Crystal's MCW Coder Hub🧬 ICD-10 CM I63.313 — Cerebral Infarction Due to Thrombosis of Bilateral Middle Cerebral Arteries
Billable Code Confirmed
ICD-10-CM I63.313 is a valid, billable 6-character ICD-10-CM code for FY2026. All six characters are present:
I63(category) +.3(due to thrombosis of cerebral arteries) +1(middle cerebral artery) +3(bilateral). No 7th character is required.
Non-Billable Parent Codes — Never Submit These
- ❌
I63.31— 5-character header — missing laterality character- ❌
I63.3— 4-character header — missing vessel and lateralityAlways submit I63.313 (all 6 characters) when cerebral infarction due to bilateral MCA thrombosis is documented.
⭐ HCC-Mapped Code — High RAF Value
ICD-10 CM I63.313 maps to HCC 85 (Ischemic or Unspecified Stroke) under CMS-HCC v28. Despite representing one of the most clinically devastating stroke presentations in the codebook, the HCC weight is the same as unilateral carotid strokes within the ischemic stroke category. The true financial and clinical complexity of bilateral MCA infarction is captured through the associated neurological deficit codes — bilateral hemiplegia, global aphasia, dysphagia — that drive DRG tier elevation.
⚠️ Critical Distinction — Cerebral Artery vs. Precerebral Artery
ICD-10 CM I63.313 is in the I63.3x family (cerebral artery thrombosis — intracranial). This is fundamentally different from I63.033 (bilateral carotid artery thrombosis — precerebral/extracranial):
Code Vessel Location Family I63.033 Bilateral carotid arteries Extracranial / neck I63.0x precerebral I63.313 Bilateral middle cerebral arteries Intracranial I63.3x cerebral The MCA arises intracranially from the internal carotid artery at the Circle of Willis and travels within the brain — it is a cerebral artery. In-situ thrombosis of the MCA itself = I63.31x family. Carotid thrombosis causing downstream MCA territory infarction = I63.03x family. This is one of the most important anatomic distinctions in the entire cerebrovascular coding section.
⚠️ Both Hemispheres Affected — Unique Bilateral Deficit Profile
Bilateral MCA infarction involves both dominant (left) AND non-dominant (right) hemispheres simultaneously:
- Left MCA component → Aphasia (R47.01), right hemiplegia (G81.01/G81.11)
- Right MCA component → Left neglect (R41.4), left hemiplegia (G81.02/G81.12)
- Combined bilateral → Global aphasia, bilateral hemiplegia, bilateral dysphagia, bilateral hemisensory loss, locked-in syndrome features in severe cases
A fully documented bilateral MCA stroke generates more codeable CC/MCC deficit codes than virtually any other ischemic stroke in the codebook. Every deficit must be captured — this is among the highest CDI-yield stroke presentations.
🔍 Code Description
ICD-10 CM I63.313 classifies cerebral infarction caused by in-situ thrombosis of both the right and left middle cerebral arteries — the most extensive form of anterior circulation ischemic stroke, involving simultaneous bilateral MCA territory infarction through a thrombotic mechanism.
The middle cerebral artery (MCA) is the largest intracranial artery and supplies the majority of the lateral cerebral cortex, including the primary motor cortex, primary sensory cortex, Broca’s area (left), Wernicke’s area (left), and the parietal cortex responsible for spatial attention (right). Bilateral MCA territory infarction therefore produces a catastrophic combination of neurological deficits spanning both hemispheres — affecting language, bilateral motor function, bilateral sensory function, spatial cognition, and consciousness.
The term thrombosis (I63.3x) specifies an in-situ clot forming within the MCA itself — distinguishing this from embolic bilateral MCA occlusion (I63.413) where clots travel from a distant source (most commonly cardiac in origin — atrial fibrillation, left ventricular thrombus, or paradoxical embolism via PFO). Bilateral simultaneous MCA thrombosis is rare as a purely thrombotic process in isolation — when bilateral MCA territory infarction is documented, the clinical workup should aggressively pursue cardiac, hypercoagulable, and vasculitic etiologies. Bilateral simultaneous MCA territory infarction from a thrombotic mechanism raises the possibility of an underlying systemic prothrombotic state or vasculitis that may carry its own additional codeable diagnosis.
🌳 Code Tree / Hierarchy
I63 Cerebral Infarction
│
├── I63.0 Due to thrombosis of PREcerebral arteries (extracranial)
│ └── I63.03x Carotid artery (extracranial) — see [[I63.031]], [[I63.032]], [[I63.033]]
│
├── I63.3 Due to thrombosis of CEREBRAL arteries (intracranial) ❌ Non-billable
│ │
│ ├── I63.30 Unspecified cerebral artery thrombosis ✅ Billable
│ │
│ ├── I63.31 Middle Cerebral Artery (MCA) ❌ Non-billable
│ │ ├── I63.311 Right MCA ✅ Billable
│ │ ├── I63.312 Left MCA ✅ Billable
│ │ ├── I63.313 BILATERAL MCA ◀ THIS CODE ✅ Billable
│ │ └── I63.319 Unspecified MCA ⚠️ Avoid
│ │
│ ├── I63.32 Anterior Cerebral Artery (ACA)
│ │ ├── I63.321 Right ACA ✅ Billable
│ │ ├── I63.322 Left ACA ✅ Billable
│ │ ├── I63.323 Bilateral ACA ✅ Billable
│ │ └── I63.329 Unspecified ACA ⚠️ Avoid
│ │
│ ├── I63.33 Posterior Cerebral Artery (PCA)
│ │ ├── I63.331 Right PCA ✅ Billable
│ │ ├── I63.332 Left PCA ✅ Billable
│ │ ├── I63.333 Bilateral PCA ✅ Billable
│ │ └── I63.339 Unspecified PCA ⚠️ Avoid
│ │
│ ├── I63.34 Cerebellar Artery
│ │ ├── I63.341 Right cerebellar artery ✅ Billable
│ │ ├── I63.342 Left cerebellar artery ✅ Billable
│ │ ├── I63.343 Bilateral cerebellar arteries ✅ Billable
│ │ └── I63.349 Unspecified cerebellar artery ⚠️ Avoid
│ │
│ └── I63.39 Other cerebral artery thrombosis ✅ Billable
│
├── I63.4 Due to embolism of cerebral arteries
│ └── I63.413 Embolism of bilateral MCA — see below (Excludes 1)
└── I63.5 Due to unspecified occlusion/stenosis of cerebral arteries
└── I63.513 Unspecified bilateral MCA occlusion
Precerebral (I63.0x) vs. Cerebral (I63.3x) — The Anatomic Boundary
The distinction between the I63.0x (precerebral) and I63.3x (cerebral) families rests on one anatomic landmark: the Circle of Willis. Vessels proximal to (before) the Circle of Willis are precerebral — the carotid artery (I63.03x) and vertebral artery (I63.01x). Vessels arising from the Circle of Willis and beyond are cerebral — MCA (I63.31x), ACA (I63.32x), PCA (I63.33x). The MCA arises from the terminal ICA at the Circle of Willis and is definitively intracranial/cerebral.
✅ Includes
The following clinical terms map to I63.313:
- Cerebral infarction due to thrombosis of bilateral middle cerebral arteries
- Bilateral MCA territory cerebral infarction, thrombotic mechanism
- Bilateral MCA occlusion with infarction — in-situ thrombus
- Bilateral anterior circulation cerebral infarction — intracranial thrombotic mechanism, both MCAs
- Malignant bilateral MCA syndrome with thrombotic occlusion (when bilateral MCA thrombosis is the documented etiology)
❌ Excludes
Excludes 1 — Cannot Be Coded Simultaneously with I63.313
| Code | Description | Note |
|---|---|---|
| I63.413 | Cerebral infarction due to embolism of bilateral MCA | Different mechanism — embolic; mutually exclusive; bilateral simultaneous MCA embolism is more common than bilateral thrombosis — query mechanism when bilateral MCA infarction is documented |
| I63.513 | Cerebral infarction due to unspecified occlusion/stenosis of bilateral MCA | Mutually exclusive — once mechanism is specified as thrombotic, I63.513 is not used |
| G45.- | TIA | Mutually exclusive — bilateral MCA TIA without infarction; use G45.x only when DWI is negative |
| I66.03 | Occlusion and stenosis of bilateral MCA without cerebral infarction | When bilateral MCA stenosis/occlusion is present without confirmed infarction |
Embolism Is More Common Than Thrombosis in Bilateral MCA
Bilateral simultaneous MCA territory infarction most commonly results from an embolic mechanism — particularly cardioembolism from atrial fibrillation, left ventricular thrombus, or paradoxical embolism. True bilateral in-situ MCA thrombosis (I63.313) is less common and should prompt evaluation for vasculitis, hypercoagulable state, or antiphospholipid syndrome. When bilateral MCA infarction is documented without a specified mechanism, query for thrombotic vs. embolic before defaulting to I63.313 — if embolic, the correct code is I63.413. If mechanism cannot be determined after query, assign I63.513 (unspecified occlusion/stenosis, bilateral MCA).
Excludes 2 — May Be Coded in Addition if Separately Present
| Code | Description | Note |
|---|---|---|
| I69.3- | Sequelae of cerebral infarction | Late effects of a prior stroke — code alongside I63.313 only when the current event is a new bilateral MCA stroke AND the patient has documented chronic sequelae from a previous separate stroke event |
📋 Clinical Overview
The Middle Cerebral Artery — Anatomy and Territory
The MCA is the largest branch of the internal carotid artery and the vessel most commonly involved in ischemic stroke. Understanding its territory explains why bilateral MCA infarction is so catastrophic:
| MCA Segment | Territory Supplied | Infarction Consequences |
|---|---|---|
| M1 (horizontal) | Putamen, internal capsule, corona radiata | Contralateral dense hemiplegia — upper AND lower extremity |
| M2 (insular) | Insular cortex, operculum | Dysphagia, dysarthria, taste; corticobulbar involvement |
| M2 superior division | Lateral frontal lobe, Broca’s area (left) | Expressive aphasia (left); contralateral arm > leg weakness |
| M2 inferior division | Temporal-parietal lobe, Wernicke’s (left), parietal attention (right) | Receptive aphasia (left); hemispatial neglect (right) |
| M3-M4 (cortical) | Primary motor and sensory cortex, parietal lobe | Contralateral sensorimotor deficits, cortical sensory loss |
Bilateral MCA territory infarction = loss of ALL of the above functions in BOTH hemispheres simultaneously. This produces the most severe possible anterior circulation stroke syndrome.
Pathophysiology — Bilateral MCA Thrombosis
For bilateral simultaneous MCA thrombosis to occur through a purely thrombotic in-situ mechanism (as coded by I63.313 rather than I63.413), one of the following pathologic processes must be operative:
-
Hypercoagulable state — antiphospholipid syndrome (APS) is the leading cause of bilateral simultaneous intracranial thrombosis in younger patients. APS generates widespread venous and arterial thrombosis including intracranial vessels. Malignancy-associated hypercoagulability (Trousseau syndrome), thrombotic thrombocytopenic purpura (TTP), and heparin-induced thrombocytopenia (HIT) can produce bilateral intracranial thrombi.
-
Intracranial vasculitis — inflammatory vessel wall disease (CNS vasculitis, giant cell arteritis with intracranial extension, infectious vasculitis in meningitis) can cause thrombosis in multiple vessels simultaneously.
-
Severe systemic hypoperfusion with bilateral “watershed” extension — profound hypotension or cardiac arrest can cause bilateral MCA territory watershed infarction with thrombus formation in the setting of stagnant flow. This is distinct from classic single-vessel MCA thrombosis.
-
Bilateral carotid occlusion with in-situ MCA thrombus propagation — thrombosis extending from bilateral ICA occlusions (I63.033) may propagate distally into both MCAs, making both I63.033 and I63.313 potentially applicable pending physician documentation.
Neurological Deficit Profile — Bilateral MCA Territory
Bilateral MCA infarction produces a combined deficit profile from both hemispheres — the most codeable neurological presentation in the stroke codebook:
| Deficit | Hemisphere | Side of Body | Code | CC/MCC |
|---|---|---|---|---|
| Expressive/Global Aphasia | Left (dominant) | Language — not lateralized | R47.01 | CC |
| Right flaccid hemiplegia | Left MCA (acute) | Right body | G81.01 | MCC |
| Left flaccid hemiplegia | Right MCA (acute) | Left body | G81.02 | MCC |
| Bilateral hemiplegia | Both MCA | Both sides | G83.3 | MCC |
| Left hemispatial neglect | Right (non-dominant) | Left attention | R41.4 | CC |
| Bilateral dysphagia | Both — corticobulbar | Swallowing | R13.12 | CC |
| Bilateral sensory loss | Both | Both sides | R20.2 | Document |
| Coma / decreased consciousness | Both hemispheres | — | R40.20 | MCC |
| Bilateral homonymous hemianopia | Both occipital — if PCA involvement | Both visual fields | H53.46x | Document |
| Dysarthria | Both corticobulbar | Speech | R47.1 | CC |
G83.3 — Monoplegia/Diplegia/Paraplegia Codes vs. G81.x Bilateral
When both sides are documented as hemiplegic, the coder must determine whether to code:
- G81.01 (right) + G81.02 (left) — two separate hemiplegia codes, one per side; or
- G83.3 — bilateral hemiplegia/diplegia (both sides — single code)
G83.3 is the preferred single code when the physician documents bilateral hemiplegia as a unified deficit. Query if documentation only specifies each side individually without a “bilateral” characterization. G83.3 carries MCC status — as do the bilateral G81.x1/G81.x2 assignments when separately documented.
NIHSS in Bilateral MCA Stroke
Bilateral MCA Strokes Drive the Highest NIHSS Scores
The NIHSS awards points for language (0-3), level of consciousness (0-3), gaze (0-2), visual fields (0-3), facial palsy (0-3), motor arm bilateral (0-4 each), motor leg bilateral (0-4 each), limb ataxia (0-2), sensory (0-2), and dysarthria (0-2). A patient with bilateral MCA infarction scoring maximally in bilateral motor, language, and consciousness items can reach scores of 30-42:
NIHSS Range Code Stroke Severity 21-25 R29.721-R29.725 Severe 26-30 R29.726-R29.730 Severe 31-35 R29.731-R29.735 Very severe 36-42 R29.736-R29.742 Maximum / catastrophic Bilateral MCA strokes routinely group into the R29.73x-R29.74x range. The tabular “use additional code” instruction for NIHSS is mandatory — high NIHSS scores provide objective severity documentation that supports medical necessity for ICU admission, intubation, and advanced interventions.
Etiology Codes to Assign in Addition
| Etiology | ICD-10-CM Code | HCC | Sequencing Note |
|---|---|---|---|
| Antiphospholipid syndrome | D68.61 | Not mapped | Code additionally — major cause of bilateral arterial thrombosis |
| Thrombotic thrombocytopenic purpura (TTP) | M31.11 | Not mapped | Sequence TTP first if driving admission |
| Malignancy-associated (Trousseau) | C-code for tumor | Varies | Active malignancy sequences first; I63.313 additional |
| CNS vasculitis | I67.7 | Not mapped | Code vasculitis additionally |
| Atrial fibrillation (if embolic suspected — query) | I48.x | HCC 96 | If thrombosis confirmed, code AF as comorbidity |
| Hyperhomocysteinemia | E72.11 | Not mapped | Thrombotic risk factor |
| DIC | D65 | Not mapped | MCC — sequences based on clinical context |
| Heparin-induced thrombocytopenia (HIT) | T45.515A/D/S | Not mapped | Code HIT as adverse effect if 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 — anticoagulation, antiplatelets, antiepileptics |
HCC 85 — Same Assignment Regardless of Severity
I63.313 carries the same HCC 85 coefficient as unilateral MCA or carotid strokes. The CMS-HCC v28 model assigns HCC 85 to all ischemic stroke codes uniformly — severity is not differentiated at the HCC level. This means the RAF contribution of I63.313 is identical to I63.031, despite the vastly greater clinical severity. The financial complexity is instead reflected in DRG tier via CC/MCC documentation.
Long-Term RAF Capture — Bilateral MCA Survivors
Bilateral MCA stroke survivors face devastating long-term disability. Their subsequent outpatient and rehabilitation encounters generate multiple I69.3xx sequela codes that all map to HCC 85:
- I69.320 — Aphasia following cerebral infarction
- I69.351 — Hemiplegia/hemiparesis, right dominant, following cerebral infarction
- I69.352 — Hemiplegia/hemiparesis, left dominant, following cerebral infarction (bilateral — both sides may be coded)
- I69.391 — Dysphagia following cerebral infarction
- I69.398 — Other sequelae of cerebral infarction
The complexity of bilateral sequela coding for bilateral MCA survivors means every post-stroke outpatient encounter is a high-value RAF recapture opportunity. Ensure all documented chronic deficits are coded at every qualifying encounter.
HCC Comorbidity Sweep — Every I63.313 Encounter
Comorbidity HCC (v28) Approx. RAF Atrial fibrillation HCC 96 ~0.18 Heart failure HCC 85 varies DM with chronic complications HCC 18 ~0.30 Antiphospholipid syndrome (if present) Not mapped 0 — but essential for clinical completeness CKD Stage 3-5 HCC 137 ~0.17 Malignancy (if Trousseau) HCC varies by cancer type High Major depression / post-stroke HCC 59 ~0.30 Morbid obesity HCC 48 ~0.25
🏥 MS-DRG Assignment
MDC 01 — Diseases and Disorders of the Nervous System
Path A — Thrombolytic Administered (DRG 61-63)
| DRG | Title | Est. Relative Weight* |
|---|---|---|
| DRG 61 | Ischemic Stroke with Thrombolytic Agent with MCC | ~3.30-3.70 |
| DRG 62 | Ischemic Stroke with Thrombolytic Agent with CC | ~2.00-2.30 |
| DRG 63 | Ischemic Stroke with Thrombolytic Agent without CC/MCC | ~1.40-1.60 |
Path B — No Thrombolytic (DRG 64-66)
| 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 | ~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.
Bilateral MCA Stroke Grouping to DRG 66 = Documentation Crisis
A fully documented bilateral MCA infarction with bilateral hemiplegia, global aphasia, dysphagia, and a high NIHSS score has multiple MCC and CC drivers simultaneously. If a case coded as I63.313 groups to DRG 66 (no CC/MCC), it is a near-certain signal of one or more of the following:
- Neurological deficit codes not assigned (G81.x, R47.01, R13.12, R41.4, R40.20)
- NIHSS code not assigned (R29.7xx)
- Systemic comorbidity CCs/MCCs not coded (atrial fibrillation, heart failure, DM complications)
- Z92.82 missing when tPA was given at an outside facility
CDI should flag every I63.313 admission for deficit code completeness review before the record closes. This is one of the highest-priority DRG integrity cases in the stroke category.
🔗 Related ICD-10-CM Codes
I63.31x — MCA Thrombosis Laterality Variants
| Code | Description |
|---|---|
| I63.311 | Cerebral infarction due to thrombosis of right MCA |
| I63.312 | Cerebral infarction due to thrombosis of left MCA |
| I63.313 | Cerebral infarction due to thrombosis of bilateral MCA ← This Code |
| I63.319 | Cerebral infarction due to thrombosis of unspecified MCA ⚠️ — query laterality |
Embolic and Unspecified Mechanism Equivalents — Bilateral MCA
| Code | Description | When to Use |
|---|---|---|
| I63.413 | Bilateral MCA embolism — cerebral infarction | Embolic mechanism confirmed — more common than bilateral thrombosis |
| I63.513 | Bilateral MCA unspecified occlusion/stenosis | Mechanism cannot be determined after query |
Bilateral MCA Occlusion WITHOUT Infarction
| Code | Description |
|---|---|
| I66.03 | Occlusion and stenosis of bilateral MCA without cerebral infarction |
Neurological Deficit Codes — Use Additional Code (Bilateral Profile)
| Code | Description | CC/MCC | Hemisphere |
|---|---|---|---|
| G83.3 | Diplegia / bilateral hemiplegia | MCC | Both |
| G81.01 | Flaccid hemiplegia, right dominant side | MCC | Left MCA |
| G81.02 | Flaccid hemiplegia, left dominant side | MCC | Right MCA |
| G81.11 | Spastic hemiplegia, right dominant | CC | Left MCA chronic |
| G81.12 | Spastic hemiplegia, left dominant | CC | Right MCA chronic |
| R47.01 | Aphasia | CC | Left MCA |
| R41.4 | Neurological neglect syndrome | CC | Right MCA |
| R13.12 | Dysphagia, oropharyngeal | CC | Bilateral corticobulbar |
| R47.1 | Dysarthria | CC | Bilateral corticobulbar |
| R40.20 | Coma, unspecified | MCC | Bilateral hemispheric |
| R29.721-R29.742 | NIHSS score 21-42 | Severity documentation | Required |
Etiology / Underlying Condition Codes
| Code | Description |
|---|---|
| D68.61 | Antiphospholipid syndrome — leading cause of bilateral intracranial thrombosis |
| M31.11 | Thrombotic thrombocytopenic purpura (TTP) |
| D65 | Disseminated intravascular coagulation (DIC) |
| I67.7 | Cerebral arteritis / CNS vasculitis |
| E72.11 | Homocystinuria / hyperhomocysteinemia |
| I48.x | Atrial fibrillation — code as comorbidity; query if embolic mechanism suspected |
Bilateral Sequela Codes — Post-Acute
| Code | Description | HCC |
|---|---|---|
| I69.320 | Aphasia following cerebral infarction | HCC 85 |
| I69.351 | Hemiplegia/hemiparesis, right dominant, following CI | HCC 85 |
| I69.352 | Hemiplegia/hemiparesis, left dominant, following CI | HCC 85 |
| I69.391 | Dysphagia following cerebral infarction | HCC 85 |
| I69.398 | Other sequelae of cerebral infarction | HCC 85 |
🛠️ CPT Procedural Crosswalk
Neuroimaging
| CPT Code | Description | Application for I63.313 |
|---|---|---|
| 70553 | MRI brain with and without contrast | DWI confirms bilateral MCA territory infarction; FLAIR maps bilateral ischemic territories; essential for diagnosis |
| 70544 | MRA head without contrast | Bilateral MCA patency — confirms bilateral intracranial occlusion |
| 70496 | CT angiography of head | Rapid bilateral MCA assessment in acute ED presentation; bilateral M1 hyperdense sign |
| 70450 | CT head without contrast | Excludes bilateral hemorrhagic transformation before intervention |
| 70547 | MRA neck without contrast | Carotid assessment — evaluates for concurrent bilateral carotid disease or proximal source |
Intervention — Bilateral MCA
| CPT Code | Description | wRVU | Asst. Surgeon? | Note |
|---|---|---|---|---|
| 61645 | Percutaneous arterial transluminal mechanical thrombectomy, intracranial | 22.50 per vessel | Yes | Bilateral thrombectomy (right MCA + left MCA) may require separate line items per vessel — verify NCCI bilateral edit status |
| 61650 | Endovascular intracranial prolonged administration of pharmacologic agent(s) | Varies | Facility-dependent | Intra-arterial thrombolysis |
Bilateral Thrombectomy Billing — NCCI Review Required
When mechanical thrombectomy is performed on both the right and left MCA in the same operative session, payer-specific rules and NCCI PTP edits govern whether each vessel’s thrombectomy is separately billable. Some payers allow bilateral modifier -50 on 61645; others require separate line items with -RT and -LT; others bundle bilateral same-session intracranial procedures. Verify current NCCI and payer-specific bilateral intracranial procedure rules before submitting bilateral 61645 claims.
Vascular Studies
| CPT Code | Description | wRVU | Application |
|---|---|---|---|
| 93886 | Transcranial Doppler (TCD), complete | 1.14 | Bilateral MCA flow velocity; emboli detection; vasospasm monitoring |
| 93890 | TCD, vasoreactivity study | 0.90 | Cerebrovascular reserve in bilateral MCA disease |
🔬 ICD-10-PCS Crosswalk (Inpatient Procedures)
IV Thrombolysis (tPA)
| PCS Section | Body System | Root Operation | Body Part | Approach | Substance |
|---|---|---|---|---|---|
| 3 (Administration) | E | 0 (Introduction) | 3 (Peripheral vein) | 3 (Percutaneous) | 7 (Thrombolytic) |
Bilateral MCA Mechanical Thrombectomy
| PCS Section | Body System | Root Operation | Body Part | Approach | Note |
|---|---|---|---|---|---|
| 0 (Medical & Surgical) | 3 (Upper Arteries) | C (Extirpation) | G (Intracranial Artery) | 3 (Percutaneous) | Right MCA thrombectomy |
| 0 (Medical & Surgical) | 3 (Upper Arteries) | C (Extirpation) | G (Intracranial Artery) | 3 (Percutaneous) | Left MCA thrombectomy — same body part character G; separate PCS code line |
Both MCAs = Same PCS Body Part Character G
In ICD-10-PCS, the intracranial artery body part character G is used for all intracranial artery thrombectomy procedures — right MCA and left MCA share the same body part character. When bilateral MCA thrombectomy is performed, two PCS codes with identical body part characters may be needed. Verify with the applicable PCS table and facility coding guidelines for bilateral intracranial procedures in the same operative session.
Hemicraniectomy (Malignant MCA Syndrome)
| PCS Section | Body System | Root Operation | Body Part | Approach | Application |
|---|---|---|---|---|---|
| 0 (Medical & Surgical) | N (Head and Facial Bones) | 8 (Division) or B (Excision) | Parietal Bone Right = 4, Parietal Bone Left = 5 | 0 (Open) | Decompressive hemicraniectomy for malignant MCA syndrome — bilateral cases may require staged bilateral procedures |
💊 Coding Scenarios and Examples
Scenario 1 — Bilateral MCA Thrombosis in Antiphospholipid Syndrome (Inpatient)
Clinical Vignette: A 34-year-old female with known antiphospholipid syndrome (APS) on warfarin presents after a witnessed sudden collapse at home. On arrival, NIHSS 32. GCS 7. CT head negative for hemorrhage. CT angiography confirms bilateral M1 MCA occlusion. MRI DWI confirms bilateral MCA territory infarction — right frontal-parietal and left frontal-temporal distributions. Supratherapeutic INR on arrival (warfarin recently started) — IV alteplase contraindicated. Bilateral mechanical thrombectomy attempted; TICI 2a achieved bilaterally. Neuro ICU admission. PT/OT document bilateral flaccid hemiplegia. SLP documents global aphasia and oropharyngeal dysphagia — NPO, NGT placed. Intubated for airway protection.
Principal Diagnosis:
- I63.313 — Cerebral infarction due to thrombosis of bilateral middle cerebral arteries
Additional Diagnoses:
- G83.3 — Diplegia, bilateral hemiplegia ← MCC
- R47.01 — Aphasia (global) ← CC
- R13.12 — Dysphagia, oropharyngeal ← CC
- R40.20 — Coma (GCS 7 = decreased consciousness) ← MCC
- R29.732 — NIHSS score 32 (use additional code per tabular)
- D68.61 — Antiphospholipid syndrome (underlying etiology — documented as causative)
- J96.00 — Acute respiratory failure (intubated for airway protection — if documented as respiratory failure) ← MCC
ICD-10-PCS:
- 03CG3ZZ × 2 — Extirpation, intracranial artery, percutaneous (bilateral MCA thrombectomy — two code entries, same body part character G)
MS-DRG Routing:
APS Is a Major Codeable Finding — Not Just a Risk Factor
In this scenario, antiphospholipid syndrome (D68.61) is explicitly documented as the underlying cause of the bilateral MCA thrombosis. Code it as an additional diagnosis — it is clinically active, influences treatment (anticoagulation strategy, INR targets, hematology consult), and represents a distinct codeable condition meeting UHDDS criteria. Do not bury APS as merely a “past medical history” item when it is the documented etiology of the current event.
Scenario 2 — Bilateral MCA Infarction After Cardiac Arrest (Inpatient)
Clinical Vignette: A 67-year-old male with known coronary artery disease suffers an out-of-hospital cardiac arrest, successfully resuscitated after 8 minutes of CPR. Post-arrest MRI on day 2 confirms bilateral MCA watershed territory infarction with areas of diffusion restriction in bilateral MCA-ACA and MCA-PCA watershed zones. No discrete intracranial vessel occlusion seen on MRA. Attending documents: “Bilateral MCA territory watershed infarction due to global hypoperfusion during cardiac arrest — anoxic brain injury with thrombotic mechanism in watershed territories.”
Global Hypoperfusion + Watershed Infarction — Code Carefully
This scenario illustrates a nuanced coding decision. The physician documents “thrombotic mechanism in watershed territories” — I63.313 is supportable if the physician explicitly confirms thrombosis. However, bilateral watershed infarction from cardiac arrest often maps to I63.30x (cerebral infarction due to thrombosis of unspecified cerebral artery) or may have a separate code path through hypoxic ischemic encephalopathy (G93.1) when the primary mechanism is hypoperfusion rather than discrete vessel thrombosis.
Query recommended: Ask the physician to confirm whether the primary mechanism is (a) discrete bilateral MCA thrombosis, (b) hypoxic-ischemic encephalopathy from global hypoperfusion, or (c) both. If discrete bilateral MCA thrombosis is confirmed → I63.313; if primarily anoxic/hypoxic brain injury → G93.1.
If physician confirms bilateral MCA thrombosis:
- I63.313 — Bilateral MCA thrombosis with cerebral infarction
- I46.9 — Cardiac arrest, cause unspecified (precipitating event)
- I25.10 — Coronary artery disease (documented comorbidity)
- G83.3 — Bilateral hemiplegia ← MCC
If physician documents primarily anoxic encephalopathy:
Scenario 3 — Bilateral MCA Infarction — Mechanism Ambiguous (Thrombotic vs. Embolic Query)
Clinical Vignette: A 72-year-old male with persistent atrial fibrillation (not anticoagulated) presents with acute bilateral neurological deficits. MRI confirms bilateral MCA territory infarctions. MRA shows bilateral M1 MCA occlusions. Discharge summary reads: “Bilateral MCA cerebral infarction — etiology unclear, cardioembolic vs. in-situ thrombosis.”
Coding Action Required:
- Do NOT default to I63.313 (thrombotic) when mechanism is documented as ambiguous
- Submit a CDI query: “Bilateral MCA infarction is documented with mechanism described as unclear/cardioembolic vs. thrombotic. For accurate ICD-10-CM assignment, could you clarify the final mechanism: (a) thrombotic — in-situ bilateral MCA clot formation; (b) embolic — bilateral cardioembolism from atrial fibrillation or other source; or (c) unspecified — mechanism undeterminable?”
| Physician Response | Code |
|---|---|
| Thrombotic | I63.313 |
| Embolic (cardioembolism from AF) | I63.413 |
| Unspecified / cannot determine | I63.513 |
AF + Bilateral MCA = Embolic More Likely Than Thrombotic
In a patient with persistent atrial fibrillation and bilateral simultaneous MCA occlusions, the clinical probability strongly favors embolic mechanism (I63.413) over bilateral in-situ thrombosis (I63.313). AF is the most common source of cardioembolism, and bilateral simultaneous emboli (fragmented clot from the left atrium) can produce bilateral MCA infarctions. This distinction matters for treatment (anticoagulation for AF-related embolism vs. antiplatelet for atherothrombotic disease) and is a CDI and compliance priority — never assign I63.313 when the clinical picture is more consistent with embolic mechanism from AF without querying.
Scenario 4 — Bilateral MCA Thrombosis with Malignant Edema, Hemicraniectomy (Inpatient)
Clinical Vignette: A 45-year-old male with no prior history presents with bilateral MCA territory cerebral infarction. Day 2 CT head shows massive bilateral cerebral edema with midline shift and impending transtentorial herniation. Neurosurgery performs emergent bilateral decompressive hemicraniectomy. Pathology later confirms CNS vasculitis as underlying etiology.
Principal Diagnosis:
- I63.313 — Cerebral infarction due to thrombosis of bilateral MCA
Additional Diagnoses:
- G93.6 — Cerebral edema ← MCC
- I67.7 — Cerebral arteritis/CNS vasculitis (documented underlying etiology — code additionally)
- G83.3 — Bilateral hemiplegia ← MCC
- R40.20 — Coma ← MCC
ICD-10-PCS (Bilateral Hemicraniectomy):
- 0N840ZZ — Division, Parietal Bone Right, Open approach (right hemicraniectomy)
- 0N850ZZ — Division, Parietal Bone Left, Open approach (left hemicraniectomy)
CNS Vasculitis — Always Code Alongside I63.313 When Documented
I67.7 (cerebral arteritis) is a distinct, separately codeable condition that directly explains the bilateral MCA thrombosis mechanism. When the physician documents CNS vasculitis as the underlying etiology, code both I63.313 AND I67.7 — the vasculitis code adds clinical specificity and may influence sequencing based on what drove the admission. Review the tabular for any “code first” or “use additional code” instructions between I63.3 and I67.7.
⚠️ Coding Pitfalls and Tips
| Pitfall or Tip | |
|---|---|
| ❌ | Never submit I63.31 (5-character) as a billable code — I63.313 (6 characters) required; parent code rejects on claim |
| ❌ | Do not default to I63.313 (thrombotic) when mechanism is embolic or ambiguous — bilateral MCA infarction with concurrent AF is more likely embolic (I63.413); always query for mechanism before assigning |
| ❌ | Do not confuse precerebral (I63.03x) with cerebral (I63.3x) — I63.033 is bilateral carotid artery (neck, extracranial); I63.313 is bilateral MCA (intracranial); entirely different anatomic locations |
| ❌ | Do not code I63.313 for watershed infarction from cardiac arrest without physician confirmation of thrombotic MCA mechanism — global hypoperfusion → query; anoxic brain damage (G93.1) may be the more appropriate principal |
| ❌ | Do not leave bilateral hemiplegia uncoded — G83.3 or bilateral G81.x codes are MCC drivers; a bilateral MCA case without a bilateral hemiplegia code is a near-certain documentation gap |
| ❌ | Do not omit aphasia in a bilateral MCA case — left MCA component = dominant hemisphere = R47.01 aphasia; this is a CC and is always present in complete left MCA territory infarction |
| ❌ | Do not forget Z92.82 in transfer cases — tPA at outside hospital within 24 hours activates DRG 61-63; without it the case defaults to DRG 64-66 |
| ✅ | Bilateral MCA = maximum deficit coding opportunity — aphasia (CC), bilateral hemiplegia (MCC), dysphagia (CC), neglect (CC), high NIHSS (R29.73x-74x) — this is the single highest-yield deficit documentation case in all of cerebrovascular coding |
| ✅ | Code the underlying etiology — APS (D68.61), TTP (M31.11), CNS vasculitis (I67.7), DIC (D65) are all separately codeable conditions that explain bilateral MCA thrombosis and must be documented and coded |
| ✅ | NIHSS code is mandatory — bilateral MCA strokes routinely reach NIHSS 25+ (R29.725+); document and code the specific score; the tabular “use additional code” instruction is non-optional |
| ✅ | Query AF cases for mechanism — atrial fibrillation + bilateral MCA = embolic until proven otherwise; do not assign I63.313 without explicit physician documentation of thrombotic mechanism |
| ✅ | Bilateral hemicraniectomy = two PCS codes — Parietal Bone Right (04) + Parietal Bone Left (05) as separate Division or Excision codes; verify applicable body part characters from current PCS table |
| ✅ | Annual sequela recapture is complex and bilateral — I69.351 (right side) + I69.352 (left side) + I69.320 (aphasia) + I69.391 (dysphagia) — all map to HCC 85; ensure all documented bilateral chronic deficits are coded at every subsequent encounter |
| ✅ | Goals of care documentation — bilateral MCA infarction carries high mortality; palliative care consultations and comfort-focused care transitions should be documented and may generate additional codeable conditions (e.g., dysphagia, pressure ulcer risk, aspiration) |
📚 Sources
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CMS/NCHS. ICD-10-CM Official Guidelines for Coding and Reporting, FY2026. Tabular List — I63.313; I63.3 Cerebral infarction due to thrombosis of cerebral arteries; I63.3x vs. I63.0x anatomic boundary (precerebral vs. cerebral arteries); Use Additional Code instructions (NIHSS, neurological deficits); Laterality guidelines; Section I.C.9 — Cerebrovascular disease coding guidelines.
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American Medical Association (AMA). CPT 2026 Professional Edition. Intracranial Endovascular Procedures — Mechanical Thrombectomy (61645, 61650); Neuroimaging (70450-70553); Transcranial Doppler (93886, 93890).
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American Heart Association / American Stroke Association. 2019 Guidelines for the Early Management of Patients with Acute Ischemic Stroke. Mechanical thrombectomy selection criteria (DAWN, DEFUSE-3 trials); bilateral stroke management considerations; palliative care guidance for malignant stroke.
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Wijdicks EFM, Rabinstein AA. Catastrophic Neurological Disorders. Oxford University Press. Bilateral MCA infarction — malignant MCA syndrome, decompressive hemicraniectomy evidence base, prognosis.
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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; CC/MCC impact on tier elevation; bilateral hemiplegia MCC status.
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CMS. ICD-10-PCS Reference Manual FY2026. Section 0 (Medical & Surgical), Body System 3 (Upper Arteries) — Intracranial Artery Body Part G (bilateral MCA thrombectomy); Body System N (Head and Facial Bones) — Parietal Bone Right (Body Part 4), Left (Body Part 5) for bilateral hemicraniectomy.
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CMS. CMS-HCC Model v28 (2024) ICD-10-CM Mappings. HCC 85 — Ischemic or Unspecified Stroke; I63.313 HCC assignment confirmed; I69.3xx bilateral sequela codes mapping to HCC 85 for post-acute annual recapture.
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Ruiz-Irastorza G, Crowther M, Branch W, Khamashta MA. “Antiphospholipid syndrome.” Lancet. 2010;376(9751):1498-1509. APS as etiology of bilateral intracranial thrombosis — mechanism and management.
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CMS. Physician Fee Schedule Final Rule FY2026. Facility wRVU values — CPT 61645, 61650, 93886.