Racial/ethnic backgroundb White, non-Hispanic Features Sex, male Black Hispanic Insurance status Medicare/private Medicaid Uninsured Immigrant statusc Born in US Not born in US Unknown Exposure to endemic region No travel out of US Exposure to endemic region Unknown travel history Positive prior history No prior history Seizure type Generalized Tonic/clonic Focal motor Partial complex Unknown/ undocumented Seizure history New onset Prior seizure history Serologic testing Seropositive Seronegative Disposition Admission 4 (10.8) 3 (8.1) 29 (78.4) 7 (18.9) 3 (8.1) 22 (59.5) 5 (21.0) 12 (50.0) 7 (29.0) 0 (0) 28 (75.7) 9 (24.3) 3 (16.0) 16 (84.0) 4 2 (5.4) 7 (18.9) 2 (5.4) 19 (51.0) 17 (46.0) 9 (36.0) 16 (64.0) 16 (43.0) Prior history of neurocysticercosisc 26 (70.3) 1,551 (86.4) Table 4. Demographic and clinical characteristics of neurocysticercosis patientsa and non-neurocysticercosis patients Neurocysticer- cosis patients n=37 (%) 27 (73.0) Non-neurocys- ticercosis patients n=1,796 (%) 1,189 (66.0) 865 (48.0) 1.0 (0.5 to 2.0) Discharge 15 (41.0) 801 (45.0) aA patient was a person who met the case definition for neurocysticercosis. See text. The median age for neurocysticercosis patients was 32 yrs, with a range of 25–44 yrs; the median age of non-neurocysticercosis patients was 40 yrs (range 30–52 yrs). bn = 36 for this category. cn = 1,343; immigrant status was not collected from the first 490 patients enrolled. dGeneralized seizure versus focal motor or partial complex seizures. eNA, not applicable. Comparison was not done since serology was part of the case defini- tion for neurocysticercosis. CI, confidence intervals. 746 (41.6) 640 (35.7) 291 (16.2) 455 (25.3) 386 (21.5) 738 (41.1) 815 (62.0) 166 (13.0) 343 (26.0) 950 (52.9) 314 (17.5) 532 (29.6) 5 (0.5) 906 (99.5) 112 (6.2) 79 (4.4) 54 (3.0) 877 (49.0) 793 (44.0) 9 (1.0) 856 (99.0) Relative risk 95% CI 17.1 (7.9 to 37.1) 2.5 (1.2 to 5.2) 11.1 (3.9 to 31.0) 158 (9.7 to 2,581) 21.6 (7.8 to 59.8) 0.38 (0.18 to 0.80)d 1.1 (0.56 to 2.02) NAe RESEARCH Previous etiologic surveys of seizures in the United States and other industrialized countries have focused on brain tumors, strokes, and birth defects (21–23). Infections such as toxoplasmosis and meningitis or meningoencephalitis consti- tute a small minority of causes in seizure patients. More recently, HIV and its attendant complications have become prominent causes of adult-onset seizures (23). Neurocysticer- cosis, while a prominent cause of seizures in less developed nations, has not appeared in these studies. An increasing number of neurocysticercosis cases (5–10) have been reported throughout the United States, which sug- gests that the prevalence of this disease may be on the rise. Because these previous case series were conducted retrospec- tively, primarily through chart reviews over periods as long as a decade, understanding the epidemiology and impact of neu- rocysticercosis is difficult. To our knowledge, this prospective study is the first to address the prevalence of neurocysticerco- sis 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 sei- zures and now appears in our study as the cause of up to 10% of seizures in some areas suggests a substantial increase in fre- quency 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 (5–10) Those studies are somewhat limited by the inadequacies and incom- pleteness 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 cysticerco- sis-endemic area) but then epidemiologic information is subse- quently reported as a result (e.g., percentage of patients who had visited an area where cysticercosis is endemic). In con- trast, 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 neuro- cysticercosis 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 neurocys- ticercosis 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 Emerging Infectious Diseases • Vol. 8, No. 6, June 2002 611