A comprehensive review of stroke: Types, epidemiology, pathophysiology, and risk factors

Abstract

Stroke, a leading cause of adult mortality, is a syndrome characterized by loss of cerebral function due to hypoxic tissue damage. It can be categorized as ischemic or hemorrhagic. Ischemic strokes, accounting for 80-85% of all strokes, are primarily due to cerebral thrombosis or embolism, often from atherosclerosis-induced narrowing of cranial blood vessels. Furthermore, cardioembolism resulting from conditions like atrial fibrillation and myocardial infarction is another source of ischemic stroke. Hemorrhagic strokes, representing 1-7% and 7-27% of all strokes in the form of subarachnoid and intracerebral hemorrhages respectively, disrupt cerebral circulation, causing hypoxic tissue damage.

Nearly 50% of all strokes are thrombotic, resulting from large and small blood vessel occlusions leading to infarction. Embolic strokes occur when clots, often originating from cardiac sources, lodge in brain's blood vessels disrupting cerebral blood flow. Stroke symptoms are dependent on the anatomical location and severity of damage, leading to sudden motor weakness, sensory disturbances, speech disorders, visual or gait abnormalities.

Stroke is a prevalent neurological issue, with approximately 800,000 cases annually in the United States alone. The incidence of stroke, around 160 per 100,000, doubles with every decade after 55. While stroke numbers are growing due to an aging population, mortality rates have decreased due to better management of risk factors and improved acute treatment.

In ischemic stroke, blood flow blockage deprives brain tissue of oxygen and glucose. The ensuing ischemic cascade has been understood better through recent research, uncovering environmental changes involved in its pathophysiology and leading to the concept of a therapeutic time window for early intervention.

Risk factors for stroke encompass non-modifiable aspects (age, gender, race, ethnic origin, and heredity) and modifiable ones (systemic hypertension, smoking, alcoholism, dyslipidemia, obesity, sedentary lifestyle, atrial fibrillation, past heart disease, and transient ischemic attacks). Stroke prevalence in rural areas of developing countries is notably lower than Western countries, likely due to varying socioeconomic factors, ethnic origins, and cultural habits. Understanding these risk factors and the pathophysiology of strokes is crucial for prevention and improved management strategies.