Is interictal EEG activity a biomarker for mood disorders in temporal lobe epilepsy?

Abstract

Objective: Psychiatric comorbidities are frequent in temporal lobe epilepsy (TLE), and symptoms of these comorbidities may be related to epilepsy activity. Here we evaluated interictal EEG activity in TLE patients with or without psychiatric comorbidities.

Methods: A cohort study of 78 patients with TLE, with evaluation of wake/sleep interictal scalp EEG. All subjects were submitted to a psychiatric structured clinical interview (SCID) for the diagnosis of lifetime psychiatric comorbidities. Three major diagnostic categories were studied: mood disorders, anxiety disorders, and psychosis. We then evaluated differences in interictal EEG activity between patients with and without these psychiatric comorbidities.

Results: Infrequent EEG interictal spikes, defined as less than one event per minute, were significantly associated with mood disorders in TLE (p=0.02).

Conclusions: Low intensity seizure disorder has been associated with a decrease in interictal EEG discharges and with an increase in psychiatric symptoms in TLE, a phenomenon known as forced normalization. In our study, we observed a low interictal spike frequency on EEG in TLE patients with mood disorders.

Significance: A low spike index might be a neurophysiological marker for depression in temporal lobe epilepsy.

Keywords: EEG; Epilepsy; Interictal epileptiform discharges; Mood disorders; Psychiatric comorbidities.