If bacteria can successfully invade the body and get into the bloodstream then penetrate what is called the blood-brain barrier to go from the bloodstream to the brain, they can survive in the cerebrospinal fluid and cause meningitis. A physician will check the cerebrospinal fluid to see if it contains the normal level of glucose and protein, because these levels will be affected by the infection.
What Is Meningitis?
Meningitis is the medical term for the inflammation of the meninges, which is the membrane that covers the brain and spinal cord. It can be caused by bacteria, viruses or fungi but is usually due to a bacterial or viral infection. Bacterial meningitis can cause neurological problems, hearing loss and even death. For this reason, someone with bacterial meningitis needs antibiotics immediately, according to Karen Bloch, M.D., Assistant Professor in Infectious Diseases and Preventive Medicine at Vanderbilt University Medical Center in "Pathophysiology of Disease." Viral meningitis usually requires only fluids, pain and fever medication.
Bacterial Meningitis, Glucose and Protein
The most common bacteria to cause bacterial meningitis are Streptococcus pneumoniae, Neisseria meningitidis and Streptococcus agalactiae. Bacteria cause meningitis when they get into the cerebrospinal fluid that surrounds and cushions the brain and spinal cord as the fluid circulates between two of the three layers of the meninges membrane. The protein level in the fluid will be high, but the glucose level will be low because bacteria use glucose.
Viral Meningitis, Glucose and Protein
The echoviruses, coxsackieviruses, human enteroviruses 68 to 71, herpes simplex virus 2 and the arthropod-borne viruses are the most common viruses that cause viral meningitis. Arthropod-borne viruses are transmitted by arthropods like mosquitoes and ticks, which is why more cases occur in the summer and early fall, explains Karen Roos, M.D., Professor of Neurology at Indiana University School of Medicine in "Harrison's Principles of Internal Medicine." Part of the examination for meningitis includes analyzing the cerebrospinal fluid, and this holds true whether the physician suspects bacterial or viral meningitis. In viral meningitis, however, the protein level will only be slightly high and the glucose level is usually normal.
The Cerebrospinal Fluid, Glucose and Protein
The University of Maryland Medical Center explains that the procedure performed to analyze the cerebrospinal fluid, or CSF, is called a spinal tap or lumbar puncture. After numbing the area, the physician inserts a spinal needle into the lumbar area, or the lower back. The needle will be inserted between two vertebrae into the subarachnoid space, or the area below the arachnoid layer of the meninges membrane. A sample of the CSF is obtained and sent to the lab for analysis. The lab checks the appearance of the fluid, the pressure, the number of blood cells, the amount of chloride, the amount of a protein called gamma globulin, and the amount of glucose and protein.
References
- "Essential Clinical Anatomy"; Keith Moore, Ph.D., Anne Agur; 1995
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al.; 2008
- "Pathophysiology of Disease: An Introduction to Clinical Medicine"; Stephen McPhee, M.D., Gary Hammer, M.D., Ph.D.; 2010
- The Merck Manual for Healthcare Professionals: Acute Bacterial Meningitis
- University of Maryland Medical Center: Cerebral spinal fluid (CSF) collection - All Information
