Neurophysiological and clinical findings on Nodding Syndrome in 21 South Sudanese children and a review of the literature

Purpose To describe the neurophysiological and clinical features of Nodding Syndrome (NS) in South Sudan. Methods The study was performed at the Epilepsy Service of "Usratuna" sited in Juba, South Sudan. The clinical history of each subject was collected along with an EEG tracing. Results Twenty-one children (10 females) were diagnosed with NS. Fifteen (72%) children were classified as Probable NS and six (28%) as Confirmed NS. They ranged in age between 6 and 14 years, and age at seizure onset ranged from 5 to 12 years. All the subjects presented with intellectual disability which was mild in severity in 12 (57%) cases, moderate in seven (33%) cases and severe in two (10%) cases. Interictal EEG was abnormal in 20 subjects. In 18 (85%) subjects, the EEG showed 2-3.5 Hz spike-and-wave discharges often intermingled with sharp waves. Intermittent light stimulation was normal. In 12 (57%) children, interictal abnormalities were activated by hyperventilation. Ictal EEG was obtained in three patients. In all ictal EEGs head nodding episodes came in clusters during hyperventilation. None of the patients achieved good seizure control even if all of them received antiepileptic treatment (carbamazepine alone [43%] or in association with phenobarbitone or phenytoin). Conclusion This study confirms that NS is an encephalopathy and intellectual disabilities are partially independent of seizure frequency and EEG pathological activity. Based on interictal and ictal EEG patterns and on the experience of other researchers, valproic acid would seem to be the first-choice antiepileptic drug. NS in South Sudan presents with clinical and neurophysiological features which are similar to those described in northern Uganda and more severe than in Tanzania.