Interictal Motor Cortex Excitability in Migraine and Chronic Tension Type Headache using Transcranial Magnetic Stimulation

ABSTRACT

BACKGROUND: The pathophysiology of migraine is only partly understood. Transcranial magnetic stimulation has been developed to study cortical physiology noninvasively. Chronic tension-type headache has not been studied with transcranial magnetic stimulation. Among other hypotheses, it has been proposed that interictal hypoexcitability could be partly responsible for the migraine. METHODS: Patients were divided into three groups: normal subjects(n=30), migraine with(n=11) or without aura(n=19) and chronic tension-type headache(n=30) according to the International Headache Society criteria. We studied cortical excitability between normal subjects and patients with migraine with or without aura and between normal and patients with chronic tension-type headache. RESULTS: The mean amplitude of cortex and spinal cord for normal subjects was 3.76 +/-1.74 mV, 2.03 +/-1.54 mV(abductor digiti minimi muscles, respec-tively) and 2.99 +/-2.04 mV, 3.88 +/-3.89 mV(abductor hallucis muscles, respectively). The mean amplitude of cortex and spinal cord for migraine with aura or without aura was 2.16 +/-1.21 mV, 0.90+0.80 mV(abductor digiti minimi muscles, respectively) and 1.88 +/-1.23 mV, 2.31 +/-2.25 mV(abductor hallucis muscles, respectively). The mean amplitude of cor-tex and spinal cord for chronic tension-type headache was 1.61 +/-0.50 mV, 0.72 +/-0.32 mV(abductor digiti minimi mus-cles, respectively) and 1.54 +/-0.55 mV, 1.51 +/-0.59 mV(abductor hallucis muscles, respectively). The amplitude of motor evoked potentials of cortex and spinal cord in migraine and chronic tension-type headache showed significant decreases compared to normal subjects( p < 0.001). CONCLUSIONS: These results are explained by cortical and spinal hypoexcitability in migraine and chronic tension-type headache. We suggest that enhanced serotonergic activity could be some rule for cortical hypoexcitability.