Presurgical evaluation of temporal lobe epilepsy: Is an outpatient prolonged ambulatory EEG study sufficient to recommend a surgical resection?

Purpose: Inpatient Video EEG Monitoring (VEM) is the typical study performed in presurgical evaluations. It is expensive and not widely available in developing countries. Recent studies suggested that in selected patients with mesial temporal lobe epilepsy secondary to unilateral mesial temporal sclerosis (MTS), the recording of unilateral interictal epileptiform activity ipsilateral to the MTS may yield sufficient presurgical EEG data. Outpatient prolonged ambulatory EEG (AEEG) could be an alternative in these cases. The purpose of this study was to compare the post-surgical seizure outcome and costs between patients evaluated with AEEG versus VEM.

Methods: Thirty patients with TLE were included: 21 evaluated with VEM and 9 with AmbEEG and underwent surgery between 2011 and 2017. The minimum, post-surgical follow-up period was 1 year.

Results: Seven of nine patients who underwent AEEG had seizures ipsilateral to MTS. In two patients only unilateral interictal activity ipsilateral to the lesion was recorded. All patients were free of disabling seizures (Engel Class I) at last follow-up. The mean cost per patient of AEEG was $980 and was $4680 for VEM.

Conclusion: AEEG may be used to identify candidates for temporal lobectomy in selected patients with unilateral lesional mesial TLE. This approach to EEG monitoring could make epilpesy surgery more affordable to some patients in developing countries.