Neurocysticercosis

How neurocysticercosis develops

The pork tapeworm life cycle involves people and pigs. A person who eats undercooked infected pork can develop an adult tapeworm in the intestine (taeniasis) and shed eggs in their stool. When eggs are swallowed by another person, or by the carrier through poor hand hygiene, larvae hatch, enter the bloodstream and form cysts in tissues. When cysts lodge in the nervous system, it is neurocysticercosis. For the whole-body infection and life cycle, see cysticercosis.

Cysts pass through stages:

Types by location

• Parenchymal: cysts within brain tissue. The most common form, usually presenting with seizures.
• Extraparenchymal: cysts in the ventricles (fluid-filled spaces) or the subarachnoid space around the brain. These can block cerebrospinal fluid flow, causing hydrocephalus, and are more serious.
• Spinal: rare; back pain, weakness or numbness.
• Ocular: cysts in the eye, causing vision problems.

Symptoms

• Seizures: the most common symptom, affecting most people with parenchymal disease; often focal seizures that may spread.
• Headaches: chronic or severe.
• Raised intracranial pressure: headache, vomiting, blurred vision, drowsiness, from hydrocephalus or many inflamed cysts ("cysticercal encephalitis").
• Focal neurological deficits: weakness, numbness or speech problems.
• Cognitive and psychiatric changes in extensive disease.

Symptoms often appear years after infection, when cysts begin to die.

Diagnosis

• MRI of the brain: best for viable and degenerating cysts and for ventricular or subarachnoid cysts. A visible scolex (the larva's head) inside a cyst is diagnostic.
• CT scan: best for detecting calcifications.
• Blood antibody test (enzyme-linked immunoelectrotransfer blot): supports the diagnosis; may be negative with a single cyst or only calcifications.
• Dilated eye exam: before antiparasitic treatment, to exclude eye cysts.
• Stool tests for tapeworm carriers in the household.
• Tuberculosis screening and other tests if steroids are planned, and to exclude other causes such as brain abscess, toxoplasmosis, tuberculosis or brain tumors.

Treatment

Treatment is tailored to cyst number, stage and location, following IDSA/ASTMH guidelines.

• Anti-seizure medicine: for everyone with seizures.
• Antiparasitic medicines: albendazole for viable parenchymal cysts; albendazole plus praziquantel for more than 2 viable cysts. Not used for calcified cysts or when there is diffuse brain swelling.
• Corticosteroids: given with antiparasitic treatment to control inflammation as cysts die, and for cysticercal encephalitis.
• Single degenerating cyst: often treated with anti-seizure medicine and sometimes a short course of antiparasitic drugs plus steroids.
• Calcified cysts only: anti-seizure medicine; no antiparasitic drugs.
• Hydrocephalus: urgent shunt placement or endoscopic removal of ventricular cysts.
• Subarachnoid disease: prolonged antiparasitic and steroid treatment under specialist care.

Outlook

Most people with parenchymal neurocysticercosis do well. Seizures are usually controlled, and many people can eventually stop anti-seizure medicine after being seizure-free and showing resolution on scans, though calcified lesions increase the risk of recurrence. Extraparenchymal disease is more serious and can be life-threatening without specialist treatment.

Prevention

• wash hands with soap after using the toilet and before handling food
• when traveling to endemic areas, drink safe water and avoid raw produce you cannot wash or peel
• cook pork to at least 63 °C (145 °F) and let it rest for 3 minutes
• treat household tapeworm carriers

Frequently asked questions

What is neurocysticercosis?

Neurocysticercosis is an infection of the brain or spinal cord by larval cysts of the pork tapeworm. It happens after swallowing tapeworm eggs from contaminated food, water or hands. It is a leading cause of seizures in adults in many parts of the world.

What are the symptoms of neurocysticercosis?

Seizures are the most common symptom, followed by headaches. Cysts that block fluid in the brain can cause severe headache, vomiting, blurred vision and drowsiness. Symptoms often appear years after infection.

Is neurocysticercosis curable?

Yes, in most cases the infection can be cleared or controlled. Live cysts are treated with antiparasitic medicines and steroids, and seizures with anti-seizure medicine. Calcified cysts are already dead but may continue to cause seizures.

Can you get neurocysticercosis from eating pork?

Not directly. Eating undercooked pork can give you an intestinal tapeworm. Neurocysticercosis comes from swallowing tapeworm eggs, usually passed by a person with an intestinal tapeworm. A tapeworm carrier can infect themselves or others.