ICD-10 Code I66.12 – Occlusion and stenosis of left anterior cerebral artery (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I66.12 – Occlusion and stenosis of left anterior cerebral artery
What it is
This code identifies narrowing or blockage of the left anterior cerebral artery, a vessel that supplies blood to the frontal lobes and medial portions of the brain. Use it when documentation specifies the left anterior cerebral artery and does not describe the event as a stroke.
Clinical signs
Clinical features vary; refer to documentation. Findings may reflect reduced blood flow in the left ACA territory, such as weakness or sensory changes affecting the opposite leg more than the arm, but the record must support the vascular diagnosis.
When to use this code
Use I66.12 when the provider documents occlusion or stenosis of the left anterior cerebral artery, including imaging-confirmed arterial narrowing or blockage. Code it when the condition is the reason for evaluation or is clearly documented as an active diagnosis. If the note describes infarction, code the stroke diagnosis instead.
Do not use for
Do not use this code for cerebral infarction, transient ischemic attack, or nonspecific cerebrovascular disease. Check documentation if the artery side, vessel, or whether the problem is occlusion versus stenosis is unclear.
Coding tip
Verify laterality and whether the record states occlusion, stenosis, or both before assigning I66.12.