Functional neurological disorder: diagnosis and red flags

Insurers are facing increasing numbers of personal injury claims with a diagnosis of functional neurological disorder (FND), where involuntary neurological symptoms occur which are not the direct result of structural damage or disease.

Common symptoms of FND include limb weakness, tremors, impaired gait, sensory abnormalities, seizure like episodes and cognitive (memory and concentration) difficulties.

Historically it was known as hysteria or, more recently, conversion or psychogenic disorder. However, FND was incorporated into DSM-5 in 2013 and the current DSM-5 criteria for an FND diagnosis are:

1. One or more symptoms of altered voluntary motor or sensory function.
2. Clinical findings can provide evidence of incompatibility between the symptom and recognised neurological or medical conditions.
3. Another medical or mental disorder does not better explain the symptom or deficit.
4. The symptom or deficit results in clinically significant distress or impairment in social, occupational, or other vital areas of functioning or warrants medical evaluation.

It is important to note that FND is a positive diagnosis and not one of exclusion, so should usually be made by a neurologist or neuropsychiatrist with a particular expertise in this area. There are a number of predisposing factors which may render individuals susceptible to FND, including:

• Prior stressful events or maltreatment such as abuse during childhood or domestic violence as an adult
• Previous functional symptoms in other body systems, irritable bowel syndrome, for example
• Chronic pain
• Health anxiety
• Recurrent or persistent anxiety and depression
• Workplace or relationship stress

Despite the above, it should be noted that a proportion of people who develop FND report no previous stressors.

Studies have shown that up to 40% of cases are preceded by physical injury although there are a significant number of other precipitating factors which can include:

• Panic attacks
• Infection
• Acute pain
• Migraine
• Neurological disease
• Drug side effects
• General anaesthesia

Two or more of these factors may be reported prior to onset.

Where an injury is involved, there does not appear to be a direct relationship between its severity and the development of FND. Even seemingly insignificant injuries can trigger the disorder, regardless of other predisposing factors being present. Further enquiry may be required as to why an apparently trivial injury was significant or distressing for an individual claimant, for example due to pain, perceived threat, subsequent poor medical care (actual or perceived) or feelings of injustice, humiliation or loss of control.

Symptoms can resolve quickly (within days) or become chronic, with predisposing factors increasing the probability of prolonged recovery. In addition, there are several additional perpetuating factors which include:

• Extended use of opiate painkillers post-injury
• Prolonged avoidance of physical activity
• Psychiatric illness (depression, anxiety, phobias, PTSD)
• Receipt of disability benefits
• Ongoing litigation

FND often co-exists with other conditions, known as comorbidities, which can include psychiatric, neurological or physical conditions. Common examples include:

•  Depression and anxiety
• PTSD
• Illness anxiety disorder
• Complex regional pain syndrome
• Post concussion syndrome
• Fibromyalgia
• Chronic fatigue syndrome
• Migraine

In summary, the onset and continued symptoms of FND post-injury is complex and often multifactorial. In the context of personal injury claims careful analysis of a claimant’s medical history is required along with expert analysis to ensure that claimant is fairly compensated. The factors we have set out may help to identify claims where FND is a concern and to deploy an appropriate strategy as a result.

Specialist legal advice from a team with previous experience of this type of claim is often required. Our Complex Injury Special Interest Group is a resource available to insurers facing a complex FND claim. For further information or assistance, contact a member of the group and make sure to request a copy of our handling guide today.