Epilepsy surgery in patients with unilateral mesial temporal sclerosis and contralateral scalp ictal onset

Concordance of EEG findings and MRI is best correlated with favored surgical outcome in patients with unilateral mesial temporal sclerosis (MTS). If there is no evidence for unilateral focus with scalp EEG, invasive recordings are undertaken. In this report we describe the investigation process for epilepsy surgery in patients with unilateral MTS and contralateral ictal scalp EEG findings.

The data of all adult patients who had undergone videoEEG recording with subdural and/or depth electrodes at our center in almost 7.5 years, were reviewed. Four patients with unilateral MTS and contralateral ictal onset on scalp EEG were included. Their invasive EEG recordings and surgical outcomes were examined.

Four patients met the inclusion criteria. Invasive recordings demonstrated ictal onset in the mesial temporal lobe ipsilateral to MRI findings. In one patient we have also proven the false lateralization of scalp EEG simultaneously during the recordings with depth electrodes. All operated cases are seizure free during follow-up.

Before the decision of epilepsy surgery we have to identify the semiology and ictal EEG findings in patients with unilateral MTS and concordant IEDs. Bilateral depth recordings must be considered to show the ipsilateral hippocampal epileptogenic focus.