A stroke occurs when the blood supply to part of the brain is suddenly interrupted, or when a blood vessel in the brain bursts.
Common diagnostic tests include blood tests, an electrocardiogram, and a brain scan such as computed tomography or CT, or magnetic resonance imaging or MRI.
Standardized Stroke Scale
One test that helps doctors judge the severity of a stroke is the standardized NIH Stroke Scale, developed by the National Institute of Neurological Disorders and Stroke at the National Institutes of Health, or NIH. Health care professionals use the NIH Stroke Scale to measure a patients neurological deficits by asking the patient to answer questions and to perform several physical and mental tests. Other scales include the Glasgow Coma Scale, the Hunt and Hess Scale, the Modified Rankin Scale, and the Barthel Index.
Health care professionals also use a variety of imaging devices to evaluate stroke patients. The most widely used imaging procedure is the computed tomography or CT scan, also known as a CAT scan. A CT scan creates a series of cross-sectional images of the head and brain.
Because it is readily available at all hours at most major hospitals and produces images quickly, the CT scan is the most commonly used diagnostic technique for acute stroke. A CT scan also has unique diagnostic benefits. It will quickly rule out a hemorrhage, and can occasionally show a tumor that might mimic a stroke.
A CT scan may even show evidence of early infarction -- an area of tissue that is dead or dying due to a loss of blood supply. Infractions generally show up on a CT scan about six to eight hours after the start of stroke symptoms.
If a stroke is caused by hemorrhage, or bleeding into the brain, a CT scan can show evidence of this almost immediately after stroke symptoms appear. Hemorrhage is the primary reason for avoiding certain drug treatments for stroke, such as thrombolytic therapy, the only proven acute stroke therapy for ischemic stroke.
Thrombolytic therapy cannot be used until the doctor can confidently diagnose the patient as suffering from an ischemic stroke because this treatment might increase bleeding and could make a hemorrhagic stroke worse.