Clinical research in ischemic stroke can be simplified into two fields:

• Acute ischemic stroke
• Prevention of ischemic stroke

Acute ischemic stroke

An important characteristic of nerve cells in the brain is that they require permanent energy supply to function and survive. This energy can be obtained almost exclusively from oxygen and blood sugar only. Hence, a continuous supply of oxygen and sugar is only possible if the nerve cells in the brain are sufficiently supplied with blood. The nerve cells in the brain can tolerate an interruption of the blood supply only for a very short time. In the vast majority of cases, the cause of an ischemic stroke is an occlusion of an artery supplying the brain. Therefore, the most important therapeutic measure in the acute phase of ischemic stroke is to reopen the occluded artery as quickly as possible ("time is brain"). Clinical research in the field of acute ischemic stroke focuses on different stages in the acute setting of ischemic stroke:

• The prehospital and early hospital phase: In order to achieve the fastest possible reopening of the occluded artery, the suspicion of a stroke must already be raised outside the hospital and a fast and safe transport to a center specialized in stroke must take place. At best, initial diagnostic and therapeutic measures can already be taken on site and during transport. In the hospital, too, the procedures for confirming the diagnosis of ischemic stroke and initiating therapy must be precisely coordinated so as not to lose any time.
   
• Acute therapy of ischemic stroke: For the rapid reopening of the vessel occlusion (revascularization), two therapy options are available, which can also be combined: medication with a thrombus-dissolving drug and mechanical removal of the thrombus with a catheter. Basically, only those stroke victims can benefit from these therapies in whom the area of the brain supplied by the occluded vessel has not yet completely died off. On the other hand, the therapies can also lead to complications (especially cerebral hemorrhage), so that the therapy can cause more harm than good. With this in mind, it is important to identify those stroke victims who have a high probability of benefiting from revascularization therapies and a low probability of suffering complications.
   
• The monitoring phase: Regardless of whether revascularizing therapy has been given or not, all stroke patients should be hospitalized for at least 24-72 hours in a specialized monitoring unit (Stroke Unit). The aim of monitoring is to detect complications at an early stage, to optimally adjust vital parameters and risk factors, to identify the cause of the ischemic stroke and to initiate therapy to prevent stroke recurrence (see secondary stroke prevention).

Prevention of ischemic stroke

In the prevention of ischemic stroke, a distinction can be made between primary and secondary prevention.

• Primary prevention: the goal of primary prevention is to reduce the probability of occurrence of a first-time ischemic stroke. Primary prevention of ischemic stroke includes lifestyle modification, including healthy diet, weight loss, smoking cessation, and regular physical activity, and treatment of risk factors such as hypertension, diabetes mellitus, and lipid disorders; antiplatelet therapy in patients at high vascular risk; and anticoagulation for atrial fibrillation.
   
• Secondary prevention: The goal of secondary prevention is to reduce the likelihood of recurrence of ischemic stroke. In addition to the key elements of primary stroke prevention (lifestyle modification, treatment of risk factors), clarification of the cause of the stroke is very important. Depending on the cause of the ischemic stroke (e.g., changes in the large or small arteries supplying the brain, the heart, or blood clotting), specific therapeutic measures can be initiated.