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: October 26, 2026 (course mechanism and rehabilitation vocabulary from Modules 6–10, automatically generated draft; human review pending); other entries retain their earlier review status.

A

Acceptance and Commitment Therapy (ACT)

A form of psychological therapy that aims to help a person respond more flexibly to difficult thoughts, feelings and symptoms while taking actions that matter to them. ACT is used for many health and mental-health problems. In FND it may be one option for selected goals or coexisting problems; its use does not imply that symptoms are imagined or caused by thoughts.

Agency

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.

Arousal

A person’s level of physiological and mental readiness or activation. Arousal can rise during exercise, excitement, illness, pain, surprise or fear and is not the same thing as anxiety. FND researchers study how arousal may interact with attention, prediction and symptoms, but arousal by itself does not diagnose FND or prove a psychological cause. See Salience, Arousal, and Feedback Loops.

Associated symptoms

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

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.

Attention types: selective, divided and sustained

Selective attention means concentrating on one source of information while other information competes for attention. Divided attention means managing more than one task or information stream at once. Sustained attention means staying with a task or information over time. These are ordinary attention functions, not FND-specific tests. Symptoms, pain, fatigue, sensory load and other conditions can all affect how demanding attention feels. See Attention: What the Brain Notices.

Augmentative and alternative communication (AAC)

Ways of communicating that supplement or replace speech when speech is difficult or unavailable. AAC can include writing, gesture, communication boards, text-to-speech devices and other tools. It may be temporary, intermittent or ongoing and does not prevent rehabilitation of speech when that is an appropriate goal.

Automatic control / automatic and task-oriented movement

Automatic control describes learned actions that can be coordinated without close, step-by-step conscious direction. Automatic or task-oriented movement is movement that emerges while carrying out an ordinary action or goal rather than concentrating closely on the body part itself. FND rehabilitation may use safe automatic or task-oriented movement when it is easier or more natural than deliberate isolated movement. A movement changing with task or attention does not mean symptoms are voluntary. See Automatic Control and Conscious Effort.

Autonomic arousal

Changes in automatic body-state systems involved in alertness and threat responses, such as heart rate, breathing, sweating or muscle tension. Arousal can influence symptoms in many conditions, including some FND presentations, but it is not a diagnostic sign and does not prove a psychological cause.

Available capacity

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.

B

Biofeedback

A technique that makes a body signal visible or audible so a person can practise changing a response. Examples include surface EMG feedback for muscle activity. Biofeedback is an adjunct used for selected goals; evidence and usefulness vary by symptom and technique.

Biopsychosocial model

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

Co-contraction

Simultaneous activation of muscles that usually work in opposite directions around a joint. Clinicians may assess co-contraction in some movement disorders, and surface EMG can sometimes help measure it. Its presence alone does not diagnose FND.

Coexisting condition / comorbidity

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.

Cognitive behavioural therapy (CBT)

A structured psychological therapy that examines links among thoughts, feelings, behaviour and physical responses and tests practical ways of responding differently. CBT is used for many conditions. In FND it can be one treatment option, especially for functional seizures or coexisting problems, but receiving CBT does not mean symptoms are imagined or deliberately produced.

Comprehensive Behavioral Intervention for Tics (CBIT) / habit reversal

CBIT is a structured behavioural treatment developed for tic disorders. It includes awareness training, competing responses and changes to situations that influence tics; habit-reversal training is one of its core components. Functional tic-like symptoms require individualized assessment, and methods developed for primary tic disorders should not automatically be assumed to work the same way.

Contracture

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.

Conversion disorder / Functional Neurological Symptom Disorder

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

Desensitization / graded sensory reintroduction

A rehabilitation approach in which a tolerable sensation, texture, touch or activity is reintroduced gradually and adjusted according to the person’s response. It may be used for selected sensory symptoms, pain or movement problems after appropriate assessment. The aim is not to force a person through severe symptoms.

Diagnostic overshadowing

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.

Differential diagnosis

The process of considering and distinguishing among different conditions that could explain a symptom or clinical pattern. In FND, differential diagnosis includes looking for positive features of FND while also considering other neurological, medical or psychiatric conditions that may mimic or coexist with it.

Dissociation

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

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).

Distractibility

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.

Drift without pronation

An examination finding in which an outstretched arm drifts downward without the usual inward turning, or pronation, expected in some forms of structural weakness. It can support functional arm weakness in the right clinical context, but it is not diagnostic by itself.

Drop attack / functional drop attack

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. Functional drop attack is used when assessment supports a functional presentation; the words drop attack by themselves do 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.

Dual-tasking / dual-task practice

Doing a movement while attention is also directed to another simple task, such as walking while carrying on a conversation or following an external cue. In selected FND rehabilitation, dual-tasking can reduce excessive self-monitoring and help more automatic movement emerge. It should not be used when the added task makes activity unsafe.

E

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.

EEG

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.

EEG-EMG and jerk-locked back averaging

Specialist neurophysiological methods that record brain electrical activity with EEG and muscle activity with EMG around repeated jerks. Jerk-locked back averaging aligns many events to look for brain activity that occurs before the movement. These tests can help characterize selected jerking or myoclonus presentations but are not required for every person.

Electromyography (EMG)

A method of measuring electrical activity produced by muscles. Surface or needle EMG may be used in neurological assessment, movement-disorder testing or rehabilitation. What an EMG can show depends on the method and the clinical question.

Emotional regulation

The ability to notice an emotional response, adjust to it and choose what to do next. It does not mean suppressing emotion or remaining calm all the time. Emotional processing and regulation are studied in FND, but difficulty regulating emotion is not a diagnostic sign of FND and does not prove what caused it. See Emotional Regulation, Irritability, and Overwhelm.

Entrainment

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

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.

External focus

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.

Exteroception

The nervous system’s sensing of information from outside the body, including sight, sound and touch. Exteroception works alongside interoception and proprioception during everyday perception and action. Describing which kind of information a person is noticing can improve communication, but it does not establish why a symptom is happening. See Interoception, Proprioception, and Outside Senses.

F

Feedback loop

A pattern in which two or more processes affect one another over time. A feedback loop can be helpful, neutral or make an experience harder to manage. FND researchers study possible interactions among attention, bodily arousal, prediction, movement and awareness, but identifying a feedback loop does not prove that someone caused an illness through thoughts or emotions. See Salience, Arousal, and Feedback Loops.

Functional

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.

Functional Cognitive Disorder (FCD)

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 cough and upper-airway symptoms

Functional symptoms involving cough, throat clearing, breathing or upper-airway control when the clinical assessment supports a functional pattern. Similar symptoms can also come from respiratory, laryngeal, swallowing, reflux, allergy and other conditions, so new or unexplained symptoms need appropriate assessment.

Functional/dissociative seizures (FDS)

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 dystonia / fixed dystonia

A functional movement disorder involving abnormal postures, sustained muscle activity or twisting movements. Some people have a fixed posture that changes little for long periods. Diagnosis depends on the overall clinical pattern and positive features; appearance alone does not establish that dystonia is functional.

Functional electrical stimulation (FES)

Electrical stimulation timed to produce or assist a useful movement, such as lifting the foot during walking. In FND it may be considered as an adjunct for selected rehabilitation goals, but it is not a standard treatment for every presentation and should be chosen with an appropriately qualified clinician.

Functional facial symptoms

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 gait disorder

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 jerks / functional myoclonus

Sudden involuntary functional movements that resemble jerks or myoclonus. Clinicians diagnose them from the history, examination and positive features, sometimes with EEG-EMG testing in selected cases. Other neurological causes of jerking may need to be considered.

Functional limb weakness / functional weakness

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 movement disorder (FMD)

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)

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

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

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

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

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 and voice symptoms

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 swallowing symptoms / functional dysphagia

Functional difficulty with swallowing when assessment supports a functional disorder and appropriate structural or physiological causes have been considered. Symptoms may include difficulty initiating a swallow, a sense of blockage or variable swallowing difficulty. Swallowing problems can have many causes, and choking, aspiration, dehydration or weight loss require medical assessment.

Functional tics / 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.

Functional tremor

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 visual symptoms

Functional changes in vision or visual experience when the clinical pattern supports an FND diagnosis. Presentations can include altered visual fields, reduced vision, double vision or other visual symptoms. New visual loss still needs appropriate eye and neurological assessment because many other conditions can cause similar symptoms.

G

Give-way / collapsing weakness

A pattern during strength testing in which initially generated force suddenly decreases in a way that may support functional weakness when interpreted with the rest of the examination. Pain, fatigue, understanding of the task and other factors can also affect effort, so this finding is not a stand-alone diagnosis.

Globus / globus sensation

A persistent or intermittent feeling of a lump, tightness or something stuck in the throat when no obstructing object is present. Globus has several possible contributors and is not automatically functional. Difficulty actually swallowing food or liquid, weight loss or other concerning changes need appropriate assessment.

Graded exposure / graded trigger practice

Planned, gradual practice with an activity, sensation, movement or situation that has become difficult, starting at a tolerable level and adjusting according to response. In FND rehabilitation it may be used for selected goals, but it should not mean forcing exposure to unsafe situations or ignoring medical warning signs.

Grounding

A group of strategies that direct attention to the immediate environment, body position or a neutral sensory cue. Some people use grounding during dissociation, functional seizures or overwhelming symptoms. It is an optional coping strategy rather than a diagnostic test or a universal way to stop symptoms.

H

Habituation

A form of learning in which the nervous system responds less strongly to a repeated, non-dangerous stimulus over time. Vestibular and sensory rehabilitation may sometimes use carefully graded practice intended to promote habituation. It should be distinguished from simply enduring severe or unsafe symptoms.

Hoover’s 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

Incongruence

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

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.

Insomnia

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.

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.

Interoception

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

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.

Irritable bowel syndrome (IBS)

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.

M

Malingering / feigning

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

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.

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.

Motor learning

Changes in how a movement or skill is planned and performed through practice and experience. FND rehabilitation may draw on motor-learning principles such as goal-directed practice, external focus and more automatic movement, but evidence from one symptom type or rehabilitation approach should not automatically be applied to every FND presentation. See How Rehabilitation Uses Learning.

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

Neuroplasticity

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.

Nociplastic pain

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.

O

Optokinetic response / optokinetic testing

An involuntary eye-movement response to a large moving visual pattern. Clinicians can observe optokinetic responses during selected visual or neurological assessments. The finding must be interpreted in context and is not a self-test for functional visual symptoms.

Organic

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.

Orthostatic intolerance

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.

P

Pacing

Planning activity and rest so that important activity is more sustainable and large cycles of overactivity followed by prolonged worsening are reduced. In FND and coexisting conditions, pacing should be individualized and flexible rather than used as a fixed rule to avoid activity.

Palilalia

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

Persistent postural-perceptual dizziness (PPPD)

A chronic vestibular disorder characterized by persistent dizziness or unsteadiness that is often worse when upright, moving or exposed to complex visual environments. PPPD can coexist with FND but is not simply another name for FND. Diagnosis uses its own clinical criteria.

Photophobia

Abnormal sensitivity or intolerance to light. It is common in migraine and can occur with eye, neurological and other conditions. People with FND may also experience photophobia, but light sensitivity by itself is not evidence that a symptom is functional.

PNES

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

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

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.

Post-exertional malaise (PEM)

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.

Predictive processing

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.

Predisposing, precipitating, perpetuating, and protective factors

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.

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.

Proprioception

The nervous system’s sense of body position and movement using information from muscles, joints and other sensory receptors. Rehabilitation may use visual, tactile or movement cues when proprioceptive processing is relevant to a task.

Psychogenic

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.

R

Rehabilitation

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

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

Salience

The priority or importance the nervous system gives to a piece of information. Pain, an unexpected sound, a movement or another personally important signal can capture attention without conscious choice. Salience is studied in FND mechanism research, but it is not a diagnostic sign and does not mean a person is deliberately focusing on a symptom. See Salience, Arousal, and Feedback Loops.

Scan-negative cauda equina presentation

A presentation with symptoms that raise concern for cauda equina syndrome, such as bladder, bowel, saddle-sensation or leg symptoms, but without compressive cauda equina pathology on appropriate imaging. Some scan-negative presentations have functional features, but urgent assessment is still required when cauda equina syndrome is suspected because true compression is a medical emergency.

Selective serotonin reuptake inhibitor (SSRI) / serotonin-norepinephrine reuptake inhibitor (SNRI)

Two classes of prescription medicines commonly used for depression, anxiety and several other conditions. They may sometimes be used for coexisting symptoms or conditions in people with FND or PPPD. They are not general-purpose medicines that directly treat every FND symptom, and medication decisions belong with the prescriber.

Semiology

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.

Sensory trick

A touch, gesture or position that temporarily changes a dystonic posture or movement. Sensory tricks are classically associated with some forms of organic dystonia and can also be reported in other movement presentations. The response must be interpreted with the full clinical examination.

Somatic symptom disorder

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

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.

Swivel-chair assessment

A comparison used in selected gait assessments in which a person propels a wheeled or swivel chair while seated and the clinician compares that movement pattern with walking. A marked difference can contribute to diagnostic reasoning in functional gait disorder, but it is not diagnostic by itself and must be used safely.

Symptom variability

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

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.

Tinnitus

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

Transcutaneous electrical nerve stimulation (TENS)

A device that delivers low-voltage electrical stimulation through electrodes placed on the skin, commonly for pain management. It may be discussed as an adjunct for selected symptoms, but evidence and suitability vary and it should not be assumed to treat the functional mechanism itself.

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.

Vestibulo-ocular reflex (VOR)

A reflex that keeps vision relatively stable during head movement by moving the eyes in the opposite direction. Vestibular rehabilitation can include gaze-stability exercises involving the VOR when assessment shows they are appropriate.

Video-EEG

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.

W

Whack-a-mole sign

A descriptive examination sign in which suppressing or holding one abnormal movement is followed by a different movement appearing elsewhere. It has been described in functional movement disorders, especially functional tremor, but it is interpreted with other positive findings rather than used alone.

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.