Neurocysticercosis 

Neurocysticercosis (NCC) is the most common parasitic disease of the nervous system and is the main cause of acquired epilepsy in developing countries. It has also been a problem in industrialized countries because of the immigration of tapeworm carriers from areas of endemic disease.^{[1, 2]}

Neurocysticercosis can be acquired via fecal-oral contact with carriers of the adult tapeworm Taenia solium. This usually indicates the presence of a tapeworm carrier in the immediate environment (ie, household) or by accidental ingestion of contaminated food. Cases of auto-ingestion, in which persons with taeniasis may ingest the eggs of T solium into their intestine, have been reported.

An example of an image of human neurocysticercosis is provided below.

See also Neuroimaging in Neurocysticercosis.

Neurocysticercosis is the result of accidental ingestion of eggs of Taenia solium (ie, pork tapeworm), usually due to contamination of food by people with taeniasis. T solium has a 2-host biologic cycle, with humans as the definitive hosts carrying the intestinal tapeworm, and pigs as the normal intermediate hosts harboring the larvae or cysticerci. This parasite has a head (scolex) with 4 suckers and a double crown of hooks, an unsegmented neck, and a large body with several hundreds of hermaphrodite proglottids.

Cysticerci are ingested by humans through poorly cooked infected pork. Cysts evaginate in the small intestine, attach to the wall by its suckers and hooks, and develop strobila or chains of proglottids. From the distal end of the strobila, fertile eggs are excreted into the gravid proglottids. Up to 60,000 eggs may be contained in a proglottid.

Pigs ingest stool contaminated with Taenia eggs, the embryos actively cross the intestinal wall, get into the bloodstream, and are transported to most tissues, where they reside as cysticerci. Larvae are found most commonly in the central nervous system (CNS), but they can also be located in the eye, muscle, or subcutaneous or other tissues.

Neurocysticercosis is the most common parasitic infection of the central nervous system (CNS). Approximately 2.5 million people worldwide carry the adult tapeworm, and many more are infected with cysticerci.

In the United States, neurocysticercosis is mainly a disease of immigrants, and the disease is prevalent in the states of California, Texas, and New Mexico. Neurocysticercosis represents a major cause of morbidity among the Hispanic population. Although most of the cases have been diagnosed in persons of Hispanic origin, the incidence is increasing in nonendemic countries because of travel to zones of endemic disease. Native cases have also been reported, presumably because of ingestion of infected food that was handled by carriers of T solium.

Globally, neurocysticercosis is endemic in Central and South America, sub-Saharan Africa, and in some regions of the Far East, including the Indian subcontinent, Indonesia, and China, reaching an incidence of 3.6% in some regions. This disease is rare in Eastern and Central Europe, in North America (with the exception of Mexico), and in Australia, Japan, and New Zealand, as well as in Israel and in the Muslim countries of Africa and Asia.

Cysticercosis can be seen in immigrant populations with a relatively high frequency, as in the US Southwest and South Africa, and subcutaneous cysticercosis is more common in Asian populations than in other peoples of other areas of endemic disease. It is not clear whether this is due to variations in parasite strain or to those in the host.

Although neurocysticercosis appears to affect men and women equally, there is some evidence to suggest that inflammation around the parasites may be more severe in women than in men.^[3] In addition, despite the fact that neurocysticercosis appears to be the most frequent cause of seizures in children^[4] and adults (peak incidence, 30-40 y), the exact incidence in children is not known.

In most patients with neurocysticercosis, the prognosis is good. Associated seizures seem to improve after treatment with anticysticercal drugs and, once treated, the seizures are controlled by a first-line antiepileptic agent. Duration of treatment, however, is not defined.

No figures are available for the burden of mortality associated with neurocysticercosis. However, the racemose^[5] form of this disease—which appears macroscopically as groups of cysticerci, often in clusters that resemble bunches of grapes located in the subarachnoid space—is associated with poor prognosis and elevated mortality rate (>20%).

Neurocysticercosis-associated epilepsy is an important cause of neurologic morbidity,^[6] and chronic epilepsy is one of the most frequent complications of neurocysticercosis. Others include headaches, neurologic deficits related to strokes, and hydrocephalus. Patients with complications such as hydrocephalus, large cysts, multiple lesions with edema, chronic meningitis, and vasculitis are acutely ill and do not respond very well to treatment. Frequently, they have complications due to medical and surgical therapy.

Neurocysticercosis is a major public health problem in developing countries and is emerging as an increasingly important condition in regions in which the disease is not endemic. Comprehensive programs of long-term intervention involve appropriate legislation, health education, modernization of swine husbandry practices, improvement of efficiency and coverage of meat inspection, provision of adequate sanitary facilities, and measures to detect and treat human tapeworm carriers.

Political and economic realities in many communities where T solium is endemic today provide little hope that all these goals can be achieved in the near future. However, short-term approaches can be effective in the long-term, and these include educational campaigns in personal hygiene and general sanitation within the disease-endemic area.

Note that the usual restrictions for patients with epilepsy would be applicable for patients with neurocysticercosis presenting with seizures.