- Author: Vinod K Dhawan, MD, FACP, FRCPC, FIDSA; Chief Editor: Russell W Steele, MD more...
Neurocysticercosis has been increasingly recognized as a major cause of neurologic disease worldwide and an important problem among immigrant populations in the United States. This recognition is largely due to the widespread availability of sensitive neuroimaging techniques. Neurocysticercosis is the most common parasitic infection of the CNS. Tissue-invading larval forms of the pork tapeworm Taenia solium cause the disease.
Historically, neurocysticercosis was endemic to only Latin America, Asia, and Africa, although it has become increasingly frequent in the United States since the 1980s. Because of this epidemiologic change, all general pediatricians should become familiar with this disease process. The disease has been the subject of several recent reviews.[1, 2, 3, 4, 5, 6]
See the images below.
The larvae of T solium (Cysticercus cellulosae) cause neurocysticercosis. This pork tapeworm can vary in size but is notable for a scolex (head) with approximately 25 hooklets, 4 suckers, and a body with 700-1000 proglottids. The ova of the tapeworm are spread via the fecal-oral route and are approximately 40 microns in diameter with a radially striated shell. The intermediate host is the pig, which harbors the larvae after eating ova, and the definitive host is the human being.
If pig products infected with larvae are ingested, a tapeworm infection in the intestines ensues; however, if ova are ingested, neurocysticercosis may occur in this normally intermediate host. The ingested ova develop into larvae (cysticerci) and lodge in soft tissues, especially skin, muscle, and brain. Cysticerci are fluid-filled oval cysts, approximately 1-2 cm in diameter, with an internal scolex.
The eggs are found in human feces because humans are the only definitive hosts. Greatest risk for infection occurs in regions where plants in gardens or farms are fertilized with human feces and humans are exposed to contaminated soil.
In the CNS, T solium is deposited in the cerebral parenchyma, meninges, spinal cord, and eyes. Unless large numbers of cysts are present, the body's immune system does not act to destroy the organism, and cysts can live for many years undetected. A live cyst can go undetected for as long as 5 years before dying or causing symptoms in the host.
Neurologic symptoms arise when the encysted worm dies and the human mounts an associated inflammatory response. If the cyst lodges in the ventricular system (especially the fourth ventricle), hydrocephalus can occur.
Neurocysticercosis is more common among immigrants from endemic areas or children in contact with these immigrants.[7, 8] Several studies report approximately 1000 cases annually in adults and children. One study reported neurocysticercosis as the cause of 2% of the neurologic and neurosurgical admissions in southern California. With increasing immigration from Mexico and other endemic areas, incidence in the southern United States has been increasing. In a recent meta-analysis of the US medical literature, 1494 cases have been reported from 1980-2004.
Neurocysticercosis is highly endemic in Latin America, Mexico, Eastern Europe, Asia, Africa, and Spain. The estimated serologic prevalence in Mexican adults is 3.6%, with positive confirmation by autopsy in 1.9%. Approximately 50 million people worldwide are infected. World Health Organization estimates that more than 50,000 individuals die each year from neurocysticercosis.
Neurocysticercosis is typically benign, and most lesions spontaneously resolve within 2-3 months; however, mortality is highly dependent on whether the disease process is simple or complicated.
Simple neurocysticercosis occurs in children with only a single exposure to cysts. These children tend to have solitary cysts and fewer complications. Often, children can be treated symptomatically and have a favorable prognosis. This type of neurocysticercosis tends to be observed in the United States and other nonendemic areas.
Complicated neurocysticercosis occurs in children in endemic areas who are repeatedly exposed to ova. Because of complications from increased intracranial pressure and difficulty controlling seizures, these children may have a less favorable prognosis. Complications can arise from uncontrolled seizures, hydrocephalus, papilledema, and occasionally, headaches and emesis, although all of these complications are rare.
Neurocysticercosis tends to be diagnosed more frequently in Hispanics because of the prevalence of the organism in the countries of origin, rather than an innate property of the host child.
No sexual predilection has been noted.
Reports of cysticercosis are unlikely in children younger than 2 years because of the prolonged incubation period of T solium. Most often, the disease is recognized in children older than 7 years because of this incubation period.
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