Headache. Abstract image of a headache as a blast of light hitting a brain. The brain is shown as a magnetic resonance imaging (MRI) scan which has been projected onto a computed tomography (CT) scan of a head. Headaches are very common, and are generally caused by the expansion of blood vessels pushing against the membranes (meninges) surroun- ding the brain. They are not usually serious, and are only rarely indicative of an underlying disorder. Most headaches can be treated with rest and painkilling drugs. Alternatively, this could represent a stroke, or cerebrovascular accident (CVA). These occur when blood vessels in the brain burst or become blocked, and can be fatal.