I66.9
Occlusion and stenosis of unspecified cerebral artery
Billable FY2026 2025-10-01 → 2026-09-30
This is the unspecified option. 5 more
specific codes sit alongside it. Worth
checking whether the documentation supports one of them.
Exclusions 12 never code together
I66code
Excludes1
- Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5)I63.3-I63.5
I00-I99chapter
Excludes2
- certain conditions originating in the perinatal period (P04-P96)P04-P96
- certain infectious and parasitic diseases (A00-B99)A00-B99
- complications of pregnancy, childbirth and the puerperium (O00-O9A)O00-O9A
- congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)Q00-Q99
- endocrine, nutritional and metabolic diseases (E00-E88)E00-E88
- injury, poisoning and certain other consequences of external causes (S00-T88)S00-T88
- neoplasms (C00-D49)C00-D49
- symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)R00-R94
- systemic connective tissue disorders (M30-M36)M30-M36
- transient cerebral ischemic attacks and related syndromes (G45.-)G45.-
Excludes1 — never code together. The excluded condition and this one are mutually exclusive.
Excludes2 — not included here, but the patient may have both. Code both when documented.
Instructional notes 12
I66code
Includes
- embolism of cerebral artery
- narrowing of cerebral artery
- obstruction (complete) (partial) of cerebral artery
- thrombosis of cerebral artery
I60-I69block
Use additional code
- code to identify presence of:
- alcohol abuse and dependence (F10.-)F10.-
- exposure to environmental tobacco smoke (Z77.22)Z77.22
- history of tobacco dependence (Z87.891)Z87.891
- hypertension (I10-I1A)I10-I1A
- occupational exposure to environmental tobacco smoke (Z57.31)Z57.31
- tobacco dependence (F17.-)F17.-
- tobacco use (Z72.0)Z72.0
Index entries leading here 2
Alongside this code 5 same parent — I66
I66.0 Occlusion and stenosis of middle cerebral artery category I66.1 Occlusion and stenosis of anterior cerebral artery category I66.2 Occlusion and stenosis of posterior cerebral artery category I66.3 Occlusion and stenosis of cerebellar arteries I66.8 Occlusion and stenosis of other cerebral arteries
Additional references
AHA Coding Clinic® Licence required
Official coding advice for this code. Published by the American Hospital Association. Not included in this installation.