A completed stroke is an ischemic event that produces a stable, permanent neurologic disability. Most ischemic strokes consist of small regions of complete ischemia in conjunction with a larger area of incomplete ischemia. This ischemic but not infarcted area is called the penumbra. The penumbra is dynamic, resulting in changes to the previously passive treatment approach in patients with acute cerebral ischemia. Clinical manifestations of cerebral ischemia reflect the functions associated with the area of ischemia and include paresis, paresthesia, vision loss, language disturbances, vertigo, diplopia, ataxia, dysarthria, headache, nausea, and vomiting.
Emboli or thrombi caused by atherosclerosis, hypertension, or diabetes mellitus and located in large, medium, and small arteries account for most strokes. Strokes caused by emboli of cardiac origin account for 20% of total ischemic stroke incidence. Atrial fibrillation is the most common cause of cardioembolic strokes, occurring in up to 20% of these patients. Mural thrombi forming on the endocardium in conjunction with myocardial infarction (MI) account for 8%–10% of total stroke incidence worldwide. Other cardiac conditions associated with intracranial embolism include mitral stenosis and atrial myxoma. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), which is a rare genetic small-vessel vasculopathy, can mimic multiple sclerosis and cause ischemic stroke.
Nonarteriosclerotic causes of thrombotic occlusion leading to TCI and stroke include internal carotid dissection (causing the classic triad of Horner sign, neck pain/headache, and neurologic signs and symptoms) and inflammatory arteritis (eg, collagen vascular disease, giant cell arteritis, meningovascular syphilis, acute and chronic meningitis, and moyamoya disease).
Another cause of cerebral ischemia is increased viscosity of the blood due to pregnancy and the postpartum period, use of oral contraceptives, postoperative and posttraumatic states, hyperviscosity syndromes, polycythemia, and sickle cell disease. In addition, stroke may occur as a result of hypoxemia caused by conditions such as carbon monoxide poisoning, chronic obstructive pulmonary disease, profound anemia, and pulmonary emboli.
Excerpted from BCSC 2020-2021 series: Section 1 - Update on General Medicine. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.