My cluster symptoms began after a traumatic brain injury with loss of consciousness However, there were other mitigating factors as well: other concussions, 2 cervical spine surgeries including a fusion (followed by an eventual 3rd surgery and 2nd fusion post-CH as a result of the TBI), sleep apnea, male, etc. But no prior drug use, heavy alcohol use, smoking, or family history of CH
So I personally believe there may be a strong connection between brain injury and/or spinal injury and cluster. But the exact mechanism in play may unique to each person.