Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction (I66) ICD-10-CM
The I66 code range covers occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction with 19 ICD-10-CM diagnosis codes. 15 of them are billable and valid for claim submission in fiscal year 2026, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- embolism of cerebral artery
- narrowing of cerebral artery
- obstruction (complete) (partial) of cerebral artery
- thrombosis of cerebral artery
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the I66 Range 19 codes · 15 billable
- I66 Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarctionNon-billable
- I66.0 Occlusion and stenosis of middle cerebral arteryNon-billable
- I66.01 Occlusion and stenosis of right middle cerebral artery
- I66.02 Occlusion and stenosis of left middle cerebral artery
- I66.03 Occlusion and stenosis of bilateral middle cerebral arteries
- I66.09 Occlusion and stenosis of unspecified middle cerebral artery
- I66.1 Occlusion and stenosis of anterior cerebral arteryNon-billable
- I66.11 Occlusion and stenosis of right anterior cerebral artery
- I66.12 Occlusion and stenosis of left anterior cerebral artery
- I66.13 Occlusion and stenosis of bilateral anterior cerebral arteries
- I66.19 Occlusion and stenosis of unspecified anterior cerebral artery
- I66.2 Occlusion and stenosis of posterior cerebral arteryNon-billable
- I66.21 Occlusion and stenosis of right posterior cerebral artery
- I66.22 Occlusion and stenosis of left posterior cerebral artery
- I66.23 Occlusion and stenosis of bilateral posterior cerebral arteries
- I66.29 Occlusion and stenosis of unspecified posterior cerebral artery
- I66.3 Occlusion and stenosis of cerebellar arteries
- I66.8 Occlusion and stenosis of other cerebral arteries
- I66.9 Occlusion and stenosis of unspecified cerebral artery
About the I66 Code Range
The ICD-10 code I66 covers occlusion and stenosis of cerebral arteries that do not cause a cerebral infarction. These codes specify blockages or narrowings in different cerebral arteries such as the middle, anterior, posterior, cerebellar, or other cerebral arteries, without resulting in a stroke or brain tissue death.
This group of codes, including subcategories like I66.01 (right middle cerebral artery occlusion) and I66.12 (left anterior cerebral artery occlusion), is used to document arterial blockages from thrombosis, embolism, or stenosis that have not led to infarction. Terms like "middle cerebral artery occlusion," "embolism of cerebral artery," or "thrombosis of anterior cerebral artery" are synonyms linked directly to these codes. These distinctions help healthcare professionals accurately record transient ischemic attacks or asymptomatic arterial narrowings. Using the appropriate ICD-10 code for occlusion or stenosis of cerebral arteries ensures clarity in diagnosis, especially when differentiating from cerebral infarction events, aiding treatment planning and outcome tracking.
Questions About This Page
How many billable codes are in the I66 range?
Of the 19 codes in this range, 15 are billable and valid for claim submission from October 1, 2025 through September 30, 2026. Category header codes group them but cannot be reported on claims.
What does the I66 range classify?
The range classifies occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2026 ICD-10-CM Tabular List and order file, effective October 1, 2025 through September 30, 2026.
