All ICD10 Codes
I66Not billable, use a more specific code below

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

In Cerebrovascular diseases (I60-I69), chapter 9: Diseases of the Circulatory System

15 billable codes under I66: none are a CC or MCC; none map to an HCC.

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Instructional notes

Includes: conditions that are coded here

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

Excludes1: not coded here, use a different code

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

Also applies, from Cerebrovascular diseases (I60-I69)

These notes sit on I60-I69 and apply to every code under it, including I66.

Excludes1: not coded here, use a different code

  • traumatic intracranial hemorrhage (S06.-)

Use additional code: add a second code for this, listed after this one

  • 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)

Official coding guidelines

From the ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027 (CMS and NCHS). Links open the PDF at the right page.

Covers hypertension with heart and kidney disease, coronary artery disease with angina, perioperative stroke, cerebrovascular sequelae, and acute myocardial infarction types and timing.

Read Section I.C.9 (page 50)

All codes under I66

I66 can't be used on a claim. Pick a billable code below; grey headings group them.

I66 MS-DRGs

As the principal diagnosis, all 15 billable codes under I66 group to these 7 MS-DRGs (v44.0). Which one applies depends on procedures performed, secondary diagnoses (CC/MCC), and the patient's age and discharge status.

Other codes that refer to I66

Notes on these codes point to I66.

  • I74 Excludes2: cerebral embolism and thrombosis (I63.3-I63.5, I66.-)

About the condition

Plain-language background from MedlinePlus (National Library of Medicine), not coding guidance.

Brain Diseases

Your brain is the control center of your body. It controls your thoughts, memory, speech, and movement. It regulates the function of many organs. It's part of your nervous system, which also includes your spinal cord and peripheral nerves. The nervous system sends signals between your brain and the rest of the body. Your nerves take in information from your senses and send it to the brain to be processed. Your brain and nerves also communicate to help you move and to control your body's functions.

Read more about brain diseases on MedlinePlus

Code history

Valid since FY2016, when ICD-10-CM took effect on October 1, 2015. No changes since.