What is the primary cause of most strokes?

The primary cause of most strokes is indeed the blockage of an artery supplying part of the brain. This condition is often referred to as an ischemic stroke, which accounts for approximately 87% of all strokes. The blockage typically results from a blood clot that forms in an artery or from a buildup of fatty deposits (atherosclerosis) that narrows the arteries. When blood flow to a part of the brain is reduced or completely cut off, brain cells begin to die, leading to the neurological deficits associated with a stroke.

While ruptured cerebral arteries and spasms can indeed cause strokes, they are less common. A ruptured artery due to an aneurysm, for example, causes a hemorrhagic stroke, which is a different category and occurs in a smaller percentage of cases. Hypertension can also lead to ruptured blood vessels but is not the most common cause. Similarly, arterial spasms can lead to transient ischemic attacks (TIAs) but are not typically the main cause of strokes either. Thus, blockage of an artery supplying part of the brain is the correct choice, as it accurately reflects the mechanics underlying the majority of strokes experienced by patients.