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A clear and colorless fluid that fills the ventricles and subarachnoid space surrounding the brain and spinal cord.
CSF provides a cushion and a suspension system for the CNS and has a role in homeostasis and nervous system metabolism.
Cerebrospinal fluid (CSF) surrounds the brain and spinal cord.
The brain and spinal cord float within the CSF.
CSF comprises 10% of the total fluid volume within the cranial cavity
The CSF flows through the four ventricles that are linked by channels or foramina into the subarachnoid space of the cortex and spinal cord
CSF fills the subarachnoid space and exerts pressure on the outside of the brain and spinal cord, and acts as a stabilizer and shock absorber as they float within the hollow spaces of the skull and vertebrae.
Normally CSF continuously circulates through the brain, its ventricles and the spinal cord and is continuously drained away into the circulatory system.
Inside of the brain, CSF-filled cavities called ventricles expand under the pressure of CSF to lift and inflate the soft brain tissue.
Cerebrospinal fluid is produced in the brain by capillaries lined with ependymal cells known as choroid plexuses.
Blood plasma passing through the capillaries is filtered by the ependymal cells and released into the subarachnoid space as CSF.
The CSF contains glucose, oxygen, and ions, which it helps to distribute throughout the nervous tissue.
CSF also transports waste products away from nervous tissues.
Volume of lumbosacral CSF with a range of 28-81 ml.
Subarachnoid has a circulating volume of 90-150 mL of cerebrospinal fluid.
The average adult has 150 mL of CSF divided between the brain and spinal cord compartments.
The ventricles contain approximately 25 mL of CSF.
Every day, the body makes roughly 600–700 ml of CSF, and about the same amount is reabsorbed into the bloodstream.
Turnover is about 3.7 times a day.
Cerebrospinal fluid in the ventricles flows through the foramens of Magendie and Luschka to the subarachnoid space.
Cerebrospinal fluid production is not pressure dependent, but its absorption is.
CSF absorption is decreased when CSF pressure is increased.
CSF is absorbed through the arachnoid villi into veins, primarily the cerebral venous sinuses.
After circulating around the brain and spinal cord, CSF enters the arachnoid villi where it is reabsorbed into the bloodstream.
Arachnoid villi of the arachnoid mater pass through the dura mater and into the superior sagittal sinus.
The superior sagittal sinus is a vein that runs through the longitudinal fissure of the brain.
The superior sagittal sinus vein carries blood and cerebrospinal fluid from the brain back to the heart.
CSF is absorbed in the arachnoid villi extending into the dural venous sinuses, the choroid plexus and the lymphatic system.
Arachnoid villi are fused projections of the arachnoid membrane and endothelium of the sinuses.
Similar smaller villi exist project into veins around spinal nerve roots.
Produced mainly from the ventricular choroids plexuses.
Cerebral spinal fluid originates via the choroid plexus, circulating through the ventricular system and recycled into the subarachnoid space.
Circulating fluid is absorbed into the venous circulation, mainly via the cranial arachnoid granulations and spinal arachnoid villi.
Flow through the villi is about 500 mL per day with a small amount of CSF being absorbed by diffusion into cerebral blood vessels.
The composition of the brain CSF is essentially the same as that of the extracellular fluid of the brain and makes up 15% of brain volume.
There is free communication between the brain interstitial fluid and the CSF.
Equilibration between CSF and the brain interstitium can take time because diffusion distances from some parts of the brain is significant.
Normal pressure is 100-200 mm of water.
The rate of CSF formation is independent of intraventricular pressure, but absorption is proportionate to the pressure.
The lateral and fourth ventricles of the brain produce 80% of circulating CSF, with the remaining 20% originating in the interstitial space, the ependymal lining of the ventricles, and the dura of the nerve root sleeves.
The average normal CSF pressure of 112 mm the filtration rate and absorption are equal.
Below a CSF pressure of 68 mm absorption stops.
When re-absorptive capacity of the arachnoid villi is impaired large amounts of CSF accumulate leading to hydrocephalus.
Normal fluid has a protein content of 20-45 mg/dL.
Normal CSF glucose range is 50-100 mg/dL.
Normal CSF glucose is about 60% of the serum glucose value.
Obese individuals have substantially less CSF partly caused by compression of the neural foramina.
Lumbar Puncture (LP) Interpretation of Cerebrospinal Fluid
Approximately 90% of immunocompetent patients with culture-proven meningitis have CSF findings characteristic of acute community-acquired bacterial meningitis.
Immunocompromised patients and patients with tuberculosis meningitis may present with acellular / low – white blood cell (WBC) – CSF meningitis.
Normal results in adults
Appearance: Clear
Opening pressure: 10-20 cm H2 O
WBC count: 0-5 cells/µL (< 2 polymorphonucleocytes [PMN]).
Glucose level: >60% of serum glucose
Protein level: < 45 mg/dL
Bacterial meningitis
Appearance: Clear, cloudy, or purulent
Opening pressure: Elevated (>25 cm H2O
WBC count: >100 cells/µL (>90% PMN); partially treated cases may have as low as 1 WBC/µL
Glucose level: Low (< 40% of serum glucose)
Protein level: Elevated (>50 mg/dL)
Additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial
antigens, CSF polymerase chain reaction (PCR), others depending on clinical findings
Aseptic (viral) meningitis
Appearance: Clear
Opening pressure: Normal or elevated
WBC count: 10-1000 cells/µL (lymph but PMN early)
Glucose level: >60% serum
glucose
Glucose level may be low in HSV infection
Protein level: Elevated (>50 mg/dL)
Additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR for herpes simplex virus [HSV], varicella-zoster virus [VZV]), others depending on clinical findings
Fungal meningitis
Appearance: Clear or cloudy
Opening pressure: Elevated
WBC count: 10-500 cells/µL
Glucose level: Low
Protein level: Elevated
Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR, CSF India ink, others depending on clinical findings
Tuberculosis
Appearance: Clear or opaque
Opening pressure: Elevated
WBC count: 50-500 cells/µL
early PMN then lymph cells
Glucose level: Low
Protein level: Elevated
Consider additional tests: CSF Gram stain and cultures, blood cultures, CSF bacterial antigens, CSF PCR, CSF tuberculosis culture/stain, others depending on clinical findings
Subarachnoid hemorrhage
Appearance: Xanthochromia, bloody, or clear
Opening pressure: Elevated
WBC count: (1 additional WBC per 1000 RBCs is considered normal correction)
Glucose level: Normal
Protein level: Elevated
Consider additional tests: CSF Gram stain and cultures, others depending on clinical findings
Multiple sclerosis
Appearance: Clear
Opening pressure: Normal
WBC count: 0-20 cells/µL (lymph)
Glucose level: Normal
Protein level: Mildly elevated (45-75 mg/dL)
Consider additional tests: Oligoclonal band analysis (serum and CSF), others depending on clinical findings
Guillain Barré syndrome
Appearance: Clear or xanthochromia
Opening pressure: Normal or elevated
WBC count: Normal or elevated
Glucose level: Normal
Protein level: Elevated