I66.21
Occlusion and stenosis of right posterior cerebral artery
This code does not map to a risk-adjusting HCC in the loaded models.
Coding notes
Excludes 1 never coded together · Excludes 2 may co-exist
traumatic intracranial hemorrhage (S06.-)
code to identify presence of: alcohol abuse and dependence (F10.-) exposure to environmental tobacco smoke (Z77.22) history of tobacco dependence (Z87.891) hypertension (I10-I1A) occupational exposure to environmental tobacco smoke (Z57.31) tobacco dependence (F17.-) tobacco use (Z72.0)
certain conditions originating in the perinatal period (P04-P96) certain infectious and parasitic diseases (A00-B99) complications of pregnancy, childbirth and the puerperium (O00-O9A) congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99) endocrine, nutritional and metabolic diseases (E00-E88) injury, poisoning and certain other consequences of external causes (S00-T88) neoplasms (C00-D49) symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94) systemic connective tissue disorders (M30-M36) transient cerebral ischemic attacks and related syndromes (G45.-)
Official Guidelines for I66.21
FY 2026 ›Sections that reference I66.21
- I.C.9.a.4)Hypertensive Cerebrovascular Disease
For hypertensive cerebrovascular disease, first assign the appropriate code from categories I60-I69, followed by the appropriate hypertension code.
- I.C.9.d.1)Category I69, Sequelae of Cerebrovascular disease
Category I69 is used to indicate conditions classifiable to categories I60- I67 as the causes of sequela (neurologic deficits), themselves classified elsewhere. …
- I.C.9.d.2)Codes from category I69 with codes from I60-I67
Codes from category I69 may be assigned on a health care record with codes from I60-I67, if the patient has a current cerebrovascular disease and deficits from an old cerebrovascular disease.
Sections whose FY 2026 text names I66.21, its I66 category, or a range containing it — the chapter guidance above is the authoritative source.