Neurocysticercosis in Radiographically Imaged Seizure Patients in U.S. Emergency Departments

Samuel Ong, David A. Talan, Gregory J. Moran, William Mower, Michael Newdow, Victor C.W. Tsang, Robert W. Pinner, and the EMERGEncy ID NET Study Group

Disclosures

Emerging Infectious Diseases. 2002;8(6) 

In This Article

Discussion

Immigrants continue to make up an increasing proportion of the U.S. population. By some reports, they will constitute up to 60% of the new immigrants and new births over the next few decades[18,19]. By the year 2037, Latinos will outnumber whites as the dominant ethnic group in California, mirroring a population surge that is sweeping across the Southwest[20]. Because neurocysticercosis is endemic in many of the countries from which these persons are emigrating, its presence in the United States reflects these immigration trends.

Previous etiologic surveys of seizures in the United States and other industrialized countries have focused on brain tumors, strokes, and birth defects[21,22,23]. Infections such as toxoplasmosis and meningitis or meningoencephalitis constitute a small minority of causes in seizure patients. More recently, HIV and its attendant complications have become prominent causes of adult-onset seizures[23]. Neurocysticercosis, while a prominent cause of seizures in less developed nations, has not appeared in these studies.

An increasing number of neurocysticercosis cases[5,6,7,8,9,10] have been reported throughout the United States, which suggests that the prevalence of this disease may be on the rise. Because these previous case series were conducted retrospectively, primarily through chart reviews over periods as long as a decade, understanding the epidemiology and impact of neurocysticercosis is difficult. To our knowledge, this prospective study is the first to address the prevalence of neurocysticercosis in seizure patients in the United States.

Neurocysticercosis was identified at 9 of 11 sites and was responsible for 2.1% of seizures overall. In some sites, e.g., Los Angeles, California, and Albuquerque, New Mexico, the prevalence was nearly 10%. That neurocysticercosis has not appeared in previous U.S. studies on the epidemiology of seizures and now appears in our study as the cause of up to 10% of seizures in some areas suggests a substantial increase in frequency of this disease. Another study from a Los Angeles-area hospital corroborates this finding: 12% of the seizures seen in the authors' emergency department were attributable to neurocysticercosis[24].

Previous reports on neurocysticercosis in the United States, mostly retrospective case series, have focused on the clinical and epidemiologic aspects of the disease[5,6,7,8,9,10] Those studies are somewhat limited by the inadequacies and incompleteness inherent in retrospective data collection. It also seems problematic when epidemiologic information (e.g., exposure to a disease-endemic area) constitutes part of the case definition/inclusion criteria (e.g., exposure to cysticercosis-endemic area) but then epidemiologic information is subsequently reported as a result (e.g., percentage of patients who had visited an area where cysticercosis is endemic). In contrast, our data were collected at the time of evaluation, and our case definition was based solely on clinical criteria. As such, our study provides additional corroboration to the findings of previous studies reporting strong associations between neurocysticercosis and Hispanic ethnicity, immigrant status, and prior exposure to disease-endemic regions. Neurocysticercosis patients were also more likely to be uninsured; however, lack of insurance was also associated with being Hispanic and an immigrant. Consistent with previous studies, most neurocysticercosis patients did come to the emergency department with a generalized tonic clonic seizure, but such patients were more likely to have focal motor or partial complex seizures than were the seizure patients without neurocysticercosis. On the basis of our results, neurocysticercosis must be strongly considered in emergency department seizure patients of Hispanic descent since nearly 1 in 10 were affected, a figure that was even higher in certain areas.

From 1988 through 1990, 7.2% of neurocysticercosis cases reported to the Los Angeles Department of Health Services were locally acquired[25]. The rate of domestic acquisition has been even higher (17% to 26%) in some studies of pediatric neurocysticercosis[6,8]. These rates of domestic acquisition appear to have increased from earlier studies in the late 1970s and early 1980s, when the rates were in the range of 2% to 3%. Because years can pass before symptoms develop, the incidence of domestically acquired cases will likely continue to rise.

The apparent increase in the prevalence of neurocysticercosis carries a substantial economic impact. Nearly half of the seizure patients in our study were admitted to the hospital. The average cost of hospitalization for seizures in one study was $1,615 per patient, not including physician charges[26]. The economic toll extends beyond such direct costs. Compared with the general population, seizure patients are seen in the emergency departments 21/2 times more frequently, admitted to the hospital 3 times more frequently, and treated by specialists 3 times more frequently; they also receive psychological counseling 7 times more frequently[27] These figures still underestimate the true economic impact of neurocysticercosis because up to 30% of patients who visit an emergency room do not have seizures but rather a variety of other neurologic symptoms such as headache, visual changes, ataxia, and confusion. Hydrocephalus may develop in a substantial number if patients, requiring neurosurgical intervention.

Any study of neurocysticercosis is limited by the difficulty in clearly establishing the diagnosis. The only true measure for the diagnosis of neurocysticercosis is brain biopsy, which is clearly impractical. This study therefore implemented a case definition that incorporates the classification scheme proposed by Del Brutto[17] but is therefore limited by the predictive value of CT scan and serology. Serology has previously been demonstrated to be sensitive in cases with multiple cysts (94%) but less sensitive with single cysts or calcified lesions (28%)[28]. Specimen storage and periodic bulk mailing may have further affected intrinsic test performance.

We found a considerable discrepancy between patients who were diagnosed with neurocysticercosis by their physicians and patients who met our case definition. Because we did not specifically ask the treating physicians how they arrived at their diagnosis, the exact reasons for this discrepancy are unclear. However, emergency room physicians appear to rely considerably on epidemiologic information when diagnosing neurocysticercosis. Of patients diagnosed by their physicians, 98% were Hispanic (compared with our 76%) and 80% were immigrants (compared with our 50%). Ten percent of the patients with physician-diagnosed neurocysticercosis had normal CT scans.

Additional limitations to the study include the fact that the participating network sites are university-affiliated emergency departments. This fact may limit the generalizability of our results to other patient populations. Ideally, serologic testing would have been performed on all patients, but laboratory testing is not routinely performed for all seizure patients seen in emergency departments. Patients who did undergo serologic testing were, however, not statistically different from those who did not, on the basis of the demographic information collected.

In summary, while neurocysticercosis accounts for a small proportion (2.1%) of all seizures in university-affiliated, U.S. emergency department patients, its geographic distribution appears diverse; the highest concentration is in the Southwest and in Hispanics. Our observations are consistent with current immigration trends that suggest the growing importance of neurocysticercosis in the United States. Continued surveillance and further studies of screening and treatment strategies appear warranted.

Presented at the 1997 annual meeting of the Society for Academic Emergency Medicine. Washington, DC, May, 1997.

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