A cerebral aneurysm is a weak or thin spot on a blood vessel in the brain that balloons out and fills with blood. An aneurysm can press on a nerve or surrounding tissue, and also leak or burst, which lets blood spill into surrounding tissues (called a hemorrhage). Cerebral aneurysms can occur at any age, although they are more common in adults than in children and are slightly more common in women than in men. The signs and symptoms of an unruptured cerebral aneurysm will partly depend on its size and rate of growth. For example, a small, unchanging aneurysm will generally produce no symptoms, whereas a larger aneurysm that is steadily growing may produce symptoms such as headache, numbness, loss of feeling in the face or problems with the eyes. Immediately after an aneurysm ruptures, an individual may experience such symptoms as a sudden and unusually severe headache, nausea, vision impairment, vomiting, and loss of consciousness.