Functional Neurological Disorder (FND)

📖 Overview

Functional Neurological Disorder (FND) causes genuine neurological symptoms — including weakness, paralysis, tremor, seizures, movement disorders, speech difficulties, and sensory symptoms — that are not explained by structural damage or disease detectable on standard tests.

WHAT FND IS
FND is not psychosomatic in the outdated sense of being imagined or made up. The symptoms are real and can be severely disabling. The disorder lies in the function of the nervous system — how the brain sends and receives signals — rather than in structural damage like a lesion or tumour. A helpful analogy is a software problem rather than a hardware problem: the brain hardware appears intact on MRI but the programming is not working correctly.

FND is common — it is the second most common reason for neurology outpatient attendance, after headache. It is often poorly managed because it does not fit neatly into neurological or psychiatric models, and it carries significant stigma from both specialties.

TYPES OF FND SYMPTOMS

Functional Weakness and Paralysis
Weakness or complete loss of movement in a limb or one side of the body that does not follow the pattern expected from a structural lesion. The weakness may fluctuate — better on some days, worse on others, better when distracted and worse when attention is focused on the affected limb. This fluctuation is a feature of FND, not evidence of fabrication.

Functional Tremor
Involuntary shaking that may differ from neurological tremors — often variable, responsive to distraction, and sometimes affecting different body parts at different times.

Functional Movement Disorders
A range of abnormal involuntary movements including dystonia (abnormal posturing), myoclonus (sudden jerks), gait disturbances, and choreiform movements.

Functional Seizures
Also called dissociative seizures, non-epileptic attack disorder (NEAD), or psychogenic non-epileptic seizures (PNES). Functional seizures look like epileptic seizures but are not caused by abnormal electrical brain activity. They are neurological events — real, involuntary, and not under the person's conscious control.

Functional seizures may involve: unresponsiveness, shaking, falling, emotional responses during the episode, prolonged duration (often longer than epileptic seizures), fluctuating intensity during the episode, and rapid recovery with full awareness. Anti-epileptic medication does not help functional seizures and may cause harm. Many people with functional seizures also have epilepsy — the two can co-exist.

Functional Sensory Symptoms
Altered sensation — numbness, tingling, altered vision, altered hearing, or pain — without a structural cause. Functional pain can be severe and disabling.

Cognitive Functional Symptoms
Brain fog, memory difficulties, concentration difficulties, and word-finding problems. These cognitive symptoms are real and affect daily function significantly.

Speech and Swallowing Difficulties
Functional dysphonia (loss or alteration of voice), functional dysarthria (slurred or difficult speech), and functional dysphagia (swallowing difficulties).

THE ROLE OF TRAUMA AND STRESS
Trauma, stress, and adverse life events are frequently associated with FND — but FND is not caused by making it up in response to stress. The relationship is neurological. Stress and trauma affect nervous system function in real ways that can precipitate FND in susceptible individuals. However, FND also occurs without any identifiable psychological trigger. The absence of a clear psychological cause does not mean FND is not present.

FND AND THE MEDICAL SYSTEM
Many people with FND have had long and damaging experiences with the medical system before receiving a diagnosis. Being told there is nothing wrong, being referred to mental health services as if the symptoms are imaginary, and being treated with disbelief and dismissal are common experiences. This history of medical invalidation is itself traumatising and makes engagement with treatment harder.

A positive diagnosis of FND — explaining what it is, not just what it is not — is the starting point for recovery. Treatment requires a specialist multidisciplinary team including neurophysiotherapy and neuropsychotherapy adapted specifically for FND.

RECOVERY
Recovery from FND is possible, particularly with early specialist intervention, but is variable and non-linear. The prognosis is better when FND is diagnosed and treated early, when the person has a clear explanation they understand, and when a specialist FND team is involved. Many people improve significantly. Some recover fully. Others have a chronic course with periods of improvement and relapse.