Aims:

Studies about the association of epilepsy and arachnoid cysts (ACs) did not provide accurate data. It can be seen in epilepsy but there is no relation to the specific seizure type or focus in electroencephalogram (EEG). We investigate the effect of ACs on EEG in order to determine the necessity of EEG in patients with arachnoid cysts and without a history of epilepsy.

Methods:

This is a retrospective, case-control study. Participants of this study are patients with incidental ACs without history of seizures as ACs group, patients with epilepsy as epilepsy group and patients without history of seizures as control group. EEG findings were classified as normal, nonspecific abnormal and specific epileptiform activity.

Results:

The study included 104 patients in ACs group, 102 patients in epilepsy group and 105 patients in control group. We identified a significantly higher proportion of slow waves (17.6%) and epileptiform EEG discharges (27.5%) in epilepsy patients compared to ACs group (slow waves: 5.8%, epileptiform EEG discharges: 1.9%, p<0.001). There was no difference on EEG activity between the ACs group and control group (slow wave: 3.8%, epileptiform EEG discharges: 1%, p=0.667). Also, there was no relation between the localization of ACs and EEG abnormality.

Conclusions:

To the best of our knowledge this is the first study which evaluate the effect of incidental ACs on EEG activity. We found that ACs do not have effect on EEG compared to control groups and also there is no correlation between the localization of ACs and EEG abnormality.

Keywords: Space-occupying mass, EEG, localization..