Crystal's MCW Coder Hub🧬 ICD-10 CM I63.031 — Cerebral Infarction Due to Thrombosis of Right Carotid Artery
Billable Code Confirmed
ICD-10-CM I63.031 is a valid, billable 6-character ICD-10-CM code for FY2026. All six characters are present:
I63(category) +.0(due to thrombosis of precerebral arteries) +3(carotid artery) +1(right). No 7th character is required.
Non-Billable Parent Codes — Never Submit These
- ❌
I63.03— 5-character header — missing laterality character- ❌
I63.0— 4-character header — missing vessel and lateralityAlways submit I63.031 (all 6 characters) when cerebral infarction due to thrombosis of the right carotid artery is documented.
⭐ HCC-Mapped Code — High RAF Value
Unlike many ophthalmic and retinal codes in this vault, I63.031 maps to HCC 85 (Ischemic or Unspecified Stroke) under CMS-HCC v28. This is one of the highest-value neurological HCC assignments. Every I63.031 encounter in a Medicare Advantage patient carries RAF weight. Document and code all associated neurological deficits, systemic comorbidities, and qualifying conditions — they carry their own HCC assignments and build the complete clinical picture.
Mechanism Specificity — Thrombosis, Not Embolism
ICD-10 CM I63.031 is specific to a thrombotic mechanism — in-situ clot formation or superimposed thrombus on an atherosclerotic plaque within the right carotid artery. If the physician documents embolic occlusion of the right carotid artery causing infarction, the correct code is I63.131 (cerebral infarction due to embolism of right carotid artery), NOT I63.031. Mechanism documentation is required and drives the code assignment — query when undocumented.
🔍 Code Description
ICD-10 CM I63.031 classifies cerebral infarction caused by in-situ thrombosis of the right carotid artery — an ischemic stroke in the anterior circulation resulting from clot formation within the extracranial or proximal intracranial segment of the right carotid artery, causing downstream ischemia and infarction of right-hemisphere brain tissue.
The carotid artery is classified as a precerebral artery — an extracranial or proximal vessel supplying the brain. Thrombosis of the right carotid artery typically causes ischemia in the territory supplied by the right middle cerebral artery (MCA) and/or right anterior cerebral artery (ACA), producing contralateral (left-sided) neurological deficits. This is in contrast to thrombosis of the basilar or vertebral arteries (I63.02/I63.01x), which affect the posterior circulation (cerebellum, brainstem, occipital lobes).
The qualifier thrombosis (I63.0x) distinguishes this code from:
- Embolism (I63.1x) — clot traveling from a distant source (e.g., heart in atrial fibrillation) that lodges in the carotid
- Cerebral artery thrombosis (I63.3x) — same thrombotic mechanism but arising within intracranial vessels (MCA, ACA, PCA) rather than the precerebral carotid
🌳 Code Tree / Hierarchy
I63 Cerebral Infarction
│
├── I63.0 Due to thrombosis of precerebral arteries ❌ Non-billable
│ │
│ ├── I63.00 Thrombosis of unspecified precerebral artery ✅ Billable
│ │
│ ├── I63.01 Thrombosis of vertebral artery (posterior circulation)
│ │ ├── I63.011 Right vertebral artery ✅ Billable
│ │ ├── I63.012 Left vertebral artery ✅ Billable
│ │ ├── I63.013 Bilateral vertebral arteries ✅ Billable
│ │ └── I63.019 Unspecified vertebral artery ⚠️ Avoid
│ │
│ ├── I63.02 Thrombosis of basilar artery (posterior circulation) ✅ Billable
│ │
│ └── I63.03 Thrombosis of carotid artery (anterior circulation) ❌ Non-billable
│ ├── I63.031 RIGHT carotid artery ◀ THIS CODE ✅ Billable
│ ├── I63.032 Left carotid artery ✅ Billable
│ ├── I63.033 Bilateral carotid arteries ✅ Billable
│ └── I63.039 Unspecified carotid artery ⚠️ Avoid
│
├── I63.1 Due to embolism of precerebral arteries (I63.131 = right carotid embolism)
├── I63.2 Due to unspecified occlusion or stenosis of precerebral arteries
├── I63.3 Due to thrombosis of cerebral arteries (intracranial)
├── I63.4 Due to embolism of cerebral arteries
├── I63.5 Due to unspecified occlusion or stenosis of cerebral arteries
├── I63.6 Due to cerebral venous thrombosis, nonpyogenic
└── I63.8/I63.9 Other/Unspecified cerebral infarction
Anterior vs. Posterior Circulation — Code Selection Decision Tree
Before selecting any I63.0x code, identify the vessel territory:
- Anterior circulation (carotid system): I63.03x → Symptoms: contralateral motor/sensory, language (left carotid), neglect (right carotid), visual field defect, ipsilateral Horner’s
- Posterior circulation (vertebrobasilar): I63.01x (vertebral) or I63.02 (basilar) → Symptoms: vertigo, ataxia, diplopia, dysarthria, crossed findings, Wallenberg syndrome, locked-in syndrome
The clinical presentation and imaging territory directly support — and validate — the code selection. Imaging (MRI DWI) showing right hemisphere anterior circulation infarct supports I63.031; posterior fossa/brainstem infarct supports I63.01x/I63.02.
✅ Includes
The following clinical terms and documentation patterns map to I63.031:
- Cerebral infarction due to thrombosis of the right internal carotid artery (ICA)
- Cerebral infarction due to thrombosis of the right common carotid artery (CCA)
- Thrombotic ischemic stroke, right carotid territory
- Right carotid artery occlusion with cerebral infarction, thrombotic mechanism
- Acute ischemic stroke, right anterior circulation, right carotid thrombosis
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with I63.031
Mutually exclusive conditions — different mechanism or different clinical entity:
| Code | Description | Note |
|---|---|---|
| I63.131 | Cerebral infarction due to embolism of right carotid artery | Different mechanism — embolic, not thrombotic; mutually exclusive at the right carotid level |
| I63.3- | Cerebral infarction due to thrombosis of cerebral (intracranial) arteries | Intracranial vessel thrombosis — not precerebral/extracranial; different anatomic territory |
| G45.- | Transient cerebral ischemic attack (TIA) and related syndromes | TIA = no infarction confirmed; I63.031 requires documented cerebral infarction |
| I65.2- | Occlusion and stenosis of right carotid artery, without cerebral infarction | When occlusion/stenosis is present but no infarction has occurred — right carotid stenosis without stroke maps here instead |
TIA vs. Cerebral Infarction — The Most Critical Excludes 1
G45.9 (TIA, unspecified) and I63.031 are mutually exclusive. TIA is defined as a transient episode of neurological dysfunction from focal ischemia without acute infarction on imaging. Once imaging confirms infarction — even a small DWI-positive lesion — the correct code is ICD-10 CM I63.031, not G45.9. This is one of the highest-stakes diagnosis code assignments in inpatient coding: the difference between TIA and acute ischemic stroke affects MS-DRG grouping, quality metrics, HCC capture, and stroke registry reporting. Query the physician if the diagnosis is documented inconsistently (e.g., “TIA vs. CVA” or “rule out stroke”) and imaging is not correlating with the working diagnosis.
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| I69.3- | Sequelae of cerebral infarction | Late effects may be coded additionally for a prior stroke when the current encounter is not for the acute event |
📋 Clinical Overview
Pathophysiology — Carotid Artery Thrombosis
Right carotid artery thrombosis causing cerebral infarction typically develops through one of three pathologic processes:
-
Atherosclerotic plaque rupture — the most common mechanism in adults over 50. Atherosclerotic plaque accumulates predominantly at the carotid bifurcation (where the common carotid divides into internal and external carotid). Plaque rupture exposes subendothelial collagen, triggering platelet aggregation and in-situ thrombus formation. The thrombus may occlude the vessel locally or propagate distally into the intracranial ICA or embolize to the MCA.
-
Arterial dissection — separation of the arterial wall layers (typically between the intima and media) creates a false lumen that compresses the true lumen and may propagate thrombosis. Right carotid dissection can be spontaneous (connective tissue disorders, fibromuscular dysplasia) or traumatic. Cervical dissections are an important cause of stroke in younger patients.
-
Hypercoagulable state — in-situ thrombosis without significant atherosclerosis, occurring in the setting of antiphospholipid syndrome, thrombophilia, malignancy, or severe dehydration.
Neurological Deficit Profile — Right Carotid Territory
Right carotid territory infarction produces contralateral (left-sided) neurological deficits, reflecting the crossed anatomy of corticospinal and sensory tracts:
| Deficit | Side | Code | CC/MCC Status |
|---|---|---|---|
| Hemiplegia/hemiparesis | Left (contralateral) | G81.92 flaccid or G81.12 spastic left-sided | MCC/CC — code when documented |
| Hemisensory loss | Left | R20.2 (diminished sensation) or G81.x2 | CC potential |
| Spatial neglect / hemispatial inattention | Left neglect (right hemisphere dominant for attention) | R41.4 neurological neglect syndrome | CC potential |
| Visual field defect (homonymous hemianopia) | Left visual field | H53.462 | Document separately |
| Dysarthria | — | R47.1 | CC potential |
| Aphasia | Typically NOT present (right hemisphere is non-dominant in right-handed patients) | R47.01 only if documented | CC potential |
| Dysphagia | — | R13.12 oropharyngeal dysphagia | CC — always code when documented |
| Ipsilateral Horner syndrome | Right eye (Horner’s from ICA sympathetic plexus disruption) | G90.2 | Document |
| Amaurosis fugax | Right eye transient monocular blindness if ophthalmic artery involved | H34.212 or G45.3 | Per documentation |
Neurological Deficit Codes Are NOT Optional — They Are CC/MCC Drivers
The neurological deficit codes listed above are “use additional code” entries and they frequently carry CC or MCC status. They directly impact DRG tier (moving from DRG 66 to DRG 65 or 64), reimbursement, and accurate clinical severity documentation. A stroke patient with documented left hemiplegia and dysphagia who is only coded with I63.031 alone is significantly undercoded — this is a DRG integrity and compliance risk. Review the H&P, nursing notes, PT/OT assessments, and SLP consults for documented deficits at the time of admission.
NIHSS — Code It Every Time
R29.700–R29.744 — NIHSS Score Is a Tabular "Use Additional Code" Instruction
The ICD-10-CM tabular instruction at I63 reads “Use additional code, if applicable, to identify the NIHSS score (R29.7-)“. The NIHSS (National Institutes of Health Stroke Scale) is a 15-item neurological examination scored 0-42 — higher scores indicate greater severity. When documented by the treating physician, NIHSS score codes must be assigned.
NIHSS Range Stroke Severity Code Range 0 No stroke symptoms R29.700 1–4 Minor stroke R29.701–R29.704 5–15 Moderate stroke R29.705–R29.715 16–20 Moderately severe R29.716–R29.720 21–42 Severe stroke R29.721–R29.742 Document and code the NIHSS — it provides objective severity quantification that supports medical necessity and clinical complexity.
Risk Factors
| Risk Factor | ICD-10-CM Code | HCC (v28) | Coding Action |
|---|---|---|---|
| Atrial fibrillation | I48.11, I48.19, etc. | HCC 96 | Code when documented — high RAF + impacts anticoagulation management |
| Hypertension | I10 | Not mapped | Code — extremely common in stroke patients |
| Carotid artery stenosis (right, without infarction, if prior) | I65.21 | Not mapped | Code history of stenosis as context |
| Hyperlipidemia | E78.5 | Not mapped | Code — cardiovascular risk factor |
| Diabetes mellitus | E11.9 or with complications | HCC 18 | Code with highest specificity |
| Tobacco use/dependence | F17.210, Z87.891 | Not mapped | Code — modifiable risk factor |
| Patent foramen ovale | Q21.12 | Not mapped | Relevant in cryptogenic stroke workup |
| Antiphospholipid syndrome | D68.61 | Not mapped | Code when documented as contributing cause |
| Carotid artery dissection (if mechanism) | I77.71 | Not mapped | Code when dissection is documented as cause |
| Obesity | E66.01 etc. | HCC 48 | Code when documented |
| CKD | N18.x | HCC 137 | Code stage when documented |
| Heart failure | I50.x | HCC 85 | Code when documented |
💰 HCC Risk Adjustment (CMS-HCC v28)
| Field | Detail |
|---|---|
| CMS-HCC Model Version | v28 (2024–2025 Implementation) |
| HCC Assignment | ✅ HCC 85 — Ischemic or Unspecified Stroke |
| HCC Category | HCC 85 |
| Approx. RAF Coefficient | ~0.267 (community, non-dual — verify current year PFS tables) |
| RxHCC Assignment | Review separately — stroke medications may carry RxHCC |
HCC 85 — High Value RAF Code
ICD-10 CM I63.031 maps to HCC 85 (Ischemic or Unspecified Stroke), one of the highest-weight neurological HCC assignments in the CMS-HCC v28 model. For Medicare Advantage plans, this code directly elevates the patient’s predicted cost and RAF score. Accurate capture and coding of I63.031 — with appropriate specificity — is essential for MA plan financial integrity and patient care appropriateness.
I69.3xx — Stroke Sequela Codes Also Map to HCC 85
Late effects of cerebral infarction (I69.3xx) also map to HCC 85 in CMS-HCC v28. In the outpatient chronic condition capture setting, patients with a prior stroke — even if the event was years ago — should be coded annually with the applicable I69.3xx sequela code (e.g., I69.351 hemiplegia/hemiparesis, right dominant, following cerebral infarction) to ensure persistent HCC capture year over year. This is one of the most commonly missed HCC recapture opportunities in Medicare Advantage populations.
HCC 85 Comorbidity Sweep — Every I63.031 Encounter
At every encounter where I63.031 is coded, actively review for the following co-occurring HCC-bearing conditions that are common in stroke patients:
Comorbidity HCC (v28) Approx. RAF Atrial fibrillation HCC 96 ~0.18 Heart failure (systolic/diastolic) HCC 85 varies by type Diabetes with chronic complications HCC 18 ~0.30 CKD Stage 3-5 HCC 137 ~0.17 COPD HCC 111 ~0.30 Peripheral vascular disease HCC 108 ~0.18 Major depression HCC 59 ~0.30 Morbid obesity HCC 48 ~0.25 Post-stroke depression, post-stroke cognitive impairment, and post-stroke seizures are also clinically significant conditions that may generate their own RAF-bearing codes in subsequent encounters.
🏥 MS-DRG Assignment
MDC 01 — Diseases and Disorders of the Nervous System
Path A — Thrombolytic Agent Administered (DRG 61-63)
When a thrombolytic agent (IV tPA or intra-arterial thrombolysis) is administered AND I63.031 (precerebral artery thrombosis) is the principal diagnosis:
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 61 | Ischemic Stroke, Precerebral Occlusion or TIA with Thrombolytic Agent with MCC | ~3.30–3.70 |
| DRG 62 | Ischemic Stroke, Precerebral Occlusion or TIA with Thrombolytic Agent with CC | ~2.00–2.30 |
| DRG 63 | Ischemic Stroke, Precerebral Occlusion or TIA with Thrombolytic Agent without CC/MCC | ~1.40–1.60 |
Path B — No Thrombolytic Agent (DRG 64-66)
Standard cerebral infarction admission without thrombolytic:
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 64 | Intracranial Hemorrhage or Cerebral Infarction with MCC or tPA in 24 Hours | ~1.80–2.20 |
| DRG 65 | Intracranial Hemorrhage or Cerebral Infarction with CC or tPA in 24 Hours | ~1.20–1.40 |
| DRG 66 | Intracranial Hemorrhage or Cerebral Infarction without CC/MCC | ~0.70–0.90 |
*Approximate. Verify against IPPS FY2026 Final Rule tables.
DRG Tier Elevation — The Deficit Codes Drive It
The difference between DRG 64 (MCC) and DRG 66 (no CC/MCC) can be thousands of dollars in reimbursement. The following documented neurological deficits carry MCC or CC status that elevate DRG tier — do not leave them uncoded:
Documented Deficit Code CC/MCC Status Hemiplegia, left dominant G81.92 / G81.12 MCC Dysphagia R13.12 CC Aphasia R47.01 CC Acute respiratory failure J96.00 MCC Atrial fibrillation with RVR I48.11 CC Acute-on-chronic systolic heart failure I50.23 MCC Coma, >1 hour R40.24x- MCC Malnutrition E43, E44.0 MCC/CC Each of these must be documented by the physician and supported by clinical evidence in the record — query for deficit documentation when the clinical picture supports it but documentation is absent.
🔗 Related ICD-10-CM Codes
I63.03x Laterality Variants
| Code | Description |
|---|---|
| I63.031 | Cerebral infarction due to thrombosis of right carotid artery ← This Code |
| I63.032 | Cerebral infarction due to thrombosis of left carotid artery |
| I63.033 | Cerebral infarction due to thrombosis of bilateral carotid arteries |
| I63.039 | Cerebral infarction due to thrombosis of unspecified carotid artery ⚠️ — query laterality |
I63.0x — Full Precerebral Thrombosis Family (All Vessels)
| Code | Description | Circulation |
|---|---|---|
| I63.011 | Thrombosis of right vertebral artery | Posterior |
| I63.012 | Thrombosis of left vertebral artery | Posterior |
| I63.02 | Thrombosis of basilar artery | Posterior |
| I63.031 | Thrombosis of right carotid artery ← This Code | Anterior |
| I63.032 | Thrombosis of left carotid artery | Anterior |
Embolic Equivalent — Same Vessel, Different Mechanism
| Code | Description | Note |
|---|---|---|
| I63.131 | Cerebral infarction due to embolism of right carotid artery | Embolic (e.g., from AF) — Excludes 1 with I63.031 |
Carotid Occlusion/Stenosis Without Infarction (Contrast)
| Code | Description | Note |
|---|---|---|
| I65.21 | Occlusion and stenosis of right carotid artery without cerebral infarction | When stenosis/occlusion is documented without confirmed stroke — use I65.21 instead of I63.031 |
Neurological Deficit Codes — Use Additional Code
| Code | Description | Always Check |
|---|---|---|
| G81.02 | Flaccid hemiplegia, affecting left dominant side | Acute-phase deficit after right carotid stroke |
| G81.12 | Spastic hemiplegia, affecting left dominant side | Sub-acute/chronic phase |
| R13.12 | Dysphagia, oropharyngeal phase | CC — code when SLP or physician documents |
| R47.01 | Aphasia | Right carotid = right hemisphere = non-dominant → less common but document if present |
| R41.4 | Neurological neglect syndrome | Right hemisphere stroke → left neglect |
| H53.462 | Homonymous hemianopia, left side | Left visual field cut — right occipital involvement |
Transclude of R29.700–R29.744 | NIHSS score | Required by tabular — “use additional code” |
Stroke Sequelae (Post-Acute Coding)
| Code | Description | When to Use |
|---|---|---|
| I69.351 | Hemiplegia/hemiparesis following cerebral infarction, left dominant | Chronic deficit — AFTER the acute stroke episode |
| I69.391 | Dysphagia following cerebral infarction | Chronic dysphagia as sequela |
| I69.320 | Aphasia following cerebral infarction | Chronic aphasia as sequela |
| I69.398 | Other sequelae of cerebral infarction | Catch-all for documented sequelae |
Acute Stroke Codes vs. Sequela Codes — Timing Matters
I63.031 is the acute cerebral infarction code — use it during the active inpatient admission and for a defined acute period. Once the patient is in the chronic phase (rehabilitation, outpatient follow-up, subsequent admissions NOT for the acute stroke itself), the applicable I69.3xx sequela codes replace I63.031 as the principal or additional diagnosis. Both I63.031 (HCC 85) and I69.3xx (also HCC 85) capture the same HCC value — continuity of coding ensures RAF capture persists year over year.
Z-Code Context Codes
| Code | Description |
|---|---|
| Z92.82 | Status post administration of tPA within last 24 hours prior to admission |
| Z86.73 | Personal history of TIA and cerebral infarction without residual deficits |
| Z82.3 | Family history of stroke |
| Z87.39x | Personal history of other conditions — prior stroke if applicable |
🛠️ CPT Procedural Crosswalk
Primarily Inpatient — CPT Used in ED and Outpatient Workup
The CPT codes below apply to the diagnostic workup and acute interventional management of right carotid artery thrombosis with cerebral infarction. Many of the surgical/endovascular procedures will generate ICD-10-PCS codes in the inpatient setting — see the ICD-10-PCS section below.
Neuroimaging
| CPT Code | Description | Application |
|---|---|---|
| 70553 | MRI brain with and without contrast | DWI confirms infarction, FLAIR/ADC maps ischemic territory; standard acute stroke imaging |
| 70544 | MRA head without contrast | Non-invasive intracranial vessel assessment — right MCA/ACA patency |
| 70547 | MRA neck without contrast | Right carotid vessel assessment — stenosis, occlusion, dissection |
| 70549 | MRA neck with and without contrast | Enhanced carotid assessment when dissection or post-intervention evaluation needed |
| 70450 | CT head without contrast | First-line ED imaging — rules out hemorrhage before tPA consideration |
| 70496 | CT angiography of head | Rapid vessel assessment — identifies carotid occlusion in acute setting |
| 70498 | CT angiography of neck | Right carotid occlusion/stenosis; dissection flap identification |
Vascular Studies
| CPT Code | Description | wRVU | Application |
|---|---|---|---|
| 93880 | Duplex scan, extracranial arterial studies (carotid/vertebral), bilateral | 1.37 | Right carotid stenosis severity — stenosis grading guides CEA vs. stent decision |
| 93882 | Duplex scan, extracranial arterial, unilateral or limited | 0.92 | Right carotid only if bilateral not needed |
| 93886 | Transcranial Doppler (TCD), complete | 1.14 | Intracranial hemodynamics, right MCA flow velocity — emboli detection |
Intervention
| CPT Code | Description | wRVU | Asst. Surgeon? | Global Period |
|---|---|---|---|---|
| 35301 | Carotid endarterectomy (CEA), common carotid, internal carotid | 20.00 | Yes — Indicator 2 | 090 days |
| 37215 | Transcervical carotid stenting with embolic protection | 18.00 | Yes — Indicator 2 | 090 days |
| 37216 | Transcervical carotid stenting without embolic protection | 16.00 | Yes — Indicator 2 | 090 days |
| 61645 | Percutaneous arterial transluminal mechanical thrombectomy, intracranial | 22.50 | Yes — Indicator 2 | 090 days |
CEA Global Period — 90 Days
Carotid endarterectomy (35301) carries a 90-day global period. Any E/M services, diagnostic imaging, or related procedures performed within 90 days of CEA that are part of normal post-operative care are bundled into the surgical fee. Modifier -24 (unrelated E/M) or -79 (unrelated procedure) may be required for separately payable services within the global period that are unrelated to the stroke repair.
tPA Administration
IV tPA Is a Drug Administration — Not a CPT Procedure Code for Billing
Intravenous alteplase (IV tPA) administration for acute ischemic stroke is captured as a pharmaceutical charge in the facility/hospital billing system, not a standalone CPT procedure code in the professional fee schedule. The clinical fact of tPA administration is captured in the inpatient record through:
- ICD-10-PCS procedure code (see below)
- ICD-10-CM code Z92.82 (when admitted within 24 hours of tPA given elsewhere)
- The DRG routing to 61-63 vs. 64-66 based on thrombolytic procedure coding
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
When I63.031 is an inpatient diagnosis and procedures are performed, the following ICD-10-PCS root operations are relevant. Full 7-character codes require consultation of PCS tables for the applicable fiscal year.
IV Thrombolysis (tPA)
| PCS Section | Body System | Root Operation | Body Part | Approach | Substance | Application |
|---|---|---|---|---|---|---|
| 3 (Administration) | E (Physiological Systems) | 0 (Introduction) | 3 (Peripheral vein) | 3 (Percutaneous) | 7 (Thrombolytic) | IV tPA via peripheral IV — most common acute stroke delivery route |
| 3 (Administration) | E | 0 (Introduction) | 4 (Central vein) | 3 (Percutaneous) | 7 (Thrombolytic) | IV tPA via central line |
| 3 (Administration) | E | 0 (Introduction) | 6 (Coronary artery) | 3 (Percutaneous) | 7 (Thrombolytic) | Intra-arterial thrombolysis — direct catheter delivery |
Mechanical Thrombectomy — Right Carotid Artery (Extirpation)
| PCS Section | Body System | Root Operation | Body Part | Approach | Application |
|---|---|---|---|---|---|
| 0 (Medical & Surgical) | 3 (Upper Arteries) | C (Extirpation) | G (Intracranial artery) or L (Internal carotid, right) | 3 (Percutaneous) | Catheter-based mechanical thrombectomy of right intracranial/carotid segment |
Carotid Endarterectomy (CEA)
| PCS Section | Body System | Root Operation | Body Part | Approach | Application |
|---|---|---|---|---|---|
| 0 (Medical & Surgical) | 3 (Upper Arteries) | C (Extirpation) | L (Internal Carotid Artery, Right) | 0 (Open) | Open right CEA — surgical removal of atherosclerotic plaque |
Carotid Stenting
| PCS Section | Body System | Root Operation | Body Part | Approach | Device | Application |
|---|---|---|---|---|---|---|
| 0 (Medical & Surgical) | 3 (Upper Arteries) | 7 (Dilation) | L (Internal Carotid, Right) | 3 (Percutaneous) | D (Intraluminal device) | Right carotid stent placement |
PCS Upper Arteries — Right vs. Left Body Part Characters
In ICD-10-PCS Body System 03 (Upper Arteries):
- Internal Carotid Artery, Right = Body Part L
- Internal Carotid Artery, Left = Body Part M
- Common Carotid Artery, Right = Body Part J
- Common Carotid Artery, Left = Body Part K
- External Carotid Artery, Right = Body Part N
- External Carotid Artery, Left = Body Part P
Always verify body part character from the applicable PCS table — do not assume bilateral symmetry of body part values.
💊 Coding Scenarios and Examples
Scenario 1 — Acute Right Carotid Thrombosis, IV tPA Administered, Left Hemiplegia and Dysphagia (Inpatient)
Clinical Vignette: A 68-year-old male with hypertension and type 2 diabetes presents to the ED within 3 hours of acute left-sided weakness and facial droop. CT head negative for hemorrhage. CT angiography shows right ICA occlusion at the bifurcation. NIHSS documented as 14. IV tPA administered. MRI DWI confirms right MCA territory infarction. Patient is admitted. SLP evaluation documents oropharyngeal dysphagia requiring tube feeds. PT/OT document left flaccid hemiplegia. Vascular surgery consults for right CEA consideration.
Principal Diagnosis:
- I63.031 — Cerebral infarction due to thrombosis of right carotid artery
Additional Diagnoses (CC/MCC — drive DRG tier):
- G81.02 — Flaccid hemiplegia affecting left dominant side ← MCC
- R13.12 — Dysphagia, oropharyngeal phase ← CC
- R29.714 — NIHSS score 14 (use additional code per tabular)
- I10 — Essential hypertension
- E11.9 — Type 2 DM without complications
ICD-10-PCS (Inpatient):
- 3E05317 — Introduction of thrombolytic into peripheral vein, percutaneous (IV tPA)
MS-DRG Routing:
- Thrombolytic administered + precerebral occlusion → DRG 61 (with MCC) (G81.02 = MCC — highest tier)
DRG 61 Is the Target Here
tPA + precerebral occlusion (I63.031) + MCC (G81.02) = DRG 61. Without the hemiplegia code → DRG 62 or 63. Without tPA → DRG 64-66. The difference in reimbursement between DRG 61 and DRG 66 is substantial. Every documented, coded deficit contributes to capturing the true clinical complexity of this case.
Scenario 2 — Right Carotid Thrombosis, Outside Hospital tPA, Transfer Admission (Inpatient)
Clinical Vignette: A 74-year-old female receives IV tPA at an outside hospital 2 hours after acute stroke onset and is transferred to the stroke center for higher level of care. On arrival, MRI confirms right carotid territory infarction. Documentation: right ICA thrombosis confirmed on CTA. No additional endovascular intervention performed at the receiving facility. NIHSS on arrival is 8. Aphasia not present; left-sided motor deficits documented. tPA given at outside facility within 24 hours of admission.
Principal Diagnosis:
- I63.031 — Cerebral infarction due to thrombosis of right carotid artery
Additional Diagnoses:
- G81.92 — Hemiplegia NOS, affecting left side ← MCC potential
- R29.708 — NIHSS score 8
- Z92.82 — Status post tPA administration within last 24 hours prior to admission (tPA given at outside facility — this code flags the tPA for DRG routing even though it was given elsewhere)
- I10 — Hypertension (documented)
- I48.19 — Atrial fibrillation (if documented as co-existing) ← CC
MS-DRG Routing:
- Z92.82 (tPA in 24 hours) activates DRG 64 consideration — DRG 64 or 65 depending on MCC/CC burden
Z92.82 — tPA at Outside Facility Still Counts for DRG
Z92.82 is the ICD-10-CM mechanism to flag that tPA was administered within 24 hours prior to admission at an OUTSIDE facility. This code routes the case to DRG 64 (“with tPA in 24 hours”) even when the receiving facility did not give tPA. Without Z92.82, the case defaults to DRG 65 or 66 based only on CC/MCC status — potentially underpaying for the clinical complexity. This is one of the most commonly missed stroke coding opportunities in transfer cases.
a Physician Query to the attending/neurologist asking them to reconcile the discharge diagnosis of “TIA” with the MRI DWI finding of acute infarction. The query should present the imaging finding and ask whether the final diagnosis should be amended to cerebral infarction.
If physician responds — cerebral infarction confirmed:
- I63.031 — Cerebral infarction due to thrombosis of right carotid artery (right ICA stenosis with in-situ thrombosis is the documented mechanism — thrombotic, not embolic)
- I65.21 — Occlusion and stenosis of right carotid artery without cerebral infarction (prior stenosis — may be coded additionally for historical context depending on clinical scenario)
If physician responds — TIA confirmed, no infarction:
- G45.9 — Transient ischemic attack, unspecified (physician determination supersedes imaging interpretation by coder — document the query and response in the record)
Never Upgrade TIA to Stroke Without Physician Confirmation
ICD-10-CM Official Coding Guidelines are clear — coders do not independently change a physician’s diagnosis. The query process is the correct pathway. If the physician reviews the DWI finding and still documents TIA as the final diagnosis, code TIA. The coder’s role is to query, not to override. Document the query and response thoroughly in the coding workflow.
Scenario 4 — Right Carotid Thrombosis, No tPA — Thrombectomy Only (Inpatient)
Clinical Vignette: A 78-year-old female presents 5 hours after symptom onset — outside the IV tPA window. CT angiography confirms right ICA occlusion with right MCA occlusion. NIHSS 19 on arrival. She is taken urgently to the neuro-interventional suite for mechanical thrombectomy of the right ICA and right MCA (M1 segment). Post-procedure, TICI 2b reperfusion achieved. She is admitted to the neuro ICU. Left flaccid hemiplegia documented by PT/OT. Left-sided neglect documented by OT. Dysphagia documented by SLP. NIHSS post-procedure drops to 11.
Principal Diagnosis:
- I63.031 — Cerebral infarction due to thrombosis of right carotid artery
Additional Diagnoses:
- G81.02 — Flaccid hemiplegia affecting left dominant side ← MCC
- R13.12 — Dysphagia, oropharyngeal phase ← CC
- R41.4 — Neurological neglect syndrome (left neglect — right hemisphere hallmark; document and code) ← CC potential
- R29.719 — NIHSS score 19 (use additional code per tabular)
- I10 — Hypertension
ICD-10-PCS:
- 03CG3ZZ — Extirpation of matter from intracranial artery, percutaneous (mechanical thrombectomy — intracranial artery, right MCA segment)
- 03CL3ZZ — Extirpation of matter from internal carotid artery right, percutaneous (thrombectomy of right ICA segment)
MS-DRG Routing:
- No tPA administered; thrombectomy only → Path B
- G81.02 = MCC → DRG 64 (with MCC)
Mechanical Thrombectomy Does NOT Activate DRG 61-63
DRG 61-63 (the higher-paying thrombolytic path) is triggered by thrombolytic agent administration (tPA), not mechanical thrombectomy. A case where only mechanical thrombectomy is performed without tPA routes to DRG 64-66 (Path B), with tier determined by CC/MCC burden. The distinction matters significantly for reimbursement — always document whether tPA was or was not administered and ensure Z92.82 is captured when tPA was given at an outside facility within 24 hours.
Scenario 5 — Right Carotid Stroke with Concurrent Atrial Fibrillation — Mechanism Query (Inpatient)
Clinical Vignette: A 74-year-old male is admitted with acute right hemisphere stroke. MRI confirms right MCA territory infarction. CTA neck shows right ICA stenosis (60%) but no acute occlusion. He has a documented history of atrial fibrillation (on warfarin, subtherapeutic INR on admission). The discharge summary reads: “Cerebral infarction, right carotid territory — cardioembolic vs. athero-thrombotic etiology unclear.”
Coding Action Required:
- When mechanism is documented as ambiguous (thrombotic vs. embolic), the coder must query the physician for mechanism clarification
- ICD-10 CM I63.031 applies to thrombotic mechanism only
- ICD-10 CM I63.131 applies to embolic mechanism (e.g., cardioembolism from AF)
- If the physician documents the mechanism as unspecified, the correct code is ICD-10 CM I63.231 (cerebral infarction due to unspecified occlusion or stenosis of right carotid artery)
- The atrial fibrillation (I48.x) is coded as an additional diagnosi regardless of whether it is confirmed as the embolic source
Query language: “The discharge summary documents cerebral infarction of the right carotid territory with etiology documented as ‘cardioembolic vs. athero-thrombotic, unclear.’ For accurate ICD-10-CM code assignment, could you please clarify the final documented mechanism of the infarction: (a) thrombotic — in-situ clot formation at a stenotic plaque; (b) embolic — clot from a distant source such as the heart (cardioembolic); or (c) unspecified — mechanism cannot be determined?”
Three Mechanism Codes — Right Carotid Territory
Mechanism Code Note Thrombotic I63.031 In-situ clot, atherosclerotic plaque Embolic I63.131 Traveling clot from distant source (AF, PFO) Unspecified I63.231 Mechanism undocumented after query Never default to thrombotic (I63.031) simply because a carotid stenosis is present — AF as a concurrent condition should prompt a mechanism query every time. Cardioembolism from AF is the most common cause of ischemic stroke overall, and the presence of both AF and carotid stenosis in the same patient demands clarification.
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Never submit I63.03 (5-character) as a billable code — I63.031 (6 characters) is required; the parent code will reject on claim |
| ❌ | Do not assign I63.031 for embolic mechanism — right carotid embolism maps to I63.131; mechanism drives the code, not just the vessel |
| ❌ | Do not assign I63.031 for right MCA/intracranial thrombosis — thrombosis in the right MCA itself maps to I63.311; carotid (precerebral) vs. MCA (cerebral artery) is the key anatomic distinction |
| ❌ | Do not code I63.031 simultaneously with G45.x (TIA) — mutually exclusive; DWI-positive imaging upgrades to I63.031 after physician confirmation via query |
| ❌ | Do not leave neurological deficit codes uncoded — left hemiplegia (G81.02 MCC), dysphagia (R13.12 CC), left neglect (R41.4 CC) are hallmark right carotid deficits; their absence is a CDI red flag and missed DRG tier opportunity |
| ❌ | Do not code left-sided aphasia as the primary deficit — aphasia is a dominant (left) hemisphere feature; its presence in a chart coded I63.031 (right carotid) warrants a clinical query — right carotid strokes produce left neglect/inattention, not typically aphasia (except in left-handed patients with right dominance) |
| ❌ | Do not forget Z92.82 in transfer cases — tPA given at an outside facility within 24 hours activates DRG 61-63 routing; without Z92.82 the receiving facility defaults to DRG 64-66 and loses the thrombolytic tier |
| ❌ | Do not default to thrombotic code when mechanism is ambiguous — concurrent AF demands a mechanism query before assigning I63.031 vs. I63.131 vs. I63.231 |
| ✅ | Code the NIHSS score every time — tabular “use additional code” instruction at I63; R29.700–R29.744 provides objective severity quantification |
| ✅ | Left-sided deficits = right carotid territory — left hemiplegia, left neglect, left visual field cut; these confirm right hemisphere involvement and support I63.031 |
| ✅ | Mechanical thrombectomy does NOT activate DRG 61-63 — only tPA administration (or Z92.82 for outside hospital tPA) routes to the higher-paying thrombolytic DRG path |
| ✅ | Code carotid dissection separately — when right carotid dissection (I77.71) is the documented mechanism underlying the thrombosis, code both I63.031 AND I77.71; dissection is a distinct codeable condition |
| ✅ | Sweep for HCC-bearing comorbidities at every I63.031 encounter — AF (HCC 96), DM with complications (HCC 18), CKD (HCC 137), heart failure (HCC 85), COPD (HCC 111); these co-occurring conditions carry RAF weight that directly benefits the MA plan’s risk adjustment |
| ✅ | Annual sequela recapture — in post-acute outpatient encounters and subsequent admissions, replace I63.031 with applicable I69.3xx sequela codes (e.g., I69.351 right hemiplegia following cerebral infarction) to maintain HCC 85 capture year over year |
| ✅ | Right CEA modifier -RT — when CEA (35301) is performed on the right carotid, modifier -RT is required; right CEA carries lower RLN risk than left CEA (see I63.032 note for left-sided RLN anatomy) |
| ✅ | Post-stroke depression is frequently missed — F06.31 or F32.x in right hemisphere stroke patients; right hemisphere strokes can produce mood disorders and emotional dysregulation that are often underdocumented; review psychiatry and nursing notes |
📚 Sources
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CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Tabular List — I63.031; I63.0 Cerebral infarction due to thrombosis of precerebral arteries; Excludes 1 notations at I63.03x; Use Additional Code instructions (NIHSS R29.7-, neurological deficits); Laterality guidelines; Section I.C.9 — Cerebrovascular disease coding guidelines.
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American Medical Association (AMA). CPT 2026 Professional Edition. Vascular Surgery — Carotid Endarterectomy (35301), Carotid Stenting (37215–37216); Interventional Neurology — Mechanical Thrombectomy (61645); Duplex Scanning (93880–93882); Transcranial Doppler (93886); Neuroimaging (70450–70553).
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American Heart Association / American Stroke Association (AHA/ASA). 2019 Guidelines for the Early Management of Patients with Acute Ischemic Stroke. IV tPA eligibility criteria, mechanical thrombectomy selection, carotid territory stroke management.
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Powers WJ, Rabinstein AA, Ackerson T, et al. “2019 Guidelines for the Early Management of Patients with Acute Ischemic Stroke.” Stroke. 2019;50(12):e344-e418.
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CMS. IPPS Final Rule FY2026 — MS-DRG Definitions Manual v43. MDC 01 — Diseases and Disorders of the Nervous System; DRGs 61–66 (ischemic stroke, thrombolytic agent, CC/MCC tier structure); DRG routing logic for precerebral occlusion codes.
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CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Medical & Surgical), Body System 3 (Upper Arteries) — Internal Carotid Right (Body Part L), Common Carotid Right (Body Part J), Intracranial Artery (Body Part G); Root Operation C (Extirpation) for CEA and thrombectomy; Section 3 (Administration) — thrombolytic introduction.
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CMS. CMS-HCC Model v28 (2024) ICD-10-CM Mappings. HCC 85 — Ischemic or Unspecified Stroke; I63.031 HCC assignment confirmed; I69.3xx sequela codes also mapping to HCC 85 for annual recapture.
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CMS. NCCI Policy Manual for Medicare Services, current version. Nervous System and Cardiovascular chapters — bundling rules for CEA, mechanical thrombectomy, neuroimaging, and E/M same-DOS billing; global period rules for 35301 and 37215–37216.
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CMS. Physician Fee Schedule Final Rule FY2026. Facility wRVU values — CPT 35301, 37215, 37216, 61645, 93880, 93882, 93886.
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Brott TG, Hobson RW 2nd, Howard G, et al. “Stenting versus Endarterectomy for Treatment of Carotid-Artery Stenosis.” N Engl J Med. 2010;363:11-23. CREST Trial — CEA vs. carotid stenting outcomes including perioperative stroke risk stratification.