Uncommon Etiologic Mechanisms in Stroke

In addition to treating the acute stroke, attention must be directed toward prevention of future strokes. Identifying and modifying potential risk factors is essential. Pharmacologic treatment using antihypertensives, statins, and agents that alter platelet function are the mainstays of prophylaxis of brain ischemia. In those patients who have residual deficits after stroke, recovery and rehabilitation are optimized.

UNCOMMON ETIOLOGIC MECHANISM OF STROKE

Although atherosclerotic abnormalities of brain supplying arteries are the most frequent causes of stroke, many other etiologies need consideration, especially in young individuals and those who do not have risk factors for atherosclerosis. Evaluation of the heart, neck and intracranial arteries and veins, and the blood are important in all patients with stroke and transient ischemic attacks. The most common conditions are brain embolism arising from the heart, especially in patients with arrhythmias and valvular disease; dissections of neck and intracranial arteries; emboli from aortic plaques, various vascular anomalies and malformations, and blood disorders that promote excess clotting or bleeding. A partial list of conditions follows.

Cardiac. A variety of different heart conditions serve as donor sources for brain embolism. Cardiac pump failure can lead to ischemic brain damage through systemic hypoperfusion. Other cardiac lesions cause strokes by providing a source of embolism to the brain: valvular conditions—rheumatic, calcific, infectious endocarditis, and noninfective fibrotic lesions (Libman-Sacks endocarditis associated with systemic lupus erythematosus and similar valvular lesions in patients with cancer and antiphospholipid antibodies), mitral annulus calcifications, and artificial surgically implanted mechanical and biological valves; myocardial abnormalities—myocardial infarcts, myocarditis, myocardiopathies; arrhythmias—atrial fibrillation, sick sinus syndrome; neoplasms—myxomas, fibroelastomas; and septal abnormalities—atrial septal defects, patent foramen ovale.

Arteries. Vascular conditions can also predispose to artery-to-artery embolism as well as causing localized ischemia due to decreased perfusion. Some vascular lesions promote bleeding. Aortic atheromas, especially those that are mobile and protruding, may on occasion lead to a stroke. Arterial dissection in either the carotid or vertebral artery system requires careful consideration. These often occur related to seemingly benign problems, such as a paroxysm of vomiting, or athletic injuries, such as from wrestling, skiing accidents, falls from horses, and so forth. Other unusual primary vascular lesions include fibromuscular dysplasia, arteritis, moyamoya syndrome, Takayasu arteritis, and severe migraine. Certain quite rare genetic conditions require consideration in the differential diagnosis of stroke. These include CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy), Ehlers-Danlos syndrome, pseudoxanthoma elasticum, progeria, and cerebral amyloid angiopathy. Vascular malformations—aneurysms, arteriovenous malformations, cavernous angiomas, developmental venous anomalies, varices—predispose to bleeding. Infections, such as with herpes zoster varicella virus, can invade blood vessels and cause stroke. Meningitis sometimes causes arterial inflammation and strokes.

Hematologic. Increase in coagulability is seen due to decreased amounts of usual inhibitors: protein S, protein C, antithrombin, activated protein C–resistance, sickle cell disease, and other hemoglobinopathies; severe anemia; thrombocythemia; thrombocytosis; and bleeding disorders—thrombocytopenia, hemophilia, and prescription of antithrombotic agents.

Veins. Thrombosis of the dural sinuses, especially the superior sagittal sinus and the lateral sinus, are often associated with brain infarction, brain edema, and brain hemorrhage. Occlusion of deep veins is an important cause of stroke in the young. Occlusion of veins on the surface of the brain can also cause infarction and seizures.

Only gold members can continue reading. Log In or Register to continue