I63.321

HCC Category Mapping

What This Code Means

A stroke caused by a blood clot blocking the right anterior cerebral artery, which supplies the front portion of the right side of the brain.

Coding Tips

• •Verify documentation specifies 'right' side and 'anterior cerebral artery' to distinguish from middle or posterior cerebral arteries
• •Confirm thrombosis is the documented mechanism of stroke

Clinical Significance

This code identifies an acute ischemic stroke caused by thrombosis (in-situ clot formation) of the right anterior cerebral artery, requiring precise documentation of the clot mechanism. The anterior cerebral artery supplies the medial surfaces of the frontal and parietal lobes, including the motor and sensory cortex for the lower extremity. Accurate coding of the mechanism, artery, and laterality is critical for risk adjustment and tracking stroke subtypes for quality measures and secondary prevention strategies.

Documentation Requirements

• ✓Provider documentation of acute cerebral infarction (stroke) as a confirmed diagnosis, not rule-out or suspected
• ✓Identification of the affected artery as the anterior cerebral artery
• ✓Documentation of laterality (right) supported by clinical findings and/or imaging
• ✓Documentation that thrombosis (in-situ clot formation) is the underlying mechanism, typically supported by vascular imaging such as computed tomography angiography or magnetic resonance angiography
• ✓Neurological examination findings consistent with the identified vascular territory (e.g., contralateral leg weakness greater than arm weakness, personality changes, urinary incontinence, and abulia)
• ✓Brain imaging (computed tomography or magnetic resonance imaging) confirming acute infarction
• ✓Timing of symptom onset to confirm acute presentation
• ✓Documentation of stroke severity (National Institutes of Health Stroke Scale score preferred)
• ✓Treatment administered (thrombolytics, thrombectomy, antiplatelet therapy, anticoagulation)

Commonly Confused Codes