CSF (Textbook)

Question 1

Meninges Layers

Answer 1

Three layers: the dura mater, the arachnoid, and the pia mater

1. Dura mater: outer layer that lines the skull and vertebral canal
2. Arachnoid: is a filamentous (spider-like) inner membrane
3. Pia mater: is a thin membrane lining the surfaces of the brain and spinal cord

Question 2

Spinal Tap Tube Order

Answer 2

• Tube 1: is used for chemical and serologic tests because these tests are least affected by blood or bacteria introduced as a result of the tap procedure
• Tube 2: is usually designated for the microbiology laboratory
• Tube 3: is used for the cell count, because it is the least likely to contain cells introduced by the spinal tap procedure.
• A fourth tube may be drawn for the microbiology laboratory to rule out contamination by skin flora

Question 3

CSF Specimen Preservation

Answer 3

• Hematology tubes are refrigerated.
• Microbiology tubes remain at room temperature.
• Chemistry and serology tubes are frozen.

Question 4

Clotting in CSF Specimens

Answer 4

Fluid collected from a traumatic tap may form clots owing to the introduction of plasma fibrinogen into the specimen. Bloody CSF caused by intracranial hemorrhage does not contain enough fibrinogen to clot.

Question 5

Cell Stability in CSF

Answer 5

WBCs (particularly granulocytes) and RBCs begin to lyse within 1 hour, and 40% of the leukocytes disintegrate after 2 hours

Question 6

CSF Cell Counts

Answer 6

An improved Neubauer counting chamber (Fig. 9–5) is routinely used for performing CSF cell counts

Calculation:

(Number of cells counted × dilution)

(Number of cells counted × volume of 1 square)

= cells/µl

Question 7

Cell Count Dilution Prep

Answer 7

• Made with normal saline, mixed, and loaded into the hemocytometer.
• Cells are counted in the four corner squares and the center square on both sides
• To count specifically WBCs, substitute 3% glacial acetic acid to lyse the RBCs

Question 8

Cell Count Prep on Non-Diluted Specimens

Answer 8

Place four drops of mixed specimen in a clean tube. Rinse a Pasteur pipette with 3% glacial acetic acid, draining thoroughly, and draw the four drops of CSF into the rinsed pipette. Allow the pipette to sit for 1 minute, mix the solution in the pipette, discard the first drop, and load the hemocytometer.

Question 9

Cytocentrifugation Process

Answer 9

• Fluid added to conical chamber
• Specimen is centrifuged
• Cells present in the fluid are forced into a monolayer
• Fluid is absorbed by the filter paper blotter, producing a more concentrated area of cells.
• Albumin is used to help preserve cells and aid sticking to the slide

Question 10

Pleocytosis

Answer 10

Increased numbers of normal cells; Lymphocytes, Monocytes

Question 11

Cell type and Menigitis Cause Correlation

Answer 11

• A high number of neutrophils is indicates bacterial meningitis.
• A moderately elevated CSF WBC count with a high percentage of lymphocytes and monocytes suggests meningitis of viral, tubercular, fungal, or parasitic origin.
• Increased lymphocytes are also seen in both asymptomatic HIV infection and AIDS.
• A moderately elevated WBC count (less than 50 WBCs/µ L) with increased normal and reactive lymphocytes and plasma cells may indicate multiple sclerosis or other degenerative neurologic disorders.

Question 12

nRBCs in CSF Specimen

Answer 12

NRBCs are seen as a result of bone marrow contamination during the spinal tap

Question 13

Hemorrhagic Findings in CSF

Answer 13

• Increased macrophages indicates a previous hemorrhage
• Degradation of the phagocytized RBCs causes dark blue or black iron-containing hemosiderin granules
• Yellow hematoidin crystals represent further degeneration; iron-free, consisting of hemoglobin and unconjugated bilirubin

Question 14

Choroidal Cells Appearance

Answer 14

Epithelial lining of the choroid plexus.

Seen singularly and in clumps.

Nucleoli are usually absent and nuclei have a uniform appearance

Question 15

Ependymal Cells Appearance

Answer 15

From the lining of the ventricles and neural canal.

They have less defined cell membranes and are frequently seen in clusters.

Nucleoli are often present

Question 16

Spindle-shaped Cells

Answer 16

Represent lining cells from the arachnoid.

They are usually seen in clusters and may be seen with systemic malignancies

Question 17

Primary CNS Tumor Cells

Answer 17

Astrocytomas, retinoblastomas, and medulloblastomas

Usually appear in clusters and must be distinguished from normal clusters of ependymal, choroid plexus, lymphoma, and leukemia cells.

Fusing of cell walls, nuclear irregularities, and hyperchromatic nucleoli are seen in clusters of malignant cells.

Question 18

CSF Chemical Test Reference Values

Answer 18

• Reference values for total CSF protein are 15 to 45 mg/dL, but are somewhat method dependent, and higher values are found in infants and people over age 40
• Abnormal values result from alterations in the permeability of the blood–brain barrier or increased production or metabolism by the neural cells in response to a pathologic condition.

Question 19

Normal Protein Components of CSF

Answer 19

• Prealbumin is the second most prevalent fraction in CSF.
• Haptoglobin and ceruloplasmin (alpha globulins).
• Transferrin (beta globulin)
• Primarily IgG, a small amount IgA (gamma globulins)
• A separate carbohydrate-deficient transferrin fraction, “tau,” is seen in CSF and not in serum.

Question 20

CSF Protein Levels and Implications

Answer 20

Low values: fluid is leaking from the CNS

High values: damage to the blood–brain barrier (most commonly meningitis and hemorrhage conditions), Ig production in CNS, decreased normal protein clearance from the fluid, and neural tissue degeneration

Question 21

IgG Production Verification

Answer 21

Comparisons between serum and CSF levels of Albumin and IgG are done to determine whether IgG is increased from being produced within the CNS or is elevated as the result of a defect in the blood–brain barrier

Question 22

CSF Protein Electrophoresis

Answer 22

• To detect oligoclonal bands, which represent inflammation within the CNS
• Two or more oligoclonal bands in the CSF that are not present in serum can help diagnose: multiple sclerosis
• Other abnormal banding patterns (not in serum): encephalitis, neurosyphilis, Guillain-Barré syndrome, and neoplastic disorders
• Use CSF immunofixation electrophoresis (IFE) and isoelectric focusing followed by silver staining

Question 23

Myelin Basic Protein in CSF

Answer 23

• Myelin basic protein (MBP) in CSF indicates recent destruction of the myelin sheath that protects the axons of the neurons (demyelination).
• Can be used to monitor Multiple Sclerosis

Question 24

CSF Glucose Values in Infection

Answer 24

• A markedly decreased CSF glucose level accompanied by an increased WBC count and a large percentage of neutrophils indicates bacterial meningitis.
• If the WBCs are mostly lymphocytes, tubercular meningitis is suspected.
• A normal CSF glucose value is found with an increased number of lymphocytes, the diagnosis would favor viral meningitis.

Question 25

Non-Infectious Causes of Changes in CSF Glucose

Answer 25

Primarily by alterations in the mechanisms of glucose transport across the blood–brain barrier and by increased use of glucose by the brain cells

Question 26

CSF Lactate

Answer 26

• Tool for diagnosing and managing meningitis cases.
• In bacterial, tubercular, and fungal meningitis, CSF lactate levels >25 mg/dL occur more consistently than decreased glucose
• Levels >35 mg/dL are seen with bacterial meningitis, whereas in viral meningitis, lactate levels remain <25 mg/dL.
• However, elevated CSF lactate can result from any condition that decreases oxygen flow to the tissues, not just meningitis
• RBCs contain lactate, and may cause a false positive/elevated result

Question 27

Glutamine

Answer 27

Produced from ammonia and α-ketoglutarate by the brain cells.

Serves to remove toxic ammonia from the CNS

CSF Reference Range: 8 to 18 mg/dL

Elevated levels are associated with liver disorders that result in increased ammonia, and 75% of children with Reye’s syndrome have elevated CSF levels

Question 28

Agents of Infectious Meningitis

Answer 28

• Streptococcus pneumoniae
• Haemophilus influenzae
• Escherichia coli
• Neisseria meningitidis

In newborns:

• Streptococcus agalactiae
• Listeria monocytogenes

Question 29

Cryptococcal Meningitis

Answer 29

• Frequently occurring complication of AIDS
• Gram stain may show classic starburst pattern produced by Cryptococcus, seen more often than a positive India ink
• Latex agglutination tests to detect C. neoformans antigen in serum and CSF provide a more sensitive method than the India ink preparation, but can give false positives if Rheumatoid Factor is present