CSF Analysis, Blood Culture, & Vector-Borne Illness Evaluation

What conditions is lumbar puncture used to evaluate?

• Meningitis

• Encephalitis

• Neoplasm of brain or spinal cord

• Cerebral hemorrhage

• Degenerative brain disease

• Autoimmune disease involving the CNS

• Neurosyphilis

• Demyelinating disorders

What are the intentions of performing a lumbar puncture?

• Measure CSF pressure

• Obtain CSF fluid

• Inject therapeutic and diagnostic agents

• Administer spinal anesthetics

• Reduction of intracranial pressure in normal pressure hydrocephalus

Where is the needle inserted in a lumbar puncture?

subarachnoid space.

What are contraindications to lumbar puncture?

• Increased intracranial pressure

• Severe degenerative vertebral joint disease

• Infection near LP site

• Anticoagulation status

What would we do in cases of suspected increased intracranial pressure?

measure pressure before doing the puncture, becasue the fluid can shoot out in cases of increased pressure.

What are complications of lumbar puncture?

• CSF leak, Introduction of bacteria

• Herniation of brain

• Puncture of spinal cord

• Puncture of aorta or vena cava

• Back pain

• Leg paresthesias/pain

• Transient postural headache

What components are evaluated in CSF analysis?

• Pressure measurement

• Color

• Blood

• Bacteria

• Protein, Glucose, Chloride, LDH, Lactic Acid, Malignant cell cytology, Special tests

How is CSF pressure measured?

Attach a sterile manometer to LP needle

What CSF pressure is considered increased?

20 cm H₂O is considered indicative of increased pressure

When should CSF pressure be measured during lumbar puncture?

Measure at beginning and end of lumbar puncture

What conditions cause increased intracranial pressure?

• Tumor

• Infection

• Hydrocephalus

• Intracranial hemorrhage

What conditions cause decreased intracranial pressure?

• Hypovolemia

• Chronic CSF leak

What conditions cause a large difference between opening and closing pressures?

Spinal cord obstruction (tumor), Hydrocephalus

Where is CSF secreted from?

Secreted from plasma by choroid plexus in brain ventricles and reabsorbed into lymphatics

How much CSF is present at any given time?

150 – 200 ML of fluid at any given time

How much CSF is produced per day?

400-600 mL of CSF being produced per day, but with filtering less is present at any given time in that space

What does CSF do?

Bathes and protects brain and spinal cord

How does CSF compare to plasma?

Similar contents as plasma except higher chloride levels

What is the normal pressure seen in CSF evaluation, and what mmHg pressure is this indicative of?

normal: 17-18 cm H20

mmHg comparison: 8-15 mmHg

What will always cause a larger difference between the opening and closing pressures?

tumors and hydrocephalus

True or False: if the pressure is elevated, we can still do a lumbar puncture

false; not really recommended

What should be done if there are bacteria in the CSF evaluation?

• culture and sensitivity

• Gram stain (can start empiric therapy)

When is glucose decreased in the CSF, and what is it compared to?

decreased in:

• presence of bacteria

• inflammatory cells

• tumor cells

compare to serum glucose level

How can tumor cells present in CSF evaluation?

tumor cells may float freely in the CSF and should be examined for pathology

What is the normal color of CSF

clear and colorless

What is xanthochromia in CSF

yellowish tinge (abnormal)

What does cloudy CSF indicate

Increased WBC, Increased protein

What does red CSF indicate

Blood

What does a traumatic tap show in CSF

fluid becomes clearer with second sample

What does cerebral hemorrhage show in CSF

Blood

What cellular evaluation is found in CSF evaluation

RBCs and WBCs.

What do neutrophils in CSF indicate

bacterial meningitis/encephalitis

What do mononuclear cells in CSF indicate

viral or tubercular meningitis/encephalitis

What are potential WBC findings in CSF evaluation

neutrophils, mononuclear, leukemia, malignant tumor.

Why is CSF protein normally low

Normally low because inability to cross blood-brain barrier

What does increased CSF protein indicate

increased permeability of blood-brain barrier (due to infection or inflammation)

What does protein electrophoresis aid in

Aids in diagnosis of CNS disease

What conditions cause decreased CSF chloride

Meningitis, Decreased serum chloride levels

What causes increased CSF chloride

Elevated serum chloride levels

When is CSF LDH elevated

Elevated in any brain or spinal cord disease

What conditions elevate CSF LDH

Infection, CNS leukemia

What do elevations in CSF lactic acid indicate

anaerobic metabolism in the brain

What conditions elevate CSF lactic acid

Bacterial/fungal meningitis, Chronic cerebral ischemia

What are the reasons for special testing in CSF evaluation

tumor markers, syphilis serology, glutamine, c-reactive protein.

What syphilis serology tests may be done on CSF

RPR, VDRL

What does elevated CSF glutamine indicate

Elevated with hepatic encephalopathy or hepatic coma

What does elevated CSF C-reactive protein indicate

Elevated with bacterial infections or inflammatory conditions

What is cultured from erythema chronicum migrans in Lyme disease

Isolate B. burgdorferi spirochete

How often can B. burgdorferi be isolated

Only able to isolate in about half of patients

What is difficult to culture in Lyme disease

Difficult to culture

What is a limitation of culturing B. burgdorferi

Takes time

What is the best method for measuring IgM and IgG titers to B. burgdorferi

ELISA

When does IgM peak in Lyme disease

3–6 weeks after onset

What is the early pattern of IgG in Lyme disease

IgG is low early on and peaks at 4–6 months

What is the confirmatory test for Lyme disease

Western Blot

When is Western Blot used

if IgM results are positive or equivocal

When can false negatives occur in Lyme disease testing

early in disease

What causes false positives in Lyme disease testing

Previous infection causes lasting IgG, Other spirochete diseases such as syphilis or leptospirosis

What type of virus is West Nile Virus

RNA flavivirus

What diagnostic samples can be used for West Nile Virus

Serology or CSF

What antibody is measured for West Nile Virus

IgM Antibody

When is IgM measurable in West Nile Virus

Measurable by ELISA or indirect Immunofluorescent antibody assay 10 days after symptom onset

Where is confirmatory testing for West Nile Virus available

CDC

What indicates a fourfold rise in West Nile Virus testing

2nd IgM 3–4 weeks later with fourfold rise