Etiologic Subtypes of Watershed Infarcts

Background: Two types of watershed infarcts (WI) are recognized. Internal WI are usually attributed to either severe stenosis in large arteries or acute hypotensive events, whereas external WI are thought to be caused by embolism. The aim of this study was to determine the etiologic background and prognosis of external and internal WI in our patients. Methods: We reviewed the medical records and diffusion-weighted images of the patients who were admitted to our stroke unit with acute ischemic stroke between January 2012 and November 2014. The demographics, clinical features, radiologic investigations, and other etiologic tests of the patients with internal or external WI were recorded. We determined etiologic stroke subtypes according to the automated Causative Classification System. Results: Fifty-three patients with WI were detected in our registry. Twenty-two (41.5%) of them were women. The mean age was 69 +/- 12.8 (33-98) years. Twenty-one (39.6%) patients had external WI: 7 (33.3%) of them had large-artery atherosclerosis (LAA), 8 (38.1%) patients had cardioembolism, 3 (14.3%) patients had stroke due to other causes (vasculitis; n = 3), and etiologic subtype was undetermined in 3 patients (14.3%). Thirty-two (60.4%) patients had internal WI: 21 (65.6.%) of them had LAA, 5 (15.6%) patients had cardioembolism, 3 (9.4%) patients had stroke due to other causes (aneurysm; n = 1, hypercoagulability due to chronic myeloid leukemia; n = 1, vasculitis; n = 1), and etiologic subtype of 3 (9.4%) patients remained cryptogenic. LAA was significantly associated with internal WI (P = .024). Hypertension was more common in patients with internal WI (P = .035). Conclusions: In this series, cardioembolism was the most common etiologic subtype in the patients with external WI, whereas internal WI were significantly associated with LAA. Uncommon causes should also be investigated in cryptogenic patients.