Surgery for drug resistant partial epilepsy in children with focal cortical dysplasia: anatomical-clinical correlations and neurophysiological data in 10 patients

Abstract

Objective: To analyse a population of children with focal cortical dysplasia operated on for drug resistant partial epilepsy, with emphasis on clinical features, seizure semiology, interictal and ictal EEG and stereo EEG findings, histological and topographical characteristics of the lesions, extension and localisation of cerebral excision, and its postoperative effect on seizure frequency. Methods: 10 patients were studied, aged between 26 months and 11 years (median 6 years). Magnetic resonance imaging (MRI) abnormalities were unilobar (temporal 3, frontal 2), bilobar (2), or multilobar (1); the two patients with negative MRI suffered from frontal seizures. Presurgical diagnostic steps varied in complexity and invasiveness depending on the anatomical/electrical/clinical features of each patient. In four patients they included only scalp video EEG monitoring, and in six, also invasive recordings using stereotactically implanted intracerebral electrodes. Surgery consisted of corticectomy plus lesionectomy in all cases. Results: 70% of the patients were seizure-free after a minimum postoperative follow up of 25 months. These included three patients with temporal lesions and four of seven patients with other lobar or multilobar extratemporal localisation. One patient had improvement in seizure control. Outcome was poor in multilobar patients, but a class Ia outcome was obtained in one case after partial lesionectomy associated with bilobar corticectomy. All patients showed developmental improvement. Conclusions: Analysis of the data in these patients allowed the production of an ''anatomical-clinical concordance'' list, which appeared to be correlated with the diagnostic steps performed. Carrying out a stereo EEG exploration in the most complex cases proved useful in defining the epileptogenic zone in extratemporal and multilobar epilepsies. Stereo EEG recordings facilitated a tailored resection of extralesional cortex.

Retrospective analysis of variables favouring good surgical outcome in posterior epilepsies

“…As suggested in several reports (see above) [7,13,19,20,27,29], the epileptogenic zone was identified as the cortical region in which ictal discharges arise and initially spread. In general, data available for epilepsy surgery in the posterior part of the brain are relatively rare compared with those of other regions of the brain.…”

“…According to Rosenow and Luders [23], the epileptogenic zone is the area of the cortex indispensable for the generation of epileptic seizures, as opposed to the seizure onset zone which is the area from which clinical seizures are actually generated. However, the French and Italian schools [7,13,19,20,27,29] identified the epileptogenic zone as the cortical region from which ictal discharges arise and initially spread. In this study we used the term epileptogenic zone according to the second definition.…”

Outcome after epilepsy surgery for cortical dysplasia in children

“…In the absence of a MRI lesion, resection of "epileptogenic areas" (seizure onset zone and areas with abundant interictal epileptiform abnormalities) as noted on intracranial EEG monitoring has been used as an indicator of complete resection [4,7]. Some studies used "histologically proven clear margins" as a criteria [26,27], and others have used intraoperative electrocorticography (ECoG) data to verify complete resection [27,28]. Despite frequent use of ECoG in epilepsy surgery, there is little to no published data on its effect on outcome in FCD.…”

Novel Animal Models of Pediatric Epilepsy

“…Abnormalities in neuronal migration (when newly developed neurons fail to reach their proper destinations) result in aberrant brain structures that are often termed cortical dysplasia. Dysplastic cell clusters and/or surrounding structures (neocortex or hippocampus) are often identified as the sites in which epileptic activities are generated, and invasive surgical resections of these "lesions" have been used to control seizures [69][70][71]. There are several animal models of neuronal migration disorders that can be induced by chemical treatments (e.g., methylazoxymethanol acetate), prenatal irradiation, modifications of cell development genes, or cortical freeze-lesions [72].…”