Moyamoya disease

This code represents 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 small, fragile blood vessels at the base of the brain. This abnormal vascular network, resembling a "puff of smoke" on angiography, is prone to ischemia, transient ischemic attacks (TIAs), strokes, and hemorrhage.

Assign this code for documented cases of Moyamoya disease, whether symptomatic or asymptomatic, and regardless of the presence of associated complications like stroke or hemorrhage. Supporting documentation typically includes neurological evaluations, cerebral angiography, MRI, MRA, or CT angiography confirming the characteristic vascular changes.

• Do not confuse Moyamoya disease with other forms of cerebrovascular occlusion or stenosis; ensure diagnostic imaging specifically identifies the "puff of smoke" appearance.
• Code any associated neurological deficits or complications (e.g., stroke, TIA, hemorrhage) separately, following sequencing guidelines for acute conditions.
• Specify laterality if documented, although Moyamoya disease often affects both hemispheres.