Stroke

Over 2,000 years ago, physicians described this condition in the Hippocratic Corpus and gave it the name apoplexia – a word that implies a sudden, violent blow. Treatment options were extremely limited: “It is impossible to cure a severe attack of apoplexy, and difficult to cure a mild one.” The celebrated Greek physician Galen therefore recommended a balanced diet in combination with running and sport – preventive measures that are just as applicable to reducing the risk of stroke today. Until the seventeenth century, it was assumed that strokes were caused by an imbalance in the mixture of blood, yellow bile, black bile, and phlegm – that is, the four humors described in the humoral theory that was developed in antiquity to explain the processes taking place in the human body.

Almost 85% of strokes are triggered by an “ischemic insult,” in which a blood clot blocks a vessel in the brain, interrupting the blood supply to certain areas of the organ. If, on the other hand, the condition is caused by a brain hemorrhage, physicians refer to it as hemorrhagic stroke. Given the fundamental differences in how these two forms are treated, it is vital to ascertain the type of stroke as quickly as possible. 

For a long time, external symptoms such as signs of paralysis were all that physicians had to go on when it came to making a diagnosis. With the discovery of X-rays on November 8, 1895, however, they were able to gain unprecedented insights into the bodies of living patients. Many diseases could now be diagnosed significantly faster and much more reliably, although imaging the brain presented a particular challenge. Our brain is very well protected, surrounded as it is by the skull, meninges, and cerebrospinal fluid – and this protective housing severely limited the quality of diagnostic images in the early days. The development of special devices and examination methods gradually paved the way for a clearer view of the brain and its vascular system, although the laborious and often protracted examinations were extremely unpleasant for patients. In the 1970s, the development of computed tomography (CT) led to a breakthrough in stroke diagnostics: For the first time, physicians could quickly and reliably discern whether they were dealing with a circulatory problem or a cerebral hemorrhage. The emergence of magnetic resonance imaging (MRI) and Doppler and duplex sonography allowed further information to be obtained about a stroke. But what use is the most accurate diagnosis unless it is accompanied by suitable treatment options? Until the mid-1990s, there was still no effective way of treating acute cases of stroke.

In the 1970s, research by the Belgian molecular biologist Désiré Collen marked the starting point for the development of a medicinal treatment for ischemic stroke. In his search for a way to dissolve blood clots, Collen developed a substance known as alteplase recombinant tissue plasminogen activator (rt-PA), which can dismantle the underlying framework of the clot (or “thrombus”) and therefore break it down. Since the mid-1990s, this drug has been used for the acute treatment of stroke in lysis therapy (from the Greek lúsis, “loosening”). Some 50–60% of vascular occlusions can be eliminated in this way, thereby restoring the blood supply to the affected area of the brain. Lysis therapy is not suitable for every patient, however, and must be administered within a 4.5-hour window after stroke onset. 
Thanks to pioneering work in the field of interventional radiology by physicians such as Werner Forssmann, Charles Dotter, and Andreas Grüntzig, lysis therapy is no longer the only treatment option available. Since approximately 2008, it has also been possible to treat vascular occlusions using mechanical thrombectomy, a technique in which physicians pass a catheter into the groin and through the carotid artery in order to reach a blood clot that is blocking a cerebral blood vessel. Using X-ray technology to monitor the procedure, the physicians can then remove the clot using a “stent retriever” (a basket-like wire mesh that travels inside the catheter) or a special aspiration catheter (a sort of tiny vacuum cleaner). Mechanical thrombectomy gives physicians a window of 24 hours between the onset and treatment of stroke, and therefore more time than is the case with lysis. Despite this, and although the two treatments can also be combined, the maxim “time is brain” always applies. The sooner a patient is treated following the onset of symptoms, the greater chance they have of avoiding lasting impairment.

Over the last 30 years, rapid advances in diagnosis and treatment options have played a key part in reducing the mortality rate after stroke. Swift treatment and optimized workflows can considerably reduce the impact of the condition, but it is still the second most common cause of death worldwide. Therefore work will also continue with a view to improving treatment options and promoting preventive measures, in the future. Mechanical thrombectomy in particular is one promising approach. Although there are still relatively few experts who can perform this procedure, stroke patients around the world could benefit from the technique thanks to artificial intelligence and robot-assisted technology in the future.