I66.1 – Occlusion and stenosis of anterior cerebral artery

ICD-10-CM 2027 diagnosis code · Cerebrovascular diseases

Non-billable header

ICD-10-CM code I66.1
Code
I66.1 (claims format: I661)
Description
Occlusion and stenosis of anterior cerebral artery
Billable
No – use a more specific code below
Valid for
Dates of service October 1, 2026 – September 30, 2027 (FY2027)
Chapter
9. Diseases of the circulatory system (I00-I99)
Block
I60-I69 Cerebrovascular diseases
Parent codes
I66

Billable codes under I66.1

I66.1 is a header code and cannot be used on claims. Choose the most specific code:

Notes inherited from parent codes

Instructional notes at a category or block level apply to every code below it.

I66 – Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction

Includes:
  • embolism of cerebral artery
  • narrowing of cerebral artery
  • obstruction (complete) (partial) of cerebral artery
  • thrombosis of cerebral artery
Excludes1 (not coded here):
  • Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5)

Block I60-I69

Excludes1 (not coded here):
  • traumatic intracranial hemorrhage (S06.-)
Use additional code:
  • 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)

Index terms for I66.1

Entries in the ICD-10-CM alphabetic index that lead to this code:

Related codes in I66

Frequently asked questions

What is ICD-10 code I66.1?

I66.1 is the ICD-10-CM code for occlusion and stenosis of anterior cerebral artery, in the block I60-I69 (Cerebrovascular diseases).

Is I66.1 a billable code?

No. I66.1 is a header code with more specific child codes; report one of the billable codes listed above.

What category does I66.1 belong to?

It belongs to category I66 – Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction.

Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.