VISSER, K., M. Koggel, J. Blaauw, H.J.v.d. Horn, B. Jacobs, and J.v.d. Naalt. Blood based biomarkers of inflammation in mild traumatic brain injury: A systematic review. NEUROSCI BIOBEHAV REV XX(X) XXX-XXX, 2021. - Inflammation is an important secondary physiological response to traumatic brain injury (TBI). Most of the current knowledge on this response is derived from research in moderate and severe TBI. In this systematic review we summarize the literature on clinical studies measuring blood based inflammatory markers following mild traumatic brain injury (mTBI) and identify the value of inflammatory markers as biomarkers. Twenty-three studies were included. This review suggests a distinct systemic inflammatory response following mTBI, quantifiable within 6 h up to 12 months post-injury. Interleukin-6 is the most promising biomarker for the clinical diagnosis of brain injury while interleukin-10 is a potential candidate for triaging CT scans. The diagnostic and prognostic utility of inflammatory markers may be more fully appreciated as a component of a panel of biomarkers. However, discrepancies in study design, analysis and reporting make it difficult to draw any definite conclusions. For the same reasons, a meta-analysis was not possible. We provide recommendations to follow standardized methodologies to allow for reproducibility of results in future studies.

Traumatic brain injury (TBI) has been described to be man’s most complex disease, in man’s most complex organ. Despite this vast complexity, variability, and individuality, we still classify the severity of TBI based on non-specific, often unreliable, and pathophysiologically poorly understood measures. Current classifications are primarily based on clinical evaluations, which are non-specific and poorly predictive of long-term disability. Brain imaging results have also been used, yet there are multiple ways of doing brain imaging, at different timepoints in this very dynamic injury. Severity itself is a vague concept. All prediction models based on combining variables that can be assessed during the acute phase have reached only modest predictive values for later outcome. Yet, these early labels of severity often determine how the patient is treated by the healthcare system at large. This opinion paper examines the problems and provides caveats regarding the use of current severity labels and the many practical and scientific issues that arise from doing so. The objective of this paper is to show the causes and consequences of current practice and propose a new approach based on risk classification. A new approach based on multimodal quantifiable data (including imaging and biomarkers) and risk-labels would be of benefit both for the patients and for TBI clinical research and should be a priority for international efforts in the field.

Objective: To determine the prognosis of adult patients with traumatic brain injury (TBI) and diffuse axonal injury (DAI). Methods: Online search (PubMed, Embase and Ovid Science Direct) of articles providing information about outcome in (1) patients with DAI in general, (2) DAI vs. non-DAI, (3) related to magnetic resonance imaging (MRI) classification and (4) related to lesion location/load. A reference check and quality assessment were performed. Results: A total of 32 articles were included. TBI patients with DAI had a favourable outcome in 62%. The risk of unfavourable outcome in TBI with DAI was three times higher than in TBI without DAI. Odds ratio (OR) for unfavourable outcome was 2.9 per increase of DAI grade on MRI. Lesions located in the corpus callosum were associated with an unfavourable outcome. Other specific lesion locations and lesions count showed inconsistent results regarding outcome. Lesion volume was predictive for outcome only on apparent diffusion coefficient and fluid attenuation inversion recovery MRI sequences. Conclusions: Presence of DAI on MRI in patients with TBI results in a higher chance of unfavourable outcome. With MRI grading, OR for unfavourable outcome increases threefold with every grade. Lesions in the corpus callosum in particular are associated with an unfavourable outcome.

Although most patients recover fully following mild traumatic brain injury (mTBI), a minority (15–25%) of all patients develop persistent post-traumatic complaints (PTC) that interfere with the resumption of previous activities. An early identification of patients who are at risk for PTC is currently performed by measuring the number of complaints in the acute phase. However, only part of this group will actually develop persisting complaints, stressing the need for studies on additional risk factors. This study aimed to compare this group of patients with many complaints with patients with few and no complaints to identify potential additional discriminating characteristics and to evaluate which of these factors have the most predictive value for being at risk. We evaluated coping style, presence of psychiatric history, injury characteristics, mood-related symptoms, and post-traumatic stress. We included 820 patients (Glasgow Coma Scale [GCS] score 13–15) admitted to three level-1 trauma centers as part of the UPFRONT-study. At 2 weeks after injury, 60% reported three or more complaints (PTC-high), 25% reported few complaints (PTC-low), and 15% reported no complaints (PTC-zero). Results showed that PTC-high consisted of more females (78% vs. 73% and 52%, p < 0.001), were more likely to have a psychiatric history (7% vs. 2% and 5%), and had a higher number of reported depression (22% vs. 6% and 3%, p < 0.001), anxiety (25% vs. 7% and 5%), and post-traumatic stress (37% vs. 27% and 19%, p < 0.001) than the PTC-low and PTC-zero groups. We conclude that in addition to reported complaints, psychological factors such as coping style, depression, anxiety, and post-traumatic stress symptoms had the highest predictive value and should be taken into account in the identification of at-risk patients for future treatment studies.