The Rise of Functional Neurological Disorder and how to tackle it

06 Apr 2021

In recent months we have seen an increase in medico-legal experts reaching a diagnosis of Functional Neurological Disorder (FND) where a claimant may have sustained a mild traumatic brain injury (mTBI).

This article considers FND in the context of mTBI claims where no organic cause can be given for ongoing debilitating functional symptoms. 

What is FND?

It is important to acknowledge that FND is a genuine disorder. It encompasses all symptoms which are found to be functional. 

FND is described in the Diagnostic and Statistical Manual of Mental Disorders (DSM 5) as:

  1. One or more symptoms of altered voluntary motor or sensory function are experienced;
  2. Clinical findings prove no correlation between the symptoms and a recognised neurological or medical condition;
  3. The symptom or deficit cannot be better explained by another medical or mental disorder; and
  4. The symptom or deficit causes clinically significant distress or impairment in social or occupational areas.

FND in the context of mild traumatic brain injury

There are several definitions of mTBI including post-concussion syndrome (PCS). PCS is a term used to describe a variety of symptoms that can occur after a suspected mTBI such as poor memory, pain, headache, fatigue, dizziness, persistent vertigo and psychiatric symptoms post trauma.

In these cases it is important to consider the findings from paramedics and hospital records rather than relying solely on the claimant’s retrospective recall.  The reporting of ”loss of consciousness”, for example, may be due to the stress and anxiety of the accident.

Whilst it is possible that an isolated mTBI can produce temporary damage to the brain, cognitive (and other) symptoms that persist beyond the expected weeks to months are likely to have a functional basis. 

Claimants who have been diagnosed with an mTBI where there is no organic cause for persistent ongoing symptoms, will usually have an extensive history of physical, cognitive and psychological symptoms in their pre-accident presentation. 

Furthermore, they often have a significant history of functional illness independent of the index accident. 

The “memory problems” described after mTBI are often deficits of attention and concentration, which are affected by anxiety, depression, fatigue, sleep deprivation, medication, pain etc., all common after mTBI. 

Often patients with mTBI have normal structural imaging.  In these cases it is important that the claimant is advised that their ongoing symptoms have a functional basis rather than being as a consequence of persistent brain damage. 

There are however arguments that abnormalities in Diffusion Tensor Imaging (DTI) reflect axonal damage.

Abnormalities in DTI found in claimants following an mTBI do not necessarily provide evidence that there has been an axonal injury. DTI changes have been found in patients with depression, borderline personality disorder, ageing, opiate addition and even in healthy volunteers. 

Management of FND

FND is treatable and the prognosis can be good.

Unfortunately, the diagnosis of FND is often not made early enough and the claimant is  often treated under the mistaken belief that they have sustained a brain injury.  This is often perpetuated by a Case Manager and the claimant’s treating consultants.

Insurers should seek to get involved in the rehabilitation process very early on in these claims to ensure that the correct rehabilitation is provided to the claimant.

FND is often misunderstood because movements may be controlled when distracted.  This is not to say that claimants with FND do not have some degree of wilful symptom control.  This may be produced to convince others of their suffering. 

At the other end of the spectrum however, is where claimants are consciously malingering and fabricating their symptoms for financial gain. It is not always possible to be sure if a claimant is fabricating or not and in this situation it is important that all the available records relating to the claimant’s past are forensically examined.  

The multi-disciplinary approach

The aim of FND treatment is to “retrain the brain” by unlearning abnormal and dysfunctional behaviour and relearning normal movement. 

A multi-disciplinary treatment approach has been found to be the most effective for FND because of the variety of symptoms the disorder encompasses.  A range of medical specialities may be involved although, ultimately, the best approach allows treatment to be tailored to the individual.  

Neurological, neuropsychiatric/psychiatric and neuropsychological assessments will be key in terms of maximising the claimant’s recovery. They are crucial to make a judgment as to whether such symptoms would likely have occurred despite the accident, to recommend the appropriate treatment and to undertake an objective review of the claimant’s previous medical history. 

Early rehabilitation and experience is key

FND is a complex and poorly understood condition but we are certainly seeing it as a more prevalent diagnosis within personal injury claims, particularly those involving mTBI. 

Early rehabilitation is recommended to implement the multi-disciplinary approach.

All potential records should be identified and forensically reviewed to ensure that the correct treatment is implemented.

Medico-legal experts who are experienced in identifying and diagnosing a claim involving FND should, where possible, be instructed to avoid the attribution of any persistent ongoing symptoms to brain damage.

Incorrect treatment or diagnosis could prove costly for insurers as if the claimant does not recover they may seek substantial awards for lost earnings, care, case management, aids and equipment and possibly accommodation.


Claire Collins is the lead Partner in the CAT/Large Loss Team in London and is a member of the Special Interest Brain Injury Group at BLM.



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Disclaimer: This document does not present a complete or comprehensive statement of the law, nor does it constitute legal advice. It is intended only to highlight issues that may be of interest to customers of BLM. Specialist legal advice should always be sought in any particular case.

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Claire Collins

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