Millions of patients suffer from medically refractory and disabling primary headache disorders. This problem has led to a search for new and innovative treatment modalities, including neuromodulation of the occipital nerves.
The primary aim of this study is to describe an implantation technique for the Bion microstimulator and document stimulation parameters and stimulation maps after Bion placement adjacent to the greater occipital nerve. The secondary aim is to document outcome measures one year post-implant.
Prospective, observational feasibility study.
Nine patients with medically refractory primary headache disorders participated in this study. Approximately 6 months after Bion insertion, stimulation parameters and maps were documented for all patients. At one year, outcome measures were collected including the Migraine Disability Assessment Score.
At 6 months, the mean perception threshold was 0.47 mA, while the mean discomfort threshold was 6.8 mA (stimulation range 0.47-6.8 mA). The mean paresthesia threshold was 1.64 mA and the mean usage range was 16.0. There were no major complications reported such as device migration, infection, or erosion. One patient stopped using her Bion before the 12-month follow-up visit. At one year, 7 of the 8 patients were judged as having obtained fair or better results in terms of reduction of disability; 5 patients had greater than a 90% reduction in disability.
Small, heterogeneous patient population without control group. Not blinded or randomized.
The Bion can be successfully inserted adjacent to the greater occipital nerve in an effort to treat refractory primary headache disorders. This microstimulator may provide effective occipital stimulation and headache control while minimizing the risks associated with percutaneous or paddle leads implanted subcutaneously in the occipital region.
I read this study to get greater details of the parameters researchers were using when using their implanted electrodes to see what I can learn when I do my electric stimulation parameters externally targeting the same nerve.
First I was happy to see that 5 of the 9 patients had a better than 90% reduction in headache disability via the MIDAS form and only 1/9 failed to make any improvement. Also 4/9 headache sufferers had cluster headaches which are particularly difficult to treat and all but one had better than 90% improvement.
So about those parameters. Pulse duration used varied from 200-350 uS, rate was 45-60 Hz, and intensity was up to 10 mA. They noted the average perception threshold was 0.4 mA, paresthesias felt at 1.6 mA, and discomfort felt on average of 6.2 mA, but a number of subjects did 10 mA, which I think is the max output of the machine. I don’t see that they standardized pulse duration with regards to mA reached. The electrodes were implanted next to the greater occipital nerve just under the skin, which makes me think the results should be easy to match with my transcutaneous electrodes but mA used with my patients is considerably greater to overcome the resistance of the skin. It gave me some ideas for my research including the use of the MIDAS test, and testing perception, paresthesias and discomfort thresholds with my transcutaneous electrodes and see how it relates to subcutaneous use.
Not explicitly stated, but what I assume from the study is that the stimulation is continuous rather than with an on and off duty cycle which I am currently using with my patients. The amount of time the stimulation was on with the Bion stimulator was highly variable between patients, ranging from as low as 30 minutes every 2 weeks to 24 hours per day (both with “excellent” outcomes) with no clear pattern with regards to which dosage works best. All are longer than what seems to work well in my data collection, which is 12 minutes. I have limited data showing an additional 12 minutes does not further affect relief of pain.
Overall I think the study provides considerable useful data. However, I still think for most headache sufferers surgical implantation of electric stimulation devices is overkill. This is especially true if common hand-held electric muscle stimulators can provide comparable relief at a fraction of the cost without the side effects (pain of surgery, infection, lead migration, additional surgery to replace defective devices, etc.). Thus far my preliminary data collection indicates that they can.
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As always, if you have any further questions or need for clarifications, please don’t hesitate to ask. Being aware that some of my blog ideas are contentious and occasionally a bit out of the field of my expertise, I encourage my readers to come forth with any questions/comments that are of interest or concern. Your comments are valued and welcomed.
Chad Reilly is a licensed physical therapist, located in North Phoenix, practicing science based medicine with treatment protocols unique and effective enough to proudly serve patients from Phoenix, Scottsdale, Mesa, Chandler, Tempe, Peoria, and Glendale.