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Parasitic Brain Infections

by John E. Greenlee, MD

In some parts of the world, brain infections may be due to worms or other parasites. These infections are more common in developing countries and rural areas. They are less common in the United States.

Cysticercosis

This infection is caused by pork tapeworm larvae (see Tapeworm Infection). It is the most common parasitic infection in the Western Hemisphere. After people eat food contaminated with cysticercus eggs, secretions in the stomach cause the eggs to hatch into larvae. The larvae enter the bloodstream and are distributed to all parts of the body, including the brain. The larvae form cysts (clusters of larvae enclosed in a protective wall). These cysts can cause headaches and seizures. The cysts degenerate and the larvae die, triggering inflammation, swelling, and symptoms such as headaches, seizures, personality changes, and mental impairment.

Sometimes the cysts block the flow of cerebrospinal fluid within the spaces of the brain (ventricles) putting pressure on the brain. This disorder is called hydrocephalus. The increased pressure can cause headaches, nausea, vomiting, and sleepiness.

Magnetic resonance imaging (MRI) or computed tomography (CT) can often show the cysts. But blood tests and a spinal tap (lumbar puncture) to obtain a sample of cerebrospinal fluid are often needed to confirm the diagnosis.

The infection is treated with albendazole or praziquantel (drugs used to treat parasitic worm infections, called antihelminthic drugs). Corticosteroids are given to reduce the inflammation that occurs as the larvae die. Seizures are treated with anticonvulsants.

Occasionally, surgery is necessary to place a drain (shunt) to remove the excess cerebrospinal fluid and relieve the hydrocephalus. The shunt is a piece of plastic tubing placed in the spaces within the brain. The tubing is run under the skin, usually to the abdomen, where excess fluid can drain. Surgery to remove cysts from the brain may also be needed.

Other infections

Echinococcosis (hydatid disease) and coenurosis are infections with other types of tapeworm larvae. Echinococcosis can produce large cysts in the brain. Coenurosis, like cysticercosis, produces cysts that can block the flow of fluid around the brain.

Schistosomiasis is an infection caused by blood flukes (see Schistosomiasis). In some people with schistosomiasis, inflamed clumps of cells (granulomas) develop in the brain.

Echinococcosis, coenurosis, and schistosomiasis can cause symptoms similar to those of cysticercosis, including seizures, headaches, personality changes, and mental impairment.

Doctors can usually diagnose these infections based on results from MRI or CT, but sometimes a spinal tap is needed. The spinal fluid may have a large number of white blood cells called eosinophils.

These three infections are usually treated with antihelminthic drugs, such as albendazole, mebendazole, praziquantel, and pyrantel pamoate, but sometimes cysts must be removed surgically.

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • ALBENZA
  • BILTRICIDE
  • No US brand name