Functional neurological disorder: is it real?

Insurers are facing increasing numbers of personal injury claims where the diagnosis is functional neurological disorder (FND). This has led our complex injury team to form a special interest group on the subject, whose handling guide can be downloaded here.

FND is a complex condition that is perhaps not yet fully understood. It appears to be caused by changes in how brain networks work, rather than changes in the structure of the brain itself as seen in many other neurological disorders. The physical symptoms of FND cannot therefore be explained organically and the exact cause is unknown.

At a systems level, a functional disorder occurs when a person experiences abnormal function in a system that can be demonstrated to be capable of normal function. So, for example, a person experiencing hand tremors can see those tremors disappear when distracted by performing another movement. 

The diagnostic criteria for FND are:

1. One or more symptoms of altered voluntary motor or sensory function.
2. Clinical findings provide evidence of incompatibility between the symptoms and recognised neurological or medical conditions.
3. The symptom or deficit is not better explained by another medical or mental disorder.
4. The symptom or deficit causes clinically significant distress or impairment in social, occupational, or other important areas of functioning; or alternatively warrants medical evaluation.

The lack of an organic cause along with the capability of normal function in an FND sufferer has led to a degree of suspicion and scepticism amongst some when defending claims where the condition is alleged.

It is noteworthy however that, outside the arena of personal injury litigation, FND is very common in clinical practice:

• It is the second most common diagnosis in neurology outpatient clinics (after headaches).
• One third of patients seen in outpatient neurology clinics are thought to have FND.
• FND accounts for 10% of admissions to hyperacute stroke units.
• The misdiagnosis rate is 0.5%, i.e. it is rare to be misdiagnosed.
• FND has been reported in ages ranging from 4–94 years old.
• It appears to effect females more than males with 60-80% of cases being in women, although the gender gap is narrower in early and later life.
• FND symptoms commonly exist with other physical and mental health problems.

The symptoms of FND can be very disabling and cause similar levels of disability and poor quality of life to those experienced by Parkinson’s and MS sufferers. Common symptoms include paralysis, limb weakness, abnormalities of movement, sensory dysfunction and cognitive difficulties.

In a personal injury context, the disabling symptoms and consequent impact on working capacity and care needs can lead to sizeable claims. Specialist advice along with careful selection of robust and knowledgeable medico-legal experts is crucial to obtaining an optimum outcome. Neurology and neuropsychiatric reports will inevitably be required, potentially accompanied by orthopaedic (initial soft tissue/bone injury) and neuropsychological (initial head injury) reports.

Careful consideration needs to be given to any proposed treatment regime. Up to 40% of sufferers remain with similar or worse symptoms after treatment. The longer there is between symptom onset and treatment, the worse the long-term prognosis. Those who report improvement rarely make a full recovery.

With any form of claims validation, it should also be remembered that inconsistency (the disorder is variable over time) and incongruity (the disorder breaks the rules that have been established from other disease causes of neurological symptoms or from basic anatomy/physiology) are said to be the twin official pillars of a positive FND diagnosis.

So, returning to the headline question, the answer is yes - FND is real and is becoming ever more so for insurers. Such claims are complex and potentially expensive in terms of both damages and costs. Faced with an FND claim, specialist advice is recommended, and the members of our special interest group would be more than happy to discuss any claims or issues as and when they arise.

Andrew Peters - FND SIG Lead