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1. Introduction
Lennox-Gastaut syndrome (LGS) is a generalized epilepsy characterized by an electroclinical trial of diffuse slow spikes-and-wave (SSW) complex with paroxysmal fast activity during sleep on electroencephalogram, mental retardation, and multiple types of generalized seizures, including atypical absences, tonic, and atonic seizures [1, 2]. LGS is usually caused by bilateral diffuse encephalopathy but localized cortical lesions, such as cortical dysplasia, cortical tuberous sclerosis, tumor, band heterotopia, and vascular malformation can also cause LGS [2–5]. In such cases, removal of cortical tumor or lesionectomy can result in seizure-free and normal development [6–9]. These observations suggest that LGS patients resulting from localized structural abnormalities are amenable to early surgical treatment with a significant impact on seizure control and cognitive development.
It has also long been noted that the interictal and ictal epileptic discharges in LGS patients are usually bilateral, synchronous, and symmetrical, but in some patients the SSW pattern shifts asymmetrically over the two hemispheres in different bursts, which suggests that multifocal lesions may exist in both hemispheres [10, 11]. Persistent focal or lateralized asymmetry of SSW activity may occur in as many as 25% of the LGS patients and is more common in patients with cognitive deficits [2, 11], which implies that focal lesions may exist in some subjects. Indeed, in sporadically reported cases multiple subpial transection with minimal cortical resection can result in satisfactory seizure control and/or IQ improvement in LGS subjects [6–8, 12]. Based on these observations, we believe that a considerable number of LGS patients may have a single- or multiple-unilateral cortical lesions causing secondary generalized epileptic discharges and that resective surgery should be effective in these patients.
Indeed, evidences have been accumulating to support our hypothesis. First, Wyllie and colleagues have demonstrated that children or adolescents with abundant generalized or bilateral epileptiform discharges on EEG can be successfully treated with surgery in selected patients [9]. Second, Lee and coworkers have recently showed that, despite abundant generalized and multiregional EEG anomalies, resective epilepsy surgery can be successful in some children with LGS [13]. However, in the study of Lee et al., patients with contralateral ictal epileptic discharges were all excluded. Here, we are the first ever to report, to the best of our knowledge, that epilepsy surgery can also be considered in...