ICD-10 Code I66.0 – Occlusion and stenosis of middle cerebral artery (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code I66.0 – Occlusion and stenosis of middle cerebral artery
What it is
I66.0 identifies narrowing or blockage of the middle cerebral artery, a major vessel supplying blood to the brain. Use it when documentation specifically names this artery and describes occlusion or stenosis.
Clinical signs
Clinical features vary; refer to documentation. Commonly, records may note acute neurologic deficits such as weakness, speech difficulty, facial droop, or sensory loss consistent with middle cerebral artery territory involvement.
When to use this code
Use this code when the provider documents occlusion or stenosis of the middle cerebral artery, whether from imaging, clinical assessment, or a confirmed cerebrovascular event. It may appear in stroke evaluations, vascular studies, or follow-up notes. If the artery or lesion type is not specified, check documentation.
Do not use for
Do not use I66.0 for carotid, vertebral, basilar, or other intracranial arteries. Do not apply it when the record only states cerebral infarction without naming middle cerebral artery occlusion or stenosis.
Coding tip
Assign I66.0 only when the middle cerebral artery is explicitly documented; otherwise, query or check documentation.