Meningitis

Meningitis is inflammation of the meninges, the protective covering that surrounds the brain and spinal cord. This inflammation is usually caused by a bacterial or viral infection in the cerebrospinal fluid (CSF), which is contained within the meninges. Other infectious agents, such as fungi, may also cause the disease.

The term meningitis represents a wide range of infections, and the bacterial and viral types are markedly different diseases. Furthermore, many different types of bacteria and viruses are capable of causing meningitis, and they may each be associated with distinct patterns of epidemiology, as well as differing signs, symptoms, prognoses, and treatment [Page 1102]requirements. Therefore, determining the causative agent is a crucial first step in the management of this disease.

Patients with meningitis often complain of a fever, headache, and stiff neck, although all three of these symptoms are not always present. Additionally, patients may report nausea, vomiting, decreased appetite, and increased sensitivity to light. To diagnose a specific type of meningitis, the patient's CSF must be sampled by inserting a needle into the lower back, which is called a lumbar puncture. Examination of the CSF will indicate which infectious agent has caused the disease. Bacterial meningitis is less common than the viral type and is associated with a far worse prognosis. In addition to the above symptoms, patients with bacterial meningitis may also experience confusion and seizures.

Meningitis can be caused by a wide range of bacterial species, and patient outcomes vary based on the specific bacterium implicated in the infection. Bacterial meningitis may progress quickly, so treatment with an antibiotic must be started immediately. The specific antibiotic used may differ based on the bacteria that have caused the infection, as specific bacteria are susceptible to different treatments.

If untreated, bacterial meningitis can progress to severe seizures, coma, and death. Patients who begin treatment during a more advanced stage of the disease have an increased risk of death; therefore, early diagnosis is essential. Those who survive severe bacterial meningitis may suffer long-term neurological damage, such as intellectual impairment. Viral meningitis, also known as aseptic meningitis, is associated with much better patient outcomes. Initially, viral meningitis may be difficult to distinguish from a common influenza infection. Patients may complain of a fever, headache, and a stiff neck, but they rarely exhibit the more alarming signs and symptoms of bacterial meningitis, such as seizures and confusion.

In most patients, viral meningitis will usually resolve without any treatment within one to two weeks. While waiting for the disease to resolve, patients may benefit from medication to alleviate the symptoms of the disease, such as treatment for the associated fever or headache. Additionally, some viruses that cause meningitis may be susceptible to antiviral therapy, and patients with severe symptoms or with compromised immune systems may benefit from antiviral treatment. The prognosis of viral meningitis is excellent, and unlike bacterial meningitis it rarely progresses toward death.

Meningitis may also be caused by fungal infections. Although this type is much rarer than bacterial or viral meningitis, it is of particular concern among HIV/AIDS patients. Cryptococcal meningitis, caused by the fungus Cryptococcus neoformans, is an opportunistic infection that is commonly associated with AIDS in the developing world. Because this organism does not normally invade a healthy immune system, cryptococcal meningitis is not often found in AIDS-free patients.

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