, new research suggests. “Reliable detection of this biomarker at very early time points may allow for prompt TBI detection and therefore intervention,” said study investigator Rachel Elizabeth Thomas, MD, PhD, a neurology resident at the University of Pennsylvania, Philadelphia, while presenting study findings at the American Academy of Neurology’s 2021 annual meeting.
“The level reflects the degree of severity and provides some degree of prognostic information,” she added.
A specific marker of acute injury?
Von Willebrand factor is a glycoprotein released in the endothelium in response to local trauma. It plays a part in hemostasis and inflammation and is an indicator of traumatic microvascular injury. Research has shown that it is a biomarker of cerebrovascular pathology. In addition, increased expression of the factor is associated with vascular and neurodegenerative dementia.
The researchers examined whether von Willebrand factor is a biomarker of mild, repetitive TBI. They measured plasma levels of von Willebrand factor in 17 professional boxers before and after boxing bouts.
Eligible participants were between the ages of 18 and 35 years. They had a score of greater than or equal to 1 on the Rivermead Post-Concussion Symptoms Questionnaire (RPQ-3), had competed in at least three 3-minute bouts, and had withstood 25 or more blows to the head.
The investigators compared the plasma levels of von Willebrand factor of the boxers with those of 42 patients who presented to the University of Pennsylvania Trauma Center with TBI and with those of 23 uninjured control persons.
There was no significant difference in plasma levels of von Willebrand factor between boxers before the bout (13.15 µg/mL) and the control persons (6.16 µg/mL). Among the boxers, levels of von Willebrand factor increased by a factor of 1.8 within 30 minutes after bouts, compared with the levels among the control persons. The mean post-bout von Willebrand factor level was 25.09 µg/mL.
“Von Willebrand factor may be more specific for acute injuries, given that it does not seem to stay chronically elevated,” said Dr. Thomas.
In addition, the researchers found a significant positive correlation (r = 0.51; P = .03) between the fold change in plasma von Willebrand factor levels and the number of blows to the head that the athletes sustained.
They also found a significant positive correlation between fold change in von Willebrand factor and RPQ-3 score (r = 0.69; P = .002). These objective and subjective data suggest that levels of von Willebrand factor reflect injury severity, said Dr. Thomas.
Among patients hospitalized with TBI, levels of von Willebrand factor were significantly higher than among control persons (73.2 µg/mL vs. 40.8 µg/mL; P < .0009). The investigators found a linear correlation between plasma von Willebrand factor level and RPQ-3 score (r = 0.24) that was not statistically significant.
Levels of von Willebrand factor among patients hospitalized with TBI were higher on average and demonstrated a greater degree of variability than the levels among boxers immediately after a bout.
“This is not unexpected, given that this group represents a more heterogeneous population with varied forms of acute blunt injury, as compared to the boxers, who have undergone relatively repetitive, milder trauma,” Dr. Thomas said.
The traditional biomarkers of neurotrauma reflect neuronal and glial injury, whereas von Willebrand factor is an indicator of vascular trauma.
“Although on its own, von Willebrand factor is not specific to intracranial vascular injury, paired together with markers such as neurofilament light, GFAP [glial fibrillary acidic protein], and tau, it could be utilized to identify TBI-associated microvascular injury and thus delineate between specific TBI endophenotypes,” said Dr. Thomas. It could distinguish, for example, predominantly neuronal injury from predominantly vascular injury.
Because von Willebrand factor plays a role in the neurovascular unit and is a marker of microvascular injury, the investigators intend to pair measurements of plasma von Willebrand factor with advanced imaging techniques to evaluate cerebral blood flow or cerebrovascular reactivity. Such a study could help determine whether von Willebrand factor levels correlate with the degree of vascular injury and cerebrovascular dysregulation.