ICD-10 Code I66.03 – Occlusion and stenosis of bilateral middle cerebral arteries (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I66.03 – Occlusion and stenosis of bilateral middle cerebral arteries
What it is
This code identifies narrowing or blockage affecting both middle cerebral arteries, the vessels that supply major areas of the brain. It is used when documentation specifies bilateral involvement.
Clinical signs
Clinical features vary; refer to documentation. Findings may include neurologic deficits consistent with middle cerebral artery territory ischemia, such as weakness, speech difficulty, or sensory loss.
When to use this code
Use this code when the provider documents occlusion or stenosis of both middle cerebral arteries, whether described as acute, chronic, or unspecified in the record. It may appear on imaging reports, specialist assessments, or discharge summaries. Confirm laterality and vessel name before assigning the code.
Do not use for
Do not use this code for unilateral middle cerebral artery disease or for generalized cerebrovascular disease without artery-specific documentation. Check documentation if the record does not clearly state bilateral involvement.
Coding tip
Assign I66.03 only when the bilateral middle cerebral arteries are explicitly named in the documentation.