Neurosurgery Coding Alert

Question: A 50-year-old woman presented with visual field loss and diplopia secondary to a midline skull base tumor invading her right cavernous sinus, suprasellar, parasellar, and clival regions for which she was operated. Through an endoscopic approach to skull base, resection of right middle turbinate, sphenoidectomy and resection of tumor, intradural from within the clivus, right cavernous sinus, sella, suprasellar, and parasellar areas were done. Frameless stereotactic navigation was done using BrainLAB system. A dural patch graft was done using Durepair.

Here's the operative note:

"Under endoscopic visualization, the high-speed drill was used to perform a craniectomy at the base of the skull with its superior border along the dorsum sella and the inferior border along the clivus. The dura was opened with endoscopic knife and upon performing this maneuver the tumor was encountered. Using a combination of suction and curettage, the tumor was removed. A cystic component was encountered and once this was decompressed, additional tumor was removed. At the conclusion of removing the tumor, the diaphragm sella was noted to be fungating downward and placing the endoscope within this allowed easy visualization of the optic chiasm and the surrounding structures. Using the BrainLAB system, we confirmed that we had resected the tumor from along the cavernous sinus on the right, the clivus, and the supra and parasellar components. The dura was patched with a single piece of Durepair and secured with Tisseel. At no point during the operation was there any evidence of CSF leak."

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Answer: While this procedure describes a primarily intradural skull base approach to the clivus, the method involved an endoscopic approach along with navigation. Although the intracranial navigation would be correctly reported with 61781 (Stereotactic computerassisted (navigational) procedure; cranial, intradural (List separately in addition to code for primary procedure)), the skull base approach codes are all considered "open approaches", whereas the operative note describes a minimally-invasive endoscopic approach. This would be reported with an unlisted code 64999 (Unlisted procedure, nervous system).  Alternatively, while code 61521 (Craniectomy for excision of brain tumor, infratentorial or posterior fossa; midline tumor at base of skull) describes excision of a midline skull base tumor, this also reflects using an open surgical approach.