Nodding syndrome and Onchocerciasis associated epilepsy (OAE).

BackgroundEpidemiological evidence suggests a strong association between onchocerciasis and epilepsy. A recent cohort study investigating the temporality of this association reported an increased risk to develop epilepsy following childhood infection with Onchocerca volvulus, with a strong dependence on the initial parasite load. Communities with high transmission of onchocerciasis are often confronted with a high burden of debilitating seizure disorders mainly affecting children and adolescents aged 3–18 years. These clinical conditions fit into the spectrum of onchocerciasis-associated epilepsy (OAE), which regroups generalized/focal epilepsy, nodding syndrome (NS), and Nakalanga features. The natural history of OAE is still poorly understood. However, follow-up data of persons with NS in Uganda suggests that the disease begins with an initial debilitating phase, which evolves towards the more conspicuous convulsive manifestations. This is confirmed by surveys in Cameroon where several persons with epilepsy (PWE) often showed signs of cognitive impairment reported to have started during their childhood or early adolescence. While seizure-related mechanisms can lead to cognitive deficits in PWE, it remains unclear if in the case of OAE, cognitive decline precedes the onset of seizures or is rather a consequence of the enduring epileptogenic state. A plausible hypothesis could be that an insidious deterioration of the cognitive function may occur before the onset of full-blown motor seizures observed in persons with OAE. Objectives and MethodsThe general objective of the proposed research is to identify early neurocognitive symptoms of OAE which could prompt rapid treatment, thus optimising patient prognosis. Specific objectives and methods include:• Neurocognitive assessment in children without epilepsy aged 5–15 years in onchocerciasis-endemic settings using validated tools• Investigating exposure to O. volvulus in these children by testing for Ov16 IgG antibodies testing by ELISA (as recommended by the World Health Organisation)• Case-control study comparing neurocognitive outcomes in onchocerciasis-exposed children (cases) and unexposed children (controls)• Community follow-up of all enrolled children to monitor signs of epilepsy onsetRelevanceOur findings would improve our understanding of the natural history of OAE, and thus inform policy makers regarding required interventions in affected communities. Our study addresses a real global health problem as it focuses on a neglected disease of poverty (onchocerciasis) and its interaction with a non-communicable condition (epilepsy). This project could result in strategies for early detection and management of OAE, but could also motivate stakeholders to strengthen onchocerciasis elimination efforts in epilepsy hotspots which are hyper-endemic for onchocerciasis.

Keywords:NODDING SYNDROME, ONCHOCERCIASIS, COGNITION, EPILEPSY

Disciplines:General diagnostics, Cognitive neuroscience