Crystal's MCW Coder Hub🧬 ICD-10-CM G45.0 - Vertebrobasilar Artery Syndrome
Overview
ICD-10-CM G45.0 classifies a Transient Ischemic Attack (TIA) of the vertebrobasilar territory, also referred to as vertebrobasilar insufficiency or posterior circulation TIA. A TIA is defined as a transient episode of neurological dysfunction caused by focal brain, spinal cord, or retinal ischemia without acute infarction. By clinical definition, symptoms resolve within 24 hours — in practice, most resolve within minutes to an hour. When neuroimaging (particularly MRI with diffusion-weighted imaging, or DWI) confirms an acute cerebral infarction, the appropriate code shifts to the I63.x category regardless of whether symptoms have clinically resolved. The absence of infarction on imaging is essential to supporting this diagnosis.
The vertebrobasilar territory (posterior circulation) is supplied by the paired vertebral arteries, which arise from the subclavian arteries, ascend through the transverse foramina of the cervical vertebrae, and merge at the pontomedullary junction to form the single basilar artery. The basilar artery bifurcates into the posterior cerebral arteries (PCAs). Collectively, this vascular territory perfuses the medulla, pons, midbrain, cerebellum, posterior thalami, posterior temporal lobes, and occipital lobes — structures responsible for balance, coordination, vision, consciousness, and cranial nerve function.
ICD-10-CM Code Tree
G45 Transient cerebral ischemic attacks and related syndromes
├── [[G45.0]] Vertebrobasilar artery syndrome ← YOU ARE HERE
├── [[G45.1]] Carotid artery syndrome (hemispheric)
├── [[G45.2]] Multiple and bilateral precerebral artery syndromes
├── [[G45.3]] Amaurosis fugax
├── [[G45.4]] Transient global amnesia
├── [[G45.8]] Other transient cerebral ischemic attacks and related syndromes
└── [[G45.9]] Transient cerebral ischemic attack, unspecified
G45 itself is a non-billable parent category. G45.0 through G45.9 are the billable, reportable codes within this block.
Includes / Excludes
Code-Level (G45.0)
No explicit includes or excludes are listed at the individual G45.0 code level. All applicable notes are carried from the parent block.
Block-Level Includes (G45)
- Transient cerebral ischemic attacks and related syndromes
- Vertebrobasilar TIA / vertebrobasilar insufficiency
Block-Level Excludes1 (G45)
Excludes1 — These conditions cannot be coded simultaneously with any G45 code. They represent mutually exclusive diagnoses:
| Excluded Code | Description |
|---|---|
| P91.0 | Neonatal cerebral ischemia |
Block-Level Excludes2 (G45)
Excludes2 — These conditions are not included in G45 but may be coded additionally when both are present and documented:
| Excluded Category | Description |
|---|---|
| H34.- | Transient retinal artery occlusion (see G45.3 - Amaurosis fugax for the appropriate G45 code) |
HCC (Hierarchical Condition Category)
| Field | Value |
|---|---|
| HCC Mapped | No |
| HCC Model | CMS-HCC V28 |
| HCC Category | None |
| Risk Adjustment Factor (RAF) | No contribution |
| Risk Score Impact | None |
Clinical & Coding Importance: G45.0 carries no HCC weight under the CMS-HCC V28 model. TIAs are not classified as chronic conditions for risk adjustment purposes. This is a pivotal distinction from cerebral infarction, which maps to HCC 100 (Ischemic or Unspecified Stroke) and related categories under V28, carrying significant RAF value. If imaging confirms infarction, even retrospectively, recoding to the appropriate I63.x code is both clinically accurate and carries meaningful risk score implications for the patient’s future care management and payer reimbursement modeling.
MS-DRG Assignment
| MS-DRG | Title | MDC | Type | Geometric Mean LOS | Arithmetic Mean LOS |
|---|---|---|---|---|---|
| 069 | Transient Ischemia | MDC 01 | Medical | ~2.1 days | ~2.7 days |
DRG Nuances:
- MS-DRG 069 is a single-tier DRG — unlike many neurological DRGs, it does not have CC or MCC splits. Comorbidities and complications documented during the admission will not drive the case into a higher-weighted DRG within this grouping.
- However, if the principal diagnosis is subsequently revised — for example, if imaging confirms cerebral infarction — the case would re-group to MS-DRGs 061-063 (Ischemic Stroke with MCC / with CC / without CC or MCC), which carry significantly higher relative weights and reimbursement.
- Query-driven recoding from G45.0 to I63.x (when supported by documentation and imaging) is one of the highest-yield DRG capture opportunities in neurology inpatient coding.
wRVU / Assistant Payable
| Field | Value |
|---|---|
| wRVU | N/A - ICD-10-CM Diagnosis Code |
| Assistant Payable | N/A - ICD-10-CM Diagnosis Code |
| Billable Code | Yes |
| POA Indicator Required | Yes (inpatient admissions) |
Work RVUs (wRVUs) and assistant payable designations are properties of CPT procedure codes, not ICD-10-CM diagnosis codes. See the Associated CPT Codes section below for procedure-level wRVU reference values commonly associated with this diagnosis.
Clinical Description
Pathophysiology
Vertebrobasilar TIA results from transient, reversible ischemia to the posterior circulation without permanent tissue injury. The major etiologic mechanisms include:
- Large artery atherosclerosis — Stenotic or ulcerative plaque in the vertebral arteries (most commonly at their ostia or intracranial segments) or the basilar artery; artery-to-artery thromboembolism is the predominant mechanism
- Cardioembolism — Atrial fibrillation (most common), patent foramen ovale (particularly in younger patients), valvular disease, dilated cardiomyopathy, intracardiac thrombus
- Small vessel disease (lacunar) — Lipohyalinosis of small penetrating branches of the basilar artery supplying the pons and thalami
- Subclavian steal syndrome — Proximal subclavian artery stenosis causes retrograde (reversed) flow in the ipsilateral vertebral artery, stealing flow from the vertebrobasilar territory, typically provoked by ipsilateral arm exercise
- Vertebral artery dissection — An important etiology in younger patients; may follow trauma, chiropractic manipulation, or occur spontaneously; associated with neck pain
- Cervical spondylosis / osteophyte impingement — Mechanical compression of the vertebral arteries within the transverse foramina during neck movement
- Hypercoagulable states — Antiphospholipid antibody syndrome, polycythemia, thrombocytosis, factor V Leiden mutation, protein C/S deficiency
- vasculitis — Giant cell arteritis (temporal arteritis), CNS vasculitis
- Hemodynamic TIA — Severe hypotension in the setting of pre-existing vertebrobasilar stenosis
Signs and Symptoms
Symptoms arise from ischemia to structures within the posterior fossa and occipital lobes. The hallmark of vertebrobasilar TIA is the combination of symptoms referable to the brainstem, cerebellum, and/or occipital cortex:
| Symptom | Anatomic Correlate |
|---|---|
| Diplopia (binocular) | CN III, IV, VI nuclei or fascicles (brainstem) |
| dysarthria | Corticobulbar tracts, cerebellar connections |
| Dysphagia | CN IX/X nuclei (medulla), corticobulbar tracts |
| Vertigo / dizziness | Vestibular nuclei (medulla/pons) or labyrinthine artery |
| Ataxia / gait instability | Cerebellum (anterior/posterior lobes) |
| Drop attacks | Sudden postural tone loss without LOC; corticospinal or reticular tracts |
| Bilateral or crossed visual field deficits | Occipital lobes (PCA territory), cortical blindness |
| Perioral or bilateral facial numbness | Trigeminal nucleus (CN V) in brainstem |
| Alternating (crossed) hemiplegia | Classic brainstem sign — ipsilateral CN palsy + contralateral hemiplegia |
| Nausea and vomiting | Vestibular nuclei, area postrema (dorsal medulla) |
| Tinnitus, sudden hearing loss | Anterior inferior cerebellar artery (AICA) territory |
| Transient loss of consciousness | Ascending reticular activating system (ARAS) |
Mnemonic: The “5 D’s + 3 N’s” of vertebrobasilar ischemia — Diplopia, Dysarthria, Dizziness, Dysphagia, Drop attacks + Nausea, Numbness (bilateral/crossed), Nystagmus
Important: Isolated vertigo, isolated dizziness, or isolated tinnitus without additional posterior fossa symptoms is generally insufficient to code G45.0 — these symptoms must be evaluated in clinical context, and physician documentation of vertebrobasilar TIA is required.
Diagnostic Workup
A structured inpatient workup for posterior circulation TIA typically includes the following, with associated CPT codes where applicable:
- MRI brain with DWI sequences (CPT 70553) — Mandatory to exclude acute infarction; DWI positivity = infarct = code I63.x, not G45.0
- MRA of the head and neck — Evaluates patency and caliber of vertebral and basilar arteries; typically ordered with brain MRI
- CTA head and neck with contrast (CPT 70498, 70496) — Alternative to MRA; superior for detecting dissection, stenosis, and calcified plaque
- Carotid and vertebral duplex ultrasound (CPT 93880) — Hemodynamic evaluation of vertebral arteries at origin
- Transthoracic echocardiography (TTE) — Evaluate for cardioembolic source (thrombus, wall motion abnormality, valvular disease)
- Transesophageal echocardiography (TEE) — Superior sensitivity for PFO, LAA thrombus, aortic arch atheroma
- 12-lead ECG (CPT 93040) — Detection of atrial fibrillation, other arrhythmias
- Cardiac telemetry / prolonged monitoring — Paroxysmal atrial fibrillation detection; often 24-48 hours inpatient, extended outpatient monitor post-discharge
- Transcranial Doppler (TCD) (CPT 93886) — Can detect microemboli and evaluate intracranial vertebrobasilar flow dynamics; also used for PFO bubble study
- Fasting lipid panel, HbA1c, CBC, BMP, coagulation studies — Standard risk factor and hematologic evaluation
- Hypercoagulable panel — Protein C, Protein S, antithrombin III, antiphospholipid antibodies, factor V Leiden (particularly in younger patients without traditional risk factors)
Associated CPT Codes
| CPT Code | Description | wRVU | Assistant Payable |
|---|---|---|---|
| 99221 | Initial hospital care, straightforward/low complexity | 1.92 | No |
| 99222 | Initial hospital care, moderate complexity | 2.61 | No |
| 99223 | Initial hospital care, high complexity | 3.86 | No |
| 99231 | Subsequent hospital care, low complexity | 0.76 | No |
| 99232 | Subsequent hospital care, moderate complexity | 1.39 | No |
| 99233 | Subsequent hospital care, high complexity | 2.00 | No |
| 99238 | Hospital discharge day management, ≤30 minutes | 1.28 | No |
| 99239 | Hospital discharge day management, >30 minutes | 1.90 | No |
| 70551 | MRI brain without contrast | 2.27 | No |
| 70553 | MRI brain with and without contrast | 2.54 | No |
| 70496 | CTA head with contrast | 1.89 | No |
| 70498 | CTA neck with contrast | 1.89 | No |
| 93880 | Carotid duplex scan, bilateral | 0.92 | No |
| 93886 | Transcranial Doppler study, complete intracranial | 1.06 | No |
| 93040 | Rhythm ECG, 1-3 leads; with interpretation and report | 0.33 | No |
Coding Guidelines & Rules
Principal Diagnosis Sequencing
G45.0 is sequenced as the principal diagnosis when it is the condition — after study — determined to have precipitated the inpatient admission, in accordance with UHDDS and ICD-10-CM Official Guideline Section II.
TIA vs. Cerebral Infarction — The Critical Distinction
This is the most important coding decision associated with G45.0:
- If MRI/DWI is negative for infarction and physician documents TIA → Code G45.0
- If MRI/DWI is positive for infarction — even if all symptoms resolved before imaging — → Code I63.x (cerebral infarction), NOT G45.0
- Per ICD-10-CM Official Guidelines, when imaging confirms infarction, the cerebral infarction code takes precedence regardless of the transient nature of symptoms
- This distinction has meaningful DRG and quality metric implications
Historical / Resolved TIA
- When a patient presents for an unrelated reason and has a prior, resolved history of vertebrobasilar TIA → Code Z86.73 (Personal history of transient ischemic attack and cerebral infarction without residual deficits) as a secondary/additional code
- Do not assign G45.0 for a historical TIA that is not being actively managed during the current encounter
Etiology Coding
Assign additional codes when an underlying etiology is documented:
| Etiology | Additional Code(s) |
|---|---|
| Atrial fibrillation (paroxysmal) | I48.0 |
| Longstanding persistent AFib | I48.11 |
| Essential hypertension | I10 |
| Hyperlipidemia, unspecified | E78.5 |
| Type 2 diabetes without complications | E11.9 |
| Vertebral artery stenosis | I65.01-I65.09 |
| Basilar artery stenosis/occlusion | I65.1 |
| Tobacco use | F17.21x series |
Laterality
G45.0 does not include laterality. The vertebrobasilar territory is a bilateral and midline system — laterality specification is not applicable.
Do Not Confuse With
- G45.4 — Transient Global Amnesia: a distinct clinical syndrome involving sudden onset of anterograde amnesia with preserved consciousness, identity, and remote memory; separate code, separate entity
- G45.3 — Amaurosis Fugax: transient monocular visual loss from retinal ischemia (typically carotid/ophthalmic artery, NOT vertebrobasilar)
- G45.9 — TIA, unspecified: use only when physician documentation does not specify the vascular territory; query physician before defaulting to this code
Coding Examples
Example 1 — Straightforward Vertebrobasilar TIA
Scenario: A 67-year-old male with hypertension and hyperlipidemia presents to the ED with sudden onset diplopia, vertigo, and truncal ataxia lasting approximately 30 minutes, now fully resolved. MRI brain with DWI sequences is negative for acute infarction. MRA demonstrates mild atherosclerotic change at the basilar artery origin. Admitted for monitoring, risk factor management, and antiplatelet initiation.
| Code | Description | Sequence |
|---|---|---|
| G45.0 | Vertebrobasilar artery syndrome | Principal Dx |
| I10 | Essential hypertension | Secondary |
| E78.5 | Hyperlipidemia, unspecified | Secondary |
MS-DRG: 069 - Transient Ischemia
Example 2 — TIA in the Setting of Atrial Fibrillation
Scenario: A 74-year-old female with known longstanding persistent atrial fibrillation (not currently anticoagulated) presents with transient bilateral visual blurring, perioral numbness, and slurred speech lasting approximately 15 minutes, now fully resolved. MRI/DWI is negative. Admitted for anticoagulation initiation, telemetry, echocardiography, and neurology consultation.
| Code | Description | Sequence |
|---|---|---|
| G45.0 | Vertebrobasilar artery syndrome | Principal Dx |
| I48.11 | Longstanding persistent atrial fibrillation | Secondary |
| I10 | Essential hypertension | Secondary |
MS-DRG: 069 - Transient Ischemia
Example 3 — TIA That Is Reclassified as Stroke (Code Change Required)
Scenario: Patient presents with acute dysarthria and bilateral leg weakness, initially documented as posterior circulation TIA. MRI DWI obtained 6 hours after admission reveals a small acute infarct in the right lateral pons. Neurologist updates the diagnosis to acute ischemic stroke.
| Code | Description | Sequence |
|---|---|---|
| I63.9 | Cerebral infarction, unspecified | Principal Dx |
| I10 | Essential hypertension | Secondary |
⚠️ Do NOT use G45.0 when infarction is confirmed on imaging. Recode to the appropriate I63.x. This changes the MS-DRG from 069 to 061, 062, or 063 (Ischemic Stroke with MCC / CC / without CC or MCC), significantly increasing DRG weight.
MS-DRG: 061, 062, or 063 (dependent on CC/MCC status)
Example 4 — Vertebrobasilar TIA with Vertebral Artery Stenosis
Scenario: A 71-year-old male smoker admitted following two episodes of transient vertigo, diplopia, and right-sided ataxia over 48 hours. MRI/DWI negative. CTA neck reveals high-grade right vertebral artery stenosis at the V1 segment. Neurology and vascular surgery consulted. Discharge on dual antiplatelet therapy.
| Code | Description | Sequence |
|---|---|---|
| G45.0 | Vertebrobasilar artery syndrome | Principal Dx |
| I65.01 | Occlusion and stenosis of right vertebral artery | Secondary |
| I10 | Essential hypertension | Secondary |
| F17.210 | Nicotine dependence, cigarettes, uncomplicated | Secondary |
MS-DRG: 069 - Transient Ischemia
Example 5 — Historical TIA at Unrelated Admission
Scenario: Patient with a resolved vertebrobasilar TIA 8 months prior is admitted for an elective laparoscopic cholecystectomy. No active neurologic symptoms.
| Code | Description | Sequence |
|---|---|---|
| K80.20 | Calculus of gallbladder without acute cholecystitis, without obstruction | Principal Dx |
| Z86.73 | Personal history of TIA and cerebral infarction without residual deficits | Secondary |
G45.0 is not appropriate here. The TIA is historical and not the condition requiring management during this encounter.
Related Codes
| Code | Description |
|---|---|
| G45.0 | Vertebrobasilar artery syndrome |
| G45.1 | Carotid artery syndrome (hemispheric) |
| G45.2 | Multiple and bilateral precerebral artery syndromes |
| G45.3 | Amaurosis fugax |
| G45.4 | Transient global amnesia |
| G45.8 | Other transient cerebral ischemic attacks and related syndromes |
| G45.9 | Transient cerebral ischemic attack, unspecified |
| I63.9 | Cerebral infarction, unspecified |
| I48.0 | Paroxysmal atrial fibrillation |
| I48.11 | Longstanding persistent atrial fibrillation |
| Z86.73 | Personal history of TIA and cerebral infarction without residual deficits |
| I10 | Essential hypertension |
| E78.5 | Hyperlipidemia, unspecified |
Quick Reference Summary
| Field | Value |
|---|---|
| Code | G45.0 |
| Type | ICD-10-CM - Diagnosis |
| Full Title | Vertebrobasilar Artery Syndrome |
| Billable | Yes |
| HCC Mapped | No |
| MS-DRG | 069 - Transient Ischemia |
| MDC | 01 - Nervous System |
| Principal Dx Eligible | Yes |
| POA Indicator Required | Yes (inpatient) |
| wRVU | N/A |
| Key Coding Pitfall | Do not use when infarction confirmed — recode to I63.x |
ICD-10-CM Official Guidelines for Coding and Reporting FY2025 · CMS MS-DRG Definitions Manual V41 · CMS-HCC Risk Adjustment Model V28 Documentation · AHA Coding Clinic for ICD-10-CM/PCS · American Stroke Association/AHA TIA Scientific Statement · ACC/AHA Guideline on the Primary Prevention of Stroke