Have you tried oxygen therapy at flow rates that support hyperventilation? It may sound scary and there are a lot of old wives tales that caution you not to breathe oxygen this fast, but it is very safe. I've 3000 hours flying Navy jet fighters and all of that flight time was spent breathing 100% oxygen at flow rates well above 30 liters/minute.

I would try this method of oxygen therapy prior to DBS surgery. In addition, most cluster headache sufferers (CH'ers) are vitamin D3 deficient. Have you had a recent 25-Hydroxyvitamin D lab test? It's also known as 25(OH)D and it's the serum level metabolite of vitamin D3. Most CH'ers presenting with active CH have 25(OH)D levels ? 50 ng/mL, (125 nmoll/L).

Take care, V/R, Batch