Abstracts

Rationale: The term “infantile spasms” has classically been associated with West syndrome, which is the triad of infantile spasms, developmental delay, and hypsarrythmia on EEG. It is also well known that spasms also occur outside of West syndrome, sometimes in other syndromes. Spasms have been described as a seizure type involving the axial musculature that often occur in clusters. The origination of spasms has not been definitively determined, with most investigators favoring a brainstem origin, as opposed to cortical. To our knowledge, electrical source analysis (ESA) has never been used to investigate this question. In this study, we looked at both the ictal EEG patterns in epileptic spasms to explore whether ESA can determine the origin of the ictal patterns.Methods: A database of epilepsy patients seen at Texas Children’s Hospital was reviewed to identify patients with epileptic spasms from 2014-2015. Seven patients were identified. Scalp EEG’s were retrospectively analyzed using the Curry Imaging Suite, developed by Compumedics, Inc. The scalp EEG was recorded using 10-20 international system. The EEG activity was digitally recorded referentially to midline electrodes using the Nicolet digital video EEG system. A neurophysiologist experienced in ESA analyzed the ictal waveforms using the software. A standardized Boundary Element Model was used in each case. The dipole sources were assessed for each patient. Clinical history, etiology, and MRI findings were also assessed for each patient.Results: Of the seven patients, two fulfilled criteria for cryptogenic West syndrome. Two other patients were also cryptogenic, one had Lennox Gastaut syndrome due to diffuse bilateral heterotopias, one had seizures due to a right temporo-occipital infarct, and one had tuberous sclerosis. All patients except one had clinical spasms temporally associated with a high amplitude slow wave in the vertex region, maximal either Fz, Cz, or Pz. The exception had a maximal negative slow wave in the right frontal region (F4). Source analysis of these waveforms all showed dipole sources in the interhemispheric regions (two frontal, four central, and one occipital). Four had vertical orientations of the dipoles, two had anterior-posterior orientations. The case with the maximal negative slow wave in the F4 region had a horizontal dipole source in the left mesial frontal region.Conclusions: Epileptic spasms are a specific seizure type characterized by prominent axial musculature activation of the neck, trunk, and limbs. Source analysis of ictal patterns associated with these seizures suggests interhemispheric frontal or central origin in most cases. Depth recordings in one case did confirm a source of the ictal slow wave in the superior bank of the cingulate sulcus. This is significant because of its proximity to the supplementary sensory motor area, which is known to cause activation of the axial musculature (both unilateral and bilateral), and may provide a reasonable hypothesis for the semiological features of epileptic spasms.