REFERENCE LIBRARY
FND Reference
Functional Neurological Disorder (FND) is a neurological disorder that affects how brain networks control and experience functions such as movement, sensation, awareness, speech, vision and thinking.
Different people can experience very different combinations of symptoms. FND is diagnosed using positive clinical features—patterns and examination findings that show how a function is working and help the clinician recognize FND.
This reference is designed for finding information quickly. If you already know the symptom you want to learn about, you can start below. Each symptom has one path for understanding and diagnosis and another for recovery techniques.
For shared explanations of diagnosis, investigations and everyday function, see Understanding an FND Diagnosis.
For a step-by-step introduction to FND, including how current research helps us understand it, visit the FND Course.
Find an FND Symptom
Common Symptoms and Conditions
Understanding FND
More Reference Topics
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Find an FND Symptom
Functional Limb Weakness
Understanding & Diagnosis
Recovery Techniques
An arm or leg may feel weak, heavy or difficult to control. Movement may be possible in some activities or circumstances but much more difficult when trying to perform another movement deliberately.
Functional Paralysis
Understanding & Diagnosis
Recovery Techniques
A person may experience periods when voluntary movement of a limb or larger part of the body becomes extremely limited or temporarily unavailable. The symptom is more extensive than the partial loss of strength usually described as functional weakness.
Functional Tremor
Understanding & Diagnosis — includes detailed distractibility and entrainment explanations.
Recovery Techniques
A hand, arm, leg or another part of the body may shake rhythmically or irregularly. The speed, strength or pattern of the shaking may change during different movements, tasks or situations.
Functional Jerks / Myoclonus
Understanding & Diagnosis
EEG–EMG diagnostic assessment
Recovery Techniques
A body part may make sudden, brief movements that feel involuntary. These jerks may happen occasionally, repeatedly or in bursts.
Functional Dystonia and Fixed Postures
Understanding & Diagnosis
Recovery Techniques
A hand, foot, limb, neck or another body part may pull, twist, curl or become held in an unusual posture. The position can sometimes become painful or difficult to release.
Functional Gait Disorder
Understanding & Diagnosis
Recovery Techniques
Walking may become difficult because of changes such as leg dragging, knee buckling, unusual stepping, swaying, freezing or difficulty coordinating the normal sequence of walking.
Functional Seizures
Understanding & Diagnosis
Recovery Techniques
Episodes can include changes in awareness, responsiveness or movement. A person may collapse, shake, stiffen, become still, lose awareness of their surroundings or experience another recurring seizure-like event.
Functional Drop Attacks
Understanding & Diagnosis
Recovery Techniques
A person may suddenly drop or fall toward the ground, sometimes with very little warning, and may recover from the event quickly.
Functional Tics
Understanding & Diagnosis
Recovery Techniques
Eight Detailed Recovery and Support Pages
Sudden movements, gestures or sounds may occur repeatedly and feel difficult or impossible to prevent at the moment they happen.
Functional Sensory Symptoms
Understanding & Diagnosis
Recovery Techniques
Touch, temperature, pain or awareness of part of the body may feel altered. An area may feel numb, strange, unusually sensitive or less connected to the person’s normal sense of their body.
Functional Visual Symptoms
Understanding & Diagnosis
Recovery Techniques
Vision may become blurred, narrowed, doubled, intermittently absent or otherwise altered. The way the visual difficulty changes across situations can provide important diagnostic information.
Functional Speech and Voice Symptoms
Understanding & Diagnosis
Recovery Techniques
Speech or voice may become quiet, strained, slowed, stuttered, unusually accented or temporarily difficult to produce. The person’s ability to speak can sometimes vary considerably across circumstances.
Functional Swallowing Symptoms and Globus
Understanding & Diagnosis
Recovery Techniques
Swallowing may feel difficult, effortful or unusual. Some people experience persistent tightness or the feeling of a lump or obstruction in the throat.
Functional Cough and Upper-Airway Symptoms
Understanding & Diagnosis
Recovery Techniques
Coughing, throat clearing or other upper-airway responses may become persistent or repeatedly triggered as the nervous system develops an established pattern of responding.
Functional Cognitive Disorder
Understanding & Diagnosis
Recovery Techniques
Memory, concentration, word finding, attention or thinking may become unreliable in everyday life. A characteristic feature can be a large difference between what feels inaccessible in one situation and what the brain can successfully do in another.
Functional Facial Symptoms
Understanding & Diagnosis
Recovery Techniques
Part of the face may pull, tighten, spasm, droop or feel difficult to control. These changes may affect the mouth, jaw, eye or larger areas of the face.
Find an FND Symptom
Common Symptoms and Conditions
Understanding FND
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Common Symptoms and Conditions That Occur Alongside FND
- Migraine and Chronic Headache
- Tinnitus
- Chronic Pain
- Fatigue
- Sleep Disorders
- Persistent Postural-Perceptual Dizziness (PPPD) and Persistent Dizziness
- Autonomic Symptoms
Find an FND Symptom
Common Symptoms and Conditions
Understanding FND
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Understanding FND
FND involves changes in how the brain and nervous system organize and control important functions.
The nervous system performs an enormous amount of work automatically. When you walk across a room, you do not consciously calculate which muscles should contract, how far each joint should move or exactly where your foot should land. Your brain normally coordinates those processes automatically.
The same principle applies to many other abilities. Speaking, maintaining balance, recognizing sensations, directing attention and retrieving familiar information all depend heavily on processes that normally operate without conscious supervision.
In FND, these systems can become disrupted.
That helps explain why a person may have the physical capacity needed for a function while still being unable to access that function normally at a particular moment. It also helps explain why the same function can sometimes work differently during another activity or under different circumstances.
These changes in function are important in diagnosis. Clinicians can sometimes demonstrate them during an examination. For example, a movement that is difficult when performed deliberately may become easier when the nervous system produces part of the same movement automatically.
This is called internal inconsistency, and in the right clinical context it can provide positive evidence for FND.
The same observation has important implications for rehabilitation.
If the nervous system can sometimes produce a movement more normally, rehabilitation may be able to build upon that available function. Treatment often works toward making movement, speech, attention or another affected ability more automatic again rather than relying on greater conscious effort.
FND Can Change From Moment to Moment
Brain function is dynamic. The ability to perform a task can change depending on what the nervous system is doing at that moment.
Attention can influence symptoms. So can pain, fatigue, sleep, illness, sensory stimulation, previous experiences, expectations, emotional states and the demands being placed on the brain and body.
These influences vary greatly between people. Understanding an individual’s pattern can help identify circumstances in which normal function becomes easier to access and circumstances in which symptoms become more difficult.
This variability is therefore useful information. It can help with diagnosis, help a person understand their symptoms and sometimes reveal opportunities for rehabilitation.
FND Can Affect Many Different Systems
The brain networks involved in movement do not work in isolation.
Movement interacts with sensation. Sensation interacts with attention. Attention interacts with awareness, prediction and memory. All of these processes interact with the brain’s understanding of the body and the environment around it.
Researchers therefore study FND as a disorder involving networks and interactions between networks rather than searching for one single brain area that explains every symptom.
This also helps explain why two people with FND can have very different experiences. One person may predominantly experience weakness. Another may experience seizures. Another may have difficulties involving movement, cognition and sensation together.
There is unlikely to be one mechanism that completely explains every symptom in every person with FND.
FND and Other Health Conditions
People with FND can also have other neurological, medical or psychological conditions.
Each condition can contribute something different to a person’s health. They can also interact. Migraine may increase sensory sensitivity. Chronic pain may change movement and attention. Poor sleep may make concentration or movement more difficult. An existing neurological condition can occur alongside functional neurological symptoms.
Recognizing these interactions helps build a more complete understanding of the person rather than trying to make one diagnosis explain everything.
The pages throughout this reference explore these ideas in greater detail.
For a more structured explanation beginning with the basic concepts and building progressively, continue to the FND Course.
Find an FND Symptom
Common Symptoms and Conditions
Understanding FND
More Reference Topics
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More FND Reference Topics
Positive Diagnosis of FND
FND has recognizable clinical features. This section explains how clinicians use the history, examination and positive diagnostic signs to build evidence for an FND diagnosis.
Understanding Positive Diagnostic Signs
Read about positive diagnostic signs
Positive signs can show how an affected function changes under different conditions. This section explains why those changes matter and what they can tell the clinician.
Diagnostic Techniques
Some positive signs can be demonstrated using specific examination techniques. These pages explain how the techniques work, what clinicians observe, the anatomy and physiology involved, and the limits of each finding.
Tests and Investigations
Read about tests and investigations
Scans, EEGs, blood tests and other investigations answer different clinical questions. This section explains what these tests can contribute to an assessment and how they fit alongside the positive diagnosis of FND.
FND Alongside Other Conditions
Read about coexisting conditions
More than one diagnosis can contribute to a person’s symptoms. This section looks at how FND can interact with other neurological and medical conditions.
Why Symptoms Vary
Read about symptom variability
FND symptoms can change across movements, situations and times of day. These variations can provide useful clues about how the affected function is being controlled.
Explaining an FND Diagnosis
A useful explanation can help a person understand what has been found during the assessment, why the diagnosis was made and what the diagnosis may mean for treatment and recovery.
Family, Friends and Other Supporters
Supporters can play an important role in understanding symptoms, responding during difficult periods, helping with rehabilitation and supporting greater independence.
Find an FND Symptom
Common Symptoms and Conditions
Understanding FND
More Reference Topics
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