This chapter explores the relationship of stroke with Susac's syndrome. In Susac's syndrome, diagnostic signs involve the retina. Fundoscopic examination shows arteriolar occlusions with narrowing of arterioles, as well as signs of other ischemic changes in the affected vascular area, such as edema and increased vascular permeability. Fluorescein angiography is often helpful in showing the vascular occlusions and leaking into the retina. Magnetic resonace imaging (MRI) is the neuroimaging study of choice and fluid-attenuated inversion recovery (FLAIR) a sensitive sequence for detecting lesions of Susac's syndrome as well as to show their heterogeneity. Small-vessel diseases are responsible for a large amount of ischemic and hemorrhagic strokes as well as encephalopathies including Susac's syndrome. Misdiagnoses include multiple sclerosis, but differential diagnosis must be done with all causes of multifocal neurologic symptoms with hearing and/or visual loss. Calcium channel blockers (nimodipine), anticoagulants, and aspirin may be useful in treatment.

This chapter explores the complex relationship of stroke with polyarteritis nodosa (PAN) and microscopic polyangiitis (MPA). MPA is a systemic necrotizing vasculitis that clinically and histologically involves capillaries, venules, or arterioles without granulomata, and is associated with necrotizing crescentic glomerulonephritis and hemorrhagic pulmonary capillaritis, which are the main causes of mortality and morbidity. Hemorrhagic strokes occur more frequently than ischemic infarction in MPA. Immunohistochemical studies from muscle and nerve biopsies showed that macrophages and T cells, mostly CD8+, are involved in the pathogenesis of PAN. Neurological symptoms and signs are a major and common feature of PAN, occurring in nearly three-quarters of patients. A close relationship between the use of corticosteroids and stroke exists in PAN. From a therapeutic point of view, antiplatelet drugs, which inhibit platelet thromboxane production, might reduce the risk of corticosteroid-induced, antiplatelet drugs in PAN. The use of aspirin and corticosteroids prospectively prevents stroke recurrence.