A 25-year-old female patient was suggested for epilepsy surgery based on a left frontal cavernoma and seizures consistent with clonic twitching of her right arm. Only after prolonged video EEG monitoring and discontinuation of current antiepileptic treatment with valproic acid could generalized sharp wave discharges (3/s) and bilateral myoclonic seizures be documented. Imaging of a lesion may lead to false interpretation of seizure semiology, false classification of epilepsy as focal, and erroneous and potentially dangerous therapeutic procedures. Ictal video EEG recordings demonstrating a causal relationship between lesion and epilepsy are indispensible prior to epilepsy surgery.