Patients don’t have much hope arguing with insurance companies but doctors do - they just have to be more aggressive than the average doctor.
First, they have to get through to a doctor on the insurer’s side - eventually, once you go up the claim management tree, these insurance companies leave the ultimate decision up to a doctor that they pay a shitload of money to have profitable medical opinions on their behalf.
Here is the thing: It is malpractice to diagnose and recommend treatment for a patient you have not evaluated, so the only valid medical opinion on the record is your physician’s medical opinion.
You just need a doctor on your side who will raise the stakes high enough to threaten their doctor’s medical license.
At that point, the insurance doctor will cave and approve the claim.
You still need a diagnosis and a treatment plan that is backed by medical science, of course.