Proposal of diagnostic criteria for human cysticercosis and neurocysticercosis

Abstract

Taenia solium cysticercosis is a major public health problem in several areas of the world. While the disease has a recognized etiologic agent, its definitive histological diagnosis is not possible in most cases because this parasite tends to lodge in cerebral tissues where routine biopsy is not feasible. Therefore, the diagnosis of human cysticercosis (and neurocysticercosis) should rest on the proper interpretation of the patients' symptoms together with data provided by radiological studies and immunologic tests for the detection of anticysticercal antibodies. Unfortunately, the pleomorphism of this parasitic disease creates confusion when non-specific clinical, radiological, or immunologic criteria alone are used to detect cases among populations or to diagnose hospitalized patients with neurological manifestations. We propose a chart of diagnostic criteria for human cysticercosis that objectively permit clinicians and health care workers to evaluate clinical, radiological, immunologic, and epidemiologic data of patients. The chart uses four degrees of criteria: absolute, major, minor, and epidemiologic, that were selected on the basis of their individual diagnostic strength. Interpretation of such criteria will result in three categories of diagnostic certainty: definitive, probable and possible, according to the likelihood that cysticercosis is present in a given person.

Introduction

Cysticercosis is a disease caused by the encysted larval stage of the tapeworm Taenia solium that occurs when humans become the intermediate host in the life cycle of this cestode by ingesting its eggs from contaminated water or food, or through the anus-to-mouth auto-infective route in individuals who harbor the adult parasite in their small intestine (Del Brutto and Sotelo, 1988). Cysticercosis occurs worldwide, and is currently considered the most common parasitic disease of the central nervous system, affecting thousands of individuals living in developing countries of Latin America, Africa, and Asia, as well as in industrialized nations with a high index of immigrant population from disease-endemic areas (Lombardo and Mateos, 1961; Gajdusek, 1978; Richards et al., 1985; Mignard et al., 1986; Earnest et al., 1987; Dumas et al., 1990; Diaz et al., 1992).

Diagnosis of human cysticercosis remains a challenge. While modern immunologic techniques and neuroimaging studies permit the recognition of an increased number of cases, such sophisticated diagnostic approaches are not always available in areas of the world where this disease is endemic. In addition, the lack of pathognomonic clinical manifestations, and the fact that many patients remain asymptomatic despite long-term and even severe infections (Sotelo et al., 1985) creates confusion when clinical criteria alone are used to detect possible cases among populations. Over- and misdiagnosis of cysticercosis has been a weakness in almost every epidemiologic study that has attempted to determine the prevalence of this disease in a given population. On the other hand, even in hospitalized patients undergoing sophisticated tests, diagnostic confusion occurs because of the lack of specificity of some neuroimaging findings, and the number of false-positive and false-negative results that may occur with some immunologic diagnostic tests.

More exact diagnostic criteria for human cysticercosis is needed to determine its prevalence in different populations, to compare epidemiologic surveys, to evaluate new therapeutic approaches, and to avoid diagnostic pitfalls in hospitalized patients. For these reasons, we joined efforts to create a chart of diagnostic criteria that objectively help physicians and health care providers to evaluate the clinical, radiological, and immunologic data of patients based on three degrees of diagnostic certainty: definitive, probable, and possible. This chart represents our experience on the diagnosis of cysticercosis after several years of community-based and hospital-based studies in America, Asia, Africa, and Europe.