New blood test shows extent of brain injury after stroke – and reveals treatment effects, finds research

In ischemic stroke, part of the brain is no longer adequately supplied with blood. Clinical decisions for people who suddenly develop paralyses or speech problems are currently based largely on CT or MRI scans. However, in the acute phase, imaging typically provides only point-in-time information. Repeated scans are logistically demanding, not always feasible, and imaging measures often reflect later recovery only to a limited extent. While acute injury to the heart or kidneys can often be monitored with blood tests, the brain has so far lacked such a marker. “In stroke care, we currently face the problem that we cannot continuously track how brain injury evolves over time – and this limits our treatment decisions,” says PD Dr. Dr. Steffen Tiedt, scientist at the Institute for Stroke and Dementia Research (ISD) and attending physician in the Stroke Unit at LMU University Hospital’s Department of Neurology.

To address this need, he initiated a study at LMU University Hospital in 2013 aimed at developing a reliable blood test that can continuously reflect brain injury and make treatment effects measurable. His team identified brain-derived tau (BD-tau) as a blood biomarker that captures tau protein originating from the central nervous system – enabling exactly that. In the study cohort established at LMU University Hospital, BD-tau was measured repeatedly from hospital admission through day 7. The findings were additionally validated in two independent multicenter cohorts, including a biomarker-based analysis within a phase 3 clinical trial. In total, data from more than 1,200 stroke patients were included in the analyses.

Promising marker for tracking brain injury over time

Blood levels of BD-tau reflected the extent of brain injury: Early levels measured within hours after symptom onset were associated with the initial degree of damage and predicted final infarct size. BD-tau also captured disease dynamics – larger increases during the first 24 to 48 hours were linked to infarct growth, and elevated levels were observed in complications such as recurrent events. Moreover, BD-tau was a strong predictor of recovery, forecasting functional outcome at 90 days and beyond at least as well as, or better than, other blood biomarkers and even imaging-based infarct volumes. Finally, BD-tau revealed treatment effects: After a thrombectomy, BD-tau rose less when the vessel was fully reopened, and in a randomized study the rise in BD-tau was markedly smaller with the neuroprotectant nerinetide than with placebo. “We don’t just need a picture from the beginning of a stroke – we need a way to follow the course of brain injury over time. BD-tau could become a kind of ‘troponin for the brain’ – an objective blood marker that makes progression and treatment effects measurable,” says Tiedt.

The researcher emphasizes that further studies are needed – for example, to define reference ranges and thresholds and to enable faster measurement of BD-tau in the future (ideally as a point-of-care test). In the long term, such a blood test could help clinicians monitor disease trajectories more closely, detect complications earlier, and evaluate new therapies more efficiently in clinical trials. In addition, BD-tau could help objectively and rapidly assess brain injury in other neurological diseases.

Reference:

Naomi Vlegels et al. ,Brain-derived tau for monitoring brain injury in acute ischemic stroke.Sci. Transl. Med.18,eadz1280(2026).DOI:10.1126/scitranslmed.adz1280