Mild TBI - What it is & Why it matters

Every year in the UK approximately 1.4 million people suffer a traumatic brain injury (TBI) and 80% are diagnosed as mild in severity (NICE Guidelines, 2019). Mild TBI is a type of acquired brain injury in which the definitions and diagnostic characteristics have varied over time. There is a common and concise definition stated in the literature as an ‘acute neurophysiological brain dysfunction resulting from impact contact forces or sudden acceleration/deceleration causing transient alteration of consciousness or amnesia’ (ACRM, 1993). However, despite significant technological advancement and increased interest and investment in clinical research, including elite sport and the military, practitioners remain conflicted by multiple definitions, lack of diagnostic certainty and poor clarity regarding management approaches.

Classification of mild TBI

Change in the patient’s level of consciousness, as measured by the Glasgow Coma Scale (GCS)?has generally been considered a ‘defining’ feature of mild TBI.??Whilst a minimum loss of consciousness of 0-30 minutes was considered necessary (ACRM, 1993), the WHO Collaborating Centre for Neurotrauma Taskforce recommended the removal of 30 minutes, deeming it restrictive and unrealistic for patients to be observed by healthcare professionals within this time frame of the injury (Carroll et al, 2004).??Subsequent research led to the inclusion of both level of consciousness and post-traumatic amnesia in the ‘definition’ of mild TBI (Silverberg et al, 2021).

In recent years the Mayo classification system has been preferred by clinicians; the system was developed to address the issue of the unreliability of some TBI severity indicators and the frequency of missing documentation in medical records. It outlines three types of TBI based on severity from ‘possible TBI’, to ‘probable mild TBI’ and ‘definite moderate-severe TBI’.??The Mayo Classification system is generally preferred by clinicians as it reflects clinical knowledge and references multiple clinical indicators rather than GCS alone.??However, its utility in terms of understanding patients with ‘mild’ TBI has remained limited.

A group of clinician-scientists with expertise in mild TBI answered a survey on their professional opinions on several matters relating to the definition and diagnosis of mild TBI. The results demonstrated agreement that observable signs and acute symptoms were more diagnostically important than subjective symptom complaints. Suggestions were made that a revised definition should consider distinguishing between ‘objective and subjective’ symptoms, with more weight for observable signs (Silverberg et al, 2021).

From Concussion to Clarity??

Following a TBI, many people experience ‘post-concussive’ symptoms (PCS) including headaches, dizziness, nausea, irritability and cognitive changes, all of which can significantly affect their daily life. Typically, these symptoms will resolve within the hours, days and weeks post-injury, however, in a small percentage of people (10-25%) these difficulties persist (Polinder et al, 2018), with the ‘constellation’ of symptoms leading some to advocate a ‘post-concussion syndrome’ (Hiploylee et al, 2016).

Notably, there is inconsistent use of the term “concussion” and various definitions employed in the literature and the symptoms experienced after a ‘mild’ head injury have eluded diagnostic clarity. Reported symptoms including headaches/migraine, irritability and emotional changes are similar to those experienced across the general population, whilst anxiety, depression, anxiety/post-traumatic stress and vestibular disorder overlap with other clinical conditions.??Commonly occurring symptoms might therefore be misattributed to brain trauma, confounding diagnosis and leading to patients receiving conflicting or confusing information and advice.??It has been proposed that referring to patients’ self-reported experiences as ‘complaints’ rather than ‘symptoms’ following injury could assist, reducing patient anxiety and the likelihood of reinforcing maladaptive beliefs and attributions.

Some researchers have therefore proposed abandoning the term ‘concussion’; Sharp and Jenkins (2015) suggested that alternatively, healthcare professionals should first classify the severity of TBI before attempting to precisely diagnose the underlying cause(s) of post traumatic symptoms. Ruff (2005) introduced the term ‘complicated’ mTBI in reference to patients that often meet the criteria for ‘mild’ TBI but show positive findings on imaging such as subarachnoid haemorrhage or small contusions associated with their symptoms. However, this term is not frequently used clinically despite support for its use in the literature.?

More recently, Baxendale et al (2019) have also advocated a change in terminology, highlighting the poor correlation between classification of brain injury severity and neuropsychological outcomes. The latter is often better explained in terms of an ‘interplay’ between premorbid factors, underlying structural damage, ‘neuropsychological reserve’ and psycho-social factors. The term ‘post-traumatic syndrome’ was considered to have greater utility.??

New terminology and new opportunities

Whilst the evolution of classification systems has reflected the growth of understanding of traumatic brain injury, their clinical utility for patients following ‘mild’ head injury has remained limited.??Indeed, the lack of consensus regarding diagnostic criteria and the non-specificity of symptoms has meant that clinical professionals and researcher have been as confused by concussion as some of the patients they have been studying.??The lack of clarity has been mirrored in the poor understanding of outcomes, with an increased appreciation of the multi-factorial aspects of mild-TBI presentations and the relevance of a bio-psycho-social models.??The need to reflect these developments in clinical thinking across health care professionals remains a key challenge which will need greater emphasis if the care, management and treatment of this patient group is to improve.????

Article by

Caitlin Thompson, Assistant Psychologist & Dr Richard Maddicks, Consultant Clinical Neuropsychologist

References?

NICE. Head Injury—triage, assessment, investigation, and early management of head injury in children, young people and adults. NICE clinical guideline 176. London: National Institute for Health and Care Excellence, 2014

American Congress of Rehabilitation Medicine, Brain Injury Interdisciplinary Special Interest Group, Disorders of Consciousness Task Force (1993). Definition of mild traumatic brain injury. J Head Trauma Rehabil 8: 86–87.

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Carroll LJ, Cassidy JD, Holm L et al. (2004). Methodological issues and research recommendations for mild traumatic brain injury: the WHO Collaborating Centre Task Force on Mild Traumatic Brain Injury. J Rehabil Med (43 Suppl.): 113–125

Hiploylee C, Dufort PA, Davis HS, Wennberg RA, Tartaglia MC, Mikulis D, et al. Longitudinal study of postconcussion syndrome: not everyone recovers.?J Neurotrauma?(2016) 34:1511–23. doi: 10.1089/neu.2016.4677

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Polinder, S., Cnossen, M. C., Real, R. G., Covic, A., Gorbunova, A., Voormolen, D. C., ... & Von Steinbuechel, N. (2018). A multidimensional approach to post-concussion symptoms in mild traumatic brain injury.?Frontiers in neurology,?9, 1113.

Sharp, D & Jenkins, P. (2015). Is?Concussion is confusing us all.?Practical Neurology. 15(3):172-86.

Silverberg, N. D., Iverson, G. L., Arciniegas, D. B., Bayley, M. T., Bazarian, J. J., Bell, K. R. & Whitehair, V. (2021). Expert panel survey to update the American Congress of Rehabilitation Medicine definition of mild traumatic brain injury.?Archives of physical medicine and rehabilitation,?102(1), 76-86.

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