Stumped on post aneurysm coiling stent placement...


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I have a case that my provider performed that has me stumped...please help!

History: Patient presents in September 2015 with aneurysmal SAH. Aneurysm is treated with coil embolization. Several months later follow-up imaging indicates coil compaction with dog ear configuration so the patient is brought back for embolization with stent placement. No additional coils are deployed; however, a Neuroform stent is deployed across the wide-neck basilar aneurysm.

Condensed procedure:
Right vertebral artery angiogram (Bundled)
3D Angiogram (Bundled)
Micro-catheter navigated into R PCA, second micro-catheter navigated into the base of the aneurysm
Angiograms were then obtained from both micro-catheters (Bundled)
Stent deployed into R PCA, Angiogram obtained demonstrates successful deployment and mild filling of the wide neck (61635) (F/U Angio Bundled)
Micro-catheter within the neck of the aneurysm was displaced
Patient was noted for changing SSEPs, angiogram obtained - images revealed developing thrombus (Bundled)
TPA was prepared and 2mg was infused for approximately 10 minutes. (61645)
Follow-up angiograms revealed complete recanalization of the R PCA. (Bundled)

Commercial insurance payer is denying the procedure (61635) as experimental. Any feedback on whether this is coded correctly or incorrectly? Should this be payable? If so, any suggestion on how to approach the appeal? I've been unsuccessful so far.

I know if the stent was placed at the same time as coil embolization (61624/75894), the stent placement would be bundled. It was not determined at the time of acute coil embolization in September 2015 that a stent would be required so it doesn't fall under the umbrella of a staged procedure. The decision to stent was made after follow-up imaging was obtained. The decision to not deploy additional coils, but to only deploy a stent was made during the procedure. It was scheduled as a coil embolization with stent placement.

Thank you!