I66Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction

I66 is the ICD-10-CM diagnosis code for occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction. It belongs to block I60-I69 (cerebrovascular diseases) and chapter 9 (diseases of the circulatory system). It is a header code, so it can't be reported by itself; one of its 6 subcodes must be used instead.

To report this condition, pick the subcode that matches the documentation: I66.0 (artery), I66.1 (artery), I66.2 (artery), I66.3 (arteries), I66.8 (arteries) and I66.9 (artery).

Don't report I66 together with the conditions in its Excludes1 note: Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5).

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.