Abstracts

Children with focal cortical dysplasia frequently present with multiple seizure types or secondary generalized seizures refractory to multiple antiepileptic drugs. Surgical interventions cannot completely stop seizures in some patients because of probable secondary epileptogenesis. To understand the temporal and spatial evolution of secondary epileptogenic foci in focal cortical dysplasia, we analyzed EEG, MEG, MRI, pathology and surgical treatments. We identified 54 patients with intractable epilepsy secondary to cortical dysplasias confirmed by MRI or pathology between 1998 and 2005. We analyzed their seizure history, MRI, ictal onset and interictal discharges on routine EEG, prolonged video-scalp EEG and video subdural EEG and MEG interictal spike sources. We defined the secondary epileptogenic foci as any independent and remote interictal epileptiform discharges, subsequently additional and remote or generalized ictal onset discharges on scalp video EEG and remote interictal MEG spike sources from the initial ictal onset zones captured on the first video scalp EEG. We used the definition of a [ldquo]mirror[rdquo] as secondary epileptogenesis over the contralateral homotopic cortex, and we used [ldquo]migration[rdquo] to describe secondary epileptogenesis involving non-homotopic cortex.( Morrel, F. 1985) Forty-one patients who went on to develop a secondary epileptogenic focus had a mean age of 4.3 years (range of 1 week to 13 years) and an average of 7.5 years seizure duration (range from 2- 15 years). Thirty-four (83%) of 41 children of these subjects developed a [ldquo]mirror focus[rdquo] located in the contralateral side while 31 subjects (75%) had [ldquo]migration foci[rdquo] which involved non-homotopic cortices. Of the 54 patients studied, 33 patients ( 61%) proceeded to surgery at an average age of 10.7 years (range 5 months [ndash] 18 years). Four patients(12%) had a dual pathology of a concomitant mesial temporal sclerosis or a dysembryoplastic tumor. Seventy-six% of pediatric patients with intractable epilepsy secondary to cortical dysplasias proceed to develop a secondary epileptogenic focus. These findings have implications on the clinical prognosis and timing of surgical intervention in patients with cortical dysplasia.
Morrel, Frank. [underline]Secondary Epileptogenesis in Man.[/underline] Arch of Neurology 1985; 42:318-325.