What is stroke

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Understanding Stroke: Definition, Causes, and Clinical Features

Definition of Stroke

Updated Definition of Stroke

Stroke is a medical condition characterized by the sudden onset of neurological deficits due to vascular injury to the central nervous system. The American Heart Association/American Stroke Association has updated the definition of stroke to include both clinical and tissue criteria. Central nervous system infarction, which includes brain, spinal cord, or retinal cell death due to ischemia, is a key component of this definition. This infarction can be identified through neuropathological, neuroimaging, and clinical evidence of permanent injury. The term "stroke" encompasses both ischemic strokes, which present with overt symptoms, and silent infarctions, which do not cause known symptoms. Additionally, stroke includes intracerebral hemorrhage and subarachnoid hemorrhage.

Traditional Clinical Definition

Traditionally, stroke has been defined by the abrupt onset of symptoms of focal neurological dysfunction lasting more than 24 hours or leading to earlier death, caused by acute vascular injury to the brain. This definition primarily focuses on the clinical presentation without incorporating modern diagnostic advancements.

Causes of Stroke

Ischemic Stroke

Ischemic stroke, which accounts for approximately 85% of all strokes, is primarily caused by inadequate blood supply to the brain. This can result from small vessel arteriolosclerosis, cardioembolism, or large artery athero-thromboembolism. In younger patients, ischemic strokes can also result from extracranial dissection.

Hemorrhagic Stroke

Hemorrhagic stroke, making up about 15% of strokes, occurs due to spontaneous bleeding into the brain. This can be deep (basal ganglia, brainstem), cerebellar, or lobar. Deep hemorrhages are often caused by hypertensive arteriopathy, while lobar hemorrhages are mainly due to cerebral amyloid angiopathy or arteriolosclerosis. A minority of hemorrhagic strokes are caused by macrovascular lesions such as vascular malformations, aneurysms, or cavernomas.

Clinical Features and Diagnosis

Symptoms and Diagnosis

Stroke is characterized by the sudden onset of symptoms such as sudden collapse, loss of movement and sensation, while respiration and heart action are preserved. The absence of a definitive diagnostic test for stroke necessitates rapid and accurate clinical diagnosis to enable timely emergency interventions .

Advances in Diagnosis and Treatment

Recent advancements in brain scanning techniques have significantly improved the diagnosis and treatment of cerebrovascular diseases. For acute ischemic stroke, endovascular thrombectomy combined with intravenous alteplase has been shown to increase functional independence in patients. Additionally, aspirin has been recognized for its greater benefits in preventing early recurrent ischemic strokes. For hemorrhagic strokes, ongoing trials are assessing the effectiveness of various therapies, including acute blood pressure lowering, haemostatic therapy, and minimally invasive surgery.

Conclusion

Stroke is a complex cerebrovascular disorder with significant implications for mortality and disability worldwide. The updated definition of stroke by the American Heart Association/American Stroke Association incorporates both clinical and tissue criteria, reflecting advancements in medical science and technology. Understanding the causes, clinical features, and advancements in diagnosis and treatment is crucial for improving patient outcomes and reducing the global burden of stroke.