The neurology of chronic nodding syndrome

Nodding syndrome is an uncommon disorder of childhood onset and unknown cause, presenting with nodding seizures, and which appears to occur exclusively in clusters in sub-Saharan Africa. An endemic pattern of disease was initially described in Tanzania and in Liberia; epidemic occurrences were later reported in South Sudan and northern Uganda. Not the least significant of the many questions remaining about nodding syndrome concerns the common presence or otherwise of neurological features other than seizures-clearly relevant to the core issue of whether this is a focal, primary epileptic disease, or a multi-system CNS disorder, with, in turn implications for its aetiology. We had the opportunity to interview and clinically to examine 57 affected individuals in rural northern Uganda some 10 years after onset. In this observational cross-sectional study, nodding onset was invariably between the ages of 5 and 14, presenting with food-triggered nodding attacks in over 75% of cases; 86% went on to develop other seizure types. In 53 of 57 nodding syndrome individuals (93%), there was a definite history of the child and his or her family having resided in or been fed from an internally displaced person camp for some time prior to the onset of nodding. A half of nodding syndrome sufferers (28/57) had focal neurological abnormalities-mainly pyramidal signs (92%), often asymmetric, some with extrapyramidal abnormalities. Many individuals (28/57) were severely functionally disabled, ranging from 'sometimes can dig' to 'can do nothing at home' or 'cannot even feed herself'. Such sufferers tended more frequently to have significant burns, and clear cognitive impairment. We conclude that nodding syndrome is a unique multisystem CNS disorder of childhood onset and then slow progression over several years often followed by spontaneous stabilisation, consistent with an underlying self-limiting neurodegenerative process. We discuss the possibility that this might be triggered by food-related mycotoxins, within a fixed window of CNS vulnerability during childhood.