Border-zone and watershed infarctions.

Border-zone (BZ) and watershed infarcts occur at the junction of two artery territories and are precipitated by a hemodynamic impairment although they cannot be excluded from microembolic etiology. These strokes may often be preceded by specifically precipitating circumstances that induce hypotension and/or hypovolemia (rising from a supine position, exercise, Valsalva's maneuver, administration of antihypertensive drugs, bleeding and anemia). Anterior BZ infarction occurs with a motor deficit of one or both contralateral limbs, associated with aphasia or mood disturbance. Campimetric disturbances are a constant feature of posterior BZ infarct associated with fluent aphasia and hemihypoesthesia. Subcortical and capsule-thalamic BZ infarctions often mimic lacunar syndrome due to small-vessel disease. Cerebellar BZ infarction is associated with non-specific vertigo syndrome or ataxia, while in brainstem BZ infarction patients are comatose with other signs of brainstem being compromised.