15. There are different kinds of "normal" strokes ...
A stroke is a loss of blood flow to the brain and can be caused by a vascular occlusion ischemia (embolotic or thrombic) or by aneurysm (burst blood vessel that causes blood to pool into the brain) -- the kind that killed Arafat.
Aneurysms are very common and can occur suddenly wherever the arteries are weakened or distorted -- there are many people walking around today with undiagnosed weakened arteries caused by arteriosclerosis, blunt trauma, or infection. Unless the site of the arterial weakening is already forming a saccular aneurysm it would be undetectable, even with an MRI.
The only way to determine the specific cause of an aneurysm is by autopsy of the damaged tissue for signs of infection or pre-aneurysm trauma. Arafat's wife and the PA Leadership refused to allow an autopsy so it would be impossible to determine the cause of the aneurysm.
Infections from one part of the body, if not completely cured, can (and frequently do) travel via the blood stream to other parts of the body where they can lay dormant and cause later problems. This is one reason why doctors always stress completing your course of antibiotics, even if your symptoms are gone. It is common for an infection from decades previous to cause arterial damage that leads to aneurysm so there isn't even a way to specifically determine what infection caused the arterial damage even with an autopsy.
People die of brain aneurysms every single day, the Brain Aneurysm Society(1) claims there is a brain aneurysm rupturing every 18 minutes in the US alone -- there is no conspiracy.