Steven Karceski, MD WHAT DID THE AUTHORS DO? In their article, “Electrographic seizures and periodic discharges after intracerebral hemorrhage,” Dr. Claassen and colleagues discuss several important issues that affect people who have bleeding into the brain (Neurology 2007; 69:1356–1365). They used a retrospective review to study problems associated with bleeding within the brain. There are problems with this type of study. However, it is this kind of study that often leads to further research. In a retrospective study, the authors select a group of people with a particular problem or illness. For instance, the authors might look for a group of people who have migraines. They start carefully looking for problems that the group share. For instance, many people with migraine take pain medications. In a retrospective study, the use of pain medications would be something shared by a large number of these people. Two statements are possible. The first is that people who are in pain are more likely to take a pain medication. A second possibility is that the medication caused the headaches. Remember that the retrospective study only shows those things that a group of people have in common. It does not necessarily tell us whether the illness caused a problem or vice versa.