Brain aneurysms are abnormal bulges in the walls of arteries in the brain. They occur where the artery walls are weak, and blood pressure causes the sides of the walls to balloon out. People with brain aneurysms, especially if they are small, often have no symptoms if they are not ruptured and are not leaking. Sometimes brain aneurysms press against brain tissue and nerves, causing dilated pupils, pain above and behind the eye, eyelids that droop and weakness, numbness or paralysis of one side of the face. Brain aneurysms can be classified by shape, size and their condition.
Shape
An aneurysm is classified as a saccular aneurysm if it has a rounded shape like a sac or pouch. These pouch-like aneurysms are attached by a neck or stem to the wall of an artery. They are also called berry aneurysms because of their shape. Aneurysms are classified as lateral aneurysms when they appear as a bulge on one wall of the blood vessel. Fusiform aneurysms are aneurysms that bulge out on all of the blood vessels walls.
Size
When an aneurysm has a diameter smaller than 11mm, it is referred to as a small aneurysm. This is approximately the size of a pencil eraser. When an aneurysm has a diameter that is between 11 and 25mm, it is referred to as a larger aneurysm. This is approximately the width of a dime. Aneurysms are called giant aneurysms when they have diameters larger than 25mm, or approximately the width of a quarter.
Condition
Brain aneurysms that are not leaking or ruptured are called unruptured aneurysms. When an aneurysm leaks a small amount of blood, it is referred to as a leaking aneurysm. According to the Mayo Clinic, a leaking aneurysm is likely to cause only a sudden headache that is very severe. The bleeding that occurs from a leaking aneurysm is usually followed by a rupture that is more severe. A ruptured aneurysm is a life-threatening situation. It can be accompanied by nausea, drowsiness, a stiff neck, a severe headache, vomiting, confusion and dizziness. Seek immediate medical attention if these symptoms occur.
