There is a growing trend of claims for provisional damages being brought for the life-long increased risks of developing dementia arising from traumatic brain injury (TBI). This is based on an increasing body of research suggesting that TBIs may increase the risk of dementia.

Dementia is a neurodegenerative disorder which is progressive and begins years before symptoms are exhibited. The risk increases with age with 1 in 3 of the UK population developing dementia in their lifetimes. Although there does appear to be an association between TBIs and increased dementia risk, it is also known that not everyone who has experienced a head injury or repeated head injuries will go on to develop dementia. A TBI is just one factor believed to play a potential role; others include age, genetics, smoking, high blood pressure and obesity.

The difficulty faced by the courts, claimants and defendants alike is that the ability to draw a definitive conclusion is complicated by the evolving research findings into the potential relevance of non-TBI factors (as discussed above), the challenge in designing adequate studies and the lack of consistency in the definition of what is a mild, a moderate and a severe brain injury. Recent high-profile studies into dementia in rugby and football have also brought the issue to the public's attention and raised awareness of the likely association between TBIs and dementia.

Helpfully, the recent case of Mathieu v Hinds & AVIVA [2022] EWHC 924 (QB) provides clear guidance on the current judicial view.

Mathieu v Hinds & AVIVA

This was a claim arising out of a serious road traffic accident when the claimant was struck by a moped and sustained a serious brain injury. It was agreed by the parties' medical experts that he had made a very good recovery from his injuries. He was, however, seeking a claim for provisional damages in relation to the development of dementia arising from his TBI. It was the claimant's case that there was a growing body of evidence which supported an increased risk of developing dementia following a TBI. Expert neurology evidence concerning the scientific research relating to the link between brain injury and dementia was provided by Dr Richard Orrell for the claimant and Dr Oliver for the defendant. The claimant based his case on, amongst others, the Barnes paper – Association of Mild Traumatic Brain Injury with and without loss of consciousness with dementia in US military veterans, JAMA Neurol 2018 which suggested that even in the absence of a loss of consciousness there was a two-fold increase in the risk of dementia arising from a mild TBI. On cross-examination, however, Dr Orrell conceded that the paper was an outlier and sought to rely on a number of other papers. Dr Foster relied on a series of meta-analyses which all had mixed results including Hicks et al, Traumatic Brain Injury as a Risk Factor Dementia and Alzheimer Disease: Critical Review of Study Methodologies, Journal of Neurotrauma. Only one paper, Plassman et al 2000, was considered to be methodologically sound but even this was open to criticism as its conclusions were based on the study of veterans who (by the very nature of their job) had been subject to multiple other contributing factors.

For a claim for provisional damages to succeed, the claimant needs to prove, on the balance of probabilities, that there is more than a fanciful chance that the TBI will cause him dementia in the future. This requires him to prove that as a matter of generality a single TBI can cause dementia and that this risk applies to him.

Hill J determined that it remains doubtful as a matter of science that a single TBI can cause dementia. The Hicks meta-analysis published in December 2019 concluded that the results of the individual studies were "mixed" and "provided no clear support either in favour or against the hypothesis that TBI is a risk factor for dementia". Importantly, the Judge agreed with Dr Foster that an association does not necessarily mean that one thing caused the other. Even if the existence of a generalised enhanced risk was clearer on the evidence, given this Claimant's exceptional recovery from his TBI and the other protective factors in place, how any such risk would apply to him remained unclear.

Hill J therefore concluded that on the current state of science the claimant could not show, to the balance of probabilities standard, the existence of a more than fanciful chance that the TBI would lead to him developing dementia. She was not satisfied that the development of post-TBI dementia could be said to be an example of "the clearest case" as envisaged in Allot v CEGB or a "clear and severable risk", "clear cut event" or "clear cut identifiable threshold" as described by Scott Baker J in Willson v Ministry of Defence.

The claimant was therefore judged to be unable to meet the first limb of the criteria set out in Willson v Ministry of Defence and his claim for provisional damages therefore failed at the first stage.

What Now?

The main issue for claimants wanting to advance a claim for provisional damages will be establishing the casual link between TBIs and the development of dementia. The findings of Hill J suggest that research and studies are not currently able to conclusively support this and that advances in medical research are required. However, the lack of epidemiological and neuro-psychiatric evidence in the case of Mathieu v Hinds & AVIVA (as referenced by Dr Orrell) may mean that claimants have another, but as yet untested, method of pursuing a claim for provisional damages for dementia arising from a TBI. It should also be remembered that the claimant in Mathieu had made an exceptional recovery which influenced the decision of Hill J and that a claimant whose recovery has not been as good may be more successful in establishing the casual link required with reference to neurological, epidemiological and neuro-psychiatric evidence.

The content of this article is intended to provide a general guide to the subject matter. Specialist advice should be sought about your specific circumstances.