The most important organs of the Central Nervous System (CNS) are the brain and the spinal cord. They are jointly responsible for all your activities, including your movements and the ability to think.
Cerebrospinal fluid (CSF), a clear, colorless, watery fluid, flows in and around your brain and spinal cord. It helps to protect the brain and the spinal cord from any serious injury.
CSF also helps eliminate waste from the brain and maintains the smooth functioning of the CNS. It is secreted constantly by the choroid plexus inside the brain’s ventricles.
Functions of CSF
The CSF mainly performs these functions:
- Protecting the brain and the spinal cord from injuries and trauma (shock absorber).
- Eliminating waste products from the cerebral metabolism.
- Supplying nutrients to the nervous system tissue.
- Providing support and buoyancy for the brain.
- Regulating intracranial pressure.
- Serving as a medium between pineal secretions and the pituitary gland.
- Ensuring stable extracellular maintenance for the brain.
Composition of CSF
The composition of CSF remains constant under normal circumstances. It contains more sodium and chlorine than blood. It contains potassium, calcium, proteins, and glucose in a lesser amount. Normally, the CSF glucose is 2/3rd of the blood glucose. The normal CSF protein is 15-60 mg/100 ml. There are no red blood cells or any clotting factors. Since CSF is a closed system, pressure tends to be an essential component of the analysis. The composition, quantity, and pressure can be altered in various acute conditions.
What is CSF Analysis?
CSF analysis is a group of tests performed to diagnose brain and spinal cord diseases. Also known as Spinal Fluid analysis, it is used to measure different substances with the sample fluid. A lumbar puncture is performed to collect the CSF sample. It is also known as a spinal tap. The analysis is based on parameters such as fluid pressure, RBCs, WBCs, viruses, proteins, bacteria, glucose, etc. The analysis includes the following:
- Gauge of the physical characteristics and appearance of CSF.
- Levels of chemicals/substances found in the spinal fluid compared to those found in the blood.
- Cell counts.
- Identification of any bacteria that can prove hazardous or cause infectious diseases.
Purpose of CSF Analysis
The tests for the analysis may be used to diagnose:
- Infections in the brain or the spinal cord, including meningitis and encephalitis.
- Identifying the WBCs, bacteria, and other substances in the fluid.
- Identifying high levels of proteins in the cerebrospinal fluid for autoimmune disorders such as Guillain-Barre Syndrome.
- Determining the bleeding in the brain, if any.
- Recognizing brain tumors from cancer that may spread to other parts of the Central Nervous System.
- Identifying Alzheimer’s disease includes memory loss and changes in behavior.
Need for a CSF Analysis
It is inevitable to perform the tests if you have the following:
- Any symptoms of bleeding in the brain.
- Infection in the brain or spinal cord.
- Possess any symptoms of an autoimmune disorder, such as multiple sclerosis (MS).
- Brain injury.
- Injury to the spinal cord.
- Cancer.
- Other CNS condition symptoms, such as headaches.
Normal Range for CSF Analysis
The CSF analysis is based on WBCs, glucose, and proteins. Let us look into their normal values:
- Opening pressure: It ranges from 10 to 100 mm in young children. It further ranges to about 60 to 200 mm post-80 years and approximately 250 mm in obese patients. Pressures above 250 mm result in intracranial hypertension. Such elevated pressure is found in meningitis, intracranial hemorrhage, and tumors.
- Cell count: The normal WBC/mm for CSF in adults is 5, while in infants is 20. A WBC count higher than 1,000/mm is common among patients with bacterial meningitis.
- Cell differential: The normal CSF of an adult’s WBC count should comprise 70% lymphocytes and 30% monocytes.
- Proteins: Protein levels for a normal CSF for infants are 150 mg/dl, while in adults is about 18-58 mg/dl. Elevated protein levels are observed in infections, malignancies, multiple sclerosis, and certain medications.
- Glucose: Although there is no normal range for CSF glucose, it is about 2/3rd of the serum glucose. This is measured during the preceding 2-4 hours in a normal adult. However, the ratio may decrease with increasing serum glucose levels. Regardless of these levels, the CSF glucose levels usually do not go beyond 300 mg/dl.
- Latex Agglutination (LA): It detects bacterial antigens in CSF. However, its sensitivity varies between different bacteria. Its sensitivity for Haemophilus influenza is 60-100% but is low for other bacteria.
CSF Test Price
The CSF test price ranges between INR 200 to INR 11,000. However, prices may differ among laboratories and cities.