CSF Composition and significance

Dr. Ashok Kumar .J.International Medical School

Management and Science UniversityMalaysia

CSF PressureCSF pressure changes with

PostureBlood pressureVenous return

factors that increase cerebral blood flow

• Normal opening pressure is 70 to 150 mm of water in left lateral decubitus position

• Slightly higher in sitting up and varies 10 mm water with respiration

• In infants and young children the normal range is 10 to 100 mm of

water • Attain adult value by 6 to 8 years of

age

• Pressure may be as high as 250 mm of water in obese individuals

Pressure above 250 mm of water are diagnostic intracranial hypertension

1. Meningitis2. Intracranial hemorrhage3. Tumors4. Thrombosis of venous sinuses5. Cerebral edema6. Conditions inhibiting absorption of CSF7. Opening pressure elevated may be the

only abnormality in cryptococcal meningitis

Decreased pressure

1. Spinal subarachnoid block2. Dehydration3. Circulatory collapse (shock)4. CSF leakage

Significant drop in CSF pressure after taking 1 to 2 ml of CSF suggests herniation or spinal block above the site of puncture

• CSF specimen should be sent to the lab immediately• Delay might initiate cellular degradation (which begins within 1 hour

of collection)

Indication for CSF analysis(Can be divided in to 4 categories)

1. Meningeal infection2. Subarachnoid hemorrhage3. Primary or metastatic malignancy4. Demylinating disease

Identification of infectious meningitis especially bacterial is important indication

CSF• CSF collected into three sterile tubes for

1. Chemical and immunological studies2. Microbiological examination3. Cell count and differentiation

• An additional tube may be inserted for cytology if malignancy is suspected• Glass tubes should be avoided since cells adhere to glass affect the

cell count• First tube should never be used for microbiological examination

( it may be contaminated with skin bacteria)

Gross examination

Normal CSF• Crystal clear• Has viscosity similar to water

Abnormal• Cloudy• Frankly purulent• Pigmented or tinted

Turbidity or cloudiness begins to appear with

• Leucocyte count over 200 cells /μL or• Red cell count of 400 cell/ μL

• Grossly bloody CSF have RBC count greater than 6000 / μL

• Turbidity• Coagulum• Color

Gross examination

Experienced observer may be able to detect cell count less than 50 cells / μL with unaided eye by observing for Tyndll’s effect

Turbidity or cloudiness• Microorganisms bacteria, fungi,

amoeba• Radiographic contrast material• Aspirated epidural fat• Protein level greater than 150 mgs/dl

• Turbidity• Coagulum• Color

Clot formation may be seen in traumatic tapNot seen in subarachnoid hemorrhage

Gross examination

Fine surface pellicles may be seen after refrigeration for 12 to 24 hours

Clot may interfere with cell count accuracy by entrapping inflammatory cells

• Turbidity• Coagulum• Color

Gross examination• Turbidity• Coagulum• Color

Viscous CSF may be encountered in • Metastatic mucin producing adenocarcinoma• Cryptococcal meningitis

Color : Pink red CSF - indicates presence of bloodMay be derived from:

Subarachnoid hemorrhageIntracerebral hemorrhagecerebral infractTraumatic tap

Xanthochromia

A pale pink to yellow color in the supernatant of centrifuged CSF, although

other colors may be present

Pale pink to orange xanthochromia from released oxyhemoglobin

usually detected 2–4 hours after the onset of subarachnoid hemorrhage

(although it may take as long as 12 hours)

Peak intensity occurs in about 24-36 hours and then gradually disappears

over the next 4-8 days

Yellow xanthochromia is derived from bilirubin

develops about 12 hours after a subarachnoid bleed

peaks at 2-4 days, but may persist for 2-4 weeks

To detect xanthochromia

The CSF should be centrifuged and the supernatant fluid

compared with a tube of distilled water

Pink RBC lysis/hemoglobin breakdown productsYellow Hyperbilirubinemia

CSF protein > 150 mg/dL (1.5 g/L)Orange RBC lysis/hemoglobin breakdown products

Hypervitaminosis A (carotenoids)Yellow-green Hyperbilirubinemia (biliverdin)Brown Meningeal metastatic melanoma

CSF supernatant color Associated diseases/disorders

CSF xanthochromia may also be due to the following:

Oxyhemoglobin resulting from artifactual red cell lysis caused by detergent contamination of the

needle or collecting tube

delay of more than 1 hour without refrigeration before examination

Bloody traumatic taps : A traumatic tap occurs in about 20% of lumbar

punctures

Rifampin therapy (red-orange)

Distinction of a traumatic puncture from pathologic hemorrhage is of vital importance

Traumatic tap : Hemorrhagic fluid usually clears between the first and third collected tubesSubarachnoid hemorrhage : Remains relatively uniform

Traumatic tap : microscopic evidence of erythrophagocytosis, or hemosiderin-laden macrophages indicate a subarachnoid bleed in the absence of a prior traumatic tap

Hemosiderin-laden macrophages (siderophages) from the CSF of a

patient with subarachnoid hemorrhage. Hemosiderin crystals (golden-yellow)

are also present

Chemical Analysis Analyte Conventional units

Protein 15–45 mg/dL

Pre-albumin 2–7%

Albumin 56–76% Alpha-1-globulin 2–7% Alpha-2-globulin 4–12% Beta-globulin 8–18% Gamma-globulin 3–12%

Total Protein. Over 80% of the CSF protein content is derived from blood plasma, in concentrations of less than 1% of the plasma level

Protein CSF (mg/L) Prealbumin 17.3Albumin 155.0Transferrin 14.4Ceruloplasmin 1.0IgG 12.3IgA 1.3Alpha-2-microglobulin 2.0Fibrinogen 0.6IgM 0.6Beta-lipoprotein 0.6

CSF protein levels of 15-45 mg/dl accepted as the ‘normal’ reference

range

infants have significantly higher CSF protein levels than older children

and adults

• CSF protein concentration fall rapidly from birth to 6 months of age (40 mg/dL)

• Plateaued between 3 and 10 years (32 mg/dL)

• Then rose slightly from 10-16 years (41 mg/dL)

for term infants and for preterm infants the upper levels were

150 mg/dl and 170 mg/dl

Increased CSF Total Protein

May be caused by• Increased permeability of the blood–brain barrier• Decreased resorption at the arachnoid villi• Mechanical obstruction of CSF flow due to spinal block

above the puncture site• An increase in intrathecal immunoglobulin synthesis

Conditions AssociatedTraumatic spinal puncture

Increased blood–CSF permeability• Arachnoiditis (e.g.,

following methotrexate therap)• Meningitis

(bacterial, viral, fungal, tuberculous)• Hemorrhage

(subarachnoid, intracerebral)

Drug toxicityEthanol, phenothiazines, phenytoin

CSF circulation defects• Mechanical obstruction

(tumor, abscess, herniated disk)• Loculated CSF effusion

Increased IgG synthesisNeurosyphilisMultiple sclerosisSubacute sclerosing panencephalitis

Increased IgG synthesis and blood–CSF permeability• Guillain–Barré syndrome• Collagen vascular diseases (e.g.,

lupus, periarteritis)

Qualitative tests for globulins

Pandy’s test :• One drop of CSF is added to one ml of Pandy’s reagent (clear 7%

solution of phenol in water)• A turbidity indicates increased globulin in CSF

Nonne-Apelt test :• One ml of CSF is slowly layered over one ml of ammonium sulphate

solution• A white ring at the junction of the two liquids indicates the

increased globulins

Turbidimetric methodsBased on trichloroacetic acid (TCA) or sulfosalicylic acid (SSA) and sodium sulfate for protein precipitationSimple, rapid, and require no special instrumentation

Quantitative test

Albumin and IgG MeasurementsPermeability of the blood–brain barrier may be assessed by immunochemical quantification of the CSF albumin-to-serum albumin ratio in grams per deciliter (g/dL)

The normal ratio of 1:230 ( 0.004)- CSF/serum albumin index- Arbitrarily calculated as follows

CSF/ Serum albumin index =CSF albumin (mg/dl)

Serum albumin (g/dl)

An index value less than 9 is consistent with an intact barrier

Slight impairment is considered with index values of 9-14

Moderate impairment with values of 14-30

Severe impairment at values greater than 30

Traumatic tap invalidates the index calculation

CSF IgG index

Elevated “IgG index” indicates increased production of IgG within the CNS : e.g Multiple sclerosis

CSF IgG index =CSF IgG mg/ dl X

Serum IgG g/ dl X CSF albumin mg/ dl

Serum albumin g/ dl

Normal upper limit is 0.8

Protein Major diseases/disorders• Alpha-2-macroglobulin Subdural hemorrhage, bacterial meningitis• Beta-amyloid and tau proteins Alzheimer's disease• Beta-2-microglobulin Leukemia/lymphoma• C-reactive protein Bacterial and viral meningitis• Fibronectin Lymphoblastic leukemia, AIDS, meningitis• Methemoglobin Mild subarachnoid/subdural hemorrhage• Myelin basic protein Multiple sclerosis, tumors, others• Protein 14-3-3 Creutzfeldt–Jakob disease• Transferrin CSF leakage (otorrhea, rhinorrhea)

Approximately 300 different proteins have been identified in CSF

Cerebrospinal fluid leakageotorrhearhinorrhea

usually presents as otorrhea or rhinorrhea following head trauma, in

some cases beginning months to years after the injury

Recurrent meningitis is a serious complication making accurate

identification of the leaking fluid very important

Transferrin- • an iron-binding glycoprotein • synthesized primarily in the liver• Two transferrin isoforms are present

in the CSF• Major isoform (beta-1-transferrin) is

present in all body fluids• The second isoform (beta-2-

transferrin), present only in the central nervous system - is produced in the central nervous system by the catalytic conversion of beta-1-transferrin by neuraminidase

Methemoglobin and BilirubinSubarachnoid and intracerebral hemorrhage are readily identified by

computed tomography (CT)

Mild subarachnoid hemorrhage Small subdural or cerebral

hematomas Blood seepage from • aneurysm or neoplasm• from small cerebral infarcts are

often not identified by this technique

CSF spectrophotometric analysis has been shown to detect methemoglobin in colorless CSF (< 0.3 μmol/L)

Increase in CSF bilirubin is now recognized as the key finding supporting the diagnosis of subarachnoid hemorrhage

Glucose

• Derived from blood glucose• fasting CSF glucose levels are normally 50-80 mg/dL

(about 60% of plasma values)• Results should be compared with plasma levels, ideally following a

4-hour fast, for adequate clinical interpretation

• The normal CSF/plasma glucose ratio varies from 0.3 - 0.9• CSF values below 40 mg/dL are considered to be abnormal• Hypoglycorrhachia is a characteristic finding of bacterial, tuberculous,

and fungal meningitis

Decreased CSF glucose results from• Increased anaerobic glycolysis in brain tissue and leukocytes • Impaired transport into the CSF

• CSF glucose levels normalize before protein levels and cell counts during recovery from meningitis, making it a useful parameter in assessing response to treatment.

Lactate

• CSF and blood lactate levels are largely independent of each other

• Reference interval for older children and adults is 9.0-26 mg/dL

• Newborns have higher levels, ranging from about 10-60 mg/dL for the first 2 days, and 10-40 mg/dL for days 3 to 10

• Elevated CSF lactate levels reflect CNS anaerobic metabolism due to tissue hypoxia.

• Lactate measurement has been used as an adjunctive test in differentiating viral meningitis from bacterial, mycoplasma, fungal, and tuberculous meningitis in which routine parameters yield equivocal results.

• Viral meningitis, lactate levels are usually below 25 mg/dL (almost always less than 35 mg/dL)• Bacterial meningitis typically has levels >35 mg/dL

• Persistently elevated ventricular CSF lactate levels are associated with a poor prognosis in patients with severe head injury

F2-isoprostanes

• F2-isoprostanes are increased in diseased regions of the brain in patients with Alzheimer's disease (AD)

• CSF F2-isoprostanes are also elevated in patients with probable AD

• In conjunction with CSF tau and beta-amyloid protein, the measurement of CSF F2-isoprostanes appear to enhance the accuracy of the laboratory diagnosis of AD

Enzymes

• A wide variety of enzymes derived from brain tissue, blood, or cellular elements have been described in the CSF.

• Although CSF enzyme assays are not commonly used in the diagnosis of CNS diseases, there are diseases/disorders whereby they may prove useful.

Adenosine deaminase (ADA).

• ADA catalyzes the irreversible hydrolytic deamination of adenosine to produce inosine. • ADA is particularly abundant in T lymphocytes• Which are increased in tuberculosis• Higher ADA levels are present in tuberculous infections than in viral,

bacterial, and malignant diseases • ADA levels greater than 15 U/L were found to be a strong indication of

tuberculous meningitis • Non-tuberculous meningitis consistently had levels less than 15 U/L

Creatine kinase (CK). • Brain tissue is rich in CK • Increased CSF CK activity has been reported in disorders • Hydrocephalus• Cerebral infarction• Primary brain tumors• Subarachnoid hemorrhage• Head trauma, CSF CK levels correlate directly with the severity of the

concussion

• CK-BB isoenzyme comprises about 90% of brain CK activity and mitochondrial CK (CKmt) the other 10%, CK isoenzyme measurements are more specific for CNS disorders

• CSF CK-BB is increased about 6 hours following an ischemic or anoxic insult• Global brain ischemia following respiratory or cardiac arrest results in

diffuse cerebral injury with peak CK-BB levels in about 48 hours

• CSF CK-BB activity less than 5 U/L (upper normal level) indicates minimal neurologic damage

• 5-20 U/L indicates mild to moderate CNS injury

• Levels between 21-50 U/L are commonly correlated with death.

• Death occurs in essentially all patients with levels above 50 U/L.

Lactate dehydrogenase (LD).

• LD activity is high in brain tissue

• A total LD activity of 40 U/L is a reasonable upper limit of normal for adults and 70 U/L for neonates • LD levels are also increased in patients with CNS leukemia, lymphoma,

metastatic carcinoma, bacterial meningitis, and subarachnoid hemorrhage

Lysozyme.

• Normal CSF activity is very low• Lysozyme (muramidase) catalyzes the depolymerization of

mucopolysaccharides. • Since the enzyme is particularly rich in neutrophil and macrophage

lysosomes, its activity is very low in normal CSF• CSF lysozyme activity is significantly increased in patients with both

bacterial and tuberculous meningitis

Ammonia, Amines, and Amino Acids.• CSF ammonia levels vary from 30-50% of the blood values• Measurement of CSF ammonia has little, if any, clinical value

• Cerebral glutamine, synthesized from ammonia and glutamic acid,• Serves as the means for CNS ammonia removal• CSF glutamine levels reflect the concentration of brain ammonia• Values over 35 mg/dL are usually associated with hepatic

encephalopathy • Elevated CSF glutamine levels have also been reported in patients with

encephalopathy secondary to hypercapnia and sepsis

Osmolality 280–300 mOsm/L

Sodium 135–150 mEq/L

Potassium 2.0–3.5 mEq/L

Chloride 120–130 mEq/L

Carbon dioxide 20–25 mEq/L

Calcium 2.0–2.8 mEq/L

Magnesium 2.4–3.0 mEq/L

LactateGlutamineIronCholesterolCreatinineUrea

10–22 mg/dL6 – 11 mg/ dL1 – 2 mg/dL0.2 – 0.6 mg/dL0.5 – 1.2 mg/dL6 – 16 mg/dL

pH

Lumbar fluid 7.28–7.32

Cisternal fluidCSE bicarbonate

7.32–7.34 18 mmol/L

PCO2

Lumbar fluid 44–50 mmHg

Cisternal fluid 40–46 mmHg

PO2 40–44 mmHg

CSF chloride

• CSF chloride level is more compared to plasma chloride

• May be due to difference in the concentration of protein in plasma and CSF

• CSF concentration of chloride decreases in meningitis – especially in tubercular meningitis

Microscopic Examination

• Total Cell Count• Cell counts are performed on undiluted CSF in a manual counting

chamber• automated flow cytometry of CSF, using the UF-100 flow cytometer,

was found to yield rapid and reliable WBC and RBC counts

Cell type Adults (%) Neonates (%)Lymphocytes 62 ± 34 20 ± 18Monocytes 36 ± 20 72 ± 22Neutrophils 2 ± 5 3 ± 5Histiocytes Rare 5 ± 4Ependymal cells Rare RareEosinophils Rare Rare

Correction when blood contaminated CSFIn the presence of a normal peripheral blood RBC count and serum

protein, these corrections amount to about 1 WBC for every 700 RBCs and 8 mg/dL protein for every 10 000 RBC/μL

CSF Reference Values for Differential Cytocentrifuge Counts

• Traumatic puncture may result in the presence of bone marrow cells, cartilage cells, squamous cells, ganglion cells, and soft tissue elements• In addition, ependymal and choroid plexus cells may rarely be seen

Cluster of blast-like cells in CSF from premature newborn

Increased CSF neutrophils occur in numerous conditions • Early bacterial meningitis - the proportion of PMNs usually exceeds

60%• About one-quarter of cases of early viral meningitis the proportion of

PMNs also increases

Causes of Increased CSF Neutrophils • Meningitis

Bacterial meningitis Early viral meningoencephalitis Early tuberculous meningitis Early mycotic meningitis Amebic encephalomyelitis

• Other infections Cerebral abscess Subdural empyema

• Following CNS hemorrhage Subarachnoid Intracerebral

Lymphocytosis (> 50%) is not uncommon in early acute bacterial meningitis

When the CSF leukocyte count is under 1000/μL Atypical reactive lymphoplasmacytoid and immunoblastic variants may be present.

Blast-like lymphocytes may be seen admixed with small and large lymphocytes in the CSF of neonates.

Causes of CSF Lymphocytosis • Meningitis

Viral meningitis Tuberculous meningitis Fungal meningitis Syphilitic meningoencephalitis Leptospiral meningitis Degenerative disorders Multiple sclerosis Guillain–Barré syndrome

Causes of CSF Plasmacytosis

• Acute viral infectionsGuillain–Barré syndromeMultiple sclerosisParasitic CNS infestationsSarcoidosisSubacute sclerosing panencephalitisSyphilitic meningoencephalitisTuberculous meningitis

• Plasma cells, not normally present in CSF, may appear in a variety of inflammatory conditions along with large and small lymphocytes and in association with malignant brain tumors

• Multiple myeloma may also rarely involve the meninges

Typical Lumbar CSF Findings in Meningitis

Test Bacterial Viral Fungal Tuberculous

Opening pressure Elevated Usually normal Variable Variable

Leukocyte count ≥ 1000/μL < 100/μL Variable Variable

Cell differential Mainly neutrophilsMainly lymphocytes Mainly lymphocytes Mainly lymphocytes

Protein Mild–marked increase

Normal–mild increase

Increased Increased

Glucose Usually ≤ 40 mg/dL Normal Decreased Decreased: may be < 45 mg/dL

CSF-to-serum glucose ratio

Normal–marked decrease

Usually normal Low Low

Lactic acid Mild–marked increase

Normal–mild increase

Mild–moderate increase

Mild–moderate increase

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