Use of mobile stroke units improves clinical outcomes

February 11, 2021

STEMOs (Stroke-Einsatz-Mobile) have been serving Berlin for ten years. The specialized stroke emergency response vehicles allow physicians to start treating stroke patients before they reach hospital. For the first time, a team of researchers from Charité - Universitätsmedizin Berlin has been able to show that the dispatch of mobile stroke units is linked to improved clinical outcomes. The researchers' findings, which show that patients for whom STEMOs were dispatched were more likely to survive without long-term disability, have been published in JAMA*.

The phrase 'time is brain' emphasizes a fundamental principle from emergency medicine, namely that after stroke, every minute counts. Without treatment, the brain will lose two million brain cells every minute. When dealing with stroke caused by an arterial blockage in the brain, prompt dissolution of the blood clot - known as thrombolysis - is essential.

Ten years ago, a team led by Prof. Dr. Heinrich Audebert (Center for Stroke Research Berlin (CSB) and Charité's Department of Neurology and Experimental Neurology) set itself the aim of further reducing time to treatment by bringing the necessary diagnostic and treatment procedures to the patient rather than the other way around. They did so with great success: Berlin's first purpose-built mobile stroke unit, developed in conjunction with the Berlin Fire Department and MEYTEC GmbH, was launched in February 2011. Following years of research, the team was able to confirm that STEMO-based stroke treatment is safe and, more importantly, reduces time to treatment. Today, the Berlin Fire Department operates three STEMO vehicles. As part of a collaboration between Charité, Vivantes - Netzwerk für Gesundheit GmbH and Unfallkrankenhaus Berlin, these vehicles cover most of the Berlin area. Data from the now-published B_PROUD study show that dispatch of STEMO mobile stroke units is associated with improved outcomes in patients with stroke.

"In our study, dispatch of a mobile stroke unit was linked to increased survival and reduced risk of disability," says Prof. Audebert. He adds: "The relative odds of these patients having significant disabilities three months after stroke was 29 percent lower than in patients cared for by the conventional emergency medical services. STEMO dispatch therefore results in significantly more stroke patients returning to an independent life after stroke." A selection of voices and opinions on the STEMO initiative - from Michael Müller (Governing Mayor of Berlin and Senator for Higher Education and Research), Prof. Dr. Heyo K. Kroemer (Chief Executive Officer of Charité), as well as the initiative's partners and other supporters - can be found here.

Under the leadership of Prof. Audebert and the study's first author, Prof. Dr. Dr. Martin Ebinger (Medical Director of the Medical Park Humboldtmühle Rehabilitation Hospital), the team studied cases of stroke emergencies which occurred in Berlin between February 2017 and May 2019. Whether a STEMO mobile stroke unit was dispatched was effectively decided by chance: if one was available within the relevant area, it was dispatched at the same time as the conventional ambulance, enabling the patient to receive treatment before their arrival in hospital. A STEMO mobile stroke unit was dispatched in 749 of a total of 1,543 cases analyzed as part of the study (49 percent). If no STEMO was available at the time of the emergency call, only a conventional ambulance was dispatched to ensure transport to a specialist hospital. In 794 cases (51 percent), patients were cared for within the conventional emergency medical system. Using a standardized protocol, the researchers then determined survival at three months post-stroke and the extent of any neurological impairment affecting the patients.

Results from their comparison of the STEMO and control groups were unequivocal. Not only did a greater number of STEMO patients receive thrombolysis (60 percent vs 48 percent in the control group), they received this treatment on average 20 minutes earlier than controls. After three months, approximately 7 percent of patients in the STEMO dispatch group had died. This figure compared with 9 percent in the conventional ambulance group. Similarly, while approximately 51 percent of patients in the STEMO group reported no stroke-related impairments in day-to-day functioning, the corresponding figure in the control group was only 42 percent. Patients in the STEMO group also scored significantly better on quality-of-life measures.
*Ebinger M et al., Association Between Dispatch of Mobile Stroke Units and Functional Outcomes Among Patients With Acute Ischemic Stroke in Berlin. JAMA 2021;325(5):454-466. doi: 10.1001/jama.2020.26345


STEMOs are special purpose emergency response vehicles which have been designed to evaluate and treat patients with stroke. Fitted with a CT scanner and a small laboratory, these mobile stroke units are manned by a neurologist who is supported by a specially trained emergency response team. STEMOs aim to bring the hospital to the patient. Following the introduction of the first mobile stroke unit in the Saarland area of Germany, the launch of the first STEMO in 2011 made Berlin the first metropolitan city to be served by a specially adapted emergency vehicle with CT scanner and miniature laboratory. Organized by and forming an integral part of the Berlin Fire Department, Berlin's STEMOs use teleradiology solutions to share information with the participating hospitals' (neuro)radiology departments. Following the launch of Berlin's first STEMO mobile stroke unit, the initiative was tested for feasibility, safety, and improvements in time to treatment. Based on pilot data, the STEMO service currently being delivered by Charité, Unfallkrankenhaus Berlin and Vivantes Klinikum Neukölln was adopted for further evaluation as a provisional standard care concept. Categorization as 'provisional standard care concept' carries an obligation to study clinical outcomes. The B_PROUD study was designed to meet this obligation. More than 20 similar projects are currently active worldwide, including in New York, Los Angeles, Melbourne and Bangkok. Berlin is the first city in the world to enjoy multiple mobile stroke units providing near comprehensive cover to its citizens. Berlin's three STEMO units are dispatched approximately 6,000 times a year.


In Germany, approximately 250,000 people are affected by stroke every year, around 12,000 of them in Berlin. Stroke remains one of the most common causes of death and, left untreated, will cause lasting disability in more than half of all patients affected. Thrombolysis can only be administered to patients with ischemic stroke, i.e. stroke caused by a blockage in an artery that supplies the brain. It is not suitable for patients with hemorrhaging stroke. The use of diagnostic techniques capable of distinguishing between these two types of stroke is therefore essential.


The B_PROUD (Berlin Pre-hospital Or Usual Delivery of stroke care) study was a prospective, controlled interventional trial with outcome assessed and evaluated by blinded assessors. The random allocation of patients to intervention groups (randomization) was not possible. Allocation to either the intervention or control group was determined by the availability of the STEMO mobile stroke unit. The degree of neurological impairment at three months post-stroke was determined using the modified Rankin Scale. Quality of life was measured using the EQ-5D questionnaire.

Charité - Universitätsmedizin Berlin

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