Somatic Symptom and Related Disorders
Functional Neurological Symptom Disorder (Conversion Disorder)
Functional Neurological Symptom Disorder, often abbreviated as FND, causes involuntary motor, sensory or episodic symptoms such as weakness, tremors, seizures or gait disturbance. The symptoms are real and can cause significant disability.
Diagnosis is based on recognised positive clinical signs of inconsistency or incompatibility with other neurological conditions, not on symptom variability alone.
What Is Functional Neurological Symptom Disorder (Conversion Disorder)?
In FND there is a problem in the way neural networks function and are controlled, not necessarily structural damage seen on imaging. Examples are limb weakness, movement disorders, sensory loss, voice or swallowing problems, and functional seizures. The term "psychogenic non-epileptic seizure (PNES)" is less commonly used because it can give the false impression that the seizure is voluntary or "just psychological". Functional seizures are not due to an epileptic electrical discharge, but remain involuntary.
Key Features and Signs
The presentation is varied and may include one or more of the following:
- Weakness or paralysis of a limb, difficulty walking, or episodes of falling.
- Tremor, seizures, jerking movements, dystonic postures, or slowness that changes in a characteristic way.
- Functional seizures with altered consciousness or movement, which need to be distinguished from epilepsy and syncope.
- Numbness, altered sensation, functional loss of vision or hearing.
- Difficulties with speech, voice or swallowing, or a globus sensation, after appropriate assessment of possible organic causes.
- Fatigue, pain, cognitive blurring, and sleep problems that may co-occur and impair functioning.
How It Is Diagnosed
Diagnosis is usually made by a neurologist based on history, examination, and positive clinical signs, while tests are used to target co-occurring or alternative causes.
- There are one or more symptoms of altered voluntary motor or sensory function.
- Clinical findings provide evidence of incompatibility between the symptom and recognized neurological or medical conditions.
- The symptom is not better explained by another medical or mental disorder and causes clinically significant distress or impairment, or warrants medical evaluation.
- A psychological stressor need not be identified, and its absence does not rule out the diagnosis.
How It Can Affect Daily Life
Symptoms may limit walking, driving, work, self-care, communication, and social participation. They may vary within the same day, which does not mean they are feigned. Chronicity and the need for help do not indicate that the person has chosen a "patient identity" or is seeking financial gain. Doubt from professionals or loved ones often increases distress and delays recovery.
Causes and associated factors
FND is multifactorial. Previous injury, pain, infection, migraine, other neurological condition, stress, traumatic experiences, and patterns of attention or expectation may play a different role in each person. None of these factors are mandatory or prove that the symptoms are psychological in nature. The modern explanation focuses on dysfunction of prediction, attention, and motor or sensory control networks.
Similar or Co-occurring Conditions
A positive diagnosis does not stop appropriate investigation of new or different symptoms:
- Epilepsy and functional seizures can co-occur, so each type of episode needs to be characterized.
- Multiple sclerosis, Parkinson's disease, migraine, neuropathy and other neurological diseases can co-occur with FND.
- Syncope, sleep disorders, cardiac events, and medication adverse effects may resemble functional seizures.
- Factitious disorder and feigning involve the deliberate production or presentation of symptoms, which is not a feature of FND.
- Anxiety, depression, PTSD and chronic pain can co-occur and are treated separately.
Treatment and Support
Care begins with a clear explanation of the positive diagnosis and is usually multidisciplinary.
- The neurologist explains what positive signs support the diagnosis and that the symptoms are involuntary and potentially reversible, although recovery cannot be guaranteed.
- Specialised physical therapy retrains normal patterns of movement and attention, with a gradual return to functional goals.
- Occupational therapy, speech therapy or swallowing therapy are added as needed.
- Psychological therapy may help with functional seizures, stress, fear of movement or co-occurring trauma. It does not imply that symptoms are imaginary.
- Medications are used for specific co-occurring conditions, not as a specific treatment of the functional neurological symptom.
When to Seek Help
A new neurological symptom, first seizure, or significant change in a known pattern requires medical evaluation. Even with FND already diagnosed, not all new symptoms should be automatically attributed to it. Sudden facial or limb weakness, slurred speech, prolonged seizure, serious injury, loss of consciousness, or difficulty breathing are emergency signs.
Frequently Asked Questions
Is functional neurological disorder "in the mind"?
Not in the imaginary or voluntary sense. It is an actual dysfunction of the way the nervous system controls movement, sensation or episodes of altered awareness, and is diagnosed by positive clinical signs.
Can FND and epilepsy co-occur?
Yes. A person can have functional and epileptic seizures. This requires a careful characterization of the different episodes and, often, a video-electroencephalogram.
Do normal tests show FND?
No. Tests help identify or rule out other conditions, but FND relies primarily on characteristically positive findings on clinical examination.