Is I66 a billable ICD-10-CM code?

No. I66 is a non-billable header code. Code to a higher level of specificity using one of its child codes.

Where does I66 sit in the tabular list?

Diseases of the circulatory system (I00-I99), in the block Cerebrovascular diseases (I60-I69).

What cannot be coded together with I66?

I66 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.

I66

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

Non-billable headerICD-10-CM

I66 is a non-billable header ICD-10-CM code for occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction. It cannot be billed on its own: choose one of the more specific child codes below.

Excludes1 — never code together

These conditions cannot occur together. Billing both on the same encounter is a denial.

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

Includes

Conditions this code covers.

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

Risk adjustment

I66 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.

Code to one of these instead I66

6 child codes. Green means billable.

Questions about I66

Is I66 a billable ICD-10-CM code?: No. I66 is a non-billable header code. Code to a higher level of specificity using one of its child codes.
Where does I66 sit in the tabular list?: Diseases of the circulatory system (I00-I99), in the block Cerebrovascular diseases (I60-I69).
What cannot be coded together with I66?: I66 carries an Excludes1 note, which means the conditions it lists can never be coded together with it on the same encounter.