I63.512
BillableCerebral infarction due to unspecified occlusion or stenosis of left middle cerebral artery
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is I63.512 an HCC code?
Yes. I63.512 maps to Ischemic or Unspecified Stroke under the CMS-HCC V28 risk adjustment model (and Ischemic or Unspecified Stroke under V24).
HCC Category Mapping
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 I63.512
For I63.512 to 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 I63.512 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
I63.512 is the ICD-10-CM diagnosis code for cerebral infarction due to unspecified occlusion or stenosis of left middle cerebral artery. A stroke caused by a narrowing or blockage of the left middle cerebral artery, one of the major arteries supplying the brain. I63.512 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, I63.512 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, I63.512 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.
Verify left-sided involvement is explicitly documented in the medical record. Because I63.512 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 I63.512 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Verify left-sided involvement is explicitly documented in the medical record
- •Distinguish from bilateral involvement, which requires a different code
Clinical Significance
This code identifies an acute ischemic stroke due to occlusion or stenosis of the left middle cerebral artery where the specific mechanism (thrombosis versus embolism) is not documented. The middle cerebral artery supplies the lateral cerebral cortex including motor and sensory areas for the face and upper extremity, as well as language areas (Broca's and Wernicke's) in the dominant hemisphere. Accurate coding of the mechanism, artery, and laterality is critical for risk adjustment and tracking stroke subtypes for quality measures and secondary prevention strategies.
Documentation Requirements
- ✓Provider documentation of acute cerebral infarction (stroke) as a confirmed diagnosis, not rule-out or suspected
- ✓Identification of the affected artery as the middle cerebral artery
- ✓Documentation of laterality (left) supported by clinical findings and/or imaging
- ✓If the mechanism (thrombosis vs. embolism) can be determined from imaging or clinical workup, a more specific code should be assigned
- ✓Neurological examination findings consistent with the identified vascular territory (e.g., contralateral hemiparesis (face and arm worse than leg), hemisensory loss, and aphasia (dominant hemisphere) or neglect (non-dominant hemisphere))
- ✓Brain imaging (computed tomography or magnetic resonance imaging) confirming acute infarction
- ✓Timing of symptom onset to confirm acute presentation
- ✓Documentation of stroke severity (National Institutes of Health Stroke Scale score preferred)
- ✓Treatment administered (thrombolytics, thrombectomy, antiplatelet therapy, anticoagulation)
Commonly Confused Codes
- •I63.312 — Cerebral infarction due to thrombosis of left middle cerebral artery; use when thrombosis is specifically documented
- •I63.412 — Cerebral infarction due to embolism of left middle cerebral artery; use when embolism is specifically documented
- •I69.3xx — Sequelae of cerebral infarction; use for residual deficits from a prior stroke during follow-up visits, not during the acute event
- •G45.9 — Transient cerebral ischemic attack, unspecified; use when symptoms resolve completely within 24 hours with no evidence of infarction on imaging