2027 ICD-10-CM Diagnosis Code I63.333Cerebral infarction due to thrombosis of bilateral posterior cerebral arteries

ICD-10-CM Codes›I00–I99›I60-I69›I63

ICD-10-CM I63.333
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I63.333 is a billable ICD-10-CM diagnosis code for cerebral infarction due to thrombosis of bilateral posterior cerebral arteries. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 23 through 24, 61 through 66, 791, 793. 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 84 closely related codes. Coders also document this condition as cerebrovascular accident due to thrombosis of bilateral posterior cerebral arteries. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Cerebral infarction.

For Medicare Advantage risk adjustment, I63.333 maps to CMS-HCC Category 249 (Ischemic or Unspecified Stroke) under the V28 model, adding a risk factor of about 0.239 for a community, non-dual, aged beneficiary in payment year 2027.

Code Identity

ICD-10-CM Code
I63.333
Billable Status
Yes — Valid for Submission
Code Describes
Cerebral infarction due to thrombosis of bilateral posterior cerebral arteries
Short Description
Cerebral infrc due to thombos of bi post cerebral arteries
Parent Code
I63.33
Cerebral infarction due to thrombosis of posterior cerebral artery

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI60-I69Cerebrovascular diseases
CategoryI63Cerebral infarction
This CodeI63.333Cerebral infarction due to thrombosis of bilateral posterior cerebral arteries

Medicare Risk Adjustment (HCC)Billing

I63.333 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 2027.

CMS-HCC V28 Category (Payment Model)
HCC 249— Ischemic or Unspecified Stroke
Payment HCC · PY 2027 one of 95 ICD-10-CM codes in this category
Risk Adjustment Factor (RAF) Weight
+0.239
community, non-dual, aged · ranges 0.081–0.377 across segments
Hierarchy
Superseded by HCC 248
a more severe related category takes the payment when both are reported
Prior Model (CMS-HCC V24)
HCC 100
V24 retired V28 pays 100% of MA risk scores since PY 2026
Other CMS Models
PACE (CMS-HCC V22): HCC 100 · ESRD (V21): HCC 100 · ESRD (V24): HCC 100
ESRD V21 weights: 0.078 dialysis, 0.105–0.252 functioning graft · ESRD V24 weights: 0.062 dialysis, 0.082–0.355 functioning graft
Part D (RxHCC)
Not mapped
I63.333 does not risk-adjust in the RxHCC prescription drug model

Source: CMS Payment Year 2027 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.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Cerebrovascular accident due to thrombosis of bilateral posterior cerebral arteries
  • Cerebrovascular accident due to thrombosis of left posterior cerebral artery
  • Cerebrovascular accident due to thrombosis of right posterior cerebral artery

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I63.333: its own notes plus those printed at I63, block I60-I69, and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From I63 Cerebral infarction applies to 91 codes
  • occlusion and stenosis of cerebral and precerebral arteries, resulting in cerebral infarction

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From I63 Cerebral infarction applies to 91 codes
  • neonatal cerebral infarction (P91.82-)
From Block I60-I69 Cerebrovascular diseases applies to 410 codes
  • traumatic intracranial hemorrhage (S06.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From I63 Cerebral infarction applies to 91 codes
  • chronic, without residual deficits (sequelae) (Z86.73)
  • sequelae of cerebral infarction (I69.3-)
From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From I63 Cerebral infarction applies to 91 codes
  • code, if applicable, to identify status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82)
  • code, if known, to indicate National Institutes of Health Stroke Scale (NIHSS) score (R29.7-)
From Block I60-I69 Cerebrovascular diseases applies to 410 codes
  • code to identify presence of:
  • alcohol abuse and dependence (F10.-)
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • hypertension (I10-I1A)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I63.333, its category, or a range that includes it.

Excludes1 3

These codes carry an Excludes1 note naming I63.333: they are not reported together with it, unless the two conditions are unrelated.

  • P91.82 Neonatal cerebral infarction
    cerebral infarction (I63.-) names I63.-, which includes this code
  • I66 Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction
    Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5) names I63.3-I63.5, which includes this code
  • I67 Other cerebrovascular diseases
    Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5-) names I63.3-I63.5, which includes this code

Excludes2 1

These codes carry an Excludes2 note naming I63.333: its condition is not part of those codes, and both may be reported when the patient has both.

  • I74 Arterial embolism and thrombosis
    cerebral embolism and thrombosis (I63.3-I63.5, I66.-) names I63.3-I63.5, which includes this code

Code First 2

These codes say to code first a condition named in the note, and I63.333 is one of the conditions named.

  • R29.7 National Institutes of Health Stroke Scale (NIHSS) score
    the type of cerebral infarction (I60.-, I61.-, I62.-, I63.-) names I63.-, which includes this code
  • Z92.82 Status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility
    acute cerebral infarction (I63.-) names I63.-, which includes this code

Code Also 11

These codes say I63.333 may also be needed to fully describe the condition. The note gives no sequencing direction.

  • D57.03 Hb-SS disease with cerebral vascular involvement
    if applicable, cerebral infarction (I63.-) names I63.-, which includes this code
  • D57.213 Sickle-cell/Hb-C disease with cerebral vascular involvement
    if applicable, cerebral infarction (I63.-) names I63.-, which includes this code
  • D57.413 Sickle-cell thalassemia, unspecified, with cerebral vascular involvement
    if applicable cerebral infarction (I63.-) names I63.-, which includes this code
  • D57.433 Sickle-cell thalassemia beta zero with cerebral vascular involvement
    if applicable cerebral infarction (I63.-) names I63.-, which includes this code
  • D57.453 Sickle-cell thalassemia beta plus with cerebral vascular involvement
    if applicable cerebral infarction (I63.-) names I63.-, which includes this code
  • D57.813 Other sickle-cell disorders with cerebral vascular involvement
    if applicable: cerebral infarction (I63.-) names I63.-, which includes this code
  • D81.32 Adenosine deaminase 2 deficiency
    stroke (I63.-) names I63.-, which includes this code
  • G43.6 Persistent migraine aura with cerebral infarction
    the type of cerebral infarction (I63.-) names I63.-, which includes this code
  • G96.81 Intracranial hypotension
    Stroke (I63.-) names I63.-, which includes this code
  • I16.1 Hypertensive emergency
    cerebral infarction (I63.-) names I63.-, which includes this code
  • I67.850 Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy
    stroke (I63.-) names I63.-, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR CIR020
Cerebral infarction
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Cerebral Infarction

    the formation of an area of necrosis in the cerebrum caused by an insufficiency of arterial or venous blood flow. infarcts of the cerebrum are generally classified by hemisphere (i.e., left vs. right), lobe (e.g., frontal lobe infarction), arterial distribution (e.g., infarction, anterior cerebral artery), and etiology (e.g., embolic infarction).

Patient EducationClinical

Ischemic Stroke

A stroke happens when there is a loss of blood flow to part of the brain. Your brain cells cannot get the oxygen and nutrients they need from blood, and they start to die within a few minutes. This can cause lasting brain damage, long-term disability, or even death.

The full article covers:

  • What is an ischemic stroke?
  • What causes an ischemic stroke?
  • What are the symptoms of ischemic stroke?
  • How is an ischemic stroke diagnosed?
  • How is an ischemic stroke treated?
  • Can an ischemic stroke be prevented?

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert I63.333 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
434.01 Crbl thrmbs w infrct
Approximate The match is approximate rather than exact.

Code History & ChangesHistory

Replacement I63.333 replaces the following previously assigned code(s):

  • I63.331 - Cerebral infrc due to thombos of right post cerebral artery
  • I63.332 - Cerebral infrc due to thombos of left post cerebral artery
FY 2019AddedAdded to the ICD-10-CM code setEffective October 1, 2018.
FY 2020–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I63.333Overview

Is I63.333 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report cerebral infarction due to thrombosis of bilateral posterior cerebral arteries on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does I63.333 group to?

When cerebral infarction due to thrombosis of bilateral posterior cerebral arteries is the principal diagnosis on an inpatient stay, it groups to MS-DRG 793, 791, 24, 64, 23, 65, 61, 62, 63, 66, with relative weights from 0.6770 to 5.7422 depending on complications. Higher weights mean higher Medicare reimbursement.

Is I63.333 a CC or MCC?

CMS lists I63.333 as an MCC (major complication or comorbidity) for FY 2027. 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 84 closely related codes in its exclusion list.

Can I63.333 be reported with a code from P91.82?

Not as a rule. The Excludes1 note at I63, which applies to I63.333, lists "neonatal cerebral infarction (P91.82-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

Does I63.333 need an additional code?

When the condition applies, yes. The Use Additional Code note at I63, which applies to I63.333, reads: code, if applicable, to identify status post administration of tPA (rtPA) in a different facility within the last 24 hours prior to admission to current facility (Z92.82); code, if known, to indicate National Institutes of Health Stroke Scale (NIHSS) score (R29.7-). The additional code is reported after I63.333.

What HCC is I63.333?

I63.333 (cerebral infarction due to thrombosis of bilateral posterior cerebral arteries) maps to CMS-HCC Category 249 (Ischemic or Unspecified Stroke), commonly written as HCC 249, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2027. It mapped to HCC 100 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 I63.333 risk-adjust for Medicare Advantage payment?

Yes. When documented and reported on a Medicare Advantage encounter, I63.333 adds a risk adjustment factor of about 0.239 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.081 to 0.377 depending on the payment segment). A more severe related category (HCC 248) supersedes it when both are reported. See the full factor table on the HCC 249 category page.