The process of lipid accumulation is accompanied by an inflammatory reaction involving lymphocytes and macrophages. Atheromatous plaques may cause narrowing or occlusion of the vascular lumen by themselves or after rupture and thrombosis. Cholesterol crystals from ruptured plaques may embolize distal vessels. Small vessel disease includes atherosclerosis of small arteries but refers more specifically to lipohyalinosis and hyaline atreriolosclerosis , vascular lesions that are seen primarily in hypertension and diabetes but occur also in old age without these predisposing conditions.
Affected vessels become thickened, and the normal components of their walls are replaced by a homogeneous, glassy hyaline substance, composed of collagen and other proteins.
Foamy macrophages are present in lipohyalinosis. The pathogenesis of this change varies: in hypertension, it is caused by endothelial injury and leakage of plasma proteins in and around vessels; in diabetes, it probably has to do with glycation of proteins and diffuse basement membrane thickening. Its effects are narrowing of the lumen and tortuosity, which lengthens the distance blood has to travel to perfuse its targets.
Ischemia, resulting from these processes, causes small infarcts lacunar infarcts and diffuse loss of axons and myelin in the white matter leukoaraiosis-thinning out of the white matter. Multiple infarcts and leukoencephalopathy cause dementia. In addition, loss of elasticity from destruction of smooth muscle leads to development of small aneurysms and makes vessels fragile, resulting in microbleeds and large catastrophic hemorrhages, which occur spontaneously or after trivial trauma.
See also genetic angiopathies further on. According to some authors, embolism is the most frequent cause of ischemic infarction. Most emboli are fragments of blood clots that originate in the heart or major vessels. Conditions causing cardiac emboli include myocardial infarcts, atrial fibrillation and other arrhythmias, rheumatic heart disease, bacterial and non-bacterial endocarditis, prosthetic valves, mitral valve prolapse, atrial myxoma, calcified mitral annulus, and cardiomyopathy.
An embolus cannot be distinguished grossly or microscopically from a locally formed thrombus. An infarct is assumed to be embolic if it is hemorrhagic, there is a source of emboli, there are multiple infarcts of the brain and other organs kidney, spleen , and there is no atherosclerosis or other vascular disease.
Some emboli consist of atheromatous material that is detached from ulcerated atheromas of the aorta or carotid arteries. Vascular manipulation angiography, carotid endarterectomy may cause atheromatous embolism. Rarer causes of embolism are fat, air, and tumor emboli.
Unlike atherothrombotic infarcts, which may evolve within hours or days, embolic infarcts have an abrupt onset. Vasculitis CNS vasculitis can be classified under the following categories:. Giant cell temporal arteritis. Disruptions of the elastic lamina with inflammation and giant cells. Patient with leukemia and mucormycosis. The basilar artery is thrombosed due to invasion by fungi. The pons is infarcted and is green because the patient was jaundiced.
Systemic vasculitis with CNS involvement : giant cell arteritis, polyarteritis nodosa, Wegener granulomatosis, Takayasu arteritis, Kawasaki disease. The most common of these entities is giant cell temporal arteritis GCA which is more frequent in older people and women and is associated with polymyalgia rheumatica. GCA is also called temporal arteritis because it frequently involves the temporal artery.
Biopsy of the temporal artery is done for diagnosis. However, GCA affects the aorta and other major extracranial and, less frequently, intracranial branches. Involvement of the ophthalmic artery causes visual loss in a significant number of cases. GCA is a T-cell mediated autoimmune condition that affects medium-size and large arteries. Lymphocytes and multinucleated giant cells infiltrate the vessel wall, disrupt the internal elastic lamina, and cause narrowing and thrombosis.
Secondary vasculitis : Infectious bacterial, fungal, spirochetal, viral ; collagen-vascular disease SLE, rheumatoid arthritis, Behset disease ; drug-induced vasculitis. Fungal vasculitis is most frequently caused by aspergillus and mucor.
CE: Acute Stroke: Pathophysiology, Diagnosis, and Treatment
Cerebral vasculitis involving a small cortical artery. Intense inflammation in and around the vessel wall. The criteria for PACNS are: The presence of neurologic or psychiatric deficits, angiographic or pathological documentation of vasculitis, and absence of evidence of systemic or secondary vasculitis. Granulomatous PACNS affects small and medium-size leptomeningeal and cortical vessels and causes headaches, seizures, focal deficits, and encephalopathy.
Affected vessels may have amyloid deposits, in addition to epithelioid cell granulomas and giant cells. There is no vasculitis outside the CNS. The nongranulomatous form shows lymphocytic inflammation.
PACNS affecting small vessels presents with focal or diffuse neurologic abnormalities and enhancing meningeal and parenchymal lesions and is not evident on angiography. The clinical picture overlaps encephalitis. The diagnosis of such cases can be made by brain biopsy, which shows lymphocytic inflammation in vessel walls and around vessels.
This inflammation may be difficult to distinguish from perivascular mononuclear infiltrates that are seen in MS and infectious diseases. MRA from patient with sickle cell disease. MCA infarct. Note absence of blood vessels corresponding to the lesion. Hematologic disorders - Polycythemia, hemoglobinopathies sickle cell disease , deficiencies of anticoagulant factors, thrombotic thrombocytopenic purpura. Metabolic disorders - Dyslipoproteinemias, Fabry disease, homocystinuria, organic acidemias, mitochondrial disorders. Some of these conditions cause ischemic infarcts even in children and infants.
Mitochondrial disorders can cause TIAs and ischemic strokes. These polymorphisms derange the delicate balance between natural anticoagulant and procoagulant pathways. They are very prevalent in the population and combine with one another and with aquired conditions that promote clotting, causing venous and arterial infarcts.
Dissecting aneurysm dissecting hematoma. Blood has dissected between the internal elastica and media, collapsing the lumen. This was a spontaneous lesion in a young man. Trauma to the head and neck can cause dissecting aneurysms and other lesions of the carotid and vertebral arteries. Most of the patients have hyperperfusion. However, a minimal to moderate increase in brain perfusion can lead to CHS.
TCD is the most commonly and widely available technique used in the perioperative period to monitor for cerebral hyperperfusion. Control of blood pressure with labetalol and clonidine may be useful for the prevention and treatment of CHS [ 2 , 3 , 18 ]. Hypertension and the post-carotid endarterectomy cerebral hyperperfusion syndrome. Eur J Vasc Endovasc Surg. Cerebral hyperperfusion syndrome. Lancet Neurol. Hyperperfusion syndrome after carotid revascularization.
J Vasc Surg.
Cerebral hyperperfusion syndrome after percutaneous transluminal stenting of the craniocervical arteries. Intracerebral hemorrhage after carotid endarterectomy. J Neurosurg.