Cerebral spinal fluid (CSF) collection is a test to look at the fluid that surrounds the brain and spinal cord. Cerebral spinal fluid acts like a cushion, protecting the brain and spine from injury. The fluid is normally clear. The test is also used to measure pressure in the spinal fluid.

See also: CSF culture

There are different ways to get a sample of spinal fluid. Lumbar puncture, commonly called a spinal tap, is the most common method. The test is usually performed in the following manner:

• The patient must lay on his or her side, with the knees pulled up toward the chest, and the chin tucked downward. Sometimes the test is done with the person sitting up, but bent over.
• After the back is cleaned, the health care provider will inject a local numbing medicine (anesthetic) into the lower spine.
• A spinal needle is inserted, usually into the lower back area.
• Once the needle is properly positioned, spinal fluid pressure is measured, and fluid is collected.
• The needle is removed, the area is cleaned, and a bandage is placed over the needle site. The patient is often asked to lie down for a short time after the test.

Occasionally, special x-rays are used to help guide the needle into the proper position. This is called fluoroscopy.

Lumbar puncture with fluid collection may also be part of other procedures, particularly a myelogram (x-ray or CT scan after dye has been inserted into the CSF).

Alternative methods of CSF collection are rarely used, but may be necessary in the event of a back deformity or infection.

Cisternal puncture uses a needle placed below the occipital bone (back of the skull). It can be dangerous because it is so close to the brain stem.

Ventricular puncture is even more rare, but may be recommended in persons with possible brain herniation. This test is usually done in the operating room. A hole is drilled in the skull, and a needle is inserted directly into one of brain's ventricles.

The patient (or guardian) must give the health care team permission to do the test.

The position may be uncomfortable, but it is extremely important that the patient stays in the bended position to avoid moving the needle and possibly injuring the spinal cord.

The anesthetic will sting or burn when first injected. There will be a hard pressure sensation when the needle is inserted, and there is usually some brief pain when the needle goes through the tissue surrounding the spinal cord. This pain should stop in a few seconds.

Overall, discomfort is minimal to moderate. The entire procedure usually takes about 30 minutes, but it may take longer. The actual pressure measurements and fluid collection only take a few minutes.

This test is done to measure pressures within the cerebrospinal fluid and to collect a sample of the fluid for further testing. CSF can be used to diagnose certain neurologic disorders, particularly infections (such as meningitis) and brain or spinal cord damage.

See also:

• CSF coccidioides complement fixation
• CSF oligoclonal banding
• CSF smear
• CSF VDRL test

Normal values vary from lab to lab but typically range as follows:

• Pressure: 50 - 180 mm H20
• Appearance: clear, colorless
• CSF total protein: 15 - 45 mg/100 mL
• Gamma globulin: 3 - 12% of the total protein
• CSF glucose: 50 - 80 mg/100 mL (or approximately 2/3 of blood sugar level)
• CSF cell count: 0 - 5 white blood cells, no red blood cells
• Chloride: 110 - 125 mEq per liter

Note: mg/mL = milligrams per milliliter; mEq/L = milliequivalent per liter

If the CSF looks cloudy, it could mean there is an infection or a build up of white blood cells or protein.

If the CSF looks bloody or red, it may be a sign of bleeding or spinal cord obstruction. If it is brown, orange, or yellow, it may be a sign of increased CSF protein or previous bleeding (more than 3 days ago).

Increased CSF pressure may be due to increased intracranial pressure (pressure within the skull). Decreased CSF pressure may be due to spinal cord tumor, shock, fainting, or diabetic coma.

Increased protein may be due to blood in the CSF, diabetes, polyneuritis, tumor, injury, or any inflammatory or infectious condition. Decreased protein is a sign of rapid CSF production.

Increased CSF gamma globulin levels may be due to diseases such as multiple sclerosis, neurosyphilis, or Guillain-Barre syndrome.

Increased CSF glucose is a sign of high blood sugar. Decreased CSF glucose may be due to hypoglycemia (low blood sugar), bacterial or fungal infection (such as meningitis), tuberculosis, or certain types of meningitis.

Increased white blood cells in the CSF may be a sign of meningitis, acute infection, beginning of a chronic illness, tumor, abscess,stroke, or demyelinating disease (such as multiple sclerosis).

Red blood cells in the CSF sample may be a sign of bleeding into the spinal fluid or the result of a traumatic lumbar puncture.

Additional conditions under which the test may be performed:

• Chronic inflammatory polyneuropathy
• Dementia due to metabolic causes
• Encephalitis
• Epilepsy
• Febrile seizure (children)
• Generalized tonic-clonic seizure
• Hydrocephalus
• Inhalation anthrax
• Normal pressure hydrocephalus (NPH)
• Pituitary tumor
• Reye syndrome

Risks of lumbar puncture include:

• Hypersensitivity (allergic) reaction to the anesthetic
• Discomfort during the test
• Headache after the test
• Bleeding into the spinal canal

There is an increased risk of bleeding in persons who take blood thinners.

Brain herniation may occur if this test is done on a person with a mass in the brain (such as a tumor or abscess). This can result in brain damage or death. This test is not done if an exam or test reveals signs of a brain mass.

Damage to the nerves in the spinal cord may occur, particularly if the person moves during the test.

Cisternal puncture or ventricular puncture carry additional risks of brain damage and bleeding within the brain.

This test should not be performed on people who have lesions that cause increased intracranial pressure. Others who should not have this test include patients with:

• Blood clotting problems
• Thrombocytopenia
• Risk of infection

Nathan, BR. Cerebrospinal Fluid and Intracranial Pressure. In: Goetz, CG, ed. Textbook of Clinical Neurology, 2nd ed. Philadelphia, Pa:WB Saunders Company; 2003:511-524.