1. Important note biochem

2. Clinical Indications for CSF Analysis
CSF is performed in cases of suspected:
1- CNS infections (infectious meningitis & encephalitis)
2- CNS malignancy (as malignant infiltrates as in leukemia ..etc)
3- CNS hemorrhages (as subarachnoid hemorrhage)
4- CNS demylineating diseases (as multiple sclerosis)

3. CSF Glucose Normal CSF glucose: 50-80 mg/dl
- The actual CSF glucose concentration may be:
1- Falsely low in the presence of hypoglycemia
Or 2- Incorrectly interpreted as normal when the patient is hyperglycemic
Accordingly, CSF glucose should always be compared with a simultaneous
plasma glucose that is drawn prior to lumbar puncture.
Normal CSF glucose/ plasma glucose ratio is approximately
(N.B. Ratio is decreased if plasma glucose is more than 500 mg/dl
due to saturation of the glucose carrier system to CSF

4. CSF Glucose cont. Elevated CSF / plasma glucose ratio (more than 0.7)
has no CSF diagnostic significance (occurs with hyperglycemia)
Decreased CSF / plasma glucose ratio (hypoglycorrhachia):
1- CNS septic (pyogenic) infections
Due to increased glycolysis by leukocytes and bacteria (with increase CSF lactate)
2- Brain tumors
due to increased metabolism of glucose by CNS
3- TB meningitis & sarcoidosis
Due to inhibition of glucose entry into the subarachnoid space
N.B. in viral CNS infections, CSF glucose is usually normal

5. CSF Protein cont. Lumbar CSF protein: 15 - 45 mg/dl (mostly albumin)
The majority of CSF protein is derived from the plasma by ultrafiltration
Certain proteins arise within the intrathecal compartment:
1- Immunoglobulins produced by CNS lymphocytes
2- Transthyretin (produced by choroid plexus)
3- Various structural proteins found in brain tissue

6. CSF Protein Decreased CSF protein:
1- Leak of CSF from a tear in the dura due to severe trauma
2- Otorrohea: leak of CSF from ear
3- Rhinorrohea: leak of CSF from nose

7. CSF Protein cont. Increased CSF protein:
1- Lysis of contaminant blood from traumatic tap
2- Increased permeability of epithelial membrane (blood-brain barrier)
in cases of:
- CNS bacterial or fungal infections
- Cerebral hemorrhages
2- Increased production by CNS tissue as in cases of:
- Multiple sclerosis (MS)
- Subacute sclerosing panencephalitis (SSPE)
3- Obstruction as in cases of :
- Tumors or abscess

8. So, it is essential to determine the source of IgG
CSF Protein cont.
Analysis of protein fractions: (Albumin & IgG)
1- Albumin of CSF
is obtained from blood by means of blood-brain barrier (as it is
produced solely by the liver)
In cases of increased permeability of BBB, albumin is increased in
CSF
2- IgG of CSF can be obtained:
from blood (By BBB) : increase in cases of increase permeab. of BBB
& by local synthesis from plasma cells within CSF (increased in cases of MS)
So, it is essential to determine the source of IgG

9. CSF Protein cont. FIRST: CHECK INTEGRITY OF BLOOD BRAIN BARRIER (BBB)
BY CSF / serum albumin index calculation
CSF serum albumin index = CSF albumin (mg/dl) / serum albumin (g/dl)
Index less than 9 indicates intact BBB (no increased permeability of BBB)
SECOND: CSF IgG INDEX IS CALCULATED
CSF IgG / Serum IgG
CSF IgG index =
CSF albumin / serum albumin
Normal : less than 0.7
Increased in cases of demylineating diseases of CNS as : Multiple sclerosis (MS)

10. Notes taken in lec.
When BBB ↓ there will be ↑ in albumin so will be Bactrial infection
If there’s ↑ in immunoglobulin the disease will be in brain
↑ in lactase > Bactria
If found glutamine is indicate for ammonia
Protein in CSF > there’s Bactria
And glutamate give false rustle in hypoglycemia
Lymphocyte > viral
Neutrophil > Bactria
CSF Red> subarachnoid hemorrhage , tumor
Yellow> bilirubin > cause it can cross BBB