A CSF glucose test checks the amount of sugar (glucose) in your cerebrospinal fluid (CSF), a clear liquid that surrounds the spinal cord and brain. The test can detect infections of the brain or spinal cord.
Why Is a CSF Glucose Test Done?
The CSF glucose test can be useful when checking for spinal cord or brain infections such as meningitis, because people with these infections have low glucose in their cerebrospinal fluid. Your doctor may order this test if you show these symptoms:
- Nausea
- Vomiting
- Serious headache
- Confusion or changes in consciousness
- Irritability
- Light sensitivity
- Severe neck pain or stiffness that limits you from moving your head
What Health Conditions Can a CSF Glucose Test Help Diagnose?
Besides meningitis, other conditions that a glucose test may help diagnose include:
- Bleeding around the brain
- Autoimmune disorders
- Cancer
- Idiopathic intracranial hypertension
- Multiple sclerosis
- Syphilis
- Guillain-Barré syndrome
- Tumors
How Is a CSF Glucose Test Done?
The most common way to check the glucose in your cerebrospinal fluid is by performing a lumbar puncture, also called a spinal tap. In some cases, your doctor can also do a glucose CSF by other methods, including:
- Ventricular puncture
- Cisternal puncture
- Removing some cerebrospinal fluid from a shunt or ventricular drain that’s already in your CSF
Lumbar puncture. Doctors typically perform lumbar punctures in their offices. To begin, your doctor will ask you to lay on your side as if in the fetal position. You will be asked to remain very still as your lower back is cleaned with an antiseptic. Next, your doctor will give you a local anesthetic to numb the area where they will perform the puncture. Your doctor will insert a special needle between two vertebrae and into your spinal canal and collect CFS samples that will be sent to a lab for analysis.
After the test, your doctor will have you lay flat on your back for an hour or two to avoid getting a headache. You should let your doctor know if you feel anything strange after the lumbar puncture, such as:
- Tingling in your legs
- Numbness
- Headache
- Pain at the puncture site
What Do CSF Glucose Test Results Mean?
A normal CSF glucose level is about two-thirds or more of the blood sugar level. If your CSF glucose falls within this range, it can help your doctor to eliminate certain conditions. Low glucose in CSF results from the presence of cells that usually aren’t there, a sign you have an illness that needs further investigation.
While analyzing the CSF glucose test, your doctor will take into account other factors, including your:
- Health history
- Age
- Gender
- Method of testing