What is Cerebrospinal Fluid Glucose?

Cerebrospinal fluid (CSF) is a clear fluid produced from the blood that circulates around the brain and spinal cord, the organs that make up the central nervous system. Glucose is the common sugar used in the body. Cerebrospinal fluid glucose, or glycorrhachia, is the level of glucose in the CSF. Normal levels of cerebrospinal fluid glucose are 50-80 milligrams of glucose per 100 milliliters of blood.

Tests for cerebrospinal fluid glucose levels are used to diagnosis certain medical conditions. These include infections, inflammation of the central nervous system and tumors. Uncontrolled diabetes involves high blood glucose levels, so it can also cause high CSF glucose levels.

Cerebrospinal fluid is formed from the blood at a structure called the choroid plexus in the brain. The liquid portion of the blood and much of the material, especially electrolytes and nutrients, becomes CSF. The CSF circulates through the central nervous system. The brain does not have blood vessels directly inside it, so the cerebrospinal fluid glucose is used to nourish the brain. CSF also helps to support and cushion the central nervous system because of its buoyancy.

Glucose is the sugar that circulates in the blood and CSF. It is the main nutrient used in the body in energy production. The brain especially runs on a great deal of glucose, so glucose is an important component of the CSF. Normal levels of cerebrospinal fluid glucose typically are about two-thirds of the normal blood glucose levels.

Testing CSF levels is often done to diagnose the medical cause of delirium, headaches or other neurological problems. The usual way to obtain a sample of CSF is a procedure called a lumbar puncture. In a lumbar puncture, a needle is inserted between the lower backbones, and CSF is drawn to be tested.

Abnormal cerebrospinal fluid glucose levels can indicate the presence of central nervous system tumors, infections or other types of inflammation in the central nervous system. Low levels of CSF glucose, called hypoglycorrhachia, is seen with a number of problems in the central nervous system. Certain tumors in the brain cause low CSF glucose levels as the tumor cells consume the glucose for growth. Infections such as meningitis or tuberculosis can also cause low levels of cerebrospinal fluid glucose. CSF glucose levels can be used to distinguish between viral meningitis and bacterial meningitis.

Cerebrospinal fluid glucose comes from the blood, so abnormal blood glucose levels also can affect the levels of CSF glucose. Low levels of CSF glucose can be caused by low blood sugar. Similarly, high blood sugar levels in the body, most commonly cause by uncontrolled diabetes, can cause high levels of CSF glucose.