Abstracts

Ictal electrographic patterns associated with epileptic spasms have not been well studied on chronic intracranial electrocorticography (ECoG) recording. Ictal ECoG changes were assessed in children with medically-refractory epileptic spasms. We have studied a consecutive series of 13 children (age: 5 months to 13 years; 7 girls and 6 boys; 8 had tuberous sclerosis complex, 3 had developmental malformations) where epileptic spasms were captured during a prolonged intracranial ECoG recording for subsequent cortical resection. Ictal onset zones were objectively delineated, using spectral analysis (Gotman et al, Electroencephalogr Clin Neurophysiol 1993;87:206-214; Asano et al, Clin Neurophysiol 2004 [in press]). The relationship between the ictal onset zone for epileptic spasms and that for focal seizures was assessed individually. Spasms were associated with widespread fast wave bursts exceeding 30 Hz over the neocortical regions on intracranial ECoG recording in all cases. Such spasm-related fast wave bursts were obscure on scalp EEG recording in 4/13 cases but well recognized on intracranial ECoG recording in all cases. Spasm-related fast wave bursts were superimposed on a delta wave activity on intracranial ECoG recording always in 11/13 cases and occasionally in 2/13 cases. Fifteen types of concomitant focal seizures were captured during the prolonged intracranial ECoG recording in 10/13 cases. Ten of the 15 focal seizures involved the neocortical regions, whereas the other five focal seizures mostly involved the medial- to sub-temporal regions. In a single child with tuberous sclerosis complex, both spasms and focal seizures originated from the same brain region along a massive frontal tuber. In the other nine children, there was no or minimal spatial overlap between the cortices showing a focal seizure onset and spasm-related fast wave bursts, although there was a close spatial and temporal relationship between the spasms and focal seizures in the majority of the patients. Cortical regions responsible for epileptic spasms may be, for the most part, distinct from those responsible for focal seizures. Further studies using other modalities such as diffusion tensor imaging or cortico-cortical evoked potential techniques may reveal the underlying connection between the cortices showing a focal seizure onset and spasm-related fast wave bursts as suggested by the temporal relationship between the two seizure types.