Neurocysticercosis
Neurocysticercosis is a parasitic infection of the central nervous system caused by the larval stage of the pork tapeworm, Taenia solium. It is the most common parasitic infection of the brain worldwide and a leading cause of acquired epilepsy in developing countries. The infection occurs when tapeworm eggs are ingested, typically through contaminated food or water, and the resulting larvae migrate to the brain and spinal cord, forming cysts. Symptoms vary widely depending on the number, size, and location of cysts.
What is it?
Neurocysticercosis develops when a person ingests eggs of the pork tapeworm Taenia solium, usually through fecal-oral transmission from contaminated food, water, or poor hygiene practices. Once ingested, the eggs hatch in the intestine, releasing larvae (oncospheres) that penetrate the intestinal wall and enter the bloodstream. These larvae are carried throughout the body and can lodge in various tissues, but they have a particular affinity for the central nervous system. In the brain and spinal cord, the larvae develop into cysticerci—fluid-filled cysts containing the larval parasite—which can range from a few millimeters to several centimeters in size.
The cysts pass through several stages over months to years: the vesicular stage (viable cyst with live larva), colloidal stage (degenerating cyst with inflammatory response), granular nodular stage (contracting cyst with granuloma formation), and calcified stage (dead, mineralized cyst). Most symptoms occur during the degenerating stages when the dying parasites trigger an inflammatory response. Neurocysticercosis is endemic in Latin America, sub-Saharan Africa, India, and parts of Asia where poor sanitation and free-roaming pigs increase transmission risk. However, it is increasingly recognized in developed countries due to immigration and international travel. The infection is entirely preventable through proper food handling, handwashing, and adequate cooking of pork.
Important to Know
The clinical presentation of neurocysticercosis varies dramatically depending on the number, location, and stage of the cysts. Seizures are the most common symptom, occurring in 70-90% of symptomatic patients, and may be the only manifestation. Other symptoms include headaches (often due to increased intracranial pressure), altered mental status or confusion, focal neurological deficits such as weakness or sensory changes, vision problems (if cysts affect the eyes or visual pathways), hydrocephalus (if cysts block cerebrospinal fluid flow), and meningitis-like symptoms during active inflammation. Diagnosis relies on neuroimaging—MRI is more sensitive than CT for detecting cysts in all stages, particularly viable cysts, while CT is excellent for detecting calcifications. Serological blood tests can support the diagnosis but are not always positive. Treatment depends on the stage and location of cysts, number of lesions, and symptoms. Antiparasitic medications (albendazole or praziquantel) are used to kill viable cysts but must be given with corticosteroids to reduce inflammatory reactions. Anti-seizure medications control seizures, which may need to be continued long-term. Surgical intervention may be necessary for intraventricular cysts, hydrocephalus, or large cysts causing mass effect. With appropriate treatment, prognosis is generally good for parenchymal disease, though seizures may persist. The calcified stage represents inactive infection and typically requires only symptomatic management.