2026 ICD-10-CM Diagnosis Code S06.A1XATraumatic brain compression with herniation, initial encounter
ICD-10-CM Codes›S00–T88›S00-S09›S06
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 399
- Not a Principal Diagnosis
- 7th Character A — Initial Encounter
- Not Chronic
S06.A1XA is a billable ICD-10-CM diagnosis code for traumatic brain compression with herniation, initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 11 through 13, 85 through 87, 963 through 965. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 3 closely related codes. The code is not accepted as a principal diagnosis by the Medicare Code Editor. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Traumatic brain injury (TBI); concussion, initial encounter.
For Medicare Advantage risk adjustment, S06.A1XA maps to CMS-HCC Category 399 (Major Head Injury without Loss of Consciousness) under the V28 model, adding a risk factor of about 0.199 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Code EditsBilling
Medicare Code Editor checks that affect claim validity for S06.A1XA.
Medicare Risk Adjustment (HCC)Billing
S06.A1XA maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Intracranial injury (S06). Use the following options for the applicable episode of care:
- A - initial encounter
- D - subsequent encounter
- S - sequela
Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Code History & ChangesHistory
Replacement S06.A1XA replaces the following previously assigned code(s):
- S06.890A - Intcran inj w/o loss of consciousness, init encntr
- S06.899A - Intcran inj w loss of consciousness of unsp duration, init
Questions About S06.A1XAOverview
What is the ICD-10 code for traumatic brain compression with herniation, initial encounter?
The ICD-10-CM code for traumatic brain compression with herniation, initial encounter is S06.A1XA (sometimes written as S06A1XA). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is S06.A1XA (Traumatic brain compression with herniation) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report traumatic brain compression with herniation, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in S06.A1XA mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for traumatic brain compression with herniation, such as an emergency visit or first evaluation.
What MS-DRG does S06.A1XA group to?
On inpatient claims, traumatic brain compression with herniation, initial encounter maps to MS-DRG 11, 12, 13, 85, 86, 87, 963, 964, 965, with relative weights from 0.9147 to 5.4541 depending on complications. Higher weights mean higher Medicare reimbursement.
Is S06.A1XA a CC or MCC?
CMS lists S06.A1XA as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 3 closely related codes in its exclusion list.
What HCC is S06.A1XA?
S06.A1XA (traumatic brain compression with herniation, initial encounter) maps to CMS-HCC Category 399 (Major Head Injury without Loss of Consciousness), commonly written as HCC 399, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 167 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. It does not map to any RxHCC in the Part D prescription drug model.
Does S06.A1XA risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, S06.A1XA adds a risk adjustment factor of about 0.199 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.052 to 0.349 depending on the payment segment). A more severe related category (HCC 397 and HCC 398) supersedes it when both are reported. See the full factor table on the HCC 399 category page.
