What is functional neurological disorder (FND) and how does it differ from neurodivergent conditions?

What is Functional Neurological Disorder and How Does It Differ from Neurodivergent Conditions?

Functional neurological disorder (FND) is a distinct neurological condition characterized by altered voluntary motor, sensory, or cognitive symptoms that are incompatible with recognized neurological diseases but cause real disability, and it is fundamentally different from neurodivergent conditions because FND is an acquired disorder of nervous system function that is potentially reversible with treatment, whereas neurodivergent conditions (like autism and ADHD) are lifelong developmental variations in brain function that are not reversible. 1

Core Characteristics of FND

FND presents with diverse neurological symptoms including:

• Weakness, movement disorders (tremor, jerks, dystonia), sensory symptoms, cognitive deficits, and seizure-like events 1
• Fatigue and persistent pain are commonly experienced as part of the disorder 1
• Symptoms are internally inconsistent—they resolve or reduce during spontaneous discussion, when attention is diverted, or during automatic functions 2
• Symptoms show inefficient and non-ergonomic patterns of movement, such as struggle behaviors including overmouthing, eye blinking, facial contortions, and excessive effort 2

The diagnosis is made based on positive clinical signs with specificities of 64-100%, not by exclusion of other conditions 3

Key Differences from Neurodivergent Conditions

Nature of the Condition

• FND is an acquired disorder of nervous system function that typically affects young and middle-aged adults and can develop after specific precipitating events 3, 4
• Neurodivergent conditions are developmental variations present from early childhood that represent different ways of processing information and interacting with the world
• FND symptoms are potentially reversible with appropriate treatment, whereas neurodivergent traits are lifelong characteristics 1, 5

Symptom Pattern

• FND symptoms are inconsistent and variable—severity changes with attention, distraction, and context in ways that don't follow predictable neurological patterns 2
• FND shows suggestibility—symptoms become more prominent when discussed 2
• Neurodivergent conditions show consistent patterns of differences in attention, social communication, sensory processing, or executive function that remain stable across contexts

Treatment Approach

• FND treatment focuses on retraining normal function through multidisciplinary rehabilitation (occupational therapy and physical therapy) with the goal of symptom resolution 1, 3
• The explanation of the diagnosis itself has therapeutic value in FND, using analogies like "a software problem, not a hardware problem" 1
• Neurodivergent conditions require accommodations, support strategies, and sometimes medication to manage specific symptoms (like ADHD), but the goal is adaptation rather than reversal of the condition 6

Diagnostic Framework for FND

The diagnosis requires positive clinical features rather than ruling out other conditions:

• Symptoms inconsistent with clinical examination and imaging findings—such as total voice loss despite normal vocal fold function 2
• Internal inconsistency—resolution during small talk or automatic functions 2
• Disproportionate severity relative to any identified injury or lesion 2

Treatment Principles

Multidisciplinary rehabilitation centered on occupational therapy and physical therapy represents first-line treatment, grounded in a biopsychosocial framework 1

Key treatment components include:

• Retraining normal movement within functional activities rather than focusing on impairment-based goals 1, 7
• Teaching self-management strategies including reestablishment of structure and routine 1
• Anxiety management techniques such as breathing techniques, progressive muscle relaxation, grounding strategies, and mindfulness 1, 7
• Intensive therapy with several sessions per week may be more successful 1

Critical Pitfalls to Avoid

• Do not treat FND like other neurological conditions by focusing on impairment rather than functional goals 1, 7
• Avoid relying primarily on pharmacological approaches 1
• Do not provide compensatory devices (wheelchairs, walkers) prematurely, as this reinforces disability 7, 6
• Never dismiss the diagnosis or suggest symptoms are "all in their head", as this increases stigma and reduces engagement 7

Expected Outcomes

Multidisciplinary studies report improvements in physical function and quality of life immediately after treatment and at follow-up periods of 12-25 months 1, 7

Many patients achieve improvement or even elimination of symptoms during the initial consultation, though this doesn't necessarily mean complete resolution 2