I66Header code — not billable
Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction
Short description: Occls and stenosis of cereb art, not rslt in cerebral infrc
- Chapter
- 9. Diseases of the circulatory system
- Category
- I66
- Effective date
- October 1, 2026
Related codes in category I66
I66.0Occlusion and stenosis of middle cerebral arteryI66.01Occlusion and stenosis of right middle cerebral arteryYesI66.02Occlusion and stenosis of left middle cerebral arteryYesI66.03Occlusion and stenosis of bilateral middle cerebral arteriesYesI66.09Occlusion and stenosis of unspecified middle cerebral arteryYesI66.1Occlusion and stenosis of anterior cerebral arteryI66.11Occlusion and stenosis of right anterior cerebral arteryYesI66.12Occlusion and stenosis of left anterior cerebral arteryYesI66.13Occlusion and stenosis of bi anterior cerebral arteriesYesI66.19Occlusion and stenosis of unsp anterior cerebral arteryYesI66.2Occlusion and stenosis of posterior cerebral arteryI66.21Occlusion and stenosis of right posterior cerebral arteryYes
Frequently asked questions
What is ICD-10 code I66?
I66 is an ICD-10-CM diagnosis code for Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction.
Is I66 a billable code?
No. I66 is a category/header code, not billable on its own — use one of its more specific child codes instead.
What ICD-10-CM chapter is I66 in?
I66 falls under Chapter 9: Diseases of the circulatory system.
When did I66 become effective?
I66 has been effective since October 1, 2026, per the CMS/CDC ICD-10-CM annual release.
What other codes are related to I66?
I66 belongs to category I66, which includes 12 other codes — see the related codes list on this page.
ICD-10-CM data maintained by CDC/CMS (public domain). Always verify codes with authoritative sources before making coding or billing decisions.