Cortical excitability in migraine and epilepsy: a common feature?

Objective: There is evidence for comorbidity of migraine and epilepsy. We used transcranial magnetic stimulation (TMS) to assess cortical excitability in migraine compared with control subjects and patients with epilepsy.

Methods: Twenty-six patients drug-naive patients with newly diagnosed migraine were studied. These were compared with 19 healthy control subjects and 50 patients with new onset epilepsy. Motor threshold (MT) and responses to paired pulse stimulation at short (2, 5, 10, and 15 milliseconds) and long (50-400 milliseconds) interstimulus intervals (ISIs) were measured.

Results: Compared with control subjects, cortical excitability was higher in migraine only at 250 milliseconds (P < 0.05; effect size 0.7), while in epilepsy, it was higher at 2, 5, 250, and 300 milliseconds. Compared with epilepsy, cortical excitability was lower in migraine only at 250 milliseconds (P < 0.05; effect size 0.6 compared with focal epilepsy and 1.1 compared with idiopathic generalized epilepsy [IGE]).

Conclusions: Cortical excitability increases in migraine suggesting the involvement of intracortical inhibitory circuits. This may be a common feature underlying some of the similarities observed in migraine and epilepsy.