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Eur J Neurol. 2002 Jan;9(1):35-40

We examined the effect of standard migraine prophylaxis with sodium valproate on repeated measures of occipital excitability using transcranial magnetic stimulation (TMS). We predicted that, comparing pre- and post-treatment assessments, a reduction in clinical migraine parameters would be paralleled by a decrease in excitability measurements.A total of 31 migraine patients enrolled in the study, for assessment prior to and 1 month after commencement of sodium valproate prophylaxis. At each assessment, we used a standardized protocol to stimulate the occipital cortex with a 90-mm circular (coil A) and 70 mm figure-of-eight (coil B) coil. We recorded the threshold stimulation intensity at which subjects just perceived phosphenes. Subjects kept detailed records of headache parameters 1 month before and also during the study period.Valproate therapy significantly improved headache indexes, as expected. In MA subjects assessed with coil B, phosphene thresholds were significantly higher post-treatment than pre-treatment, but those for MO did not change. Modest correlations were observed in MA patients between increase in phosphene threshold and decrease in headache index. Although preliminary, the findings with coil B lend some support to the notion that effective migraine prophylaxis may be achieved through lowering cortical excitability by gamma-aminobutyric acid (GABA)-ergic intervention. Further investigation of the effect of sodium valproate or other similarly acting substances on cortical excitability in migraine is warranted.

Comment: This paper provides a useful noninvasive human model in which to study the potential development of prophylactic treatments for migraine with aura. It will be important to standardize experimental conditions and to establish a rigorous experimental protocol for simulation parameters. However, this promises to be an important technique for use in future drug development. DSM