What condition is characterized by a sudden onset of excessively high blood pressure?

The condition characterized by a sudden onset of excessively high blood pressure is a hypertensive crisis. This condition generally occurs when blood pressure rises rapidly and severely, often exceeding 180/120 mmHg. It can result in acute damage to organs such as the heart, brain, and kidneys, making it a medical emergency. Symptoms may include severe headache, chest pain, shortness of breath, or vision changes.

In contrast, autonomic dysreflexia is a condition that predominantly occurs in individuals with spinal cord injuries above the T6 level, resulting in an exaggerated response of the autonomic nervous system. While it can lead to significant hypertension, it is triggered by a noxious stimulus below the level of injury, such as a full bladder or bowel, rather than being characterized solely by its blood pressure elevation.

Orthostatic hypotension is characterized by a drop in blood pressure when a person changes positions, typically from sitting to standing, and does not relate to excessively high blood pressure. A cerebral vascular accident, or stroke, may involve changes in blood pressure but is defined by acute neurological deficits resulting from disrupted blood flow to the brain rather than a primary focus on hypertension.