Section 6. Brain, Spinal Cord, and Nerve Disorders

Chapter 89. Infections of the Brain and Spinal Cord

Topics: Introduction | Acute Bacterial Meningitis | Chronic Meningitis | Viral Infections | Brain Abscess | Subdural Empyema | Parasitic Infections

Chronic Meningitis

Chronic meningitis is inflammation of the meninges that lasts a month or longer.

Chronic meningitis affects people whose immune system is impaired because of AIDS, cancer, use of chemotherapy, or long-term use of the corticosteroid prednisone. However, tuberculosis, Lyme disease, or another infection can cause chronic meningitis in people whose immune system is functioning competently.

The distinction between acute and chronic meningitis is not always clear, and sometimes the meningitis is described as subacute instead.

Causes

Some infectious organisms invade the brain or the meninges and multiply slowly over weeks, months, or even years. Such organisms include Cryptococcus fungus (in people with an impaired immune system, such as those with AIDS) and the bacteria that cause tuberculosis, syphilis, or Lyme disease. Acute bacterial meningitis that has been partially treated but not eliminated by antibiotics may evolve into chronic meningitis.

Some noninfectious disorders, such as sarcoidosis and some cancers (leukemia, lymphoma, brain tumors, and metastases to the brain), can invade and irritate the meninges, producing chronic meningitis. Chemotherapy drugs that are injected directly into the cerebrospinal fluid (such as methotrexate), drugs used in organ transplantation (such as cyclosporine and OKT3), and even nonsteroidal anti-inflammatory drugs (NSAIDs, such as ibuprofen (see Section 6, Chapter 78)) can inflame the meninges, leading to chronic meningitis.

See the sidebar Some Infections That Can Cause Meningitis.

See the sidebar Some Noninfectious Causes of Meningitis.

Symptoms and Diagnosis

The symptoms of chronic meningitis are similar to those of acute bacterial meningitis, but they develop more slowly and gradually, usually over weeks rather than days. Fever is often less severe than that in people with acute bacterial meningitis. Headache, confusion, and backache are common. Weakness, pins-and-needles sensations, numbness, and facial paralysis, which are also common, indicate that the cranial or peripheral nerves are affected.

Computed tomography (CT) or magnetic resonance imaging (MRI) of the head, followed by a spinal tap with examination of the cerebrospinal fluid, can help with the diagnosis. In chronic meningitis due to bacterial infection, the number of white blood cells in the fluid is higher than normal but is usually lower than that in acute bacterial meningitis. Also, the type of white cells is different--lymphocytes rather than neutrophils (see Section 14, Chapter 174). Some infectious organisms that cause chronic meningitis, such as Cryptococcus fungi, are readily visible under the microscope, but many, such as the bacteria that cause tuberculosis, are not.

The cerebrospinal fluid is always sent to be cultured, so that any organisms present can be identified. However, culturing may take weeks. The fluid may be analyzed for the bacteria that cause tuberculosis and syphilis and for certain fungi and viruses. For example, polymerase chain reaction (PCR) techniques, which cause DNA to make copies of itself, are used to detect the bacteria that cause tuberculosis. Results from these analyses may be available more quickly than those from culturing.

Treatment

Chronic meningitis due to sarcoidosis--which is thought to be a noninfectious disorder--is usually treated with corticosteroids (such as prednisone) for several weeks. Chronic meningitis due to cancer is treated with chemotherapy, radiation therapy, or both. The chemotherapy is injected directly into the cerebrospinal fluid through an Ommaya reservoir. This device is implanted under the scalp and delivers the drug slowly, over days or weeks, to the spaces around the brain through a small tube.

Treatment of chronic meningitis due to an infection depends on the organism. Chronic meningitis due to a fungus is usually treated with antifungal drugs given intravenously. Amphotericin B, flucytosine, and fluconazole are used most often. When the infection is particularly difficult to cure, amphotericin B is sometimes injected directly into the cerebrospinal fluid, either by repeated spinal taps or through an Ommaya reservoir. When chronic meningitis is due to the Cryptococcus fungus, amphotericin B is usually combined with flucytosine.