I63.5 vs I66
I63.5 and I66 can never be reported together. ICD-10-CM declares them mutually exclusive with an Excludes1 note, meaning the two conditions cannot occur in the same patient — so exactly one of them is correct for any given encounter.
The official note, declared on I66
Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5)
I63.5
Cerebral infarction due to unspecified occlusion or stenosis of cerebral arteries
Not billable
- Chapter 9
- Diseases of the circulatory system
- Section
- I60-I69
Indexed under
- Occlusion, occluded › cerebrovascular › with infarction
- Softening › brain › occlusive
- Occlusion, occluded › artery › brain or cerebral › with infarction
- Infarct, infarction › cerebral › due to › occlusion NEC › cerebral arteries
- Infarct, infarction › cerebral › due to › stenosis NEC › cerebral arteries
I66
Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction
Not billable
- Chapter 9
- Diseases of the circulatory system
- Section
- I60-I69
Use when the record says
- embolism of cerebral artery
- narrowing of cerebral artery
- obstruction (complete) (partial) of cerebral artery
- thrombosis of cerebral artery
Excludes1 is not always absolute: where two conditions covered by the note are genuinely unrelated, CMS guidance permits reporting both. Document the reasoning rather than assuming it. More on Excludes1 vs Excludes2 · FY2027