Cerebrospinal Fluid Analysis
cerebrospinal fluid
selective secretion of plasma, not an ultrafiltrate
sodium, chloride and magnesium
contained in higher levels in CSF than in plasma
potassium calcium and protein
contained in lower levels in CSF than in plasma
meninges
the three membranes surrounding the brain and spinal cord
dura mater
outer layer next to the bone
arachnoid mater
middle layer resembling a spider web
pia mater
innermost layer adhering to the surface of neural tissue
subarachnoid space
the space between arachnoid mater and pia mater where CSF is held
bathe and protect brain and spinal cord
purpose of CSF
hydrocephalus
the build up of CSF if reabsorption process is blocked
85-150 mL
normal adult volume of spinal fluid
10-60 mL
neonate normal volume of spinal fluid
blood-brain barrier
interface between blood and CSF only allowing certain substances to cross
protein glucose and lactate, microorganism cultures, and antigen presence
routinely measured tests for CSF analysis
aseptic lumbar puncture in third or fourth lumbar interspace with local anesthesia
cerebrospinal fluid specimen collection
1-2 mL
amount of CSF that should be removed if CSF pressure is less than or greater than normal
chemistry, serology, immunology
CSF #1
microbiology
CSF #2
cell counts and cytology
CSF #3
stat
examination and testing timing of CSF
falsely low cell count, falsely high lactate caused by glycolysis
inaccurate results caused by delated testing
clear, colorless and viscosity like water
three physical characteristics of normal CSF
pleocytosis
increased number of cells in CSF
cloudy CSF
associated with white blood cells greater than 200 cells/mL or red blood cells greater than 400 cells/mL
cloudy CSF
associated with microorganisms or increased protein
xanthochromia
abnormal color of CSF, usually yellow, orange, or pink due to various conditions
traumatic tap
greatest amount of blood in tube 1, least in tube 3; colorless supernatant after centrifugation
hemorrhage
consistent amount of blood in all three tubes; xanthochromic supernatant after centrifugation; macrophages with phagocytized RBCs which stain positive for hemosiderin and may include hematoidin crystals
0-5 WBC/uL, no RBC presence
normal cell count for CSF
hemacytometer
used to perform cell counts on CSF
normal saline
used if a dilution is needed to perform microscopic examination
RBC count
performed to aid in the differentiation of a recent hemorrhage from a traumatic tap experience
WBC count
performed to diagnose CNS disease and variety of other conditions
2% acetic acid
used to lyse RBCs and enhance visualization of WBC nuclei
lymphocytes and monocytes
predominate white blood cells in CSF
neutrophils
present in bacterial meningitis, early viral, fungal, TB, or parasitic infections, and some noninfectious conditions
lymphocytes
increased in viral, TB, fungal, or syphilitic meningitis particularly in later stages
plasma cells
abnormal when seen in MS and acute viral and chronic inflammatory conditions
monocytes
may be increased in a mixed cell pattern such as TB or fungal meningitis, chronic bacterial meningitis, or rupture of cerebral abscess
eosinophils
>10% presence in parasitic, fungal, or allergic reactions (sometimes caused by malfunctioning shunt)
macrophages
often found after hemorrhage because of phagocytic ability
other cells
need to be distinguished between malignant cells and others
15-45 mg/dL
normal CSF total protein
increased protein
in CSF caused from contamination with blood during tap, change in blood-brain barrier, decreased reabsorption into venous blood, and increased synthesis in CNS
increased protein
seen in disorders such as bacterial, viral, and other meningitis, cerebral infarction, hemorrhage, endocrine disorders, MS, obstruction of CSF flow, and trauma
decreased protein
seen in increased reabsorption because of increased intracranial pressure and loss of fluid because of trauma or invasive procedures
CSF/serum albumin index
used to assess permeability of blood-brain barrier; <9 normal, 9-14 minimal impairment, and 15-100 moderate to severe, >100 complete breakdown of barrier
0.30 to 0.70
CSF to IgG Index reference range
greater than .70
CSF/IgG Index associated with increased intrathecal production of IgG
less than .30
CSF/IgG Index that indicates compromised blood brain barrier
MS
most patients (90%) have IgG index greater than .70
tau protein
second band of transferrin specific for CSF
electrophoresis
performed to identify oligoclonal bands that are present in CSF but absent in serum in MS
myelin basic protein
surrounds axons of nerves and is necessary for proper nerve conduction; may be seen in MS and other demyelinating diseases
glucose
values reflect plasma value 30-90 minutes before CSF collection (60-70% of plasma concentration)
50-80 mg/dL
normal glucose range in CSF
decreased glucose
associated with many conditions including meningitis hypoglycemic states, and metastatic or primary tumors
increased glucose
has no clinical significance
lactate
increased in conditions impairing blood supply or transport of oxygen to CNS (anaerobic conditions)
10-22 mg/dL
normal lactate range in CSF
increased lactate
cerebral infarction, intracranial hemorrhage, hydrocephalus, traumatic brain injury, and meningitis
viral meningitis
lactate level rarely exceeds 25-30 mg/dL
bacterial meningitis
lactate levels greater than 35 mg/dL and decreased glucose
gram stain
look for bacteria and fungi
india ink
for Cryptococcus neoformans
acid-fast stain
for TB meningitis
Wright's stain
for ameba Naegleria fowleri
culture
to detect bacterial cause
detection of microbial antigens
to assist in identifying bacterial and fungal antigens in CSF