Meningitis Diagnosis

  • Diagnosis

    Meningitis is an inflammation of the meninges, the membranes that surround the brain and spinal cord Figure 01. Meningitis, a common disease worldwide, is relatively uncommon in the United States. Meningitis can result from either a bacterial or a viral infection, or from noninfectious diseases such as cancer and sarcoidosis. Meningitis affects people of all age groups; however, children, the elderly, and people with compromised immune systems are most at risk. Meningitis can appear abruptly, and the illness can last from 48 hours to several weeks.

    Click to enlarge: Meninges

    Figure 01. Meninges

    Chronic meningitis, which is a brain infection that causes inflammation of the meninges, can last a month or longer.

    While the symptoms are similar, bacterial meningitis is much more serious than viral meningitis. Any symptoms of meningitis should be treated as a medical emergency. If you suspect that you have meningitis of either type, you must contact your doctor. Bacterial meningitis requires hospitalization, and, if untreated, can lead to severe disability or death.

    Meningitis can be caused by various types of bacteria or viruses. Infectious organisms—bacteria, viruses, or fungi—travel through the bloodstream into the space between the meninges, resulting in an infection. Bacterial meningitis often follows an infection of the middle ear, sinuses, or upper respiratory tract, or pneumonia. Head trauma or neurosurgery can also allow bacteria to pass into the meninges, triggering an infection.

    Viral meningitis (also called aseptic meningitis) is primarily caused by a group of viruses called enteroviruses.

    Chronic meningitis is caused by slow-growing organisms such as fungi, or the bacteria that cause tuberculosis. Chronic meningitis is often a problem for people who are immunocompromised, such as those with AIDS, cancer, Lyme disease, syphilis, cytomegalovirus infection, or those who have used prednisone for a long period of time.

    Viral meningitis, the more common yet less serious form, is contagious. Viruses responsible for meningitis are airborne, and can therefore be transmitted from person to person. For this reason, outbreaks of viral meningitis sometimes occur in epidemic-like waves.

    Some of the bacteria responsible for bacterial meningitis, on the other hand, are normally present in the environment, and may even exist in your body without causing harm.

    Characteristic symptoms of meningitis in adults include fever, headache, stiff neck, an inability to bend the chin to the chest, and an inability to tolerate light Table 01. Symptoms of meningitis appear rapidly; adults can fall seriously ill in fewer than 24 hours. Older adults may not show typical symptoms, but may have a low-grade fever, and appear confused. Typically, older individuals will be suffering from another infection, (usually pneumonia) at the same time.

    Symptoms of viral meningitis are milder than those of bacterial meningitis, and may only consist of headache, fever, or a sore neck. Generally, fever is less severe for viral meningitis than it is for bacterial meningitis. Headache, confusion, backache, weakness, tingling, numbness, and facial paralysis may also be present.

    The symptoms of chronic meningitis are similar to those of bacterial meningitis, but develop more slowly, over the course of several weeks.

    Table 1.  Common Symptoms of Meningitis in Adults

    Fever
    Chills
    Malaise
    Headache
    Vomiting
    Stiff neck
    Inability to tolerate bright light
    Deep red or purplish rash
    Inability to lower chin to the chest, or severe pain upon attempt
    If the infection is not treated promptly, the following symptoms may become apparent:
    Drowsiness
    Irritability
    Confusion
    A loss of consciousness
    Shock
    Strokelike symptoms, including paralysis

    Young children, the elderly, and people with immune deficiency are at the highest risk for meningitis. People whose immune systems are more likely to be compromised (i.e., the elderly, and people with underlying medical problems) have an increased risk of getting meningitis. Those at highest risk for bacterial meningitis include people with head injuries, people who have an abnormality of the immune system, people who abuse alcohol, people who have had their spleens removed, people who have chronic ear and nose infections, and those who have sickle cell disease, cirrhosis, or pneumonia.

    People who live in crowded conditions are especially susceptible to viral meningitis. Viral meningitis is airborne, and is contagious.  Therefore, people who live in crowded conditions, such as military recruits or college students, are at increased risk for the disease.

    Because bacterial meningitis is a medical emergency, oftentimes treatment will be started before a diagnosis is confirmed. Your doctor will take a medical history to determine if you have experienced a previous respiratory or ear infection, or head trauma. If you are suspected of having meningitis, your doctor will perform a physical exam to look for characteristic signs, which include neck stiffness, a skin rash, and a flexing of the hips and knees (which is especially prevalent in children). If these findings indicate meningitis, you will be started on drug therapy immediately.

    Your spinal fluid must be tested to determine if you have meningitis. A lumbar puncture is a medical test that must be performed to diagnose meningitis. In this procedure, a small hollow needle will be inserted into the lower part of your spinal cord, usually between the third and fourth lumbar vertebrae. The fluid it collects is then allowed to drip into a test tube. Normal cerebral spinal fluid (CSF) appears clear; however, if you have meningitis, it will look cloudy, and medication will be started immediately.

    At the laboratory, the CSF is analyzed for the number and types of white blood cells present, glucose levels, and protein levels. The fluid is also cultured to determine whether bacteria are present, and if so, what type is present. Blood, urine, and throat mucus samples may also be cultured to help determine bacterial type.

    Neuroimaging tools may be used to screen for complications of meningitis. A computed tomographic (CT) scan or magnetic resonance imaging (MRI) scan of the head may be done to check for complications of meningitis, such as an abscess or fluid accumulation on the brain.

    Diagnosis will help rule out other factors that might be responsible for the observed symptoms. Conditions such as brain abscess, epidural abscess, subdural empyema, encephalitis, syphilis, Lyme disease, tuberculosis, rickettsial infections, chemical exposure, mumps, and herpes can all produce symptoms similar to those of bacterial and viral meningitis.

    Vaccines are available against certain common strains of bacteria that can cause meningitis. Currently, there are three vaccines available against three different bacterial causes of meningitis.

    • The vaccine for Haemophilus influenzae is recommended for children, and vaccination should start at two months of age
    • The vaccine for Neisseria meningitidis is now recommended for pre-adolescents at age 11 and for unvaccinated college students who plan to live in a dormitory. Members fo the military living together in close quarters should also get the vaccine.
    • The vaccine for Streptococcus pneumonia is recommended for people over the age of 65, for those with chronic illnesses, for those with compromised immune systems, and for people with HIV infection.

  • Prevention and Screening

    Vaccines are available against certain common strains of bacteria that can cause meningitis. Currently, there are three vaccines available against three different bacterial causes of meningitis.

    • The vaccine for Haemophilus influenzae is recommended for children, and vaccination should start at two months of age
    • The vaccine for Neisseria meningitidis is now recommended for pre-adolescents at age 11 and for unvaccinated college students who plan to live in a dormitory. Members fo the military living together in close quarters should also get the vaccine.
    • The vaccine for Streptococcus pneumonia is recommended for people over the age of 65, for those with chronic illnesses, for those with compromised immune systems, and for people with HIV infection.

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