Carotid artery syndrome (hemispheric)

This code represents a transient neurological deficit resulting from temporary ischemia in the territory supplied by the carotid artery, often manifesting as monocular blindness (amaurosis fugax), hemiparesis, or aphasia. It indicates a temporary disruption of blood flow to one cerebral hemisphere, typically due to an embolus or severe stenosis in the ipsilateral carotid artery.

Use this code when documentation clearly indicates symptoms consistent with transient ischemic attack (TIA) specifically attributed to the carotid artery system, such as transient monocular vision loss or unilateral weakness. Supporting documentation should include a physician's diagnosis of carotid artery syndrome or TIA with a clear link to the carotid circulation.

• Do not use this code for completed strokes (cerebral infarction); those require specific stroke codes.
• Ensure documentation specifies "hemispheric" or provides symptoms clearly localized to one side of the brain to differentiate from vertebrobasilar syndromes.
• Code any underlying conditions, such as carotid artery stenosis (I65.2-), as additional diagnoses.