Is the anatomical lesion always guilty?: A case report

During a presurgical workup, when discordant structural and electroclinical localization is identified, further evaluation with invasive EEG is often necessary. We report a 44-year-old right-handed woman without significant risk factors for epilepsy who presented at 11 years of age with focal seizures manifest as jerking of the left side of her mouth and arm with frequent evolution to bilateral tonic-clonic seizures during sleep with a weekly frequency. During video-EEG monitoring, we observed interictal left fronto-central sharp waves and some independent sharp waves in the right fronto-central region. Habitual seizures were recorded and during the post-ictal state, the patient had left arm weakness for a few minutes. The ictal discharge on EEG was characterized by a bilateral fronto-central rhythmic slow activity more prevalent over the right hemisphere. MRI of the brain revealed a left precentral structural lesion. Considering the discordant structural and electroclinical information, we performed bilateral fronto-central stereo-EEG implantation and demonstrated clear right fronto-central seizure onset. Stereo-EEG-guided radiofrequency thermocoagulation was performed in the right fronto-central leads with subsequent seizure freedom for 9 months. The patient then underwent surgery (right fronto-central cortectomy), and histology revealed focal cortical dysplasia type Ia. The post-surgical outcome was Engel Ia. This case underscores the presence of a structural lesion is not sufficient to define the epileptogenic zone if not supported by clinical and EEG evidence. In such cases, an invasive investigation is typically required.