What it is: A weak spot on a blood vessel in your brain that balloons out and fills with blood. It may leak or burst, causing severe brain damage or even death. One in 50 people is at risk.
How it feels: Sufferers usually have a sudden onset of severe headaches, double vision, neck stiffness, nausea, vomiting, pain above and behind the eye, and/or a change in mental functioning or awareness.
Why it happens: Most aneurysms are due to an artery-wall abnormality that youre born with or are prompted by trauma or injury to the head, vascular disease, or high blood pressure. The problem is thought to run in families.
What it is: Most strokes occur when a blood clot blocks an artery or a blood vessel, interrupting blood flow to an area of the brain over a period of minutes or hours, causing brain cells to die.
How it feels: Often there is sudden loss of speech, numbness or weakness of the face or on one side of the body, vision problems, and dizziness. Headaches are a possible, although less common, symptom.
Why it happens: Strokes, the third-leading cause of death in the United States, usually happen to older people because the disorder is associated with hardening of the arteries, which occurs more as you age. But recent research suggests that the risks are climbing fast for middle-aged women, possibly because of weight gain.
What it is: Abnormal cells grow into a mass that interferes with brain activity. About 22,000 Americans are diagnosed with cancerous brain tumors every year.
How it feels: Common symptoms are frequent headaches, especially ones that wake you up at night or in the morning, blurry vision, nausea and/or vomiting, personality or cognitive changes, and seizures.
Why it happens: The causes are unknown.
What it is: A blow or bump anywhere on the head. As many as 10% of these injuries are fatal, and almost 550,000 people are hospitalized annually. The injury often leads to fluid (water or blood) pooling near or in the brain, which can create a buildup of dangerous pressure.
How it feels: If youre conscious, you may feel OK at first or feel woozy and lethargic, have trouble with short-term memory, be unaware of your surroundings, or find communicating difficult. You may have a mild-to-severe headache.
Why it happens: Car accidents, falls, and sports-related injuries (like what happened to Natasha Richardson) are among the most common causes.