Excludes1 pair
I63.5- vs I66-
I63.5 and I66 are not coded together. ICD-10-CM declares them mutually exclusive with an Excludes1 note — the two conditions are not expected to occur together, so exactly one of them is normally correct for a given encounter. The Official Guidelines carve out one exception: if the two conditions are clearly unrelated to each other, both may be reported.
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 (due to)
- 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