Does the direction of impact influence how the athlete presents following a sport-related concussion?

Background: Previous research has investigated the biomechanics of head injury including impact location as it relates to sport-related concussion (SRC). However, there is limited data investigating the potential association between the direction of impact and its influence on SRC outcomes. The purpose of this study was to investigate if impact direction influences athlete symptomology and video signs of SRC. Methods: Broadcast footage of 98 diagnosed concussions was reviewed from the 2017 and 2018 National Rugby League (NRL) seasons. All videos were coded by an experienced rater for the presence or absence of the 6 consensus signs of SRC (lying motionless, motor incoordination, impact seizure, tonic posturing, no protective action – floppy, blank/vacant look), and the direction of impact sustained by the athlete. Direction of impact was categorised as either being from the front (45° to the left or right from the sagittal plane), side (from 45-90° from the sagittal to coronal plane), behind (posterior to the coronal plane) or combined (athlete incurred more than one impact). Symptom number and severity scores were additionally retrieved from the day of game head injury assessment (HIA). Differences between groups for the variable of interest (i.e., direction of impact), were evaluated against the number of symptoms, severity of symptoms, and number of video signs using a Kruskal Wallis H analysis. Results: Of the 98 diagnosed concussions, 20 were struck from the front, 42 from the side, 9 from behind, 27 were combined. For the entire cohort, the mean number of video signs was 1.7 (SD 1.3), number of symptoms was 4.5 (SD 5.2) and symptom severity was 9.5 (SD 14.2). There were no significant differences between directions and number of video signs (H(3)=3.214, p=0.360), number of symptoms (H(3)=3.821, p=0.281) and symptom severity (H(3)=5.183, p=0.159). Discussion: Previous research has demonstrated the brain is subjected to varying strain based upon impact location and acceleration type (linear versus rotational). It has been postulated that athletes subjected to more strain, particularly from an impact that is not anticipated, may present differently to athletes who brace for impact. The findings of this study indicate that concussions can occur from any impact direction, and that this feature had minimal influence on the number of video signs or immediate symptomology of the athlete. Further research with larger sample sizes is needed to verify these results. Conflict of interest statement: Andrew Gardner, Ph.D. serves as a scientific advisor for hitIQ, Ltd. He has a clinical practice in neuropsychology involving individuals who have sustained sport-related concussion (including current and former athletes). He has been a contracted concussion consultant to Rugby Australia since July 2016. He has received travel funding or been reimbursed by professional sporting bodies, and commercial organisations for discussing or presenting sport-related concussion research at meetings, scientific conferences, workshops, and symposiums. Previous grant funding includes the NSW Sporting Injuries Committee, the Brain Foundation (Australia), an Australian-American Fulbright Commission Postdoctoral Award, a Hunter New England Local Health District, Research, Innovation and Partnerships Health Research & Translation Centre and Clinical Research Fellowship Scheme, and the Hunter Medical Research Institute (HMRI), supported by Jennie Thomas, and the HMRI, supported by Anne Greaves. All other authors acknowledge that they have no conflict of interest of relevance to the submission of this abstract.