ICD-10 Code I66.01 – Occlusion and stenosis of right middle cerebral artery (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I66.01 – Occlusion and stenosis of right middle cerebral artery
What it is
This code identifies narrowing or blockage of the right middle cerebral artery, a major vessel supplying blood to the right side of the brain. Use it when documentation specifies the right MCA and does not indicate a different cerebral artery.
Clinical signs
Clinical features vary; refer to documentation. Findings may reflect reduced blood flow in the right MCA territory, such as focal neurologic deficits or imaging evidence of arterial stenosis or occlusion.
When to use this code
Use this code when the provider documents occlusion or stenosis of the right middle cerebral artery, including chronic or acute vascular narrowing if no more specific code is given. It is appropriate when imaging, angiography, or clinical notes clearly identify the right MCA. If the record only says “cerebral artery disease,” check documentation.
Do not use for
Do not use this code for transient ischemic attack, cerebral infarction, or hemorrhagic stroke unless the provider separately documents right MCA occlusion or stenosis. Do not assume laterality or vessel location from nonspecific cerebrovascular terms.
Coding tip
Verify the exact vessel and side in the report; if right MCA is not explicitly stated, check documentation before assigning I66.01.