Occipital nerve stimulation for chronic migraine--interpreting the ONSTIM feasibility trial.

Chronic migraine, which affects approximately 2% of the population, results in substantial costs to individual sufferers and to society (1). Current treatment options for chronic migraine are often inadequate, with a proportion of chronic migraine patients being intractable to conventional therapy. Clearly, better treatment strategies are needed to reduce the burden from this common and disabling disorder. Dr Saper and co-investigators report the results from the ONSTIM trial, a Medtronic sponsored study of occipital nerve stimulation for the treatment of chronic migraine patients who had been intractable to standard pharmacotherapy (2). Subjects had suffered from migraine for an average of 22 years and chronic migraine for 10 years, had approximately 23 days per month with headache, had pain in the distribution of the occipital nerves, were intractable to prophylactic medications from at least two standard classes and had transient relief of pain following occipital nerve block. These subjects were randomized to one of three groups: (i) adjustable stimulation (N1⁄4 33); (ii) sham stimulation (pre-set stimulation for one minute daily) (N1⁄4 17); or (iii) continued medical management (N1⁄4 17). In order to assess whether or not response to occipital nerve block was a useful predictor for response to occipital nerve stimulation, a subset of subjects who did not benefit from the blocks were placed into an ancillary group that also received treatment with adjustable stimulation (N1⁄4 8). Safety and efficacy data were derived from three months of follow-up. The primary aim of this study was to collect preliminary data regarding the safety and efficacy of occipital nerve stimulation for the treatment of chronic migraine. The study was not designed to yield conclusions regarding this treatment modality. Consistent with the study goals, the sample size was small and multiple outcomes were investigated independently. Many of these outcomes showed numerical superiority (although not necessarily statistically significant superiority) of adjustable stimulation over sham stimulation and over continued medical management. Despite the small sample size, adjustable stimulation was associated with statistically superior benefit for a few disability and quality-of-life outcomes when independently analyzed (not corrected for multiple comparisons). These results suggest that occipital nerve stimulation is a promising treatment for chronic migraine and that further clinical trials are warranted. In addition to the study power and methods of analysis, a few other study specifics should be considered when interpreting the results.