No one knows exactly how cocaine causes strokes and blood supply cutoff in the brain.
Cocaine use causes a brief, sudden wave of high blood pressure.
This comes partly from the sudden shrinkage of blood vessels all over the body and partly from a sudden increase in the heart rate. Cocaine has also been shown to slow the conversion of blood nutrients to energy within the brain. If the flow of blood to an area of the brain drops below a certain point, damage to brain tissue results. Some evidence suggests that cocaine causes the walls of blood vessels in the brain to become weak and thin in places, allowing them to be more easily broken. The exact reasons for cocaine damage to brain tissue are still being worked out by researchers.