Functional Neurological Disorders (FND)


Functional neurological disorders are some of the most common neurological problems and are conceptualised as disorders of the functioning of the nervous system (rather than the structure). They can cause a wide array of symptoms, such as seizures, weakness and dizziness, and typically there are clinical features that actively support the diagnosis of FND. Previously deemed untreatable and labelled as ‘medically unexplained symptoms’, there are now therapeutic options available with neurological mechanisms being recognised as underpinning these disorders. 

Definitions/ Essential features (ICD11 criteria)

 -It is no longer a diagnosis of exclusion, owing to examination and history findings possessing high sensitivity for these disorders. 
-‘Involuntary disruption or discontinuity in the normal integration of motor, sensory or cognitive function, lasting at least several hours’
-‘Clinical findings not consistent with disease of the nervous system or another medical condition’
-Symptoms not due to a recreational drug, medication or alcohol use/withdrawal, or sleep-wake disorders. 
-‘Not accounted for by another mental disorder’, for example, post-traumatic stress disorder (PTSD) or schizophrenia.
-These symptoms lead to an impairment in functioning, such as social, occupational, and relationships.

Symptoms of FND

 -Functional seizures (also can be termed dissociative)
-Motor symptoms (e.g. weakness, tremor)
-Sensory symptoms (numbness, pins and needles)
-Mixed motor/ sensory
-Cognitive symptoms (e.g. poor memory and attention)

 The diagram below gives examples of the variety of possible symptoms at presentation:

FND image

In addition, there are other symptoms that are commonly associated with FND, such as fatigue, headache, anxiety, pain and poor sleep.

Potential history features

The challenge in these cases is the diversity and often multiple co-existing symptoms and clinical signs present. For a non-specialist junior, it is recognising that the presentation in front of you does not reflect alternative pathologies, whilst also not experiencing diagnostic overshadowing in a patient with a history of functional neurological disorder. 

The following outline the common characteristics of the presenting population, however, patients can fall outside of these: 

 -Typical age range is between puberty to young adults (35 years of age)
-Female: Male 2-3:1
-Previous history of trauma e.g. physical trauma, childhood abuse, parental neglect
-Previous history of mental health or physical health condition e.g. schizophrenia, epilepsy, multiple sclerosis
-Experience symptoms similar to that of a relative with a condition e.g. functional seizures in a relative of an epileptic.

Examination findings of motor or sensory FND

The table below outlines some of the presenting features that can be elicited on examination. Some have high specificity (positive Hoover’s sign) but low sensitivity. Therefore, their presence is highly specific for FND, but often they are not present.  

FND table

Table outlining the potential findings from limb and truncal neurological examination.

FND face table 1

Table outlining the potential findings from cranial nerves examination.

Functional seizures

This is the most common subtype of functional neurological disorder. The previous names for this condition include non-epileptic seizures and pseudoseizures. This diagnosis makes up as much as a quarter of all cases presenting to epilepsy clinics, with 80% of these patients being female and 90% having a history of other psychiatric comorbidities and/or previous adverse life events.

Functional seizures table

Making and communicating the diagnosis

These conditions are typically made by a senior, most commonly in the specialties of neurology, psychiatry and paediatrics. However, as the junior, you may meet those with a suspected or a known diagnosis, where you are the clinician listening and answering their questions and concerns. For some patients, a functional diagnosis is accepted and is reassuring, but stigma remains. A thoughtfully delivered diagnosis with signposting to support services and extra information can be a way to show the patient that there are therapies available.

Treatment of functional neurological disorders

It should be first noted that the treatment of these disorders can be first hampered by strain on services, with long waiting times being commonplace for these conditions. This should be explained to the patient early on to manage expectations. 

 The mainstay of treatment is non-pharmacological and is instead through psychotherapy and cognitive behavioural therapy (CBT). There are a small number of specialist functional neurological disease centres that can provide inpatient therapies for these patients, but there are issues with high demand and long waiting times. First-line therapies for motor FND includes physiotherapy. There is also occupational therapy and speech and language therapy (SLT) inclusion in the multidisciplinary team, particularly for motor type with dysarthria. 

 Another important treatment a specialist will do is weaning patients off medications that have been prescribed for an organic disease that they do not have, such as anti-epileptic medications in a patient with functional seizures. This should be done thoughtfully, with the involvement of the patient and their family. The role of SSRIs and SNRIs is if comorbid mental health disorders co-exist, not directly for FND.

Take-home messages

-FND is common and usually presents as a recognisable syndrome.
-Referral to a neurologist for diagnosis enables patient access to treatment, with prevention of potentially further unnecessary investigation or treatment (e.g. antiepileptic medications).
-FND can co-exist with other neurological and physical health conditions therefore, avoid diagnostic overshadowing in this cohort.


Diagnosis and management of functional neurological disorder, Selma Aybek and David L Perez, BMJ 2022.

Functional Seizures, Evie Marcolini and Benjamin Tolchin, Emergency Medicine clinics of North America, 2021.

Functional neurological disorder: new subtypes and shared mechanisms, Mark Hallett et al, Lancet 2022.

Examples of media related to this area of interest

Braincast- a Maudsley Learning podcast hosted by Dr Sotiris Posporelis, a very charismatic host with a variety of guests in the field of Functional Neurological disorders and the broader field of Psychiatry.

This Article was written by Dr Isobel Platt (FY2 Neurology) and was edited by Dr Jacob Day (Neurology Specialty Registrar)

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2 thoughts on “Functional Neurological Disorders (FND)”

  1. Hello,
    I feel that it would be helpful to link you in to response from FND action regarding Dr Sullivans books and podcast.
    I urge you to reconsider the email content that you have sent as a mail out as it it has the potential to misinform health practitioners and the patients in their care.

    BW Elle Shuttelton

    “Recently Dr Suzanne O’Sullivan joined Maudsley Learning Podcast, By the Thinking Mind Podcast. Their goal is “to help educate the general public, as well as healthcare practitioners, with more nuanced conversations about mental health.“

    The introduction posted with the recording of the interview is “Dr. Suzanne O’Sullivan is a neurologist specializing in psychosomatic medicine. O’Sullivan gained recognition for her expertise in diagnosing and treating epilepsy and in improving services for people who suffer with functional neurological disorders. She is the author of three books: It’s all in your head: True stories of imaginary illness, Brainstorm: The Detective Stories from the World of Neurology and The Sleeping Beauties and Other Stories of Mystery Illness.”


    At the time Dr O’Sullivan published her book ‘It’s All in Your Head: True Stories of Imaginary Illness’ there was understandably a backlash from the FND community given the title of the book. She later republished the book with an amended title to ‘It’s all in your head: Stories from the frontline of psychosomatic illness’. In 2016 the book was awarded the £30,000 Wellcome prize.

    Last week we were approached by The Thinking Mind Podcast for feedback on this interview. We have responded with a statement explaining our misgivings about Dr O’Sullivan’s work and why we do not agree with her position on FND. You can read it below.


    Thank you again for contacting FND Action, and for giving us the opportunity to be able to comment on Suzanne O’Sullivan’s work as we have had concerns for some time about the detrimental impact it is having on FND patients. Our position on her work is as follows.

    While we don’t doubt Dr O’Sullivan’s good intentions, and applaud her calls for greater compassion for people suffering from Functional Neurological Disorder, we do not agree with her view on the aetiology of the condition. We also have concerns that she propagates an outdated viewpoint that is not in line with the latest research developments in FND.

    We have summarised our main points here-

    Point 1
    Dr O’Sullivan appears to present a purely psychosocial or largely ‘Freudian’ interpretation of FND. However most of the leading edge researchers, such as Stone, Carson, Edwards, Perez et al, now view FND from a ‘non-dualistic’ framework. In so far as there is an acknowledgement that disorders of the brain and nervous system cannot be split into simplistic ‘physical versus psychological’ or ‘organic versus non organic’ categories of the kind Dr O’Sullivan promotes. The consensus is that FND is now viewed as a ‘brain network disorder’. fMRI brain imaging scans from recent years have shown disruptions to the normal function of brain networks in FND patients, including areas such as the amygdala, insular cortex and temporo parietal junction. Recent studies have also shown disruptions to grey and white matter volumes in the brains of FND patients suggesting the condition does in fact have underlying neurobiology.

    Point 2
    The latest treatment approaches involve viewing FND as an ‘error of predictive processing’ in the brain based on Bayesian hierarchical models. In the podcast interview Dr O’Sullivan presents what sounds like a very simplistic interpretation of ‘predictive processing’. Her position appears to be that FND is caused by ‘incorrect illness beliefs’ and attentional processes, and that these are the primary driver of the illness. However she does not address the complex problem of how to define the term ‘belief’ within a Bayesian hierarchical framework. From our experience the majority of FND patients have found that even when the ‘incorrect illness belief’ is discarded, the underlying ‘predictive error’ and brain network dysfunction still remains. So while addressing illness beliefs can certainly be helpful as a component of treating FND, Dr O’Sullivan’s assertion that they are the primary cause of the illness is in our view simplistic and in many cases incorrect.

    Point 3
    Dr O’Sullivan appears to believe the majority of FND patients are converting psychological trauma into physical symptoms, however studies have shown there are a large proportion of FND patients who do not have any significant preceding psychological trauma. While we acknowledge that for some patients addressing psychological trauma can be very helpful as one component of a wider bio/psycho/social approach, we are again unable to agree with Dr O’Sullivan’s one sided and in many ways outdated ‘Freudian’ viewpoint on this issue. Simplistic causation models are not helpful when considering there are a range of patient subsets within FND.

    Point 4
    Dr O’Sullivan also appears to take the position that viewing FND through a neurobiological framework is the incorrect approach as it reinforces the patient’s belief in the permanence of the condition. We firmly disagree and feel statements of this kind are in many ways extremely unhelpful and potentially damaging. Our view is that research into brain networks and the neurobiological underpinnings of FND have been key to developing effective treatments within a larger bio/psycho/social framework. Furthermore we view these as absolutely essential in attempting to fully understand the aetiology of this complex condition, and in order to develop much needed new and innovative treatments.

    Point 5
    Our understanding is that Dr O’Sullivan is an expert in epilepsy and is not an active specialist FND researcher. She also has had little or no interaction with the FND community or the major charities. She does not back up any of her assertions with citations to research papers, and many of her views on FND are extremely outdated and contradict the latest scientific research. For this reason, in our view she is not best placed to be a spokesperson for the condition. For a genuinely expert viewpoint on FND we would recommend contacting one of the leading researchers such as Professor Jon Stone of Edinburgh university or Professor Mark Edwards of Kings college London.

    In the spirit of good-natured scientific debate, and to present a wider ‘non dualistic’ view of FND, If you would be interested in interviewing a representative from FND Action on your podcast to discuss these issues we would be very happy to provide one. We greatly appreciate you contacting us and thank you for your interest in the condition. “

    1. Dear Elle,

      Many thanks for your email and highlighting the issues with the book that was referenced.

      We have updated the section of the article listing other media resources to remove the book highlighted by yourself. Our original aim was to provide a couple of resources for extra reading and apologies this had been a limited list. I have left the podcast Braincast on the reading list for now. Once we have more time we will update the resources section to better illustrate the current and future directions of the field, we welcome your suggestions for this. The aim of the article is for junior colleagues and we want to promote recognition and support for patients with these conditions.

      Bw Isobel Platt, co-lead Psychiatry

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