Mechanisms of stroke in patients with intracranial atherosclerotic disease

Mechanisms of stroke in patients with ICAD.
(A) Thrombotic occlusion is a rare phenotype of ICAD. MRA shows in situ thrombotic occlusion at the site of stenotic plaque. DWI shows territorial infarcts by severe hemodynamic compromise and embolic infarcts on the cortex. High-resolution MRI can show vulnerable plaque on intracranial vessels.
(B) Artery-to-artery embolism is one of common phenotypes of ICAD. Artery-to-artery embolism is usually associated with a severe degree of intracranial stenosis, and transcranial Doppler ultrasonography can detect symptomatic or asymptomatic embolism during microembolic signal monitoring. DWI shows small, scattered, cortical embolic infarcts.
(C) Hemodynamic impairment is another phenotype of ICAD. This phenotype is usually associated with a severe stenosis and a marked hemodynamic compromise, as seen on a PWI. DWI typically shows borderzone-type infarcts, and infarct growth is common with clinical deterioration.
(D) Branch occlusive disease is a common phenotype of ICAD. This phenotype is often misclassified as small arterial disease due to a mild degree of stenosis on MRA, small deep infarcts on DWI, and relatively small perfusion defects. High-resolution MRI can reveal plaque without stenosis near the orifices of penetrating arteries.