Every DBS Patient is Unique
What Works For One May Not Work for Another
Neither First nor Last
Current regulations require that you try several therapies prior to DBS and are shown to be treatment resistant or refractory. However, I want to stress that you do not have to literally try every single different combination or "cocktail mix" of therapies before considering DBS. In my strictly patient opinion (again bear in mind I am not a doctor) if your treatment is still unsatisfactory after two years, you should at least have a discussion about DBS.
Ensemble of Treatments
I suggest not viewing DBS as the "star of the show" but instead as part of an ensemble of treatments. For example while not a cure, the addition of DBS may for all practical purposes "add up to a cure." Or, if you are experiencing side effects from high doses of medications or neurotoxins, the relief provided by DBS, may be enough to lessen the doses to levels that will not produce side effects.
Ongoing Therapy
During your programming sessions your doctors can adjust four areas: pulse width, frequency, voltage and contact location. While there are no set rules, as DBS is not an exact science, there are certain principles that guide doctors along programming. However, even though there are principles, not all doctors come from the same "school of thought" when it comes to the ART of programming. Thus you may find varying approaches from doctor to doctor when it comes to adjusting your stimulation.
There are thousands of different programming combinations for your doctor to choose from. Settings that work for one patient may not work for another.
Likewise the implant location of electrodes is unique to each patient. And "brain geography" is so complex that even a millimeter difference in location can make a huge difference.