Association between etiology and lesion site in ischemic brainstem infarcts

Objective: To assess the anatomical distribution of the ischemic strokes of the brainstem, the effect of anatomical distribution on clinical features and prognosis, and the association between etiology and anatomical involvement. Materials and Methods: A retrospective search of the patient database of our institution was performed for a total of 227 patients who were admitted to the Department of Neurology, Medical Faculty of Bezmialem Vakıf Universty between January 2012 and September 2014. Patients with adequate diagnostic data and 3-month follow-up visit were included in the study. Demographic characteristics, laboratory and imaging studies, history of chronic disease, risk factors, neurological manifestations at the time of presentation, NIHSSS and MRS at the time of presentation and MRS at 3 months were recorded. Brainstem infarcts were categorized into three main groups based on the site involved: mesencephalon, pons, or medulla oblongata. Each of these anatomical sites were divided into the following four sub groups: anteromedial, anterolateral, lateral, and posterior. The association between the site of the infarction and etiology was examined. Results: The mean age of the patients was 63.34 ± 12.170 years. Twenty-one (9.2%), 136 (59.9%) and 65 (28.6%) patients had an infarction only at mesencephalon, pons, and bulbus, respectively. On the other hand a single patient (0.4%) had an infarction both at mesencephalon and pons, 3 (1.3%) at pons and bulbus, and 1 (0.4%) at mesencephalon, pons, and bulbus. While anterior involvement was more common in mesencephalon and pons, posterior and lateral involvement occurred more frequently in bulbus. Larger arterial atherothrombosis was the predominant cause of the strokes in all anatomical sites, particularly in infarcts involving pons. Cardio-embolic events were more common in patients with mesencephalic infarcts and in subjects who had infarcts at other locations in addition to brainstem. Also, ischemia due to dissection was more common in infarctions involving bulbus, especially lateral bulbus. While the frequency of anteromedial, anterolateral and lateral infarcts was similar, posterior infarcts represented the least common category. In subjects with simultaneous infarcts at other sites in addition to brainstem, there was a significantly higher co-occurrence of bulbar infarcts with cerebellar infarcts, mesencephalic infarcts with PCA infarcts, and pons infarcts with anterior circulation and multiple infarcts.