Functional Neurological Disease: A Hardware Or Software Condition?

In personal injury matters quantifying physical and psychiatric injuries have established albeit sometimes imperfect methods of quantifying the associated impairment. This is particularly true when the injured person exhibits both physical and psychiatric symptoms. In this article Dr Rodney Marsh (psychiatrist) and Associate Professor Cecilie Lander (neurologist) discuss Functional Neurological Disease (FND), a difficult to diagnose but common condition characterised by both physical and psychological symptoms, from the perspectives of psychiatry and neurology.

Functional Neurological Disease

Dr Rodney Marsh


Traditionally known as Conversion Disorder, Functional Neurological Disease is a common neurological disorder with morbidity and health economic consequences which belie it disenfranchised status. Prevalence estimates suggest up to 1 in 7 neurology consultations are because of this diagnosis; total economic cost estimates are imperfect but in the realm of $20 billion per year in the US have been suggested.

Since its early descriptions in the 19th Century, FND has been a neglected, poorly understood cause of significant disability and stigma, with a cumbersome interface with medicine and the law.

While the cause is not fully understood, there has been much progress in the field in the past 15 years. While beyond the scope of this article, a disorder of attention regulation is believed to lie at the core of FND.

Traditionally a diagnosis of exclusion, FND is a disorder that is characterized by a loss of neurological function which can fluctuate through time, which is not explained by a traditional neurological diagnosis. Examples of common features of the disorder include tremor, weakness, seizure like events, sensory loss, speech and swallowing difficulties and cognitive problems.

The diagnosis is made by a neurologist but is supported by a psychiatrist. It is best made purposefully, on positive signs elicited by the neurologist. From a psychiatric perspective, FND is conceptualized as one of the many downstream consequences of trauma, with a remote history of trauma thought to prime the patient to a risk for FND; and a psychological or physical trauma commonly (but not invariably) immediately preceding the disorder’s onset. Indeed, the DSM-5 amended the diagnostic criteria such that a psychological stressor was no longer deemed necessary to attract the diagnosis.

Often the preceding injury may seem relatively trivial, although clearly appearing to precipitate the disorder. Whilst the injury sometimes may not be considered legally or scientifically causal given the absence of expected, commensurate tissue pathology, the final medical and legal chapter is yet to be written on this significant matter, and warrants our continuing consideration.

‘Neuromimesis’ first coined by Paget in 1873, is at the heart of the status difficulties for FND both as a medical diagnosis and as a compensable disorder from an insurance perspective. Patients with FND can present with signs that look like established neurological diagnoses with identifiable tissue pathology – stroke, multiple sclerosis and epilepsy are examples. When patients are investigated and it is found they do not have these diagnoses, they are often told they have a ‘software rather than a hardware problem’, but that has often been the end of their useful interactions with the medical profession. Patients are then left with a ‘double problem’ of, commonly, a severe disability, and a narrative from those who they seek out to help them, that, ‘it is all in their head’, or ‘there is nothing wrong with them’.

One of the difficulties with the diagnosis of FND has been the fear of ‘missing a serious diagnosis’ which has perpetuated an uneasy dance between patients suffering this disorder, and clinicians investigating them in a litigious world. We now recognize that FND is a stable diagnosis through time. Once comprehensively investigated, patients and their families need to be given a diagnosis and management plan, which no longer includes recurrent investigations.

There is an ongoing difficulty for doctors and insurers alike in understanding the issue of volition in this disorder. Malingering is rare. FND symptoms are involuntary. Patients need to be understood and believed as a core element of their recovery.

Unsurprisingly, this difficulty is often reflected in how the patient population is dealt with through 3rd party payers, and standard impairment rating scales which commonly specifically exclude the diagnosis (along with others in the somatoform spectrum) from compensation.

A substantial subgroup of FND sufferers have significant, enduring disability equal or worse than their ‘mimicked’ neurological disorders. A majority have some enduring symptoms. Currently we employ a combination of physical rehabilitation and psychotherapy, along with treatment of any comorbid psychiatric diagnoses in a tailored fashion for each patient.

There is an urgent need to develop better evidence-based therapies for this patient population, and importantly, address the stigma attached to the diagnosis.

FND is a common, serious and disabling condition which has been misunderstood for a long time. Recent developments in the field offer hope that FND will find its rightful place among the pantheon of other diagnoses in standard pathology texts. Its sufferers will in turn receive better treatments and their plight will be better understood by those they turn to for help.

Functional Neurological Disease Associate Professor Cecilie Lander MBBS MTh FRACP FRCP(Edin) CIME

“Things are not always what they seem.
The first appearance deceives many.
The intelligence of a few perceives.
What has been carefully hidden.”

The Phaedrus (Plato ~ 350 BCE)

What are the symptoms and who gets Functional Neurological Disease?

Functional Neurological Disease (FND) is a common condition and may present with physical symptoms, such as shaking, weakness, seizures and numbness. The severity and type of symptoms may change over time. FND
symptoms may simulate other neurological diseases and may also involve symptoms in other body systems e.g. elevated heart rate, breathlessness, swallowing problems, complex pain, bladder and bowel symptoms.

Although FND can affect anyone, in most age groups females outnumber males and it is less common in very young children.


There is no single mechanism for the development of FND. Usually FND is the result of interacting biological, psychological and social (environmental) factors

Biological FactorsPsychological FactorsSocial Factors
Genetic predispositionPersonality typeAdverse life events

Using a computer analogy, FND is sometimes described as a problem with the ‘software’ rather than the ‘hardware’ i.e., in FND there is an abnormality in how the nervous system is working and therefore to cure FND the ‘software’ needs to be updated or re-programmed. FND may occur concurrently with other neurological diseases such as together
with epilepsy with the individual suffering psychogenic non-epileptiform attacks (sometimes called also dissociative attacks) in addition to epileptic seizures.

An acute traumatic or stressful situation may precipitate FND symptoms and ongoing psycho-social stressors may perpetuate them. An individual with FND is not imagining their symptoms and is not ‘making it up’.


Although the mechanisms of FND are not clearly elucidated, when the neurological basis of FND has been examined with functional brain imaging, there is evidence of distinct changes in the activation of relevant areas of the brain
that indicate an altered brain state. Because the possibility of having both the disease state and the FND occurring concurrently is always present, significant delays in diagnosing FND may occur when symptoms closely mimic potential underlying neurological diseases. Early investigations e.g. a normal MRI Brain, and a normal EEG during an apparent epileptic seizure may help to resolve any diagnostic doubt.

A thorough history with a comprehensive examination is the first step towards effective diagnosis and treatment. Allowing ample time for an individual with FND to explain all of their symptoms is both therapeutic for the individual with FND person and informative for the practitioner. The diagnosis of FND is made by a skilled clinically adept practitioner (usually a neurologist) making a careful clinical assessment of the individual’s symptoms and signs. Asking the individual what they think is wrong and what should be done may yield valuable information that may indicate whether the patient is desiring to resolve the problem. When a trusting rapport with the treating doctor is established, then carefully explaining the anatomical incongruity to the patient may itself be therapeutic.

The clinical examination may reveal ‘positive’ signs of FND such as incongruous signs of apparent weakness of a muscle group that is shown to have normal strength when a different examination approach is used. Sensory examinations may yield anatomically impossible areas of sensory loss.


It is important that the individual with FND understands the functional nature of their disease and that medications for specific neurological diseases will therefore not be effective. For those with physical symptoms, encouraging the patient to have confidence that their body is capable of ‘working normally’ though skilled physiotherapy and occupational therapy facilitates the of retraining the ‘software’ is helpful.

A detailed explanation and unhurried conversation is needed to ensure that the individual understands the basis for their diagnosis, that effective treatment is available, that there may be ups and downs in treatment and that a full recovery is possible. Sometimes, the understanding of the diagnostic reality of FND together with insight into personal vulnerabilities is sufficient for the patient to find their own solution and for their symptoms to resolve.

Approximately 30% of FND patients have co-morbid psychiatric symptoms such as anxiety, depression, and panic attacks. Empowering the FND patient to use and develop self-help strategies is to be encouraged Therefore both psychiatric, and psychological support is invaluable. Specific strategies such as concurrent use of anti-depressant medications has been shown to facilitate a better outcome in FND even in patients who are not depressed.

There are some FND persons who do not accept their diagnosis; others are compliant but fail to respond to appropriate treatments. FND continues to cause substantial disability and distress to sufferers and carers.

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Functional Neurological Disease: A Hardware Or Software Condition?

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