There are 3 basic mechanisms that can cause interruption of cerebral blood flow.
blockage of downstream arterial blood flow by embolism originating from the exhaustive end.
local occlusion: often due to proximal or distal in situ thrombosis.
whole brain hypoperfusion.
Most ischemic strokes are due to embolism (25% cardiogenic embolism) and in situ thrombosis, and a few are due to chronic hypoperfusion. In macrovascular disease, all 3 of these mechanisms may be involved. For example, severe stenosis of one carotid artery (caused by a large atherosclerotic plaque), distal ischemia due to emboli and/or further stenosis and distal hypoperfusion from acute plaque rupture and thrombosis, and cerebral hypoperfusion can be further exacerbated by both low cardiac output and extracorporeal hypocirculation. At a given stage of cerebrovascular disease, one mechanism of occurrence may play a primary role and others may play a secondary role.
I. Embolism.
1, arterial-arterial embolism
(1) Intracranial and extracranial macrovascular lesions from any cause
Atherosclerosis is the most common.
Non-atherosclerotic diseases (myofibrillar dysplasia, entrapment, vascular tortuosity, vasculitis/arteritis, vasospasm, vasoconstriction, etc.)
(2) Abnormalities of the aortic arch from any cause (atherosclerosis, entrapment/aneurysm, connective tissue disease, infection, etc.)
2.Cardiogenic embolism
(1) Cardiac arrhythmia (atrial fibrillation is common)
(2) Heart valve disease
Rheumatic heart disease, artificial heart valve disease, endocarditis (infectious, non-bacterial embolic)
II. Local occlusion
1, any cause of small vessel lesions
(1) Multiple cause related (hypertension, diabetes, hyperlipidemia, smoking, alcohol, etc.)
(2) cerebral arteritis
(3) cerebral amyloid angiopathy
2.Coagulation abnormalities
(1) Malignant disease
(2) Hormonal: pregnancy and puerperium, oral contraceptives, hormone replacement, etc.
(3) Hereditary coagulopathy
(4) Abnormal platelet function, heparin-induced thrombocytopenia, thrombotic thrombocytopenic purple
(5) Hyperviscosity, hyperfibrinemia, sickle cell anemia, erythrocytosis
III. Hypoperfusion
1, any cause of extracorporeal hypocirculation
2, heart failure/low cardiac output
3, cardiac arrest, arrhythmia