Stroke - is when a blood vessel of the brain becomes blocked, so that blood cannot carry oxygen to the cells beyond the blockage. If the blockage clears before permanent damage has occurred it is sometimes called a "mini-stroke" (or transient ischemic attack; "TIA" for short). If the blockage stays for long enough, brain cells begin to die, leading to permanent damage. Depending upon which cells in the brain die, patients may have difficulty moving arms or legs, talking or may even go into a coma. If a stroke is treated within a few hours and there is no bleeding into the brain, "clot-busting" drugs, like "TPA," can be used to dissolve the blockage. However, more often patients don't get to the hospital in time and once the cells have died, there is nothing that can bring the dead brain cells back to life. Aspirin and blood thinners may help to prevent more strokes, but can't bring back the brain cells that have already died. With time, some functions may return, but often patients with strokes have permanent disabilities.
Encephalopathy - is a term used to describe when patients aren't thinking clearly or are confused. An infection or other illness that directly involves the brain may cause encephalopathy. Many illnesses that cause critical illness can cause encephalopathy without directly involving the brain. Encephalopathy is quite common, especially in older patients who get critically ill for any reason. In addition, medicines used to help the patient may also cause encephalopathy.