Abstracts

RATIONALE: The functional reorganization of dysplastic cortex is poorly understood and becomes a crucial issue when ablative surgery is considered for treatment of refractory epilepsy.
METHODS: We report a retrospective study of eleven adults patients with malformations of cortical development demonstrated by MRI who underwent presurgical evaluation including stereotaxic implantation of depth electrodes for direct recording seizures and cortical stimulation. All patients had medically intractable epilepsy associated with focal cortical dysplasia (n=4), hippocampal dysgenesis (n=3), occipital polymicrogyria (n=2) and subcortical heterotopia (n=2). The functional mapping was performed by using the intracortical contacts to delivered high-frequency electric stimulation.
RESULTS: In eight patients the lesion was located in potential eloquent area. Cortical stimulations evoked symptoms suggestive of a functional role of the abnormal cortex in five of them.For this patients, the dysgenesic cortex was shown to be involved in important cortical functions despite of its cytoarchitectural disorganization: language in two patients (temporal heterotopia and focal cortical dysplasia), motor control in two patients (central focal cortical dysplasia and subcortical heterotopia) and vision in one patient (occipital polymicrogyria). In the later patient, visual evoked potential recorded in the dysgenesic cortex itself were normal.
CONCLUSIONS: We conclude that functional mapping of the abnormal cortex is mandatory before the surgical resection of epileptic malformation of cortical development.