Abstracts

Rationale: Nodding syndrome (NS) is a childhood-onset, progressive epileptic disorder characterized by pathognomonic paroxysmal spells of repeated head drops lasting for minutes, often triggered by sensory stimuli (e.g. food and cold) [1]. While epidemic outbreaks of NS have been reported in several countries in eastern sub-Saharan Africa [1], the neurophysiology and the clinical characteristics of this syndrome remain poorly understood.  We describe the interictal and ictal electrographic features of head nodding and associated clinical features. Methods: Nested within a prospective cohort, a sibling-pair analysis was performed. 20 pairs of children with NS and their unaffected younger sibling who were clinically normal from a northern Ugandan rural community with high prevalence of NS underwent cognitive assessment, detailed neurological exam, and extended video-EEG using a portable system. Two board-certified epileptologists blinded to the clinical features of the subjects reviewed the EEG. STATA 12 was used for statistical analysis. Results: Children with NS were aged 12-18 (mean 16) years and their siblings 7-14 (mean 10) years. Mean age of onset of repeated clusters of head drops with dorsoventral movement was 6.7 (range: 3-14) years. At the time of evaluation children with NS had head nodding spells for a mean duration of 9.6 (range: 3-14) years. Over half (55%) subsequently developed generalized tonic-clonic seizures 2.2 (mean, range: 0-8) years after onset of head nodding. Children with NS performed poorly on a cognitive screen test (assessing orientation, immediate and delayed memory, and concentration) compared to their unaffected younger siblings (p=0.03). Nodding spells were not precipitated by food or sight of food in our study. During the cluster of head nodding subjects appeared to have impaired awareness. Interictal EEG frequently showed 2-Hz generalized spike-and-wave discharges and a slow (delta-theta range) background. Ictal EEG time-locked to the head-nodding episodes, which always occurred in clusters, revealed two electrographic phenomena: 1) sharp and slow wave complex followed by superimposed generalized fast activity, and 2) high amplitude bifrontally predominant slow wave followed by irregular sharply contoured rhythmic activity. Conclusions: Our results indicate that head nodding episodes in NS are likely late-onset epileptic spasms. Similar to spasms, the semiology of head nodding always occurs in clusters with repeated dorsoventral movement of the head and occasional trunk flexion. The electrographic findings of high voltage slow wave followed by brief generalized fast activity resemble the electrographic findings of spasms [2,3]. Using ILAE 2017 operational classification, we propose NS to be included as epileptic spasms of unknown etiology.References:1. Tumwine et al. African Health Sciences 2012;12:242-248.2. Sotero De Menezes et al. Epilepsia 2002;43:623-630.3. Fusco et al. Epilepsia  1993;34:671-678,. Funding: American Epilepsy Society Seed Grant