory proposes lessened absorption the CSF at the arachnoid granulations or the olfactory lymphatics as the cause. This condition has an annual incidence rate of 0.9/100,000 in the general population. Before puberty, both females and also males space equally affected, yet after puberty, females are influenced nine times much more often.

PTCS most commonly affects obese women of childbearing age. Women between the eras of 20 to 44 years and who weigh 20% an ext than their right body weight have an incidence price of 19.3/100,000. A spinal fluid examination is an important in the diagnosis that PTCS. CSF pressure is better than 250 mm CSF in adults and also 280 mm CSF in children. Teens are the embraced values because that diagnosis that PTCS. Headache is the most typical presenting symptom, despite there are no particular distinguishing features of a PTCS headache. Periodically asymptomatic patients present with papilledema detected during routine eye exams. Pulsatile tinnitus, transient visual obscurations, visual field defects, and also visual lose are various other symptoms the PTCS.

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Traditional therapy includes medications come decrease CSF cheap from the choroid plexus. Surgery is suggested for patients through worsening vision caused by papilledema. Surgical alternatives include optic nerve sheath fenestration and CSF shunting. Many patients with PTCS have a an excellent outcome, back a small percentage the patients continue to endure persistent headaches or blindness.<12>