Little late in reply, but the trigeminal nerve complex most certainly extends to the neck below the brainstem in some cases below C4 which is greater than half way down and accounts for many head and facial pain syndromes. In addition structures associated with these areas ( even lower) can be involved.
Originally the DREZ procedure was directed at these structure, fortunately out of favour due to bad outcomes.
There seems to be a fixation on upper chiro care, massage and posture, relaxation can be positive in addition to lifestyle changes. While physical therapy of whatever kind may benefit, lack of wasn’t the cause.
I’d like to think, manipulation of the upper cervical spine which possibly led to stroke or worse ( though I believe stats are so minimal it can’t be proven statistically) have been administered inappropriatley, with a lack of clinical judgement, this happens in every area of medicine, MVD and prescriptions.
Interestingly a UK chiro has been arrested on suspicion of manslaughter recently, where the derivation of the word came from can’t begin to imagine.
Physical therapists including chiros have several modalities of treatment available not just manipulation, snap/ crack. State your case and fears and hopefully a treatment protocol can be agreed on.