Billing code 61598: Skull base approachMedicare rate & RVUs in Delaware
Reports transpetrosal surgical exposure of the skull base to reach lesions near the petrous temporal bone, petroclival region, or brainstem.
CMS doesn’t publish an office rate for 61598 in Delaware.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
On this page 9 sections
What 61598 covers
A transpetrosal approach creates access to the skull base through the petrous portion of the temporal bone. Neurosurgeons and otologic or neurotologic surgeons may use this corridor for selected lesions near the petrous bone, petroclival region, or brainstem. The operation is typically performed in a hospital operating room as part of complex skull base surgery; the operative report should identify the route and the exposure performed.
Report this code when the documented skull base exposure uses a transpetrosal corridor, rather than selecting it solely because a lesion is nearby. The record should distinguish the approach from the definitive treatment and describe relevant bone work and the operative target. This major surgery has a 90-day global period, including the day-before preoperative visit and related postoperative care during that period. When multiple procedures are performed in the same session, the highest-valued procedure is paid in full and other procedures are subject to the standard 50% reduction. Modifier 50 is inappropriate for this code. Assistant-at-surgery payment may be available; co-surgeon payment requires supporting documentation, and team surgery is permitted.
This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.
61598 in Delaware
| Payment locality | Office | Facility |
|---|---|---|
| Delaware | Unavailable | $2,789.10 |
How the 61598 rate is calculated
Each of 61598’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.
How the rate is built · 61598
RVUs × geographic indexes × conversion factor
Swap in your local Medicare rate.
Work 35.62Practice expense 34.60Malpractice 15.04
All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.
Payment rules and modifiers for 61598
61598 has a 90-day global period: related visits in that window are included in the surgery payment.
CMS payment indicators · 61598
Skull base approach
| Rule | CMS value | What it means |
|---|---|---|
| Global period | 090 | Major surgery: the day before, the day of, and 90 days after are included. |
| Multiple procedures | 2 | Standard reduction: highest-valued procedure at 100%, others at 50%. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 2 | Paid. |
| Co-surgeons (62) | 1 | Permitted with supporting documentation. |
| Team surgery (66) | 2 | Permitted. |
| Professional/technical | 0 | Physician service: no professional/technical split. |
| Split (54/55/56) | 0.11/0.76/0.13 | Share of the payment for pre-op, the procedure itself, and post-op care. |
Global surgery period · 61598
Skull base approach
90-day global period ends
Dec 30, 2026
Covers Sep 30, 2026 through Dec 30, 2026 (92 days, including the day before surgery).
Visit on Oct 31, 2026
Day 30 of the 90-day post-op period: related follow-up care is included in the surgical payment.
Pre-op dayGlobal period
What modifiers do to the payment
Modifier 51 · payment effect
With and without the modifier
61598 without 51 · national facility
$2,847.76
Skull base approach
61598-51 · Second procedure: 50%
$1,423.88
When this isn’t the highest-valued procedure in the session, Medicare pays 50% of its fee schedule amount (the highest is paid at 100%).
61598 compared with similar codes
Compare codes
61598 vs 61595 vs 61596 vs 61597: national Medicare rates
Swap in your local Medicare rate.
How to choose
- 61595Skull base approach
- 61598 identifies a transpetrosal route through the petrous temporal bone; 61595 is used for a transtemporal approach.
- 61596Skull base approach
- Use 61596 when the documented exposure is transcochlear, rather than transpetrosal.
- 61597Skull-base approach
- 61597 represents a transcondylar skull base corridor. The operative route, not simply the lesion's location, separates it from 61598.
61598 billing questions
How is this approach distinguished from a transtemporal approach?
Choose this code when the operative report identifies a transpetrosal route through the petrous temporal bone. A transtemporal approach is a different skull base corridor.
Should the approach and the definitive operation be reported separately?
The approach code represents the surgical exposure, not the pathology being treated. Review the operative report and applicable coding instructions to determine whether a separately described definitive procedure is also reportable.
Can modifier 50 be used for bilateral work?
No. CMS identifies bilateral adjustment as inapplicable to this code, so modifier 50 is inappropriate.
What documentation supports reporting the transpetrosal approach?
Document the skull base route used, the exposure and bone work performed, and the operative target. The record should make clear why the approach was transpetrosal rather than another skull base corridor.
How does the 90-day global period affect postoperative billing?
The global period includes the day-before preoperative visit and 90 days of related postoperative care. Those services are included in the surgical global period.
Can an assistant or co-surgeon be reported?
Assistant-at-surgery payment may be available. Co-surgeon payment requires supporting documentation; team surgery is permitted.
Where these rates come from
FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.
CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027
Show the CMS file lines behind this rate
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