False lateralization of scalp EEG and semiology in cavernous malformation-associated temporal lobe epilepsy: A case report

Several cases of temporal lobe epilepsy (TLE) showing false lateralization of ictal scalp electroencephalography (EEG) have been reported. However, TLE with cavernous malformation indicating false lateralization of both ictal scalp EEG and semiology as in the present case is rare. The aim of this report is to call attention to avoiding overestimation of ictal scalp EEG findings in epilepsy patients with cavernous malformation. A 25-year-old man without any medical history suffered from seizures for a year despite appropriate anti-epileptic medication. Magnetic resonance imaging (MRI) revealed cavernous malformation in the left amygdala. The seizure type was brief impaired consciousness with left dystonic posturing, preceded by a sensation of blood rushing to the head. Long-term video EEG with scalp electrodes showed periodic sharp waves beginning from the right temporal area during seizures. Although both semiology and ictal scalp EEG indicated right TLE, intracranial EEG revealed the onset of low-voltage fast activity from the left hippocampus near the cavernous malformation. This patient therefore underwent removal of cavernous malformation and left amygdala, and achieved freedom from seizures postoperatively. We reinforce the importance of performing intracranial EEG for cavernous malformation-associated epilepsy when discrepancies between scalp EEG and MRI are evident. •Scalp ictal electroencephalogram (EEG) showed false lateralization.•Semiology sometimes indicates false lateralization.•Intracranial EEG may be important in cavernous malformation-associated epilepsy.