Neuropsychological Testing

NEUROPSYCHOLOGICAL TESTING IN SUBTLE BRAIN INJURY CASES – HELP OR HINDERANCE?

It has long been the accepted practice in a legal case where the Claimant is alleging brain injury that neuropsychological reports should be obtained. This is still the case but it must be understood that this sometimes produces no evidence of cognitive impairment even though the person has a brain injury. The reason for this is because the tests are notoriously poor at identifying problems with executive functions or behaviour, characteristics that are so typical of subtle brain injury.

It is important to understand that negative or inconclusive neuropsychological results do not rule out brain injury. This principle is poorly understood by medical experts and Solicitors alike.

It also must be understood that neuropsychological testing can never prove brain injury, it can only provide evidence of a pattern of functioning which must then be interpreted in the context of clinical history.

A cerebral injury is not diagnosed by neuropsychological testing but as a result of a careful assessment of post traumatic amnesia (PTA) carried out by an appropriately qualified clinician such as a neurologist, neurosurgeon or clinical psychologist. Taking a post traumatic amnesia history involves obtaining a meticulous account of the patient’s recollections, frame by frame at the moment of the accident/injury and until clear and uninterrupted memory returns. Some loss of consciousness at the time of impact may occur but sometimes it does not. Loss of consciousness is not necessary for cerebral injury to occur – LINK – NO LOC , however some interruption in the continuum of laying down memories will be sustained following head injury. A patient may appear alert and orientated  and be able to answer simple questions but the process in which their memories are laid down is interrupted such that they fail to lay down memories for key events. It is the absence of these key memories, usually interspersed with islands or “snapshots” memory that characterises PTA.

Diffuse Axonal Injury (DAI) is the most common type of brain injury that is the result of traumatic shearing forces that occur when the head is rapidly accelerated or decelerated. It may occur in car accidents, falls, and assaults. It usually results from twisting or rotational forces (angular momentum), rather than forward and back impacts (linear mementum).

This can cause damage to the axons which disrupts the connections between the neurons and hence the brain’s ability to transfer information – IMAGE

A patient may appear quite well immediately after such an injury but deteriorate later, sometimes as long as 72 hours later. This is because there is often a delayed onset of symptoms because the damage can take up to 72 hours to develop. Whilst it was once thought that the main cause of axonal separation was tearing due to mechanical forces during the trauma, it is now understood that secondary biomechanical cascades are largely responsible for the injury, which occur in response to the primary injury and take place from hours to days after the initial injury.

CT, MRI, PET or SPECT scans (listed in order of increasing sensitivity in terms of their ability to detect brain injury) may provide hard evidence of brain injury but often they do not because the damage is too microscopic to be detected.

In very serious brain injury cases there is no question that neuropsychological evidence is a very valuable tool in helping to identify the extent of cognitive impairment. However in the more subtle brain injury cases it’s lack of sensitivity must be appreciated and understood. The simple fact is that it is an adjunct to a diagnosis and a lack of neuropsychological evidence can never rule out brain injury.

Neuropsychological testing was never designed to be used in a medico-legal context. Because of its limitations neuropsychological testing should not be viewed as the gold standard when determining whether a brain injury has been sustained.  In subtle brain injury cases over reliance on neuropsychological testing is not to be advised.

In the more subtle brain injury cases neuropsychological testing may actually be quite unreliable for several reasons. Most people who have suffered a subtle brain injury almost invariably go on to suffer with at least one psychological disorder, possibly more than one disorder.  Any psychological disorder can affect neuropsychological testing and invalidate the results. For that reason there is little point in performing the testing until the patient has been treated for the presenting psychological disorder.  At Dickinson Solicitors we understand the importance of treating out any anxiety as soon as possible and that is always our goal where funding can be obtained. To leave the anxiety untreated complicates the picture and gives the Defendant the inevitable ” psychological” defence.

Post traumatic stress disorder, obsessive compulsive disorder and depression are the most common psychological disorders that tend to present with head injury. Over the years we have seen only one case of subtle brain injury where there has been no psychological reaction and that was because the lady’s emotional part of the brain had been damaged. Usually there is a psychological reaction even if it is only a reactive depression once the impact of the head injury sinks in as the person starts to realise that they are never going to be able to function at the same level again.

The problem for the neuropsychologist when testing for cognitive impairment is that many of the features of brain injury (such as generalised problems with memory, concentration and fatigue etc) are also listed in DSM iv and ICD10 as symptoms of a depression. The reality is that there are some specific types of memory problems which don’t tend to present with a depression but do present in head injury, such as difficulty remembering peoples names and the names of places.

There are also certain distinguishing features which don’t tend to present with psychological disorder such as explosive temper outbursts, fiscal impulsivity, alcohol intolerance and general disinhibition.

Depression can also impair neuropsychological performance because it can undermine drive and motivation that will reduce effort on neuropsychological tests, not as a desire to obtain increased compensation but simply because problems of drive and motivation are intrinsic to the psychological disorder. This problem also occurs after subtle frontal injuries affecting the ventro-medial cortex; an area of the brain that is directly involved with arousal and drive.

Other uncontrolled factors such as fatigue and anxiety can also cause inconsistent performance on neuropsychological testing. Even non-brain injured individuals have good and bad days but with those who have suffered brain injuries this is magnified. When you put all of these possible variations together (and they all can exist simultaneously in some people) it is hardly surprising that some individual’s performance can vary hugely even during one session of neuropsychological testing. If you then repeat the neuropsychological testing on perhaps several further occasions (as often happens in the more complicated and longer running cases), the chance of inconsistent performance from one occasion to another increases.

Despite this claimants will find themselves being criticised for such inconsistent performance when in reality inconsistency should be expected. These criticisms may quickly be turned into allegations of exaggeration or malingering, a defence that is commonly run by Defendants against innocent Claimants. If they fail the notorious “validity tests” they will almost certainly be accused of being a fraud but there are actually very good reasons why someone might score below the cut off on these tests.  Validity tests were developed to try and catch out those who are seeking to consciously exaggerate their symptoms. However the very use of many of the validity tests is highly questionable in anyone who is also suffering from psychological disorder. They should not be used at all for this population group because they have not been validated on individuals suffering from multiple psychopathology. If the tests have not been scientifically validated on people with head injury and at least one identifiable psychological disorder then any results obtained must be considered unreliable.