Brief potentially ictal rhythmic discharges on intraoperative electrocorticography predict a good outcome of focal cortical dysplasia after surgical resection: a case report

Background Focal cortical dysplasia(FCD)is a common cause of drug-resistant epilepsy.Electroencephalography(EEG)biomarkers that predict good postoperative outcomes are essential for identifying patients with focal epilepsies.Case presentation We report the case of a 21-year-old female with seizure onset at the age of 9,characterized by left-hand dystonic posturing and impaired awareness,which evolved to bilateral tonic-clonic seizures,evaluated in a neurological referral center in Lima,Peru.During 6-h video-EEG,interictal EEG revealing focal brief potentially ictal rhythmic discharges(BIRDs)over the right frontal central region,lasting less than 10 s.The ictal features were characterized by low-voltage fast activity over the same area.Brain magnetic resonance imaging(MRI)demonstrated a focal lesion of focal cortical dysplasia type II in the right frontal lobe.The patient underwent a lesionectomy guided by electrocorticography,which showed continuous polyspikes.BIRDs showing a brief burst of spikes lasting longer than 0.5 s,were also identified on intraoperative electrocorticography(ECoG)and helped define the extent of resection.The patient obtained an Engel Outcome Class IA at 6 years of follow-up.Conclusions The atypical BIRDs on ECoG can be used as a prognostic biomarker for prolonged seizure-freedom outcome in patients with epilepsy.Additional reports are needed in developing countries with and without brain MRI lesions to advance outpatient presurgical evaluations despite limited resources.