One of the consequences of the current debate over health care in the U.S. is becoming reacquainted with just what a low % of treatments are grounded in good science. We expect/demand a high level of success from medicine when, in fact, so much of what is done is based on local patterns of practice, habit, best guess, etc.
We are the carriers of this tradition at a much higher level of "best guess". It is surprising to me just how far we have come in the last 30-years, realizing that until Goadsby remarkable work on brain function, medicine had no idea about the origin of CH/migraine. Notwithstanding the limitations, the meds we have today are a miracle compared to what was available when I started my trip with CH 40-years ago.
I agree with another comment about the frustrating reality of meds starting/stopping being effective. Another element is that experience about dosing, combinations of meds, etc. have slowly evolved with experience. This two variables suggest that it might be helpful for you prepare a full history of all med use--frequency of use of any single med, dosing, duration of use, etc. and compare your long experience with current use recommendations. It may open some new possibilities.
Re. DBS: the articles I have, even the most recent ones, don't excite me. However, if you do the meds reevaluation and find nothing new, then increasing your risk taking (with DBS) may be a reasonable move.
You are in the position of have access to some of the best in neurological medicine. (Assume you are working with OUCH/UK, yes? Multimedia File Viewing and Clickable Links are available for Registered Members only!! You need to

or

)
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A couple of articles to give to your doctor:
Curr Opin Neurol. 2009 Jun;22(3):262-8.
Neurostimulation approaches to primary headache disorders.
Bartsch T, Paemeleire K, Goadsby PJ.
Department of Neurology, University Hospital of Schleswig Holstein, University of
Kiel, Germany.
PURPOSE OF REVIEW: Conventional management options in medically intractable
chronic-headache syndromes, such as chronic migraine, chronic cluster headache
and hemicrania continua, are often limited. This review summarizes the current
concepts, approaches and outcome data of invasive device-based neurostimulation
approaches using occipital-nerve stimulation and deep-brain stimulation. RECENT
FINDINGS: Recently, there has been considerable progress in neurostimulation
approaches to medically intractable chronic-headache syndromes. Previous studies
have analysed the safety and efficacy of suboccipital neurostimulation in
drug-resistant chronic-headache syndromes such as in chronic migraine, chronic
cluster headache and hemicrania continua. The studies suggest suboccipital
neurostimulation can have an effect even decades after onset of headaches, thus
representing a possible therapeutic option inpatients that do not respond to any
medication. Similarly, to date over 50 patients with cluster headaches underwent
hypothalamic deep-brain stimulation. From these, an average of 50-70% did show a
significant positive response. SUMMARY: These findings will help to further
elucidate the clinical potential of neurostimulation in chronic headache.
PMID: 19434793 [PubMed - indexed for MEDLINE]
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. J Clin Neurosci. 2009 Jul;16(7):861-6. Epub 2009 Apr 23.
Deep brain stimulation for cluster headache.
Grover PJ, Pereira EA, Green AL, Brittain JS, Owen SL, Schweder P, Kringelbach
ML, Davies PT, Aziz TZ.
Nuffield Department of Surgery, University of Oxford and Oxford Functional
Neurosurgery, Department of Neurological Surgery, The West Wing, John Radcliffe
Hospital, Headley Way, Headington, Oxford, OX3 9DU, UK.
Cluster headache is a severely debilitating disorder that can remain unrelieved
by current pharmacotherapy. Alongside ablative neurosurgical procedures,
neuromodulatory treatments of deep brain stimulation (DBS) and occipital nerve
simulation have emerged in the last few years as effective treatments for
medically refractory cluster headaches. Pioneers in the field have sought to
publish guidelines for neurosurgical treatment; however, only small case series
with limited long-term follow-up have been published. Controversy remains over
which surgical treatments are best and in which circumstances to intervene. Here
we review current data on neurosurgical interventions for chronic cluster
headache focusing upon DBS and occipital nerve stimulation, and discuss the
indications for and putative mechanisms of DBS including translational insights
from functional neuroimaging, diffusion weighted tractography,
magnetoencephalography and invasive neurophysiology.
PMID: 19398342 [PubMed - indexed for MEDLINE]