brain, spinal cord, and nerve disorders
Acute Bacterial Meningitis
Diagnosis of Acute Bacterial Meningitis
Spinal tap and analysis of cerebrospinal fluid If a child 2 years old or younger has a fever and a parent senses that the child is inexplicably irritable or sleepy, the parent should see or call a doctor immediately, particularly if symptoms do not resolve after an adequate dose ofacetaminophen. Children require immediate medical attention, usually in an emergency department, if they do any of the following: Become increasingly irritable or unusually sleepy Have a low body temperature Refuse to eat Have seizures Develop a stiff neck Adults require immediate medical attention if they have any of the following: A headache and a stiff neck especially if they have a fever Confusion or decreased alertness Sluggishness or listlessness Seizures Rash with a fever or stiff neck During the physical examination, doctors look for telltale signs of meningitis, particularly a stiff neck. They also look for a rash, especially in children, adolescents, and young adults, and for other symptoms, which may suggest a cause. Doctors may strongly suspect bacterial meningitis based on symptoms and results of the examination, but tests are needed to confirm the diagnosis and to identify the specific bacteria causing it. As soon as doctors suspect bacterial meningitis, they take a sample of blood to be grown in a laboratory (cultured) and analyzed. Then they start treatment with antibiotics and corticosteroids immediately, without waiting for test results, because meningitis can progress rapidly. When doctors suspect acute bacterial meningitis, they immediately start treatment with antibiotics, without waiting for test results, because meningitis can progress rapidly. Once treatment has started, doctors quickly do a Spinal Tap (lumbar puncture), if it seems safe, to confirm the diagnosis. However, if they suspect that pressure within the skull is greatly increased (for example, by an abscess, tumor, or another mass in the brain), computed tomography (CT) or magnetic resonance imaging (MRI) may be done first to check for such masses. Doing a spinal tap when pressure within the skull is increased may be dangerous. Parts of the brain may shift downward. If these parts are pressed through the small openings in the tissues that separate the brain into compartments, a life-threatening disorder called Herniation: The Brain Under Pressure results. After pressure within the skull is lowered or if no mass is detected, a spinal tap is done, and doctors adjust treatment, if needed, after they get the results. During a spinal tap, a thin needle is inserted between two bones (vertebrae) in the lower spine to withdraw cerebrospinal fluid. Then the following are done: Close examination of the cerebrospinal fluid: The fluid is normally clear but may be cloudy in people with meningitis. Measurement of the pressure in the subarachnoid space (which contains the cerebrospinal fluid) before the cerebrospinal fluid is withdrawn: Pressure is usually high in meningitis. Analysis of cerebrospinal fluid in a laboratory: Sugar and protein levels and the number and type of white blood cells in the fluid are determined. This information helps doctors diagnose meningitis and distinguish between bacterial and viral meningitis. Examination of cerebrospinal fluid under a microscope to check for and identify bacteria. A special stain (called Gram stain) is used to show the bacteria more clearly and to help identify them. Other tests Other tests may be used to rapidly identify certain bacteria, such asNeisseria meningitidisandStreptococcus pneumoniae. Some of these tests identify specific bacteria by detecting specific proteins (antigens) on the surface of the bacteria. The polymerase chain reaction (PCR) technique, which produces many copies of a gene, may be used to identify the bacteria’s unique DNA sequence. Some tests can rapidly analyze large stretches of genetic material. These tests can identify otherwise undetectable microorganisms in cerebrospinal fluid. However, these tests are not always available. The cerebrospinal fluid is also cultured (to make bacteria grow). Culture helps doctors determine whether bacteria are present and, if so, which bacteria are present and which antibiotics may be most effective. Culture results usually take 24 hours or more. If culture or other tests detect bacteria in cerebrospinal fluid, bacterial meningitis is confirmed. Until the cause of meningitis is confirmed, other tests using samples of cerebrospinal fluid or blood may be done to check for viruses, fungi, cancer cells, and other substances that routine tests do not identify. Testing for Diagnosis , which can infect the brain (causing Doctors also take samples of blood, urine, and mucus from the nose and throat. In people who have a rash, they may use a small needle to remove fluid and tissue from under the skin where the rash is. These samples are cultured and examined under the microscope to see whether bacteria are present. 