Transcript Cerebrospinal_Fluid_Analysis

Lab Medicine Conference :
Cerebrospinal Fluid Analysis
Cerebrospinal Fluid (CSF)
ƒ Adults produce 450 to 500 cc per day
ƒ 150 cc in adult CNS at any one time
–Neonates have 30 to 60 cc
–Children have 100 cc
ƒ 80 % produced by ventricular choroid
plexuses
ƒ Reabsorbed by arachnoid villi
ƒ Drains into dural sinuses
Suspected Diagnoses for
Which CSF Exam is Indicated
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Meningitis
Encephalitis
Brain abscess
Neurosyphilis
Subarachnoid hemorrhage
Demyelinating conditions :
–Multiple sclerosis
–Guillian-Barre
ƒ CNS malignancies
Usual Recommended Tests to Run on
Sequential Tubes of CSF from an LP
ƒ First and third tubes
–Cell count & differential
ƒ Second tube
–CSF total protein, glucose, +/- other chemistries
ƒ Fourth tube
–Gram stain, other stains, cultures
Priority Ranking of Tests to Run If Only
Small Amount of CSF Obtained
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Gram stain / culture
Cell count / differential
Protein / glucose
Chemistries
Contraindications to Lumbar
Puncture
ƒ Intracranial mass lesion with
impending herniation
ƒ Cutaneous infection or suspected
subcutaneous abscess at LP site
ƒ Systemic coagulopathy
–Could result in cord compression from
para-spinal hematoma
ƒ Unrestrainable patient
Potential Complications of
Lumbar Puncture
ƒ Uncal or brainstem herniation
–0.3 to 1.2 % mortality if papilledema present
–less likely if smaller amounts of fluid removed
ƒ Arachnoiditis : can occur if needle carries in povidone-iodine
ƒ Epidermoid tumors (delayed) : from use of needle without stylet
ƒ Nerve root injury : less likely if needle bevel vertical
ƒ Induced meningitis ; paraspinal abscess
ƒ Mortality
–from hyperflexion of head & tracheal obstruction
–or from vagally induced asystole
ƒ Post-procedure headache : 12 to 39 %
CSF Exam
ƒ First step is measure the opening pressure
(OP) :
–normal 80 to 180 mm H2O with pt. recumbent
–can be "falsely" elevated by Valsalva, head-up
position, or jugular compression
–should vary 5 to 10 mm H2O with respiration
–Queckenstedt & Tobey Ayer tests (involving jugular
compression & seeing the effect on OP) are no
longer recommended
Causes of Elevated CSF Opening
Pressure
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Meningitis
Intracranial mass lesions
SAH
CHF
SVC obstruction
Thrombosis of intracranial venous
sinus
ƒ Acute elevation of serum osmolarity
Causes of Low CSF Opening
Pressures
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Severe dehydration
Circulatory collapse
Chronic serum hyperosmolality
Dural tears with CSF leak
Neurosurgical procedures
Subdural hematomas in elderly
Barbiturate intoxication
Complete spinal subarachnoid block
CSF Appearance
ƒ Normal is clear & consistency similar to
H2O
ƒ Causes of visual turbidity :
–> 200 WBC's per mm3
–> 400 RBC's per mm3
–Bacteria
–Aspirated epidural fat
–Evil aliens (this was to see if you are paying
attention)
Causes of CSF Clot Formation
ƒ Traumatic tap
ƒ Increased protein from :
–subarachnoid block
–neurosyphilis
–tuberculosis
ƒ Metastatic mucinous adenocarcinoma
of the meninges
Xanthochromia of the CSF
ƒ Is yellow - orange - brown coloration
in supernatant of centrifuged CSF
ƒ Produced by lysis of red cells
ƒ Involves 3 pigments :
–oxyhemoglobin (red) : occurs in CSF
within 2 hours of a SAH
–bilirubin (yellow) : converted from
hemoglobin in 12 hours
–methemoglobin (brown)
Causes of Xanthochromia
Besides Red Cell Lysis
ƒ Direct serum bilirubin levels > 10 to 15 mg
%
ƒ CSF protein levels > 150 mg %
ƒ Sample contamination with povidone iodine
ƒ Systemic hypercarotenemia
ƒ CSF melanin from meningeal
melanosarcoma
CSF Glucose
ƒ Normally 60 to 70 % of serum level
ƒ Is 100 % ratio in neonates (immature CSF /
blood barrier)
ƒ In adults with serum glucose > 300 mg %, no
further increase in CSF glucose occurs
ƒ CSF level takes 2 hours to equilibrate with
change in serum glucose
Causes of Hypoglycorrhachia
(CSF to Serum glucose ratio < 0.6)
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Systemic hypoglycemia
Impaired glucose transport
Increased CNS use of CSF
Increased use of CSF glucose by
bacteria & leucocytes
–Typical with bacterial, tuberculous, or
fungal meningitis
–Also sometimes with SAH, viral
meningitidies, sarcoidosis, neoplasms
CSF Protein
ƒ Normal adult range is 17 to 55 mg %
ƒ Normal neonate level is up to 150 mg %
ƒ Increased levels usually associated with
CNS inflammatory processes, especially
infections
ƒ Has relation ratio with serum protein
levels, so elevations of serum protein
may cause elevations in CSF protein
Noninfectious Causes of
Elevated CSF Protein
ƒ Traumatic LP
–1 mg % increase per 1000 RBC's per mm3
ƒ Interference with CSF / blood barrier
–Cerebral hemorrhage
–SAH
–Cerebral thrombosis
ƒ Endocrine
–Diabetes mellitus
–Hyperthyroidism
–Hypoparathyroidism
–Hyperadrenalism
Other Noninfectious Causes of
Elevated CSF Protein
ƒ Guillian-Barre Syndrome
ƒ Multiple sclerosis
ƒ Collagen vascular diseases
ƒ Subacute sclerosing panencephalitis
ƒ Mechanical obstruction of CSF circulation
–tumors, abscesses, cord compression
ƒ Elevated serum protein levels (multiple myeloma,
etc.)
ƒ Medications / toxins :
–Phenytoin, ethanol, heavy metals
Causes of Low CSF Protein Levels
ƒ Chronic leakage from CSF otorrhea or
rhinorrhea
ƒ Chronic increased ICP
ƒ Removal of CSF via neurosurgical
procedures or repeated LP's
CSF Cell Counts
ƒ Normal adult : 0 to 5 lymphs or monos
ƒ Even one poly is abnormal
ƒ Normal neonates have 0 to 30 cells &
up to 60 % polys
ƒ Increased neutrophils usually indicate
infectious process
Comparisons of Cell Counts in
Viral Versus Bacterial Meningitis
ƒ Bacterial
–Typically > 500 WBC's / mm3 & mainly polys
–10 % of cases have < 50 % polys
ƒ Viral
–Typically < 100 WBC's / mm3 & mainly monos
–10 % of cases have > 50 % polys (especially if
early)
ƒ 90 % convert to mononuclear pleocytosis by 12
hours
Infectious Causes of Very Low
CSF Cell Counts
ƒ Meningitis from :
–Neisseria meningitidis
–Hemophilus influenzae
–Overwhelming Strep. pneumoniae
infection
Causes of Increased
Neutrophils in the CSF
ƒ Infectious
–Bacterial meningitis
–Early tuberculous meningitis
–Early viral meningitis
–Early mycotic meningitis
ƒ Noninfectious
–3 to 4 days post - hemorrhagic infarct
–SAH or intracerebral hematoma
–Injection of antibiotics or antimetabolites
–Injection of contrast media
–Repeated LP's
Causes of Increased
Lymphocytes in the CSF
ƒ Infectious
–Tuberculous, fungal, or leptospiral meningitis
–Partially treated bacterial meningitis
–Viral or syphilitic meningoencephalitis
–Subacute sclerosing panencephalitis
–Measles
ƒ Noninfectious
–Multiple sclerosis, Guillian-Barre Syndrome
–Polyneuritis
–Temporal arteritis or periarteritis
–Chronic ethanol abuse
–Intravenous drug abuse
Causes of Increased
Eosinophils in the CSF
ƒ Infectious
–Bacterial, fungal, or viral meningitis
–Cysticercosis
ƒ Noninfectious
–Allergic reaction to foods, meds, dyes, or envenomation
–Intrathecal foreign substances or contrast dye
–Synthetic intrathecal shunts
–Periarteritis nodosa
–Allergic bronchial asthma
–Acute polyneuritis
–Rabies vaccination
Causes of Increased
Macrophages in the CSF
ƒ Infectious
–Tuberculosis
ƒ Noninfectious
–Presence of erythrocytes
–Acute intracranial bleeding
–Mycotic meningitis
–Trauma to CNS
–Contrast media
Age Related Causes of Bacterial Meningitis
Intersection with line B. Join the marks on lines A & B with the ruler, and
read off the probability of acute bacterial versus acute viral meningitis
where the ruler intersects the central probability scale.
CSF Gram Stain
ƒ Should be done on uncentrifuged CSF
if CSF cloudy
ƒ Should be done on centrifuged CSF if
CSF clear
ƒ Identifies 80 % of bacterial CSF
infections
ƒ False positive only if LP tray or stain
itself is contaminated
CSF gram stain showing E. coli
CSF gram stain showing Listeria monocytogenes
CSF gram stain showing Neisseria meningitidis
CSF gram stain showing Streptococcus pneumoniae
CSF gram stain showing Staphylococcus aureus
CSF gram stain of Pneumococcal meningitis
Use of Acrinidine Orange Stain
(AOS) for CSF
ƒ Is fluorochrome stain for bacterial nucleic
acids
ƒ Bacteria stain bright orange
–Background of cellular debris stains yellow - pale
green
ƒ Takes 2.5 minutes to prepare (versus 3.5
minutes for gram stain)
ƒ Useful if bacteria not seen on gram stain
(increases pickup rate > 75 %)
Other CSF Tests for Meningitis
ƒ Lactic acid
–Levels > 35 mg % in 90 % of bacterial meningitis
–Numerous false positives (neoplasm, injury, etc.)
ƒ LDH
–Elevated (especially LDH-5) with bacterial meningitis, but is
nonspecific
ƒ C-reactive protein
–If elevated has high sensitivity & specificity for bacterial
meningitis, but is a technically difficult assay
ƒ Quelling Reaction
–Antisera cause swelling in pneumococci & Hemophilus
influenzae
Other CSF Tests for Meningitis
(cont.)
ƒ Limulus amebocyte lysate assay
–Requires 60 minutes
–Not 100 % sensitive
ƒ CSF amino acids
–Elevated with bacterial meningitis
–May be useful for dx if partial treatment
ƒ Countercurrentimmunoelectrophoresis CIE)
–Takes 30 to 60 minutes
–Precipitant line forms between bacterial antigens &
serum with known antibodies
–Can be useful in partially treated meningitis
–False positives & cross-reactions occur
Causes of False Negative CIE
ƒ Amount of antigen too small (if <
10,000 bacteria per ml.)
ƒ If infection early, not enough time for
antigen to dissolve off the bacteria
ƒ Poor antibody quality for some strians
(as for group B meningococcus &
pneumococci types 7 & 14)
Sensitivity of CIE in Meningitis
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Meningococcal : 50 to 90 %
Strep. pneumoniae : 50 to 100 %
Hemophilus influenzae : 80 %
Group B strep : 60 to 90 %
Latex Agglutination Antigen
Tests for Meningitis
ƒ More sensitive than CIE for
pneumococci & meningococci
ƒ Only takes 15 minutes to perform
ƒ Not affected by antigen excess
ƒ Less false negatives than CIE
Other Tests to Consider for Suspected
Non-Bacterial, Non-Viral Meningitis
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Acid fast stain
Mycobacterial culture
India ink prep (for Cryptococcus)
Cryptococcal antigen
Fungal culture
Charges at H.M.C. for CSF
Cultures & Microbial Stains
ƒ Gram stain & culture : $ 48
ƒ Sensitivity (antibiotic) : $ 45 to $ 105
–Agar diffusion vs. dual vs. add anerobic
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Fungal smear : $ 21
Fungal culture : $ 48
AFB smear & culture : $ 50
CIE : $ 37
Charges at H.M.C. for Other
Standard Studies on CSF
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Cell count & diff. : $ 67 (stat)
Glucose (stat) : $ 35
Protein (stat) : $ 35
Cryptococcal antigen : $ 35
Lactate : $ 26
Charges at H.M.C. for
Miscellaneous Studies on CSF
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Darkfield exam : $ 54
VDRL : $ 16
India ink prep : $ 22
IgG : $ 20
Immunochemistry eval. : $ 126
ph by electrode : $ 26
Sperm count (rule out sperm embolus) : $16
Total Charges at H.M.C. for Different
Patterns of CSF Test Ordering
ƒ CBC/diff., gm. stain / culture, glucose,
protein : $ 185
ƒ All standard, & culture / sensitivity studies
: $ 322
ƒ All standard, & culture / sensitivity, & misc.
studies : $ 462
Summary of Lab Studies on
CSF for Meningitis
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Measure opening pressure
Send four tubes
Check gram stain
If gram stain negative :
–Consider AOS
–Consider CIE +/- LA
ƒ If clinical suspicion for meningitis,
start broad spectrum antibiotics prior
to initial lab results