Moyamoya disease

This code describes Moyamoya disease, a rare, progressive cerebrovascular disorder characterized by the narrowing or occlusion of the internal carotid arteries within the skull, leading to the formation of a compensatory network of tiny, fragile blood vessels at the base of the brain. This abnormal vascular network, resembling a "puff of smoke" on angiography, is prone to hemorrhage and ischemia.

Use this code for documented cases of Moyamoya disease, whether presenting with ischemic events (e.g., transient ischemic attacks, strokes) or hemorrhagic events. Documentation should clearly state the diagnosis of Moyamoya disease, often confirmed by cerebral angiography or MRI/MRA findings.

• Differentiate from other cerebrovascular diseases; Moyamoya has distinct angiographic features.
• Code any associated neurological deficits or complications (e.g., stroke, TIA) separately as secondary diagnoses.
• Ensure documentation specifies "Moyamoya disease" rather than just "cerebrovascular disease" for accurate coding.