For years I had suffered from mild dystonia, and I finally got to see a neurologist.
He gave me a prescription, and said to persevere with it, it would take a few weeks to start working.
But soon I was much worse, twitching and jerking all over including my mouth and tongue.
I went to my GP, but it was a young doctor temporally with our group,and when I told him I was having difficulty swallowing, he insisted on an endoscopy, and wouldn't listen to my explanation that it was the meds causing it.
A few days later I saw my usual GP, and the meds were stopped, All the nasty twitches stopped, and I could swallow normally.
But in the meantime the endoscopy had found cancer of the esophagus. It was T1N0M0, much too early have any symptoms, and wouldn't have been found in time but for that lucky chance.