[Epidemiology and Pathophysiology of Acute Ischemic Stroke]

Over the past few decades, the treatment of acute ischemic stroke (AIS) has advanced significantly. Although age-standardized stroke incidence and mortality rates have declined globally thanks to improved preventive and acute therapies, population growth and aging have meant that the absolute disease burden continues to increase. In Japan, data from the Japan Stroke Data Bank indicate a trend towards milder neurological severity at onset and improved functional outcomes at discharge. However, approximately 80% of all patients with AIS remain ineligible for acute reperfusion therapies such as intravenous thrombolysis and endovascular therapy, highlighting the critical importance of appropriate medical management based on pathophysiological assessments. To deliver optimal medical treatment, physicians must precisely understand the different stroke subtypes. Although the conventional TOAST classification remains the standard for identifying primary stroke etiologies, in clinical practice, it commonly fails to account for overlapping pathologies. ASCOD phenotyping addresses this limitation by categorizing overlapping etiologies in a graded fashion. Neurosurgeons who frequently manage such complex cases must accurately evaluate the diverse pathophysiological backgrounds and foster multidisciplinary team approaches to optimize both acute care and secondary prevention in patients with AIS.