Selecting Skull Base Surgical Approaches

Question:

How should we bill for a skull base surgery approach when the surgeon accessed both the middle and posterior cranial fossae (e.g., CPT® 61591 and 61595), and the main lesion was resected from the posterior cranial fossa (e.g., CPT® 61616)?

Answer:

Per CPT® guidelines, codes 61591 and 61595 represent distinct surgical approaches to the middle and posterior cranial fossae, respectively. They do not denote which area of the brain is accessed. Each code includes specific required components:

• 61591 – Infratemporal post-auricular approach to middle cranial fossa (internal auditory meatus, petrous apex, tentorium, cavernous sinus, parasellar area, infratemporal fossa) including mastoidectomy, resection of sigmoid sinus, with or without decompression and/or mobilization of contents of auditory canal or petrous carotid artery

• 61595 – Transtemporal approach to posterior cranial fossa, jugular foramen or midline skull base, including mastoidectomy, decompression of sigmoid sinus and/or facial nerve, with or without mobilization

To report both codes, the operative note must clearly support that all required elements of each code were performed as separate and distinct procedures. Importantly, the mastoidectomy is not optional in either code, and the work on the sigmoid sinus must be a resection for 61591 and decompression for 61595. If these elements overlap or are not separately performed, reporting both codes is not supported.

The middle and posterior cranial fossae are anatomically adjacent, and surgical access to one may involve access to the other. Traversing the middle fossa to reach a posterior lesion does not, by itself, justify reporting a separate middle fossa approach code.

In cases involving resection of a vestibular schwannoma, CPT® instructs coders to use the traditional combined approach and resection codes (61520, 61526, or 61530) rather than the skull base code sets (61580–61619). These codes bundle the approach and resection into a single code and are generally more appropriate for cerebellopontine angle tumors like vestibular schwannomas.

If the lesion is confined to the posterior fossa and the middle fossa was only used as a surgical corridor, then 61595 alone is appropriate. Modifier -22 may be considered if additional complexity is well-documented.

While CPT® does not explicitly prohibit reporting two approach codes, it emphasizes the following principles:

• Duplicative work must be avoided

• Each code must be fully supported by documentation

• Overlapping anatomical access does not justify separate approach or resection codes

If documentation does not support all elements of both codes, and duplication exists, then the coding is not clinically supported. In such cases, CPT® guidance suggests that an unlisted procedure code may be more appropriate.

*This response is based on the best information available as of 9/25/25.