Introduction

A “mild traumatic brain injury” is an injury to the brain that occurs following a biomechanical insult to the head or body leading to neurological dysfunction. Neurological dysfunction can be manifested in a variety of signs (such as loss of consciousness, alteration of mental status immediately following the injury, amnesia, and/or other neurological signs) and symptoms (such as confusion, disorientation, headache, balance problems, dizziness, difficulty concentrating and/or emotional symptoms) with or without trauma-related changes on brain imaging. The symptoms and signs of mTBI/concussion should not be better accounted for by another condition/diagnosis or effects of drugs/alcohol/medications and should not meet criteria for more severe forms of TBI. Moderate and severe forms of TBI can be diagnosed when the conscious level is more severely impaired (loss of consciousness for more than 30 minutes, Glasgow Coma Score of less than 13) or the length of post-traumatic amnesia is longer than 24 hours.

The criteria for mTBI were revised by Delphi consensus in 2023 to improve clarity and aid clinical care²⁰. In brief, firstly, there should be a biomechanically plausible mechanism of injury. In addition, there should be one or more of the following: i) an acute physiological disruption of brain function as manifested by loss of consciousness, alteration in mental status, complete or partial amnesia following the event, or other neurological sign/s; ii) two or more acute symptoms (e.g. subjective altered mental status, physical, cognitive or emotional) and clinical (e.g. cognitive, balance, oculomotor, vestibular-oculomotor signs on examination) or laboratory findings (e.g. blood biomarker indicative of intracranial injury); and iii) neuroimaging evidence of TBI. Lastly, symptoms and signs must not be fully accounted for by an alternative diagnosis or a more severe form of TBI. The term “concussion” can be used interchangeably with mTBI when there is no structural injury on conventional CT or MRI brain^20,21. In these guidelines, we use the term mTBI/concussion to avoid confusion.

Any impact to the head causing injury is considered a “head injury” but does not necessarily mean there has been a brain injury. When communicating that an injury to the brain has occurred, we suggest refraining from using terms such as “head knocks”, “head dings”, “trivial head injury”, or “blow to the head” and that the terms “mild traumatic brain injury” or “concussion” are used instead.

“Physical activity” is any bodily movement produced by skeletal muscles that requires energy expenditure. Exercise is a form of physical activity that is planned, structured, and repetitive and aims to improve physical fitness. Sport refers to a human activity that involves physical exertion and skill as its primary focus, often involving competition or social participation.

In this document, a child is a person between 0 and 18 years. Elderly or old age includes individuals who are 65 years or older, except in Aboriginal and Torres Strait Islander people where old age is considered to be 50 years or older due to the decreased life expectancy in this population. While life expectancy among Māori is also lower than in the general Aotearoa New Zealand population³³, no age range has been specified as “elderly” in this group.

There are select communities and large geographical regions in Australia and Aotearoa New Zealand  where access to health care is more limited. The term “appropriately qualified health professional” is used to indicate a licensed health care professional (not necessarily a doctor) whose scope of practice, education, experience, training and accreditation are appropriate for the situation or condition of the patient who is the subject of the consultation or referral. These individuals have a wide range of professional backgrounds and include medical doctors, psychologists, allied health professionals, and indigenous health workers.

There were two topics in particular that produced extensive debate within the GDG. These were return to sport and chronic traumatic encephalopathy. Over the last year, there has been a shift internationally towards a minimum time away from sport. The recommendations from national bodies such as New Zealand Accident Compensation Corporation (ACC)³⁴, UK government (non-elite sports)³⁵, and sporting organisations such as World Rugby³⁶ were reviewed. The GDG also reviewed the protocols across the sporting codes in Australia and Aotearoa New Zealand, most of which did not have a common return to play’ strategy. The evidence guiding return to play decisions was reviewed noting that delaying return to play decreases the risk of repeat injury and improves recovery time but also the lack of evidence supporting optimal timing of return to play. The research demonstrating ongoing changes in brain microstructure even when the person has clinically recovered was also discussed including whether these changes were indication of ongoing recovery or compensatory changes. The GDG was unable to reach unanimous consensus. All agreed that return to play should be individualized. Most members were concerned about the variability in number days away from sport across the sporting codes, that they are not based on evidence, and the potential conflict between timing of return based on the next game day versus player health. The majority of members advised that the lack of a common protocol creates confusion in the community and endorsed a minimum time away from play. A few members did not agree with a minimum time away from sport, the danger that as a result players may not report concussions setting the field back, and that return should be based on the International Conference on Concussion in Sport 2023 alone.

To resolve this issue, a Delphi poll was conducted. In addition to minimum time away from play, the GDG was asked to consider if recommendations should differ between children and adults, all sports versus contact sport, and community versus elite sport. 87% agreed on a fixed time away from contact sport; 66% felt this should apply to all sports (including community sport, 75%); and 86% recommended 21 days away from play (as opposed to 14 or 28 days) in adults and children alike. All agreed that the graduated return to activity paths should be followed to guide recovery as an overriding principle. It was acknowledged that elite athletes were likely to have increased access to specialised medical care to guide recovery when compared to the general community. All agreed that increased community resources will be necessary to facilitate recovery of individuals with concussion/mTBI. This consensus was reached independently, before the recommendations of the Australian Institute of Sport (AIS)³⁷ were released.

Chronic Traumatic Encephalopathy

There is increasing pubic concern about the potential link between concussion/mTBI and neurodegenerative disease later in life. The GDG reviewed the evidence, including recent systemic reviews, about whether repetitive head injuries are associated with increased risk of dementia,  and neurological problems. As yet, there is no conclusive data to support this risk and so the GDG was unable to develop a recommendation around this. The GDG agreed that the focus of guidance should be on assessment, differential diagnoses and managing treatable symptoms such as mental health issues and practice points were created.