Chapter 97 - Neurocysticercosis

Abstract

Known as a disease of swine in ancient civilizations, cysticercosis is currently considered the most common helminthic infection of the nervous system, and a leading cause of acquired epilepsy worldwide. The disease occurs when humans become intermediate hosts of the tapeworm Taenia solium by ingesting its eggs from contaminated food or, most often, directly from a Taenia carrier by the fecal-oral route. Once in the human intestine, Taenia eggs evolve to oncospheres that, in turn, cross the intestinal wall and lodge in human tissues - especially the nervous system - where cysticerci develop. The brain is a hostile environment in which parasites attempt to escape the immune surveillance while the host is trying to drive out the infection. In some cases, cysticerci are destroyed by this immunological attack, while in others, parasites may live unchanged for years. Cysticerci may be located in brain parenchyma, subarachnoid space, ventricular system, or spinal cord, causing a myriad of pathologic changes that are the main changes responsible for the clinical pleomorphism of neurocysticercosis. Seizures are the most common clinical manifestation of the disease, but some patients present with focal deficits, intracranial hypertension, or cognitive decline. With the exception of cystic lesions showing the scolex as an eccentric nodule, neuroimaging findings of neurocysticercosis are nonspecific and may be seen in other diseases of the nervous system. Likewise, immune diagnostic tests have been faced with problems related to poor sensitivity or specificity. Accurate diagnosis is possible after interpretation of clinical data together with findings of neuroimaging studies and results of immunologic tests, in a proper epidemiologic scenario. The introduction of cysticidal drugs has changed the prognosis of neurocysticercosis. Praziquantel and albendazole have been shown to reduce the burden of infection in the brain (as seen on neuroimaging studies) and to improve the clinical course of the disease in most patients. Further efforts should be directed towards eradicating this disease through the implementation of control programs for all the interrelated steps in the life cycle of T. solium, including human carriers of the adult tapeworm, infected pigs, and eggs in the environment.