In the WHO investigations conducted in southern Sudan in late 2001, skin snip positivity and higher microfilaria loads of O. volvulus were found in children with NS when compared to children without the condition, consistent with similar observations of a possible association between seizures and onchocerciasis from other studies (5, 10, 11, 12, 13, 14, 15, 16, 17, 44, 46). These, and subsequent investigations in 2002 by WHO could not identify any environmental pollutants, chemical agents or food toxins, nor several infectious agents, as possible causes for the seizures. EEG among 31 children assessed showed progressive epileptic encephalopathy.