The Neurocognitive Burden of Onchocerciasis-associated Epilepsy in an onchocerciasis-endemic zone in Cameroon: a case-control study

Abstract

Background A specific form of epilepsy called onchocerciasis-associated epilepsy (OAE) is common in onchocerciasis-endemic communities. Data on the prevalence and pattern of neurocognitive impairment caused by OAE is sparse in Africa. This aim of this study was to determine the spectrum and severity neurocognitive impairment among patients with OAE in two onchocerciasis-endemic communities. Methods A case-control study was conducted in two rural villages in an onchocerciasis-endemic zone in the central region of Cameroon. Based on diagnostic criteria established in other studies, we diagnosed patients with onchocerciasis-associated epilepsy and matched by age, sex, and educational level to controls. Neurocognitive functions were assessed using the Montreal Cognitive Assessment Test, Frontal Assessment Battery, International HIV Dementia Scale, Dubois’ Five Words Tests and Isaac Set’s tests. Data were analyzed using SPSS software version 19. The threshold for statistical significance was set at P < 0.05. Results The study included fifty people with OAE and fifty healthy controls. The mean age for the cases was 26.3 years, and for the controls, it was 26.4 years. Cases were more impaired cognitively than the controls, 96% for the cases vs. 78% for the controls (P = 0.007, OR;7.7). The main cognitive functions affected were memory (86% of cases Vs 30% of controls, P < 0.001, OR = 34.4), verbal fluency (80% of cases Vs 42% of controls, P < 0.001, OR = 15.6), attention, and executive functions (80% of cases as against 42% of controls, P < 0.001). The main factors associated with poorer neurocognitive outcomes were longer duration of epilepsy (P < 0.001), frequent seizures (P < 0.001), low educational level (P = 0.027), generalized tonic-clonic seizures (P < 0.001) and early age of onset of epilepsy (0.001) Conclusion Onchocerciasis-associated epilepsy causes severe neurocognitive impairment in those affected. The need to eliminate onchocerciasis and, hence, reduce the prevalence of OAE has never been more imperative.