An updated estimate of the proportion of neurocysticercosis among people with epileptic seizures: a systematic review and Bayesian meta-analysis

Abstract

BACKGROUND: Neurocysticercosis (NCC) is an infection of the central nervous system caused by the larval stage of Taenia solium. This systematic review (PROSPERO identifier: CRD42021266596) aimed to estimate the pooled proportion of NCC among people with epileptic seizures (PWES) between 1990 and 2023, and to assess whether this proportion changed between January 1990 to May 2008 and June 2008 to May 2023 across endemic regions. METHODS: Twenty electronic databases were searched in May 2023 for records on NCC published between January 1, 1990, and May 9, 2023. Two reviewers independently screened all records. Original studies that reported NCC frequency among PWES, used neuroimaging, biopsy, or autopsy to diagnose NCC, and were not prone to high level of selection bias were included. Reviews, book-chapters and case series with fewer than 20 participants were excluded. Methodological quality of the included studies was assessed using the Joanna Briggs Institute checklist for prevalence studies. Bayesian models were used to estimate pooled NCC proportions and assess their changes by study periods and regions. RESULTS: Among 16,202 screened records, 77 studies met the inclusion criteria. Thirty-five studies included PWES from both sexes, all age groups (children and adults), and used clear case definitions. The pooled proportion of NCC among PWES in these studies was 25.2% [95% Bayesian credible interval (BCI): 19.5%-32.2%], with fairly-high between-study heterogeneity (τ = 1.0; 95% BCI: 0.8-1.3). Studies without clear definitions for NCC or epileptic seizures reported considerably lower proportions, suggesting misclassification error. NCC proportion did not vary by sex or age. NCC proportion declined between June 2008 and May 2023, across Africa, the Americas and Southeast Asia. CONCLUSION: This study provides an updated estimate of NCC proportion among PWES between 1990 and 2023, with implications for burden estimation, and highlights its decline in endemic regions. However, substantial between-study heterogeneity indicates context-specific differences; therefore, the pooled estimates should be interpreted cautiously and not as universally generalizable. Further research should determine whether the observed decline in NCC proportion is real or reflects an apparent reduction resulting from changes in case definitions, study populations, neuroimaging technologies, or underlying causes of epileptic seizures.