The genetics of migraine: implication for treatment approaches

Reduced cerebellar inhibition in migraine with aura: a TMS study

Subtle clinical cerebellar alterations have been found in migraine. Moreover, abnormalities in visual and motor cortex excitability consistent with a lack of inhibitory efficiency have been described in migraine, and it is known that cerebellum exerts an inhibitory control on cerebral cortex. Here, we investigated if impairment of cerebellar activity on motor cortex, i.e. reduced inhibitory control, can be found in migraine. Ten migraineurs with aura and seven healthy controls underwent a transcranial magnetic stimulation (TMS) protocol to investigate the cerebellar inhibitory drive on motor cortex: a conditioning pulse on right cerebellar cortex was delivered 5, 7, 10, 15 ms before a test stimulus (TS) on contralateral motor cortex. The cerebellar conditioning stimulus inhibits the size of the motor-evoked potential (MEP) produced by the TS alone by approximately 30-50%. Amplitude of MEP to TS alone showed no significant difference between patients and controls. Cerebellar conditioning TMS showed a significant deficit of cerebellar inhibition in migraine patients as compared to controls at all interstimulus intervals (5-15 ms) tested. Cerebellar inhibition is reduced in migraineurs. This could account, at least in part, for the reduced inhibitory efficiency previously showed in cerebral cortex of these patients.

Genetics of migraine and pharmacogenomics: some considerations

Migraine is a complex disorder caused by a combination of genetic and environmental factors. Although family and twin studies show that there is a genetic component in migraine, no genes predisposing to common forms of the disorder, migraine with and without aura, have been identified. Patients with migraine respond differently to a given drug administered. The efficacy of therapy and the occurrence of adverse drug response are a consequence of individual variability. Genetic profiling of predisposition to migraine should facilitate the development of more effective diagnostic and therapeutic applications. The development of International Hap Map project could provide a powerful tool for identification of the candidate genes in this complex disease and pharmacogenomics research could be the promise for individualized treatments and prevention of adverse drug response.