I66.9 Occlusion and stenosis of unspecified cerebral artery

Billable ICD-10-CM code, FY2026.

Applies from I66 Occlusion and stenosis of cerebral arteries, not resulting in cerebral infarction

Includes

• embolism of cerebral artery
• narrowing of cerebral artery
• obstruction (complete) (partial) of cerebral artery
• thrombosis of cerebral artery

Excludes1 (never code together)

• Occlusion and stenosis of cerebral artery causing cerebral infarction (I63.3-I63.5)

MS-DRG index

Defines the logic of DRG(s) 061-063 in MDC 01.

Approximate ICD-9-CM (GEMs)

• 434.10 Cerebral embolism without mention of cerebral infarction (approximate)
• 434.90 Cerebral artery occlusion, unspecified without mention of cerebral infarction (approximate)

Code annotations containing back-references to I66.9

Back-references to I66

• Type 1 Excludes: G31.84 Mild cognitive impairment of uncertain or unknown etiology ("cerebrovascular diseases (I60-I69)")
• Code First: G46 Vascular syndromes of brain in cerebrovascular diseases ("underlying cerebrovascular disease (I60-I69)")
• Type 2 Excludes: I10 Essential (primary) hypertension ("essential (primary) hypertension involving vessels of brain (I60-I69)")
• Type 2 Excludes: I15 Secondary hypertension ("secondary hypertension involving vessels of brain (I60-I69)")
• Type 2 Excludes: I74 Arterial embolism and thrombosis ("cerebral embolism and thrombosis (I63.3-I63.5, I66.-)")

Diagnosis Index entries for I66.9

• Occlusion, occluded › artery › brain or cerebral
• Occlusion, occluded › artery › cerebral
• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › cortical
• Thrombosis, thrombotic (bland) (multiple) (progressive) (silent) (vessel) › intracranial (arterial)

Nearby codes

• I66.22 Occlusion and stenosis of left posterior cerebral artery
• I66.23 Occlusion and stenosis of bilateral posterior cerebral arteries
• I66.29 Occlusion and stenosis of unspecified posterior cerebral artery
• I66.3 Occlusion and stenosis of cerebellar arteries
• I66.8 Occlusion and stenosis of other cerebral arteries
• I66.9 Occlusion and stenosis of unspecified cerebral artery (this code)