In this case the MRI showed the suspected cause, which was confirmed at post mortem. Other findings related to her history of hypertension were found, such as the atheroma in different vessels, and left ventricular hypertrophy. No source of an embolus was found elsewhere in the body, but the atheromatous changes to the basilar artery would have precipitated the aneurysm (ballooning of an artery) that killed her by weakening the muscle layer (media).
Strokes are caused either by infarction of part of the brain (where the affected area dies because its blood supply is blocked), or by bleeding into the brain (haemorrhage). Symptoms usually have a sudden onset, but may present in a progressive fashion over hours or days. Signs and symptoms vary depending on the artery in the brain that is affected, and the extent of collateral circulation.