Cortical excitability affects mood state in patients with idiopathic generalized epilepsies (IGEs)

Previously, we demonstrated an association between cortical hyperexcitability and mood disturbance in healthy adults. Studies have documented hyperexcitability in patients with idiopathic generalized epilepsies (IGEs; long-interval intracortical inhibition [LICI]) and high prevalence of mood comorbidities. This study aimed to investigate the influences of cortical excitability and seizure control on mood state in patients with IGEs. Single and paired-pulse transcranial magnetic stimulation (TMS) was applied to 30 patients with IGEs (16 controlled IGEs [cIGEs], 14 with treatment-resistant IGEs [trIGEs]), and 22 healthy controls (HCs) to assess cortical excitability with LICI. The Profile of Mood Sates (POMS) questionnaire was used to assess total mood disturbance (TMD), as well as, six mood domains: Depression, Confusion, Anger, Anxiety, Fatigue, and Vigor. To assess the effects of seizure control (HC vs. cIGEs vs. trIGEs) and LICI response (inhibitory vs. excitatory) on TMD, a two-way multivariate analysis of variance (MANOVA) was performed. Analyses revealed a significant main effect of long-interval intracortical inhibition (LICI) response on TMD (F(1, 46) = 4.69, p = 0.04), but not seizure control (F(2, 46) = 0.288, p = 0.75). Excitatory responders endorsed significantly higher TMD scores, indicating greater mood disturbance, than inhibitory responders (MD = -2.12; T (50) = -2.47, p = 0.04). Also, excitatory responders endorsed more items than inhibitory responders on the Depression (MD = -2.12; T (50) = -2.47, p = 0.04) and Fatigue (MD = -3.42; T (50) = -2.96, p = 0.03) subscales of the POMS. These findings provide further evidence of a relationship between hyperexcitability and mood disturbance, and indicate that cortical excitability may have greater influence on mood state than seizure control in patients with IGEs. Results also support theories for the underlying role of gamma-aminobutyric acid (GABA) network dysfunction in the etiology of depression. To better understand the clinical relevance and causal nature of these relationships, further investigation is warranted.