Dr. Parikh is Fellow in Pediatric Neurology, Weill Cornell Medical College.
Dr. Kosofsky is Professor of Pediatrics and Neurology, Weill Cornell Medical College.

Dr. Parikh reports no financial relationships relevant to this field of study.
Dr. Kosofsky reports that he is a major stockholder of b2d2, a biotechnology company.

SYNOPSIS: In a prospective cohort study of pediatric patients, aged 7 to 21 years, diagnosed with concussion, salivary microRNAs were found to be a potential biomarker for predicting prolonged concussion symptoms.

SOURCE: Johnson JJ, Loeffert AC, Stokes J, et al. Association of salivary microRNA changes with prolonged concussion symptoms. JAMA Pediatr. Published online Nov. 20, 2017. doi:10.1001/jamapediatrics.2017.3884.

Concussions continue to confer a significant disease burden for children and adolescents, without adequate tools to diagnose or monitor symptomatology objectively. Many of the clinical tools currently used rely on subjective reporting of nonspecific symptoms, making it difficult to predict which patients will have persistence of symptoms and develop prolonged concussion symptoms (PCS).

MicroRNAs (miRNAs), which are small, noncoding RNAs that circulate in exosomes and microvesicles, have been considered ideal biomarkers because of their abundance and stability. In the past few years, a number of miRNA studies performed in adult patients with traumatic brain injury (TBI) have demonstrated variability of expression that correlated with the severity of their TBI. This is the first report of the pattern of miRNA expression in the pediatric TBI/concussion population.

This study enrolled 52 pediatric patients (age 7 to 21 years) who had been diagnosed with concussion (mTBI) within two weeks of injury in an outpatient setting. The symptom portion of the Standardized Concussion Assessment Tool (SCAT3) was administered to both patients and their parents at the time of enrollment and repeated at four weeks and, in more symptomatic cases, eight weeks following injury. Patients with SCAT3 scores
> 5 four weeks after injury were identified with PCS, and those with scores < 5 with acute concussion syndrome (ACS). Salivary miRNA collected from all participants at the time of enrollment was then extracted and sequenced.

Between the ACS (n = 22) and PCS (n = 30) groups, there were no significant differences with respect to demographic, medical, or concussion characteristics. Forty-two percent of the participants were females, with a mean age of 14 years. Most participants were enrolled within one week of their concussion. The most common mechanism was sports-related participation (42%), and 46% of the patients had previous concussions.

Of the 52 miRNA samples obtained, 15 miRNA concentrations were able to differentiate between ACS and PCS. Levels of five of those 15 miRNAs accurately identified patients in the PCS group with an accuracy rate of 85% (area under the curve = 0.856; 95% confidence interval, 0.82-0.89), a sensitivity of 80%, and a specificity of 75% for PCS status. Three miRNAs were associated with specific symptomatology four weeks after injury, including difficulties with memory (miR-320c-1), headaches (miR-629), and fatigue (let-7b-5p).

COMMENTARY

This is a seminal study, as it is the first of its kind to try to identify a biomarker in pediatric patients for predicting prolonged concussion symptoms. Using a verified biomarker would help to identify and stratify those patients most likely to have prolonged symptomology, to optimize their management early on with targeted therapy, and to serve as an objective measure to help monitor recovery and appropriate time periods for initiating return to play. Additionally, using saliva to extract miRNA is a unique and convenient tool in the pediatric population that could be used in a wide range of clinical and even school-based sports program settings.

From a mechanistic perspective, the particular miRNAs differentially induced in the PCS group point to the potential relevance of neurotrophin signaling via TRK and sortilin-1, implicating BDNF and its known role in brain injury and repair. Recent preclinical evidence (Giarratana et al. Society for Neuroscience 2017, abstract #140.03) has identified that a common polymorphism in the human BDNF gene (val -> met) increases the extent of brain injury following experimentally induced, cortical impact. Such findings not only reinforce the relevance of the current study, but suggest the possibility of achieving even greater predictive value of PCS using miRNA testing in combination with commonly available genetic testing (i.e., single nucleotide polymorphisms).

Because of the small sample size of this study, larger cohort studies will be required to validate the predictive nature of this set of miRNAs predictive of PCS in the pediatric population. Additionally, adjustments for potential confounding factors related to changes in concentrations of specific miRNAs due to interval from injury, genotype (see above), age, gender, medication use, and history of previous concussions may need to be considered. Ideally, this should be performed in conjunction with determining longitudinal miRNA concentrations as it relates to type of brain injury, as well as therapies such as graded exercise.

Overall, the use of miRNAs could be the start of identifying specific and targeted biomarkers to help prevent and modify concussion/TBI burden in pediatric patients as well as adults, which would be particularly beneficial in athletes. This study provides optimistic evidence for the evolution of better tools to assist in the diagnosis and management of concussion patients.