2027 ICD-10-CM Diagnosis Code I65.1Occlusion and stenosis of basilar artery

ICD-10-CM Codes›I00–I99›I60-I69›I65

ICD-10-CM I65.1
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

I65.1 is a billable ICD-10-CM diagnosis code for occlusion and stenosis of basilar artery. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 61 through 63, 67 through 68. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Occlusion or stenosis of precerebral or cerebral arteries without infarction.

Code Identity

ICD-10-CM Code
I65.1
Billable Status
Yes — Valid for Submission
Code Describes
Occlusion and stenosis of basilar artery
Short Description
Occlusion and stenosis of basilar artery
Same as the full description in the CMS dataset.
Parent Code
I65
Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction

Code Classification

ChapterI00–I99Diseases of the circulatory system
SectionI60-I69Cerebrovascular diseases
CategoryI65Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction
This CodeI65.1Occlusion and stenosis of basilar artery

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Asymptomatic occlusion of artery
  • Asymptomatic occlusion of basilar artery
  • Asymptomatic stenosis of basilar artery
  • Asymptomatic stenosis of intracranial artery
  • Basilar artery embolism
  • Basilar artery occlusion
  • Basilar artery occlusion without infarction
  • Basilar artery stenosis
  • Basilar artery thrombosis
  • Occlusion of branch of basilar artery
  • Occlusion of distal basilar artery
  • Occlusive embolus of basilar artery
  • Pontine artery occlusion
  • Pontine artery thrombosis

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to I65.1: its own notes plus those printed at I65, block I60-I69, and Chapter 9. A note printed at a category, block or chapter applies to every code under it.

Includes

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

From I65 Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction applies to 11 codes
  • embolism of precerebral artery
  • narrowing of precerebral artery
  • obstruction (complete) (partial) of precerebral artery
  • thrombosis of precerebral artery

Excludes1

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

From I65 Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction applies to 11 codes
  • insufficiency, NOS, of precerebral artery (G45.-)
  • insufficiency of precerebral arteries causing cerebral infarction (I63.0-I63.2)
From Block I60-I69 Cerebrovascular diseases applies to 410 codes
  • traumatic intracranial hemorrhage (S06.-)

Excludes2

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

From Chapter 9 (I00-I99) Diseases of the circulatory system applies to 1,433 codes
  • certain conditions originating in the perinatal period (P04-P96)
  • certain infectious and parasitic diseases (A00-B99)
  • complications of pregnancy, childbirth and the puerperium (O00-O9A)
  • congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
  • endocrine, nutritional and metabolic diseases (E00-E88)
  • injury, poisoning and certain other consequences of external causes (S00-T88)
  • neoplasms (C00-D49)
  • symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)
  • systemic connective tissue disorders (M30-M36)
  • transient cerebral ischemic attacks and related syndromes (G45.-)

Use Additional Code

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

From Block I60-I69 Cerebrovascular diseases applies to 410 codes
  • code to identify presence of:
  • alcohol abuse and dependence (F10.-)
  • exposure to environmental tobacco smoke (Z77.22)
  • history of tobacco dependence (Z87.891)
  • hypertension (I10-I1A)
  • occupational exposure to environmental tobacco smoke (Z57.31)
  • tobacco dependence (F17.-)
  • tobacco use (Z72.0)

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

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name I65.1, its category, or a range that includes it.

Excludes2 1

These codes carry an Excludes2 note naming I65.1: its condition is not part of those codes, and both may be reported when the patient has both.

  • I74 Arterial embolism and thrombosis
    basilar embolism and thrombosis (I63.0-I63.2, I65.1)

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

Clinical ClassificationClinical

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

CCSR CIR023
Occlusion or stenosis of precerebral or cerebral arteries without infarction
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Vascular Diseases

Your vascular system is your body's network of blood vessels. It includes your:

The full article covers:

  • What are vascular diseases?
  • What causes vascular diseases?
  • Who is at risk for vascular diseases?
  • What are the symptoms of vascular diseases?
  • How are vascular diseases diagnosed?
  • How are vascular diseases treated?
  • Can vascular diseases be prevented?

Read the full article at MedlinePlus

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

Convert I65.1 to ICD-9-CMHistory

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

ICD-9-CM
433.00 Ocl bslr art wo infrct
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About I65.1Overview

What is the ICD-10 code for occlusion and stenosis of basilar artery?

The ICD-10-CM code for occlusion and stenosis of basilar artery is I65.1 (sometimes written as I651). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is I65.1 a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report occlusion and stenosis of basilar artery on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does I65.1 group to?

When occlusion and stenosis of basilar artery is the principal diagnosis on an inpatient stay, it groups to MS-DRG 68, 67, 61, 62, 63, with relative weights from 0.9011 to 2.7211 depending on complications. Higher weights mean higher Medicare reimbursement.

Can I65.1 be reported with a code from G45?

Not as a rule. The Excludes1 note at I65, which applies to I65.1, lists "insufficiency, NOS, of precerebral artery (G45.-)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of I65.1?

Under the General Equivalence Mappings, occlusion and stenosis of basilar artery converts to ICD-9-CM 433.00 (ocl bslr art wo infrct). The mapping is a direct match.