In memory of Nils Wahlgren (1947-2026)

Professor Nils Wahlgren was a visionary leader in stroke medicine and a pioneer whose work transformed acute stroke care across Europe and beyond. He founded the SITS International Stroke Thrombolysis Registry, creating a global platform that has shaped clinical practice and research for decades. As the leading investigator of the SITS-MOST study, he laid the scientific foundation for the approval of intravenous thrombolysis in acute ischemic stroke in Europe — a milestone that has benefited countless patients.

Nils Wahlgren also served as chairman of the Karolinska Stroke Update from 1996 until his retirement, fostering international collaboration and advancing knowledge in the field of stroke medicine. At Karolinska University Hospital, he was the driving force behind the establishment of the Hyperacute Stroke Triage (HASTA) system in the Stockholm region and a strong advocate for the implementation of endovascular treatment in stroke care. His vision, determination, and unwavering commitment have enabled us today to work in a field that is both scientifically pioneering and profoundly meaningful.

Beyond his remarkable professional achievements, Nils Wahlgren was a colleague, mentor, and friend to many. He meant a great deal to all of us at SITS, as well as to colleagues at Karolinska Institutet and Karolinska University Hospital, where many of us shared long and close professional and personal relationships with him.

We remember him with warmth, laughter, and gratitude — and with great pride in all that he accomplished during his lifetime. Nils Wahlgren's legacy will continue to inspire future generations of clinicians and researchers.

Our thoughts are especially with his family, whom we came to know through his vivid and loving stories. We extend our heartfelt condolences to them during this difficult time.

Niaz Ahmed on behalf of friends, colleagues, and researchers at Karolinska Institutet and Karolinska University Hospital