Functional Neurological Disorder

A condition guide by Mr Mohammed Madi, Consultant Orthopaedic & Spinal Surgeon.

Functional neurological disorder is a common condition in which the nervous system stops working properly, producing genuine symptoms such as weakness, altered sensation, tremor, walking difficulty and pain — yet without the structural damage seen in conditions like a stroke or a slipped disc. It is included here because its symptoms frequently resemble spinal problems, and people are often referred to a spinal surgeon. Recognising it matters, because the right treatment is quite different from surgery, and operating on an unrelated scan finding can make things worse.

Functional neurological disorder, or FND, is a problem with how the brain and nervous system function rather than how they are built. A helpful way to picture it is the difference between a computer's hardware and its software: in FND the hardware — the brain and nerves — is structurally intact, but the software, the way signals are sent, received and coordinated, is not running as it should. The result is real, involuntary symptoms that the person cannot simply switch off.

This is an important point to state plainly: the symptoms of FND are genuine. They are not imagined, not "put on," and not a sign of weakness of character. FND is one of the most common reasons people see a neurologist, and it can be just as disabling as conditions caused by structural damage.

In plain terms: the wiring is intact, but the signalling has gone awry — like a fault in the software rather than a broken part.

FND often produces exactly the symptoms that suggest a spinal problem: weakness or heaviness in an arm or leg, numbness or tingling, difficulty walking, tremor, and persistent back, neck or limb pain. People with these symptoms are frequently sent for scans and referred to spinal surgeons. Sometimes a scan then shows a common, age-related change — a disc bulge or mild wear — that is present in many pain-free people and does not explain the symptoms. Mistaking such an incidental finding for the cause can lead to surgery that does not help and may worsen matters. Recognising FND for what it is protects people from unnecessary operations and points them towards treatment that actually works.

The mechanisms of FND are still being understood, but it is best thought of as a disorder of the brain's networks for movement, sensation and attention — particularly the way the brain predicts and directs the body, and where attention is focused. Symptoms can be triggered by a physical event such as an injury, an illness, an operation or a panic attack, and are sometimes associated with stress or difficult life experiences — but not always, and many people have no obvious trigger at all. It is not a moral failing, and it is not something a person is doing on purpose. Understanding this mechanism is itself part of recovery, because it explains why the symptoms are real and why they can improve.

FND can affect almost any neurological function. Common patterns include:

Functional limb weakness — heaviness, weakness or a sense that a limb will not obey, often varying from moment to moment.

Functional movement symptoms — tremor, jerks, spasms or abnormal postures.

Functional sensory symptoms — numbness, tingling or altered sensation, often not following the usual nerve patterns.

Walking and balance difficulty — an unsteady or unusual gait.

Dissociative (non-epileptic) seizures — episodes resembling fits or blackouts that are not caused by epileptic electrical activity.

Persistent pain and fatigue, and sometimes functional cognitive symptoms such as brain fog or memory lapses.

A characteristic feature is variability — symptoms that change with attention, distraction, activity or emotion. This variability is a clue to the diagnosis, not a sign that the symptoms are not real.

Because some symptoms of FND overlap with those of serious conditions, new weakness, numbness, speech difficulty, facial droop or visual loss should always be assessed urgently in the first instance to exclude conditions such as a stroke. A diagnosis of FND is made by a clinician after appropriate assessment — not assumed.

A crucial and often misunderstood point is that FND is a positive diagnosis, made by finding specific, recognised clinical signs — not simply a label applied when scans come back normal. Neurologists look for features such as Hoover's sign (leg weakness that returns to normal strength when attention is directed elsewhere), tremor entrainment (a functional tremor that changes or stops when the person performs a rhythmic task with the other hand), give-way weakness, and the variability and distractibility of the symptoms.

Scans (such as MRI) and other tests are often performed, mainly to exclude other conditions; in FND they are typically normal or show only incidental changes unrelated to the symptoms. The diagnosis rests on the pattern of the history and these positive examination findings, ideally explained clearly and compassionately so the person understands what is — and is not — happening.

The good news is that FND is treatable, and treatment is often very different from what people expect. The foundations are:

A clear, validating explanation. Understanding the diagnosis — that the symptoms are real, that the problem is one of function rather than damage, and that it can improve — is itself the first and one of the most important steps in treatment.

Specialised physiotherapy. For functional movement and weakness, physiotherapy designed specifically for FND helps retrain normal, automatic movement by redirecting attention, and there is good trial evidence that it helps.

Psychological therapy where appropriate, such as cognitive behavioural therapy, particularly for dissociative seizures or where stress, anxiety or low mood are part of the picture.

A multidisciplinary approach. The best results often come from a team working together — physiotherapy, occupational therapy, psychology, and sometimes speech and language therapy — addressing movement, function, mood, sleep and pain together.

Treating any coexisting pain, fatigue, sleep difficulty and mood problems is part of good care. Crucially, surgery is not a treatment for FND, and operating on an unrelated, incidental spinal finding will not relieve functional symptoms.

The course of FND varies. Many people improve substantially with the right understanding and treatment, especially when the diagnosis is made early, explained well, and acted on without delay. Others have more persistent symptoms that need ongoing management. What consistently helps is early, confident diagnosis, a clear explanation, and access to the right therapies — and avoiding a long, fruitless search for a structural cause that is not there.

"It's all in my head." No — the symptoms are real and physical, arising from how the nervous system is functioning.

"I'm imagining it or making it up." FND is involuntary; people cannot simply switch the symptoms off.

"A normal scan means nothing is wrong." A normal scan supports the diagnosis; FND is real even when imaging is normal.

"Surgery will fix it." Surgery does not treat FND, and operating on an incidental scan finding can make things worse.

"Nothing can be done." FND is treatable, often with physiotherapy and a clear understanding of the diagnosis.

Functional neurological disorder is a common, genuine condition in which the nervous system functions abnormally despite being structurally intact. Its symptoms — weakness, altered sensation, tremor, walking difficulty and pain — often look like a spinal problem, which is why recognising it matters: it protects people from unnecessary surgery and points them to treatment that works. The diagnosis is made positively, on specific clinical signs, not merely because scans are normal. With a clear explanation and the right therapies, particularly specialised physiotherapy, many people improve.

This page is for general education and does not replace advice from your own clinical team. New or sudden weakness, numbness, speech difficulty, facial droop or visual loss should always be assessed urgently to exclude conditions such as a stroke.

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• —Espay AJ, Aybek S, Carson A, et al. Current Concepts in Diagnosis and Treatment of Functional Neurological Disorders. JAMA Neurology. 2018;75(9):1132–1141.
• —Nielsen G, Stone J, Matthews A, et al. Physiotherapy for functional motor disorders: a consensus recommendation. Journal of Neurology, Neurosurgery & Psychiatry. 2015;86(10):1113–1119.
• —Bennett K, Diamond C, Hoeritzauer I, et al. A practical review of functional neurological disorder (FND) for the general physician. Clinical Medicine. 2021;21(1):28–36.
• —Aybek S, Perez DL. Diagnosis and management of functional neurological disorder. BMJ. 2022;376:o64.

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.