When is ICD-10 code I66 used?

Doctors, hospitals, and insurers may use ICD-10 code I66 when recording occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction in a standardized format. This entry may also act as a broader category that points toward more specific child codes.

Does ICD-10 code I66 confirm a diagnosis?

No. A code helps standardize documentation and claims, but it should not be read as a substitute for a clinician's full assessment.

ICD10

ICD-10 Code I66: Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction

Name: ICD-10 Code I66: Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction
Creator: HealthAssure Clinical Team
Published: 2026-05-21T06:13:07.857Z

I66 is an ICD-10 diagnosis entry used to group records related to Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction. You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen. ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the circulatory system (I00-I99).

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

ICD-10 entries help standardize how diagnoses are organized for coding, reporting, analytics, and documentation. This code sits within the broader ICD-10 area for Diseases of the circulatory system (I00-I99).

When is it used?

May be used when a clinician documents occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction in a patient's medical record.
May appear in hospital records, claims, referrals, and clinical documentation.
This code may act more like a grouping or parent code, so a more specific child code may be used in final documentation when available.

What it does not mean

A code alone does not explain severity, treatment plan, or outcome.
A medical code should not be treated as a substitute for a doctor's diagnosis or advice.
This entry may represent a broader category rather than the most specific billable code.

Code hierarchy

chapter

9Diseases of the circulatory system (I00-I99)

block

I60-I69Cerebrovascular diseases

currentI60-I69

Official coding notes

Includes

embolism of cerebral artery
narrowing of cerebral artery
obstruction (complete) (partial) of cerebral artery
thrombosis of cerebral artery

Excludes1 (do not code together)

Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5)

Where you may see this code

You may see this entry in coding references, medical records, or claims workflows when a broader diagnosis category is being reviewed before a more specific code is chosen.

Related specialists

CardiologistGeneral Physician

Sibling codes

I60Nontraumatic subarachnoid hemorrhage I61Nontraumatic intracerebral hemorrhage I62Other and unspecified nontraumatic intracranial hemorrhage I63Cerebral infarction I65Occlusion and stenosis of precerebral arteries, not resulting in cerebral infarction I67Other cerebrovascular diseases I68Cerebrovascular disorders in diseases classified elsewhere I69Sequelae of cerebrovascular disease

Coding guidelines

Compatibility

Legacy code aligns to an official FY 2026 category. Frontend should resolve to the official category page and surface the billable child codes.

Legacy codes

I66

Replacement codes

I66.3 — Occlusion and stenosis of cerebellar arteriesI66.8 — Occlusion and stenosis of other cerebral arteriesI66.9 — Occlusion and stenosis of unspecified cerebral artery

Common synonyms

Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction

Frequently asked questions

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from ICD-10. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.