Your leg gives way, your hand shakes, or you have attacks that look like seizures. The scans are clear and the blood tests are normal. Someone suggests it might be “stress”, and you leave the appointment wondering whether anyone believes you.
Functional neurological disorder (FND) is the name for this kind of problem. It is common, it is real, and it can improve. This guide explains what FND is, how it shows up, how neurologists diagnose it, what is thought to cause it and what helps.
Key points
- FND is a problem with how the nervous system works, not with its structure. NHS inform describes it as a problem with how the brain sends and receives messages to and from the body (NHS inform).
- It is common. In a study of 3,781 new neurology outpatients in Scotland, 16% had functional and psychological symptoms as their main diagnosis (Stone et al., 2010).
- The diagnosis is made on positive signs found on examination, not only on normal tests.
- Treatment centres on understanding the diagnosis and active rehabilitation: physiotherapy, psychological therapy and, where needed, speech or occupational therapy.
On this page
- What FND is
- Is FND real?
- Symptoms
- How FND is diagnosed
- FND compared with other conditions
- Causes and risk factors
- Treatment
- Recovery and outlook
- Frequently asked questions
What FND is
In FND, parts of the nervous system that control movement, sensation or awareness stop working as they should, although nothing is damaged. A useful comparison is a computer with intact hardware running software that keeps freezing. A scan looks at the hardware, so it usually comes back normal.
The condition has had several names. “Hysteria” and later “conversion disorder” came from the idea that emotional distress is converted into physical symptoms. That idea does not fit many patients, and the old names carried stigma. Today neurologists mostly say functional neurological disorder. In the psychiatric classification DSM-5-TR it is called functional neurological symptom disorder (conversion disorder), and in ICD-11 dissociative neurological symptom disorder. They describe the same thing.
Current research models focus on how the brain handles attention, expectation and the sense of being in control of a movement. When those processes go wrong, a movement can feel as if it is happening on its own, or a limb can stop responding to the intention to move it (Hallett et al., 2022).
Is FND real?
Yes. This is often the first question people ask, and the answer matters. FND symptoms are involuntary. People with FND are not faking, exaggerating or choosing their symptoms, and neurosymptoms.org, written by neurologists who specialise in FND, makes the same point: the condition is not your fault, not imagined and not due to disease (neurosymptoms.org).
Part of the confusion comes from the normal scan. A normal MRI rules out certain diseases. It cannot show a problem with function, in the same way that a scan of a piano cannot tell you whether the pianist is playing well. Another part comes from variability: symptoms that ease when attention is elsewhere can look voluntary from the outside. That variability is a feature of how FND works, and neurologists use it to make the diagnosis.
Symptoms
FND can affect almost any function the nervous system controls, and most people have more than one symptom. Neurosymptoms.org groups them roughly as follows (neurosymptoms.org):
- Movement: weakness or heaviness of a limb, tremor, jerks, spasms and abnormal postures (functional dystonia), walking and balance problems
- Attacks: functional (dissociative) seizures and episodes of collapse; see functional seizures vs epilepsy
- Sensation: numbness, tingling or altered sensation, often down one side of the body
- Other neurological symptoms: speech and swallowing problems, visual disturbance, dizziness, bladder symptoms, memory and concentration problems
- Commonly linked symptoms: fatigue, pain and poor sleep
The non-motor symptoms are covered in more depth in understanding FND symptoms, with separate guides on vision problems, facial symptoms and chronic fatigue.
FND is diagnosed more often in women, but men get it too, at any age.
How FND is diagnosed
FND is diagnosed by a neurologist, using features found in the history and on examination that are typical of FND. Two examples:
- Hoover’s sign. In functional leg weakness, the leg may be weak when you try to push it down, but strength returns automatically when you lift the other leg against resistance.
- Entrainment. A functional tremor in one hand often changes rhythm, or pauses, when you tap a different rhythm with the other hand.
Scans, blood tests and EEGs still have a place. They check for other conditions, which can occur alongside FND. But a diagnosis made only because “nothing was found” is incomplete, and it is worth asking your neurologist which positive signs led to the diagnosis.
FND compared with other conditions
Multiple sclerosis (MS). MS damages the protective layer around nerve fibres, and the damage shows on MRI. FND causes no such damage. The two can share symptoms such as weakness, numbness and fatigue, and some people with MS also develop functional symptoms, which is why a specialist needs to look at the whole picture.
Epilepsy. Epileptic seizures come from abnormal electrical discharges; functional seizures do not. Video-EEG is the most certain way to tell them apart, and some people have both. The details are in functional seizures vs epilepsy.
Somatic symptom disorder. This diagnosis describes excessive and distressing thoughts, worry and behaviour around physical symptoms of any kind. FND describes a specific neurological symptom with positive signs on examination. They are different diagnoses, though a person can have both.
Causes and risk factors
There is no single cause. Neurosymptoms.org describes FND as the result of several factors that make someone vulnerable, trigger the symptoms and then keep them going (neurosymptoms.org). Common triggers include:
- a physical injury, illness, infection or operation
- a sudden physical event such as a faint, migraine or panic attack
- a period of high stress or exhaustion
- for some people, past trauma or adversity
Many people have no clear trigger. Once symptoms start, they are often kept going by understandable responses: watching the affected limb closely, avoiding activity, worrying about what the symptom means, and repeated tests that keep the search for a structural cause open. Anxiety and depression are common alongside FND, and treating them matters. They are not the whole explanation, and FND is not “just stress”. The role of stress is covered in FND causes and triggers.
Treatment
The first step is a clear explanation of the diagnosis that makes sense to you. Many people find that understanding how FND works, and that it can improve, is itself a turning point.
After that, neurosymptoms.org lists the main treatments as physiotherapy and exercise, occupational therapy, psychological therapy, speech and language therapy and, for some, medication for pain, sleep or mood (neurosymptoms.org). Specialist FND physiotherapy retrains movement using attention and automatic movement rather than effort, and psychological therapy, often CBT-based, works with the thoughts, behaviours and emotions that keep symptoms going.
The evidence is still developing. In the two largest UK trials, specialist physiotherapy for functional motor disorder (Physio4FMD) and CBT for dissociative seizures (CODES) did not beat the comparison group on their main outcome at 12 months, though both helped on several secondary measures. That is a reason to keep treatment active and well coordinated, not a reason to give up on it. The full range of options is covered in FND treatment options.
Hypnotherapy is one complementary approach that some people find useful, particularly for practising movement and calming the body’s alarm response. What the research does and does not show is set out in hypnotherapy for FND.
Recovery and outlook
FND does not damage the nervous system and is not degenerative. Many people improve, and some recover fully. Outcomes vary a great deal, though. A systematic review of long-term follow-up studies of functional motor symptoms found that, on average, 39% of patients were the same or worse after several years. A short duration of symptoms, early diagnosis and satisfaction with care predicted better outcomes, while delayed diagnosis predicted worse ones (Gelauff et al., 2014).
In practice, recovery is rarely a straight line. Good weeks and setbacks are normal, and a setback does not mean treatment has failed. Families matter too: explaining FND to the people around you can reduce a lot of pressure, and there is a guide on how to explain FND to family and friends.
Frequently asked questions
Is FND real?
Yes. FND causes genuine, involuntary symptoms such as weakness, tremor or seizures. It is a problem with how the nervous system functions rather than with its structure, which is why scans are usually normal. The symptoms are not imagined and not put on.
Is FND a mental illness?
It sits between neurology and psychiatry. It appears in the psychiatric classification DSM-5-TR as functional neurological symptom disorder, but the symptoms are neurological, the diagnosis is made by a neurologist, and treatment usually combines physical rehabilitation and psychological therapy.
How is FND diagnosed?
A neurologist makes the diagnosis on positive clinical signs, such as Hoover’s sign in functional leg weakness or a tremor that changes with distraction. It is not only a matter of tests coming back normal. Tests are still used to check for other conditions, which can coexist with FND.
Can FND be cured?
Many people improve, and some recover fully, especially with early diagnosis and active rehabilitation. Outcomes vary: in a review of long-term studies of functional motor symptoms, on average 39% of patients were the same or worse at follow-up. Getting the right treatment early helps.
Is FND the same as multiple sclerosis or somatic symptom disorder?
No. Multiple sclerosis causes visible damage to nerve fibres on MRI, while FND does not. Somatic symptom disorder is a diagnosis about excessive worry and attention around physical symptoms; FND is about a specific neurological symptom with positive signs on examination. A person can have FND alongside either of them.
Conclusion
FND is a real and common condition in which the nervous system stops working properly without being damaged. It is diagnosed on positive signs, it varies a great deal from person to person, and it can improve with a clear explanation and active rehabilitation.
If you have an FND diagnosis and want to explore whether hypnotherapy could support your current treatment, get in touch. I work online from Jersey, and in person with clients on the island.
About the author
Fabio Morus is a behavioural therapist and clinical hypnotherapist in Jersey, Channel Islands, focused on anxiety, phobias, sleep and trauma. His training covers Neuro-Systemic Hypnotherapy, CBT (Beck Institute) and EMDR (EMDR Association UK). He works online in Portuguese and English. Clients in Jersey are also seen in person.
This article is for information only. It does not replace assessment by a neurologist or other qualified health professional. Seek medical advice for any new, different or rapidly worsening symptom. If you are struggling to cope, you can contact Samaritans on 116 123 (UK and ROI, free, 24/7). In Jersey, contact your GP, emergency services or the local crisis line.
