What is ICD-10 code I63.12?

I63.12 is the ICD-10-CM diagnosis code for Cerebral infarction due to embolism of basilar artery. A stroke caused by a blood clot blocking the basilar artery, a major artery at the base of the brain that supplies critical brain regions. I63.12 is a billable code, meaning it can be reported on a claim as a primary or secondary diagnosis when supported by documentation. I63.12 is part of the FY2026 ICD-10-CM code set published by the CMS National Center for Health Statistics and used on Medicare, Medicaid, and commercial claims in the United States.

Yes. I63.12 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. I63.12 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

What is the V28 vs V24 difference for I63.12?

CMS phased in the V28 risk adjustment model over payment years 2024 (33%), 2025 (67%), and 2026 (100%), replacing V24. V28 consolidates HCC categories, removes some lower-acuity conditions, and recalibrates RAF weights across the entire model. For I63.12, V28 maps to Ischemic or Unspecified Stroke at RAF 0.289 while V24 mapped to Ischemic or Unspecified Stroke at RAF 0.262. Both models can still appear in legacy data and in payer-specific lookback periods.

What should coders know when reporting I63.12?

Basilar artery occlusion is a medical emergency; ensure the diagnosis is clearly documented as embolism. This code does not require laterality specification since the basilar artery is a single midline structure. Because I63.12 maps to a payment HCC, the documentation must also satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's risk adjustment score.

I63.12 ICD-10 Code: Cerebral infarction due

ICD-10-CM Code View

HCC Buddy Code Card

Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.

Code lookupI63.12Effective periodFY2026 Apr Update (Apr 1-Sep 30)

FY 2026 Apr update / Diseases of the circulatory system (I00-I99) / Cerebrovascular diseases (I60-I69)

I63.12

Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidance

Cerebral infarction due to embolism of basilar artery

A stroke caused by a blood clot blocking the basilar artery, a major artery at the base of the brain that supplies critical brain regions.

Buddy Insight

Cerebral infarction due to embolism of the basilar artery is a neurological emergency.

CMS-HCC V28

Mapped

HCC 249

Ischemic or Unspecified Stroke

RAF 0.289

CMS-HCC V24

Mapped

HCC 100

Ischemic or Unspecified Stroke

RAF 0.262

ACA/HHS

Not risk-adjusted for this model/period.

RAF 0

ESRD/PACE

Mapped

HCC 100

Ischemic or Unspecified Stroke

RAF 0.0

RXHCC

Not risk-adjusted for this model/period.

RAF 0

Code Trumping

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Code Book Path

Official

I63Cerebral infarction

I63.1Cerebral infarction due to embolism of precerebral arteries

I63.12Cerebral infarction due to embolism of basilar artery

Inclusion Terms

Official

ICD-10-CM does not list inclusion terms for I63.12 in this effective period.

Excludes 2

Official

ICD-10-CM does not list Excludes 2 notes for I63.12 in this effective period.

Related Child Codes

Official

I63.10Cerebral infarction due to embolism of unspecified precerebral artery

I63.11Cerebral infarction due to embolism of vertebral artery

I63.13Cerebral infarction due to embolism of carotid artery

I63.19Cerebral infarction due to embolism of other precerebral artery

Includes

Official

ICD-10-CM does not list Includes notes for I63.12 in this effective period.

Excludes 1

Official

ICD-10-CM does not list Excludes 1 notes for I63.12 in this effective period.

Code First

Official

ICD-10-CM does not list Code First sequencing instructions for I63.12 in this effective period.

Use Additional

Official

ICD-10-CM does not list Use Additional Code instructions for I63.12 in this effective period.

Code Also

Official

ICD-10-CM does not list Code Also instructions for I63.12 in this effective period.

Buddy Documentation Tip

HCC Buddy guidance

Imaging confirmation of posterior circulation cerebral infarction

Vascular imaging confirming basilar artery occlusion by embolism

Documentation specifying embolism as the mechanism vs. thrombosis or stenosis

Comprehensive neurological examination with brain stem assessment

MEAT Support

HCC Buddy guidance

Imaging confirmation of posterior circulation cerebral infarction

Vascular imaging confirming basilar artery occlusion by embolism

Documentation specifying embolism as the mechanism vs. thrombosis or stenosis

Comprehensive neurological examination with brain stem assessment

Audit Caution

HCC Buddy guidance

Not distinguishing between embolic and thrombotic occlusion of the basilar artery

Confusing basilar artery occlusion with vertebral artery occlusion near the vertebrobasilar junction

Coding basilar stenosis without actual cerebral infarction as a stroke code

Failing to code the embolic source condition (atrial fibrillation, cardiac thrombus) alongside the stroke

Common Mistakes

HCC Buddy guidance

I63.02 — Thrombosis of basilar artery; in situ clot, not a traveling embolus

I63.22 — Unspecified occlusion of basilar artery; mechanism not identified

I63.11x — Embolism of vertebral artery; different artery feeding into the basilar

I65.1 — Occlusion of basilar artery without cerebral infarction; no stroke has occurred

Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.

Is I63.12 an HCC code?

Yes. I63.12 maps to Ischemic or Unspecified Stroke under the CMS-HCC V28 risk adjustment model (and Ischemic or Unspecified Stroke under V24).

HCC Category Mapping

V28HCC 249, Ischemic or Unspecified Stroke

0.289

V24HCC 100, Ischemic or Unspecified Stroke

0.262

ESRDHCC 100, Ischemic or Unspecified Stroke

0.000

RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.

MEAT Criteria for I63.12

For I63.12to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically, it has to be re-documented and supported each calendar year.

MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
EEvaluate: test results, medication response, or physical findings reviewed by the provider
AAssess: explicit mention in the assessment or plan with acknowledgment of status
TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis

Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed I63.12 during that encounter, not just copy-forwarded from a problem list.

What This Code Means

I63.12 is the ICD-10-CM diagnosis code for cerebral infarction due to embolism of basilar artery. A stroke caused by a blood clot blocking the basilar artery, a major artery at the base of the brain that supplies critical brain regions. I63.12 sits in the ICD-10-CM chapter for diseases of the circulatory system (i00-i99), within the section covering cerebrovascular diseases (i60-i69).

Under the CMS-HCC V28 risk adjustment model, I63.12 maps to Ischemic or Unspecified Stroke (HCC 249) with a community, non-dual, aged base RAF weight of 0.289. Under the older V24 model, I63.12 mapped to the same category but with a base RAF weight of 0.262, V28 recalibrated weights across the entire model. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.

Basilar artery occlusion is a medical emergency; ensure the diagnosis is clearly documented as embolism. Because I63.12 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.

HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for I63.12 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.

Coding Tips

•Basilar artery occlusion is a medical emergency; ensure the diagnosis is clearly documented as embolism.
•This code does not require laterality specification since the basilar artery is a single midline structure.

Clinical Significance

Cerebral infarction due to embolism of the basilar artery is a neurological emergency. The basilar artery supplies the brain stem and posterior brain structures, and embolic occlusion can cause devastating deficits including coma, locked-in syndrome, and death. Identifying the embolic mechanism is crucial because it directs treatment toward the source of embolism and determines anticoagulation therapy needs.

Documentation Requirements

✓Imaging confirmation of posterior circulation cerebral infarction
✓Vascular imaging confirming basilar artery occlusion by embolism
✓Documentation specifying embolism as the mechanism vs. thrombosis or stenosis
✓Comprehensive neurological examination with brain stem assessment
✓Urgent embolic source evaluation (cardiac echocardiogram, rhythm monitoring)
✓Emergency treatment documentation including thrombectomy or thrombolysis decisions

Commonly Confused Codes

•I63.02: Thrombosis of basilar artery; in situ clot, not a traveling embolus
•I63.22: Unspecified occlusion of basilar artery; mechanism not identified
•I63.11x: Embolism of vertebral artery; different artery feeding into the basilar
•I65.1: Occlusion of basilar artery without cerebral infarction; no stroke has occurred