[Clinical Features of Very Elderly Patients Aged 90 Years or Above with Acute Ischemic Stroke: A Study by Using Diffusion Weighted Brain Magnetic Resonance Imaging]

We investigated the diffusion weighted magnetic resonance imaging (DWI) features of 76 very elderly patients aged 90 years or above with acute ischemic stroke. Stroke subtypes were classified into five types according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) and the Japanese Stroke Databank. The incidence rates of atherothrombotic brain infarction (ATBI), atherothrombotic brain embolism (ATBE), lacunar infarction (LI), cardiogenic brain embolism (CBE) and undetermined type of brain infarction (UTBI) were 2.6%, 17.1%, 10.5%, 50.0% and 19.8%, respectively. We estimated that the incidence of acute ischemic stroke in women was 3.5-fold higher than that in men. This is likely because survival rate of females is higher than that of males in populations aged 90 years or above. The prevalence of atrial fibrillation (AF) was 46.1% in patients with brain infarctions, and 92.1% in patients with CBE. The frequency of multiple infarctions is 52.6% and that of single infarction is 47.4%. In DWI of lesions, the frequencies of territorial infarction in the cerebral hemisphere, borderzone infarction, and vertebrobasilar infarction were 85.5%, 13.2% and 17.1%, respectively. The frequencies of massive territorial infarction and cerebellar infarction were 23.7% and 13.2%, respectively. With regard to the relationship between DWI lesion topography and stroke subtypes, superficial infarctions in the cerebral hemisphere were seen in patients with ATBE, CBE and UTBI. Single infarctions deep in the cerebral hemisphere were seen in all patients with any of the five stroke subtypes. Massive territorial infarctions with infarctions in other sites of the cerebral hemisphere or vertebrobasilar region were seen only in patients with CBE, and single pontine infarction was seen only in patients with LI. (Received November 19, 2015; Accepted July 3, 2017; Published November 1, 2017).