A study published in JAMA Neurology demonstrated that ice hockey players with postconcussion syndrome (PCS) had higher levels of neurofilament light proteins and lower levels of amyloid β.
The objective of the study was “to determine whether persistent symptoms after mTBI are associated with brain injury as evaluated by cerebrospinal fluid biochemical markers for axonal damage and other aspects of central nervous system injury,” the study authors wrote.
To do this, they studied professional Swedish hockey players who had repeated mild traumatic brain injury, postconcussion symptoms for more than three months, and met criteria for PCS. The participants were matched with neurologically healthy controls.
Of the 16 players with PCS, nine had PCS symptoms for more than one year. The remaining seven returned to play within one year. Researchers, led by Pashtun Shahim, MD, PhD of the University of Gothenburg in Sweden, found significantly higher levels of neurofilament light proteins in the cerebrospinal fluid of players with PCS for more than one year as compared to players whose PCS resolved in one year and controls.
In addition, neurofilament light protein concentrations correlated with Rivermead Post Concussion Symptoms Questionnaire scores and lifetime concussion events. Finally, players with PCS had significantly lower amyloid β levels in the cerebrospinal fluid as compared to controls.
The results, elevated levels of neurofilament light protein and lower levels of amyloid β, indicate that there may be axonal white matter injury and amyloid deposition.
Amyloid β is the name for peptides, or short chains of amino acid monomers linked by peptide bonds, of 36 to 43 amino acids. Deposition of amyloid β is seen in the brains of patients with Alzheimer’s disease, which shares microscopic changes with the disease CTE, which is found in people with a history of repeated head trauma, such as athletes and military veterans.
Neurofilaments are composed of polypeptide chains and found in neurons. There are three subunits, with the neurofilament light protein having the smallest mass. In independent studies in 2015, increased levels of neurofilament light proteins were found to be associated with neurodegenerative disorders, particularly Alzheimer’s disease, and indicates injury to large-caliber myelinated axons in the white matter.
The study authors are hoping that “measurement of these biomarkers may be an objective tool to assess the degree of central nervous system injury in individuals with PCS,” they write.
The other motivation behind the study is “to distinguish individuals who are at risk of developing chronic traumatic encephalopathy.”
The only limitation of this study was its relatively modest sample size, with only 16 participants with PCS and 15 neurologically healthy controls.