Litigating traumatic brain injury: hidden deficits and the frontal lobe paradox

13/05/2022

Headway’s Action for Brain Injury week (16-22 May 2022) is this year focussing on hidden disability. In litigation arising from brain injury, the task of lawyers and medico-legal experts is to ensure that no disability remains hidden. The frontal lobe paradox presents a challenge to this objective.

The frontal lobe paradox is a phenomenon that has been formally recognised since at least 1985. The frontal lobes of the brain are primarily responsible for what are called executive functions, which include activities such as planning, making decisions, regulating behaviour and multi-tasking. It is very common for the frontal lobes to be injured during trauma but measuring the effects of that injury can be difficult.

The gold standard for detecting the existence and severity of acquired brain injury is neuropsychological testing, often called ‘psychometric testing’. Whilst these tests are highly sensitive to many effects of brain injury, they are known to be somewhat unreliable for identifying executive dysfunction caused by frontal lobe injury. Often, a claimant’s performance on psychometric tests of executive function in the carefully controlled clinical environment will suggest that they have little or no deficit, whereas in the “real world” they describe problems taking decisions, multi-tasking etc. Resolving this paradox is the key to getting to the bottom of the claimant’s real disabilities.

If formal clinic-based testing is not reliable in detecting executive dysfunction, then how are courts supposed to decide whether it is present? “Real world” Performance-Based Tests (PBTs) such as the ‘multiple errands test’ (MET) have been devised to assess executive function on practical tests in a non-clinical environment. In these tests the person is, for example, taken to a shopping centre and set a series of tasks and their performance is monitored and recorded.  However, these tests have not become widely adopted in medico-legal practice, perhaps for reasons of cost, as much as question marks over their validity and sensitivity to TBI. Virtual Reality versions have been devised to bring the outside world into the clinical consulting room, but these have not been widely taken up.

In a world where scientific testing is often regarded as infallible, how does a claimant overcome the innate scepticism as to whether something which cannot be scientifically identified, or measured can still be said to exist? The sceptic will argue that it is a “heads-I-win-tails-you-lose” situation for a claimant: if they do badly on some aspects of psychometric testing it is because of the brain injury but if they do well on other aspects it is because of the frontal lobe paradox (see e.g., Hibberd-Little v Carlton [2018] EWHC 1787 (QB)).

So how do the parties get to the truth of the situation in any given case? Unless and until psychometric tests are devised that eliminate the paradox, neuropsychology expert witnesses and ultimately courts will continue to rely on the evidence of those who see the claimant in everyday life: family members, friends, work colleagues, professional case managers/carers etc. Their evidence will be adduced either to prove or refute that the claimant struggles with tasks requiring executive function in daily life.

Given that collating that evidence is the lawyer’s role, the importance of the legal profession understanding the frontal lobe paradox and how to prove or refute its existence in any given case will be key to ensuring that disabilities do not remain hidden.