FND Education Project

GLOSSARY

FND Terminology Glossary

Plain-language explanations of terms used in FND research, clinical care, rehabilitation, and this project.

Purpose: A plain-language reference for terms commonly used in Functional Neurological Disorder (FND) research, clinical care, and this project.

Audience: People living with FND, family and other supporters, clinicians, contributors, and readers who encounter unfamiliar terminology.

Limitations: This glossary explains vocabulary; it is not a diagnostic checklist. Terms may be used differently across papers, specialties, countries, and classification systems. Historical terms are included because readers will still encounter them in medical records and older research. Mechanism terms are labelled as models or hypotheses where the science remains unsettled.

Status: Project reference resource. Final wording remains subject to human editorial review.

Last terminology addition: September 23, 2026 (co-occurring condition and functional-paralysis rehabilitation terms, automatically generated draft; human review pending); other entries retain their earlier review status.

A

Agency

Type: research concept

The sense that I am the person causing or controlling this movement, action, or experience. Altered sense of agency has been studied in FND, particularly in functional movement symptoms. It is one part of several developing models and is not a diagnostic test by itself.

Available capacity

Type: preferred plain-language course term

The usable physical, cognitive, sensory, emotional, social and upright-activity capacity a person has at a particular time, including the recovery cost that may follow. It may vary with fatigue, pain, sleep, migraine, medication, symptoms, environment, recovery and coexisting illness. This project uses the term as practical descriptive language, not as a measurable biological unit or an autonomic-state diagnosis. See Available Capacity, Spoons, and Early Action and spoon theory.

Associated symptoms

Type: general clinical term

Symptoms that commonly occur alongside FND but may not themselves be defining features of the FND diagnosis. Examples can include pain, fatigue, sleep problems, migraine, cognitive symptoms, dizziness, or other health conditions. Each symptom still deserves appropriate assessment rather than automatic attribution to FND.

Attention

Type: general term and research concept

The brain’s selective focus on some information while filtering other information. Research and rehabilitation models suggest that attention can influence some functional symptoms, but this does not mean a person is choosing, imagining, or deliberately producing the symptom.

B

Biopsychosocial model

Type: clinical framework

A way of organizing biological, psychological, and social factors that may influence illness, disability, recovery, or treatment. In FND, it should not be used as shorthand for “psychological cause.” Different factors may matter for different people, and psychological trauma or stress is not required for the diagnosis.

C

Contracture

Type: physical complication

A lasting restriction in a joint’s movement. It needs assessment and is different from a limb temporarily not moving on command. See equipment, positioning and joint care.

Coexisting condition / comorbidity

Type: general clinical term

Another condition present in the same person. FND can coexist with neurological disease, psychiatric conditions, pain disorders, migraine, epilepsy, sleep disorders, or many other diagnoses. Finding FND does not prove that every symptom is caused by FND.

Conversion disorder / Functional Neurological Symptom Disorder

Type: classification and historical terminology

Terminology still encountered in psychiatric classification systems and medical records. Modern FND practice does not require clinicians to identify a psychological stressor or psychological cause before diagnosing FND. Many clinicians and researchers now use Functional Neurological Disorder as the broader clinical term.

Coprolalia

Involuntary socially inappropriate or taboo words or phrases. It is not required for Tourette syndrome, not unique to it, and not a reliable expression of intent. See functional tics for assessment and sources.

D

Diagnostic overshadowing

Type: safety term

When an existing diagnosis causes new or different symptoms to be too quickly explained by that diagnosis, so another medical problem may be overlooked. In FND, a new, severe, or substantially changed symptom should not automatically be assumed to be functional.

Dissociation

Type: clinical and research term

A broad term for altered integration of awareness, memory, identity, perception, emotion, or sense of connection to oneself or surroundings. Some people with FND experience dissociation and some do not. Dissociation is therefore relevant to some FND presentations but is not a universal explanation for FND.

Dissociative seizures

Type: current alternative term

A term used for seizure-like episodes that are not epileptic seizures and are commonly included within FND. It is especially common in some countries and classification traditions. In 2025, an International League Against Epilepsy task force proposed the combined term functional/dissociative seizures (FDS).

Drop attack

Type: event description

A sudden fall from standing or walking. In the functional-drop-attack literature, the usual presentation has no definite blackout, often little or no warning and relatively rapid recovery. The term alone does not identify the cause: syncope, epilepsy, cataplexy, vestibular events, gait or weakness problems and other conditions may also cause sudden falls. See Functional Drop Attacks and the seven recovery and safety pages.

Distractibility

Type: positive clinical sign

A change in a symptom when attention is directed elsewhere. For example, some functional tremors or movements may lessen, stop, or change during distraction. Clinicians interpret distractibility together with the history and other examination findings; it is not a self-test and does not mean the symptom is deliberate.

E

External focus

Type: rehabilitation term

Directing attention toward the purpose or result of an action, such as turning a page, rather than continually checking the moving body part. In FND it is an individually assessed practice option, not a test of whether symptoms are real. See meaningful task practice.

EEG

Type: diagnostic test

Electroencephalography records electrical activity from the brain using electrodes placed on the scalp. EEG can help assess epilepsy and other conditions. A normal routine EEG does not by itself prove that an episode is a functional seizure.

Entrainment

Type: positive clinical sign

A change in the rhythm of a tremor when a person is asked to perform a different rhythmic movement with another body part. Entrainment can support a diagnosis of functional tremor when interpreted by a clinician in context.

Epilepsy / epileptic seizure

Type: neurological diagnosis

Epileptic seizures result from abnormal seizure-related electrical activity in the brain. They are different from functional seizures, although a person can have both epilepsy and functional seizures. The correct distinction can require specialist assessment and sometimes video-EEG.

Echolalia

Repetition of another person’s words. This description can occur in different contexts and does not itself establish a functional diagnosis. See functional tics for assessment and sources.

F

Functional

Type: core FND term

In FND, functional refers to a disorder of how nervous-system processes are functioning rather than a diagnosis defined by one specific structural lesion. It does not mean “imaginary,” “minor,” “voluntary,” or “nothing is wrong.” Research has also reported group-level structural and network differences in FND, so the word should not be interpreted as proof that the brain is structurally normal in every possible sense.

Internal inconsistency in cognition

A clinically meaningful difference in access to the same cognitive ability across contexts, interpreted with task demands, cues and other explanations taken into account. It is involuntary; ordinary fluctuation or one good result is not enough to diagnose FCD. See FCD diagnostic signs.

Metacognition

Judging and responding to your own thinking—for example, assessing whether you understood an instruction. Repeated monitoring can become unhelpful for some people, but is not the cause of everyone’s FCD. See working models.

Functional Cognitive Disorder (FCD)

Type: clinical diagnosis / related functional disorder

FCD involves disabling or distressing cognitive difficulties with positive clinical evidence of a functional pattern. Cognition includes memory, attention, language access, processing speed and executive functions. Recognition, visual recall or imagery complaints deserve assessment but are not established hallmark FCD signs. Migraine, pain, fatigue, sleep disorders and other conditions may independently affect cognition or coexist; they are not automatically FCD. See Everything We Know About FCD.

Functional facial symptoms

Type: FND symptom group

Functional symptoms affecting facial movement or control. They may include facial spasm or pulling, apparent droop, functional facial weakness, active eye closure, ptosis, jaw or tongue movement, or difficulty keeping the lips closed. Apparent droop can result from overactive muscles pulling the mouth downward rather than weakness. New or suddenly changed facial droop still needs urgent medical assessment and should not automatically be attributed to FND. See Functional Facial Symptoms — Spasm, Droop and Weakness.

Functional/dissociative seizures (FDS)

Type: proposed international terminology

The term proposed in 2025 by an International League Against Epilepsy task force for episodes previously described by several labels, including functional seizures, dissociative seizures, and PNES. The slash is intentional: it allows use of “functional,” “dissociative,” or both according to clinical and cultural context. Other current terms remain in use.

Functional gait disorder

Type: FND symptom subtype

A functional disorder affecting walking or standing. Patterns can include dragging, buckling, swaying, unusual slowness, difficulty initiating movement, or other changes. Diagnosis depends on positive clinical features and the overall neurological assessment rather than appearance alone.

Functional movement disorder (FMD)

Type: FND symptom group

Functional neurological symptoms involving movement. Examples include tremor, jerks, functional tic-like symptoms, dystonia, gait problems, or other abnormal movements. FMD is part of the broader FND spectrum.

Functional neurological disorder (FND)

Type: preferred umbrella term in this project

A disorder in which people experience neurological symptoms involving movement, sensation, awareness, cognition, speech, seizures, or related functions, with clinical features that support a functional diagnosis. Modern diagnosis is positive or rule-in, based on characteristic features when possible, rather than simply concluding that tests are normal. Symptoms are genuine and experienced as involuntary. FND can coexist with other neurological or medical conditions.

Functional neurological symptoms

Type: general term

Neurological symptoms occurring as part of FND or a related functional presentation. The phrase may be used before the clinician has decided whether the overall pattern meets criteria for a specific FND diagnosis.

Functional paralysis

Type: severe functional motor presentation

Complete or near-complete loss of voluntary movement in one or more limbs when positive clinical findings support a functional motor diagnosis. This project treats it as the severe end of functional limb weakness, while giving it a separate page because safety, access and rehabilitation starting points differ from partial weakness. Immobility confined to a functional seizure is described as part of that event unless a separate motor symptom persists. See Functional Paralysis.

Functional seizures

Type: current preferred term used by this project and the 2026 AAN guideline

Episodes involving changes in movement, responsiveness, awareness, sensation, behaviour, or experience that can resemble epileptic seizures but are not caused by the seizure-related electrical activity that defines epilepsy. They are experienced as involuntary. Other names include dissociative seizures, functional/dissociative seizures, and the older term PNES.

Functional sensory symptoms

Type: FND symptom subtype

Functional changes in sensation, such as numbness, altered touch, tingling, or other sensory experiences, when the clinical pattern supports a functional diagnosis. Similar sensations can also arise from many other neurological or medical conditions.

Functional speech or voice symptoms

Type: FND symptom subtype

Functional changes affecting speech, voice, fluency, articulation, or related communication functions. Assessment may involve neurology and speech-language pathology because many other conditions can produce similar symptoms.

Functional tremor

Type: FND symptom subtype

A tremor with clinical features supporting a functional movement disorder. Features such as variability, distractibility, and entrainment may help clinicians make a positive diagnosis.

Functional weakness

Type: FND symptom subtype

Weakness or loss of voluntary movement in which examination shows positive features supporting a functional mechanism. The weakness is experienced as real and involuntary. Functional weakness may affect one limb, one side of the body, both legs, or other distributions.

Functional tic-like symptoms

Involuntary motor movements and vocal/phonic sounds or words assessed as functional. Research also uses “functional tic-like behaviours” (FTLBs); this does not mean deliberate action. Can coexist with a primary tic disorder. See functional tics for assessment and sources.

H

Hoover’s sign

Type: positive clinical sign

An examination sign used particularly when assessing functional leg weakness. It compares voluntary hip movement with automatic hip movement generated when the opposite leg performs a task. A characteristic difference can provide positive evidence of functional weakness when interpreted by a trained clinician.

I

Insomnia

Type: clinical term

Difficulty falling asleep, staying asleep or returning to sleep despite an adequate opportunity, with daytime effects. Exhaustion and insomnia can occur together. See insomnia and treatment options.

Irritable bowel syndrome (IBS)

Type: clinical diagnosis

Recurrent abdominal pain with changes in bowel habit, understood as a disorder of gut–brain interaction. It is distinct from inflammatory bowel disease and from FND. See IBS.

Incongruence

Type: diagnostic concept

A clinical pattern that does not fit the expected anatomy or physiology of a particular recognized neurological disease. Incongruence can contribute to an FND diagnosis, but clinicians should use specific positive findings and appropriate differential diagnosis rather than simply labeling a symptom “unusual.”

Inconsistency

Type: diagnostic concept

A meaningful difference in neurological function under different conditions—for example, movement being impaired in one task but more available during another. In FND, this can reveal preserved capacity and support a positive diagnosis. It does not mean the person is being inconsistent on purpose.

Interoception

Type: research concept

The nervous system’s sensing and interpretation of signals from inside the body, such as heartbeat, breathing, nausea, temperature, or internal arousal. Altered interoception is being studied in FND and related conditions, but it remains part of developing mechanism models rather than an established single cause.

Involuntary symptom

Type: core clinical concept

A symptom that is not consciously chosen or deliberately produced. FND symptoms are understood clinically as involuntary even when attention, expectation, context, or learned nervous-system patterns can influence them.

M

Malingering / feigning

Type: different concept — not synonymous with FND

Deliberate production or exaggeration of symptoms for an external purpose is conceptually different from FND. An FND diagnosis does not mean that a person is faking symptoms, and variability or distractibility should not be treated as evidence of deception.

Medically unexplained symptoms

Type: older broad terminology

A phrase historically used for symptoms without an identified conventional medical explanation. It is not synonymous with FND. Modern FND diagnosis aims to identify positive clinical features of FND rather than defining the disorder only by lack of explanation.

Motor tic

A tic involving movement. Movement appearance alone does not distinguish a primary tic disorder from a functional tic-like symptom. See functional tics for assessment and sources.

N

Nociplastic pain

Type: pain-mechanism descriptor

Pain associated with altered pain processing when tissue damage or a lesion of the sensory nervous system does not adequately explain it. Different mechanisms may coexist; this term is not a synonym for FND. See persistent pain.

Neuroplasticity

Type: general neuroscience term

The nervous system’s ability to change through learning, practice, experience, injury, and adaptation. Rehabilitation often makes use of learning and repeated practice. “Neuroplasticity” should not be used as a promise that every FND symptom can be quickly or completely reversed.

O

Orthostatic intolerance

Type: clinical term

Symptoms that worsen when upright and often improve when lying down. POTS is one possible syndrome, not a synonym for all upright symptoms. See autonomic symptoms.

Organic

Type: older contrast term — use cautiously

Historically, clinicians sometimes contrasted “organic” neurological disease with “functional” disease. This can misleadingly imply that FND is not biological or not neurological. Modern writing is usually clearer when it names the actual comparison—for example, FND versus stroke, epilepsy, multiple sclerosis, neuropathy, or another specific condition.

P

Post-exertional malaise (PEM)

Type: clinical term

Worsening after exertion that may be delayed and prolonged, involving more than ordinary tiredness. Physical, cognitive, emotional and social demands can contribute. It changes activity planning, particularly in ME/CFS. See fatigue and post-activity worsening.

PNES

Type: common older/current search term

Psychogenic nonepileptic seizures. This term remains common in medical literature and records. It is increasingly criticized because “psychogenic” can imply an unproven psychological cause and “nonepileptic” defines the condition mainly by what it is not. This project primarily uses functional seizures, while also teaching PNES because readers will encounter it.

Positive clinical sign / positive diagnostic sign

Type: diagnostic concept

An examination or clinical feature that actively supports an FND diagnosis. Examples include Hoover’s sign in functional weakness or distractibility and entrainment in some functional tremors. “Positive” means evidence for the diagnosis; it does not mean the symptom is desirable or that one sign alone settles every case.

Positive diagnosis / rule-in diagnosis

Type: diagnostic approach

Diagnosing FND because characteristic clinical features support it, rather than diagnosing it only after every other conceivable disease has been excluded. Appropriate tests may still be necessary to assess alternative or coexisting conditions.

Predisposing, precipitating, perpetuating, and protective factors

Type: clinical formulation framework

A way of organizing factors that may have made a person vulnerable (predisposing), occurred near symptom onset (precipitating), help symptoms continue (perpetuating), or support recovery and resilience (protective). These factors vary between people. None is automatically required to diagnose FND, and identifying a factor does not prove that it caused the disorder.

Predictive processing

Type: developing mechanism model

A neuroscience framework in which the brain continually combines incoming sensory information with prior expectations or predictions. Some researchers use predictive-processing ideas to model FND symptoms. This is a scientific framework under investigation, not a proven single explanation for every case of FND.

Psychogenic

Type: historical/disputed causal term

Meaning caused primarily by psychological processes. The word appears in older diagnoses such as PNES and “psychogenic movement disorder.” Modern FND diagnosis does not require proof of psychological stress, trauma, or another psychological cause, so this project avoids using “psychogenic” as a default causal explanation.

Palilalia

Repetition of one’s own words. The description alone does not determine its cause. See functional tics for assessment and sources.

Premonitory urge

A sensation before a tic or tic-like symptom. Some people notice one and some do not. Its presence or absence does not decide the diagnosis. See functional tics for assessment and sources.

R

Rehabilitation

Type: treatment and management term

Structured work aimed at improving function, participation, independence, confidence, and quality of life. Depending on the person and symptoms, FND rehabilitation may involve physiotherapy, occupational therapy, speech-language therapy, psychological treatment, education, medical management, and other supports.

Relapse / setback

Type: course-management term

A return or worsening of symptoms after improvement or a period of greater stability. FND can fluctuate. A setback does not automatically mean treatment has failed, but new, severe, or substantially changed symptoms may still need medical reassessment rather than being assumed to be FND.

S

Semiology

Type: clinical term

The detailed description of what happens during a symptom or episode—what starts first, movements, awareness, sensations, duration, recovery, and other observable or reported features. Semiology is important in evaluating seizures and episodic symptoms, but appearance alone may not determine the diagnosis.

Somatic symptom disorder

Type: separate psychiatric diagnosis

A psychiatric diagnosis involving excessive or disproportionate thoughts, feelings, or behaviours related to physical symptoms. It is not another name for FND and is not required for an FND diagnosis, although the diagnoses can coexist in some people.

Spoon theory

Type: community metaphor

A metaphor introduced by Christine Miserandino to describe limited, fluctuating usable capacity and the often invisible cost of ordinary tasks while living with chronic illness. A “spoon” is not a clinical unit, an FND biomarker or a position on a sympathetic–parasympathetic graph. The course prefers available capacity when precise shared language is needed. See Available Capacity, Spoons, and Early Action.

Symptom variability

Type: common clinical feature

A symptom changing in severity, pattern, context, or availability of function. Variability is common in FND and can sometimes form part of positive diagnostic findings. It does not mean symptoms are voluntary, and variability can also occur in other medical conditions.

T

Tinnitus

Type: symptom term

Hearing a sound without a corresponding external sound. Management may improve sleep and reduce intrusion even when the sound remains. See tinnitus.

Tic

A sudden, recurrent, usually non-rhythmic movement or sound. Classification depends on clinical history and assessment, not the word alone. See functional tics for assessment and sources.

Tic attack

A description of an intense or prolonged bout of tic or tic-like symptoms. It does not automatically mean a functional seizure; safety and treatment follow assessment. See functional tics for assessment and sources.

V

Vestibular rehabilitation and gaze stability

Vestibular rehabilitation uses individually selected movement, balance and visual tasks to support function after assessment. Gaze stability means keeping vision steady during head movement; gaze exercises are not necessary for everyone with PPPD. A guideline for impaired inner-ear function does not automatically apply to PPPD. See the individual plan and gaze-stability discussion.

Video-EEG

Type: diagnostic test

Simultaneous video recording and EEG monitoring. When a person’s typical episode is captured, clinicians can compare the observable event with the brain’s electrical activity. Video-EEG is especially useful in distinguishing many functional seizures from epileptic seizures, although the appropriate diagnostic approach depends on the individual event and clinical context.

Vocal / phonic tic (also called a verbal tic)

A tic involving a sound, which may be a non-word sound, a word or a phrase. “Verbal tic” is a common search phrase; vocal/phonic is broader because not all sounds are words. See functional tics for assessment and sources.

Terminology principles used by this project

  • Prefer Functional Neurological Disorder (FND) as the umbrella term.
  • Prefer functional seizures in ordinary project language while recognizing the 2025 ILAE proposal functional/dissociative seizures (FDS) and the continued use of dissociative seizures in some settings.
  • Teach PNES, conversion disorder, psychogenic, and other older terms because readers may encounter them, but identify their limitations rather than silently treating them as equivalent modern terminology.
  • Describe FND as a positive neurological diagnosis when supported by characteristic clinical features, not merely as unexplained symptoms or normal tests.
  • State clearly that symptoms are genuine and involuntary.
  • Do not use psychological stress, trauma, or psychiatric diagnosis as a required explanation for FND.
  • Do not present attention, predictive processing, interoception, agency, network models, or other proposed mechanisms as settled causes.
  • Keep open the possibility of coexisting neurological and medical disease.

Main evidence sources

This glossary uses the project’s stable citation index. The most relevant sources are:

Functional tics — further reading: Eight recovery and supporting-care pages, including explanations of CBT, CBIT, urge acceptance and pattern mapping.