Neurocysticercosis
A brain infection caused by pork tapeworm larvae forming cysts
Quick Facts
- Type: Parasitic brain infection
- Cause: Larvae of the pork tapeworm (Taenia solium)
- Most common symptom: Seizures
- Spread: Swallowing tapeworm eggs
Overview
Neurocysticercosis is an infection of the brain and nervous system caused by the larval stage of the pork tapeworm, Taenia solium. When a person swallows the tapeworm's eggs, the larvae travel through the bloodstream and can settle in the brain, where they form small fluid-filled cysts. Over time these cysts trigger inflammation as the immune system responds, which is what causes most symptoms.
It is one of the most common parasitic infections of the nervous system and a leading cause of acquired epilepsy in many parts of the world, particularly where pigs roam freely and sanitation is limited. The good news is that neurocysticercosis is treatable, and many people improve significantly with the right combination of anti-parasitic medicine, anti-inflammatory treatment, and seizure control.
Symptoms
Symptoms depend on where the cysts are located, how many there are, and how much inflammation they cause. Some people have no symptoms for years. The most common problems include:
- Seizures: the most frequent symptom, sometimes the first sign of infection
- Headaches, which may be persistent or severe
- Confusion or difficulty concentrating
- Problems with balance or walking
- Vision changes
- Weakness or numbness in part of the body
When cysts block the flow of fluid in the brain, pressure can build up, causing severe headache, vomiting, and drowsiness. A first-time seizure, sudden severe headache, or rapidly worsening confusion is a medical emergency and needs immediate care.
Causes
Neurocysticercosis is caused by swallowing microscopic eggs of the pork tapeworm. Importantly, it is the eggs, not eating pork itself, that cause this brain infection. Eggs are passed in the stool of a person who carries an adult tapeworm in their intestine.
- Contaminated food or water: eggs can be spread when food, water, or hands are contaminated with infected stool.
- Poor sanitation and hygiene: areas without clean water and good waste disposal have higher rates of infection.
- Close contact with a tapeworm carrier: a household member with an intestinal tapeworm can spread eggs to others.
Once swallowed, the eggs hatch and larvae travel through the body, lodging in the brain, muscles, eyes, or other tissues.
Risk Factors
The risk of neurocysticercosis is higher in certain settings and situations, including:
- Living in or traveling to regions where the pork tapeworm is common, such as parts of Latin America, sub-Saharan Africa, and Asia
- Areas with poor sanitation and limited access to clean water
- Free-roaming pigs and traditional pig farming practices
- Living with someone who carries an intestinal tapeworm
- Limited hand-washing and food-hygiene practices
Diagnosis
Diagnosis usually combines imaging with the person's symptoms and history. Tests include:
- Brain imaging: CT and MRI scans can reveal the cysts at various stages, including calcified spots from older, dead cysts.
- Blood and fluid tests: antibody tests can support the diagnosis, though they are not always conclusive.
- Eye examination: recommended before some treatments, because cysts in the eye need special handling.
- Spinal fluid analysis: sometimes done to assess inflammation or rule out other infections.
The pattern and stage of the cysts on imaging help guide which treatment is appropriate.
Treatment
Treatment is tailored to the number, location, and stage of the cysts and the symptoms they cause. It often combines several approaches:
- Anti-parasitic medications: drugs such as albendazole or praziquantel kill the larvae, used in selected cases.
- Anti-inflammatory medication: steroids are often given because killing the parasites can increase brain inflammation.
- Anti-seizure medication: to control and prevent seizures, which may be needed for an extended period.
- Surgery or drainage: to remove cysts in critical locations or relieve fluid buildup, sometimes by placing a shunt.
Treatment is carefully managed by specialists, since the timing and combination of medicines matter. Many people do well, although some are left with ongoing seizures that require continued medication.
Prevention
Prevention focuses on stopping the spread of tapeworm eggs and improving hygiene and food safety. Useful steps include:
- Washing hands thoroughly with soap, especially before eating and after using the toilet
- Washing and peeling raw fruits and vegetables
- Drinking safe, clean water when traveling in affected areas
- Cooking pork thoroughly to prevent intestinal tapeworm infection
- Treating people found to carry an intestinal tapeworm to prevent spread to others
- Improving sanitation and proper waste disposal in affected communities
When to See a Doctor
See a doctor if you have unexplained, persistent headaches, vision changes, or new neurological symptoms, especially if you live in or have traveled to an area where the pork tapeworm is common. Seek emergency care immediately for:
- A first-time seizure or repeated seizures
- Sudden, severe headache
- Confusion, severe drowsiness, or difficulty waking
- Repeated vomiting with headache, which can signal rising pressure in the brain
Frequently Asked Questions
How do people get neurocysticercosis?
People get it by swallowing microscopic pork tapeworm eggs, usually through food, water, or hands contaminated with infected stool. It is not caused by eating pork itself; eating undercooked pork causes a different, intestinal tapeworm infection.
Is neurocysticercosis contagious?
The brain infection itself is not passed directly from person to person, but a person carrying an intestinal tapeworm can shed eggs that infect others. Good hygiene and treating tapeworm carriers help prevent spread.
Why does neurocysticercosis cause seizures?
Cysts in the brain, and the inflammation that develops as the immune system reacts to them, irritate surrounding brain tissue. This can trigger seizures, which are the most common symptom and sometimes the first sign of infection.
Can neurocysticercosis be cured?
Many people improve greatly with anti-parasitic medicine, anti-inflammatory drugs, and seizure control, and some are effectively cured. However, some people continue to have seizures and need long-term medication even after the parasites are gone.
How can neurocysticercosis be prevented?
Prevention includes thorough hand-washing, washing fruits and vegetables, drinking safe water, cooking pork well, and treating people who carry intestinal tapeworms. Improved sanitation in affected areas greatly reduces the risk.
References
- Centers for Disease Control and Prevention (CDC). Parasites — Cysticercosis.
- World Health Organization (WHO). Taeniasis/Cysticercosis.
- MedlinePlus, U.S. National Library of Medicine. Cysticercosis.
- National Institute of Neurological Disorders and Stroke (NINDS). Neurological Infections.