Cerebrospinal Fluid (CSF) Analysis

Flashcards covering the formation, physiology, collection, handling, and clinical analysis (physical, chemical, microscopic) of Cerebrospinal Fluid.

Cerebrospinal Fluid (CSF)

A fluid that supplies nutrients to the nervous system, removes metabolic waste, and serves as a mechanical barrier to cushion the brain and spinal cord.

Dura Mater

The outer layer of the meninges that lines the skull and vertebral canal.

Arachnoid Mater

The middle, spiderweb-like filamentous inner membrane of the meninges.

Subarachnoid space

The space between the arachnoid and pia mater where CSF flows.

Pia Mater

The innermost layer of the meninges that lines the surface of the brain and spinal cord.

Choroid Plexus

The specific part of the brain that produces CSF by selective filtration.

Rate of CSF production

The speed at which CSF is formed, which is $20\text{ mL/hr}$.

Arachnoid Villi/Granulations

The structures responsible for the reabsorption of CSF.

Blood Brain Barrier (BBB)

A protective mechanism that shields the brain from chemicals and harmful substances circulating in the blood.

Lumbar Puncture

The procedure for collecting CSF, typically performed between the 3rd, 4th, or 5th lumbar vertebrae.

CSF Total Volume (Adults)

$$90-150\text{ mL}$$

CSF Total Volume (Neonates)

$$10-60\text{ mL}$$

Tube 1

Used for Chemistry/Serology; least affected by procedural contamination and should be frozen.

Tube 2

Used for Microbiology; stored at room temperature.

Tube 3

Used for Hematology; least likely to contain cells introduced by the tap and stored at refrigerator temperature.

Xanthochromia

An abnormal appearance of CSF due to RBC degradation products, appearing pink, yellow, or orange.

Traumatic Tap

A complication of CSF collection showing uneven blood distribution (Tube 1 > 2 > 3) and clot formation due to fibrinogen.

Intracranial Hemorrhage

Internal bleeding indicated by even blood distribution across all tubes, absence of clotting, and xanthochromic supernatant.

Pellicle

A characteristic finding in the CSF of patients with tubercular meningitis.

Normal WBC Count (Adults)

$$0-5\text{ WBCs/uL}$$

Normal WBC Count (Neonates)

$$0-30\text{ WBCs/uL}$$

CSF WBC Count Formula

\text{cells} = \frac{\text{# cells counted} \times \text{dilution}}{\text{area} \times \text{depth}}

WBC Diluting Fluid

$3\text{\%}$ acetic acid with methylene blue.

WBC Correction for Traumatic Tap

$$\text{WBCs added} = \frac{\text{WBC(blood)} \times \text{RBC(CSF)}}{\text{RBC(blood)}}$$

Lymphocytes (CSF)

The predominant cell type in normal adult CSF (L:M ratio – 70:30).

Pleocytosis

An abnormal finding characterized by increased numbers of normal cells.

Neutrophils (in CSF)

Cells increased in bacterial meningitis and early cases of viral, tubercular, and fungal meningitis.

Erythrophages

Macrophages containing phagocytized RBCs, indicating previous hemorrhage.

Plasma Cells (in CSF)

Cells found in multiple sclerosis due to lymphocyte reactions.

Normal CSF Protein

$$15-45\text{ mg/dL}$$

Tau Protein

A carbohydrate-deficient beta-2 transferrin found only in CSF, used as a marker for fluid identification.

CSF/Serum Albumin Index

Evaluates BBB integrity; values $\ge 9$ indicate destruction of the barrier.

IgG Index Formula

$$\text{IgG Index} = \frac{\text{CSF IgG (mg/dL) / Serum IgG (g/dL)}}{\text{CSF Albumin (mg/dL) / Serum Albumin (g/dL)}}$$

Oligoclonal Bands

The presence of 2 or more bands in CSF but not in serum, valuable for diagnosing Multiple Sclerosis.

Normal CSF Glucose

$60-70\%$ of blood glucose.

CSF Lactate

An indirect measure of oxygenation; levels $> 35\text{ mg/dL}$ indicate bacterial meningitis.

CSF Glutamine

An indirect measure of CSF ammonia, elevated in liver disorders and Reye's Syndrome.

LDH 4 & 5

Lactate dehydrogenase isoenzymes that are increased in bacterial meningitis.

India Ink

A stain used to detect Cryptococcus neoformans.

Limulus Lysate Test

A test using Horseshoe Crab Blood (containing hemocyanin) to detect gram-negative bacterial endotoxins.

VDRL (CSF)

The CDC-recommended serologic test for detecting active cases of neurosyphilis.