Cortical Dysplasias and Epilepsy: Multi‐Institutional Survey in Japan
Authors: Shimada Morimi , Iinuma Kazuie , Hashimoto Toshiaki , Kondoh Ikuko , Miike Teruhisa , Takano Tomoyuki 
Published: August 2005

Purpose: Cortical dysplasia (CD) is a major brain malformation causing intractable epilcpsy. Neurosurgery now succcssfully controls some intractable epilepsies associated with CD. In this study, thc incidence 11 epilepsy and thc frequency of seizurcs were analyzed in different types 01 CD.

Methods: This study, supported by a rcse;lrch grant from the Ministry of Health and Wellare of Japan, is part of a research project on the clinical presentation and pathogcnesis of brain dysgenesis. Questionnaires regarding the type of CD, family and pact historics, clinical signs and symptoms and their severity were distributed to I200 institutions comprising child neurologists or pediatricians. CDs werc classified into following 6 types; lissencephaly (agyria‐pachygyria spcctrum), cobblestone lissencephaly, polymicrogyria including schizencephaly and hilateral perisylvian syndrome, diffuse heterotopia, focal heterotopia, and hemiinegalencephaly. All patients who had been diagnoscd as CD either by MRI, CT, autopsy or histological cxamination at or after surgical treatment wcre included. Diagnosis of CD by CT or MRI was mainly made by a radiologist, child neurologist, or pediatrician. Double classification was corrected. Epilepsy was classified according to criteria of the ILEA. Seizure frcquencies wcre recorded.

Results: A total or 676 cases from 328 institutions was availablc, and distributed as follows: 277 of lissencephaly, I48 of cobblestone lissencephaly (10 cases of Walkcr‐Warburg syndrome and 138 Fukuyaina type congcnital muscular dystrophy), I30 of polymicrogyria, 40 of diffuse heterotopia (24 subcortical band hetcrotopia and I6 perivcntricular nodular hcterotopia), 37 of focal heterotopia, and 44 of hemimegalencephaly. In 130 cases of polymicrogyria, 13 cases of bilatcral perisylvian syndrome, and 38 cases of schizencephaly were includcd. Of 667 cases available for study, 500 (75.0%) had epilepsy in which generalized epilepsy including West and Lcnnox syndromes comprised 54.1 % and localization‐related epilepsies comprised 46.7%. Thc frequency of seizures could be ascertained in 455 cases, of which 36.0% had daily seizures, and I I .4%) had more than onc seizure per week. The incidencc of epilepsy in cach type of CD was as follows: 86% inlissencephaly, 50% in cobblestone lissencephaly (patients with WalkcrWarburg syndrome had epilepsy in 90%, whercas those with Fukuyama type congenital muscular dystrophy had epilepsy in 46.7%), 71.3% in polymicrogyria, 77.5% in diffusc hetcrotopia (9 1.7% in subcortical band heterotopia and 56.2% in periventricular nodular heterotopia), 74.3% in focal heterotopia, and 93.2% in hemimegalcncephaly.

Conclusion: As recent investigations have reported, this study confirmed the high incidence of intractable cpilepsy in CDs. Epilepsy was more prevalcnt in cases with subcortical heterotopia than i n cascs with periventricular nodular helcrotopia. Thc incidcnce or epilepsy was also higher in the focal hcterotopias located subcortically than those dccper in white matter or in the periventricular region. Thcse differences in incidence of epilepsy depending on the location of hcterotopia may give somc clues to the nature of epileptogenesis in CD.