So after 17 years with a very severe chronic cough, my current specialist (an ENT in Sydney, the 9th specialist I have seen, plus 2 specialised speech pathologists) has been doing botox shots bilaterally to the superior laryngeal nerve every 3 months since February.  This has helped by almost eliminating the laryngospasms (an almost daily occurrence, and terrifying), but has not addressed the coughing at all.  I still cough more than 100 times each day, sometimes until I vomit.  He ordered an MRI of my brain because he was surprised that the botox was not reducing the cough.
The MRI report notes "left PICA contacts the anterior aspect of the left vagus nerve.  No nerve deviation."  ENT said this suggests I may have hemi-larnygopharyngeal spasm (HeLPS) and/or VANCOUVER syndrome.  He has suggested a neuro-surgical consult to investigate surgical decompression of the nerve.
Along the way, I have been treated with various medications - gabapentin, amytriptaline, dom peridone, anti-histamines, asthma puffers, codeine, reflux medications..., none of which worked.  I guess not that surprising if there is a physical issue like a nerve compression?
I've made the "mistake" of googling all this, and feel like the descriptions of symptoms related to HeLPS in particular, are very indicatie of what I have suffered - cough, stridor, vomiting, nausea, headaches, feeling faint/almost blacking out, losing weight (from inability to eat without coughing until I vomit - lucky I was overweight to start with), reflux (which my Gastroenterologist blamed on chemo), fatigue and brain fog (which I blamed on chemo).  So perhaps they are FINALLY onto something.
However, I feel a bit daunted by the cough choice of live with the dreadful coughing, that episodically and increasing really makes my life very very miserable, or have brain surgery.
I would welcome comments from anyone who knows anything about this, and particularly advice on what questions I should ask the neurosurgeon to help me make this hard decision.