Huh, this is weird. If you do try to bill for 98941 they will still only reimburse for 98940. Since the symptom was new, this technically counts as a new "incident" and would therefore warrant a new and updated treatment plan according to conventional wisdom. I would appeal what they told you, but Optum is one of the strictest private insurers about chiro policy, so expect the original decision to stand. Still, it's worth a try. Maybe they will at least increase the # of visits to allow the new problem to be addressed on its own.