I63.542

HCC Category Mapping

What This Code Means

A stroke caused by a blocked or narrowed artery on the left side of the brain that supplies the cerebellum (the part of the brain controlling balance and coordination).

Coding Tips

• •Document left-sided cerebellar artery occlusion or stenosis before assigning this code.
• •Cerebellar infarctions can lead to increased intracranial pressure; clinical severity should be noted separately.

Clinical Significance

This code identifies an acute ischemic stroke due to occlusion or stenosis of the left cerebellar artery where the specific mechanism (thrombosis versus embolism) is not documented. The cerebellar arteries (posterior inferior, anterior inferior, and superior) supply the cerebellum. Infarction can cause life-threatening posterior fossa swelling. 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 cerebellar artery
• ✓Documentation of laterality (left) supported by clinical findings and/or imaging
• ✓If the mechanism (thrombosis vs. embolism) can be determined from imaging or clinical workup, a more specific code should be assigned
• ✓Neurological examination findings consistent with the identified vascular territory (e.g., acute vertigo, ataxia, dysarthria, nausea/vomiting, nystagmus, and risk of brainstem compression from cerebellar edema)
• ✓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