Abstracts

Rationale: Lennox-Gastaut syndrome (LGS) is an age specific epileptic encephalopathy with multiple seizure types, slow spike-waves in waking EEG and fast rhythmic bursts during sleep, and cognitive impairment. The International League Against Epilepsy (ILAE, 1989) classifies LGS as cryptogenic or symptomatic. The symptomatic group accounts for approximately 75% of cases and includes disorders such as cerebral palsy, cerebral trauma, encephalitis or malformations of cortical development (MCD). MCDs are a heterogeneous group of cerebral abnormalities determined by disrupted stages of neuronal development. We aimed to delineate the spectrum of MCDs, which cause LGS and compare the epileptology and types of MCDs associated with LGS and focal epilepsies due to MCDs. Methods: We identified 222 patients (118 women/ 104 men) aged 1-75 (mean 30.8; median 28.5) years with MCD and epilepsy at the Departments of Neurology and Pediatrics, Medical University of Innsbruck, Austria. All were clinically examined, underwent EEG and high-resolution MRI (1.5-Tesla). Seizure types and epilepsy syndromes were categorised according to the ILAE classification (1981, 1989). Fisher’s exact test and t-test for independent samples were used for comparison of categorical data. Mann-Whitney test was used for the comparison of age at seizure onset in relation to epilepsy syndrome. P-values < 0.05 were regarded as statistically significant. Results: LGS was observed in 25/222 (11.3%) of patients with MCD. MCD spectrum causing LGS included microcephaly (n=8), tuberous sclerosis (n=7), polymicrogyria (n=4), hemimegalencephaly (n=2), subcortical band heterotopia (n=2), lissencephaly (n=1) and periventricular nodular heterotopia (n=1). The majority of patients with microcephaly 8/12 (67%; p=0.001) and about the third of patients with tuberous sclerosis 7/23 (30%; p=0.001) had LGS. The minority of patients with periventricular nodular heterotopia 1/29 (3.4%; p=0.214), polymicrogyria 4/40 (10%, p=0.792) and hemimegalencephaly 2/11 (18%; p=0.357) had LGS. None of patients with focal cortical dysplasia (n=62), ganglioglioma (n=26) and dysembryoplastic neuroepithelial tumour (n=8) had LGS. Two out of four patients with subcortical band heterotopia and one out of two with lissencephaly had LGS. The majority of patients with LGS had diffuse/ multifocal MCD - 22/25 (88%) compared to patients with focal epilepsies - 68/197 (34%); p<0.001. Learning disability was prevalent in patients with LGS - 22/25 (88%) compared to patients with focal epilepsies - 71/197 (36%); p<0.001. The rate of pharmacoresistant seizures was higher in patients with LGS - 22/25 (88%) versus patients with focal epilepsies due to MCDs- 77/197 (39%); p<0.001. Patients with LGS had earlier onset of seizures - mean 29.4±39 months compared to the ones with focal epilepsies - mean 157.4 ±139.3 months.