Electrophysiological basis for antiepileptic drugs in migraine prevention

Migraine and epilepsy share in many ways with regard to their clinical presentation and pathophysiological mechanisms. A state of central hyper-excitability or hyper-responsivity is fundamental in their pathophysiology. Antiepileptic drugs (AEDs) have long been used for migraine prevention, other than for seizure control. Evidence from numerous clinical trials has well demonstrated the therapeutic effects of some of the AEDs in this regard. In this paper, we will first discuss the clinical similarity between migraine and epilepsy. Then, to address the rationale of AEDs usage in migraine prevention, we focus on those electrophysiological studies conducted in patients with migraine demonstrating evidence of central hyper-excitability or hyper-responsivity. Although controversies remain, three common findings are derived from the literature: (1) cortical hyper-excitability, (2) impaired intra-cortical inhibition or increased intra-cortical facilitation, and (3) dis-habituation (hyper-responsivity). Each single feature may actually represent one of the different manifestations derived from an overall central excitation/inhibition imbalance. Finally, we review those studies addressing the therapeutic effects of AEDs and the associated alteration in central excitability. These studies provided direct evidence that effective prevention by AEDs is associated with the restoration of excitation/inhibition imbalance.