Conversion Disorder (Functional Neurological Disorder)

Conversion disorder, now called functional neurological symptom disorder or functional neurological disorder (FND), is a condition in which a person experiences genuine neurological symptoms, such as weakness, seizures, tremor or numbness, that are not explained by a recognized neurological disease and show a pattern that clinicians can positively identify as functional. The symptoms are real, not feigned, and can cause major disability. FND is one of the most common reasons people see a neurologist, yet it has long been among the most misunderstood and stigmatized diagnoses in medicine.

A common way to explain FND is through a computer analogy: the "hardware" of the nervous system (its structure) is intact, but the "software" (how the brain sends and receives signals about the body) is not working properly. This helps explain why scans can be normal while symptoms are very real.

History and Names

Functional symptoms have been described for thousands of years, historically under the label "hysteria." In the late nineteenth century, the French neurologist Jean-Martin Charcot studied such patients at the Salpêtrière hospital in Paris. Sigmund Freud and Josef Breuer then proposed that unbearable emotional conflict could be "converted" into physical symptoms, which gave rise to the term conversion disorder.

Over the past two decades, neurologists and psychiatrists have moved toward the term functional neurological disorder. The DSM-5 (2013) listed "conversion disorder (functional neurological symptom disorder)," removed the requirement to identify a psychological cause, and the DSM-5-TR (2022) reversed the order to "functional neurological symptom disorder (conversion disorder)." The ICD-11 classifies these symptoms as dissociative neurological symptom disorder. Many patients find "functional" less stigmatizing, because it describes how the nervous system is working rather than implying the symptoms are "all in the head."

DSM-5 Diagnostic Criteria

The DSM-5-TR criteria for functional neurological symptom disorder (ICD-10-CM F44.4–F44.7) describe what a clinician looks for:

1. One or more symptoms of altered voluntary motor or sensory function.
2. Clinical findings provide evidence of incompatibility between the symptom and recognized neurological or medical conditions.
3. The symptom or deficit is not better explained by another medical or mental disorder.
4. The symptom or deficit causes clinically significant distress or impairment, or warrants medical evaluation.

Clinicians specify the symptom type: weakness or paralysis; abnormal movement (such as tremor, dystonia or gait problems); swallowing symptoms; speech symptoms; attacks or seizures; anesthesia or sensory loss; special sensory symptoms (vision, smell or hearing); or mixed symptoms. They may also note whether symptoms are acute (under 6 months) or persistent, and whether a psychological stressor is present.

Notably, the DSM-5 dropped earlier requirements that a psychological stressor be identified and that the person not be feigning. Research had shown that stressors are not always present, and that the "not feigning" judgment cannot be reliably made.

Common Presentations

Many people also experience fatigue, pain, poor sleep, memory and concentration difficulties, and dizziness. Some have functional symptoms alongside a neurological disease such as epilepsy or multiple sclerosis, which can make diagnosis more complex.

How Diagnosis Is Made

FND is no longer considered a diagnosis of exclusion, made only when tests come back normal. Instead, neurologists look for positive clinical signs that show a functional pattern, such as:

• Hoover's sign: in functional leg weakness, hip extension is weak when tested directly but returns to normal when the person flexes the opposite hip.
• Tremor entrainment: a functional tremor changes rhythm to match a tapping movement made with the other hand.
• Distractibility and variability: symptoms often improve when attention is drawn elsewhere.
• Features of functional seizures: such as eyes closed during the event, prolonged duration and side-to-side movements. The most reliable test is capturing a typical episode on video-EEG.

Imaging, EEG and other tests are used to check for other or co-occurring conditions, but the diagnosis rests on these positive features. Follow-up studies show that misdiagnosis is uncommon, at around 4% in modern series, similar to other neurological and psychiatric conditions.

Distinguishing related conditions

• Somatic symptom disorder: focuses on excessive thoughts, feelings and behaviors about symptoms, which may or may not be functional.
• Factitious disorder: involves deliberately producing or exaggerating symptoms, without obvious external reward.
• Malingering: deliberately faking symptoms for external gain; not a mental disorder and not the same as FND.
• Dissociative disorders: FND can overlap with dissociation, and ICD-11 places it within the dissociative disorders.

Mechanism

Research over the past two decades has transformed understanding of FND:

• Brain networks: functional imaging studies show altered activity and connectivity between brain networks for motor control, attention, emotion and the sense of agency (the feeling of being in control of one's movements).
• Predictive processing: neurologist Mark Edwards and colleagues proposed that FND involves abnormal predictions or expectations about the body, combined with excessive attention to it, which shape how movements and sensations are experienced.
• Triggers: symptoms often begin after a physical event such as an injury, infection, surgery, migraine or panic attack.
• Psychological factors: adverse childhood experiences, trauma, anxiety and depression are more common in people with FND and increase vulnerability, but they are not present in everyone and do not "cause" the disorder in a simple way.

This biopsychosocial understanding moves away from the older idea that symptoms are purely psychological, while still recognizing that emotions and stress influence the nervous system.

Treatment

Diagnostic Communication

The first step in treatment is a clear, respectful explanation. Neurologists such as Jon Stone recommend explaining what FND is, showing the person the positive signs that confirm it, stating that symptoms are genuine, common and potentially reversible, and avoiding any suggestion of faking or attention-seeking. Studies suggest that people who understand and accept the diagnosis tend to have better outcomes.

Specialized Physiotherapy

Physiotherapy designed for FND helps retrain movement, often using distraction and focusing attention away from the affected limb, gradually restoring normal movement patterns. Early trials were promising. However, the large Physio4FMD trial, published in 2024, found that specialist physiotherapy did not lead to significantly better physical function at 12 months than standard community physiotherapy, although some secondary outcomes favored it. Research is ongoing into who benefits most.

Psychological Treatment

Cognitive behavioral therapy adapted for FND helps people understand symptom triggers, reduce avoidance and unhelpful attention to the body, and manage stress, anxiety and low mood. The large CODES trial (2020) found that CBT added to standardized care for dissociative seizures did not significantly reduce seizure frequency at 12 months, but did improve several secondary outcomes, such as distress, seizure-free periods and quality of life. Treatment for co-occurring anxiety, depression or PTSD is also important. See cognitive behavioral therapy.

Multidisciplinary Programs

For people with more severe or complex symptoms, coordinated care combining neurology, psychiatry or psychology, physiotherapy, occupational therapy and speech therapy may be offered, sometimes in inpatient rehabilitation programs. Occupational therapy can help people manage fatigue and return to daily activities.

Medication

No medication treats FND directly. A doctor may discuss medication for co-occurring conditions such as depression, anxiety, pain or sleep problems. For people wrongly diagnosed with epilepsy, a careful review of anti-seizure medicines by their specialist is often part of care, since those medicines do not help functional seizures.

Self-management and support

Many people find it helpful to learn about FND from reputable sources, pace activities, maintain routines, and build skills for managing stress, such as grounding techniques. Patient organizations such as FND Hope and FND Action provide information and peer support.

Course and Outlook

Outcomes vary widely. Some people, particularly those with recent onset, recover fully within weeks or months. Others have persistent or recurring symptoms for years. Shorter symptom duration, younger age, clear understanding of the diagnosis and early access to rehabilitation are generally linked to better outcomes. Living with FND can also bring stigma, frustration with health services and financial strain, so practical and emotional support matter.

Conclusion

Functional neurological disorder is one of the most common and under-treated conditions in modern medicine. The historical framing as "hysterical" or "psychogenic" left many people dismissed. Modern understanding recognizes FND as a real disorder of how the brain controls and perceives the body, diagnosed by positive signs and treated with clear explanation, rehabilitation and psychological therapy. Research is still refining which treatments work best, but many people improve, and respectful, informed care makes a real difference.