Blood Test Shows Extent of Brain Injury After Stroke

Ischemic stroke is a medical emergency, yet clinicians can only observe brain injury through snapshots provided by CT or MRI scans. These images offer limited insight into how damage evolves over hours and days and are not always feasible to repeat. Unlike heart or kidney injury, which can be monitored using blood tests, the brain has lacked a reliable circulating marker of acute injury. Researchers have now identified a blood biomarker that reflects the extent of brain damage after stroke and predicts long-term patient outcomes.

Researchers at LMU University Hospital (Munich, Germany), in collaboration with international research partners, focused on developing a blood-based test capable of continuously tracking brain injury and treatment effects following ischemic stroke. They focused on brain-derived tau (BD-tau), a form of the tau protein originating specifically from the central nervous system. Measuring BD-tau in blood makes it possible to capture ongoing brain injury without relying solely on repeated imaging.

In the main study cohort, BD-tau levels were measured repeatedly from hospital admission through the first seven days after stroke. The researchers then validated their findings in two independent multicenter cohorts, including patients enrolled in a phase 3 clinical trial. Altogether, data from more than 1,200 stroke patients were analyzed, allowing the team to assess how BD-tau reflects injury severity, disease progression, and response to treatment over time.

BD-tau levels closely reflected the extent of brain injury. Early measurements taken within hours of symptom onset were associated with initial damage and predicted final infarct size. Rising BD-tau levels over the first 24 to 48 hours were linked to infarct growth and complications such as recurrent strokes. The study, published in Science Translational Medicine, demonstrated that BD-tau predicted functional outcomes at 90 days and even years later, performing as well as, or better than, imaging-based measures.

BD-tau also captured treatment effects. Levels rose less in patients who achieved successful vessel reopening after thrombectomy and were significantly lower in patients treated with the neuroprotective drug nerinetide compared with placebo. The researchers suggest that BD-tau could enable closer monitoring of disease trajectories, earlier detection of complications, and more efficient evaluation of new therapies. Future work will focus on defining reference thresholds and developing faster, point-of-care testing, with potential applications across other neurological conditions.

“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,” said Dr. Steffen Tiedt.

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