The "nodding syndrome" mystery illness

From Scientific American:

Nodding syndrome is a poorly understood and seemingly growing problem in eastern Africa, where it is devastating communities in South Sudan and northern Uganda. It has existed separately for decades in a secluded mountainous area of southern Tanzania. In South Sudan, "it's affecting thousands of children..."

Most children it strikes are aged between 5 and 15. It impairs both physical growth and cognitive development. Its hallmark head nodding--often brought on by eating, and sometimes by cold--occurs when abnormal brain activity causes a brief lapse in neck muscle tone, causing the head to fall forwards. Electroencephalograms conducted by CDC investigators and others have shown subtler, sub-clinical seizures in many children, and some magnetic resonance imaging scans have revealed brain atrophy and damage to the hippocampus and to supportive brain cells known as glia...

And although a study in southern Tanzania showed familial clustering, genetics alone cannot explain the rapid emergence of so many cases. In one village that the CDC team visited during the recent trip, almost every family had an affected child...

Via Salon.  Some discussion re possible etiology at both links.