Guidelines for Diagnosis and Management of Functional Neurological Disorder (FND)

Definition and Core Diagnostic Principles

• FND is diagnosed by identifying positive clinical signs of internal inconsistency rather than by exclusion, requiring one or more symptoms of altered voluntary motor or sensory function that are incompatible with recognized neurological conditions and that cause clinically significant distress or impairment. 1
• Clinical examination findings that demonstrate incompatibility with known neurological or medical diseases constitute the cornerstone of the diagnosis. 1, 2
• The diagnosis is established by positive signs, not by ruling out structural disease. 1, 2

Positive Clinical Signs

Internal Inconsistency

• Symptom variability during distraction – symptoms resolve or lessen when the patient’s attention is diverted (e.g., during spontaneous conversation or automatic tasks). 3
• Suggestibility – symptoms become more prominent when they are discussed or examined. 3
• Disproportionate severity – the observed speech or motor deficits far exceed what would be expected from any documented injury or lesion location. 3

Movement Pattern Abnormalities

• Inefficient movement patterns – patients display excessive struggle behaviors such as over‑mouthing, frequent eye blinking, facial contortions, exaggerated breathing effort, neck/shoulder tension, and frequent postural shifts. 3
• Paradoxical fatigue pattern – in cases of reported weakness, speech, voice, or swallowing fatigue occurs in the direction of muscle hyper‑function rather than hypo‑function. 3

Specific Functional Seizure Sign

Symptom Spectrum (Coded Manifestations)

• Speech/communication – functional dysphonia, dysarthria, stuttering, and functional foreign‑accent syndrome. 1
• Other functional manifestations – functional cough and laryngeal hypersensitivity syndrome. 1

Essential Historical Elements

• A thorough history must capture the functional impact of symptoms on daily activities, work, and relationships. 4
• Identification of precipitating physical triggers (e.g., recent infection, injury, head trauma, or surgery) is essential. 4

Biopsychosocial Framework (Three‑Factor Model)

• FND is conceptualized using a three‑factor biopsychosocial model that remains aetiologically neutral. 5, 4

Predisposing Vulnerabilities

• Biological – genetic factors, prior functional symptoms, pre‑existing medical illness (especially traumatic brain injury). 4
• Psychological – personality traits such as neuroticism, high stress reactivity, perfectionism, low self‑esteem, interpersonal difficulties, and suggestibility. 4
• Social – adverse life events, chronic stress, poor relationships, and symptom modeling within families. 4

Precipitating Mechanisms

• Physical triggers (injury, strain, pain, surgery, medical illness, infection, head trauma) are often more relevant than psychological stressors. 4

Perpetuating Factors

• Self‑directed attention – heightened focus on symptoms exacerbates them. 5, 6
• Avoidance behaviors – activity restriction and dependence on aids or equipment maintain dysfunction. 5
• Abnormal movement patterns – habituated inefficient motor patterns perpetuate symptoms. 3, 4

Diagnostic Pitfalls

• Absence of psychological stressors or psychiatric comorbidity does not exclude FND. 7
• Diagnosing by exclusion alone is incorrect; FND requires the presence of positive clinical features. 1, 2

Co‑existence with Structural Neurological Disease

• FND can co‑occur with structural neurological pathology; the presence of organic findings does not rule out a functional overlay, which is identified through positive clinical features distinguishing functional from structural elements. 3, 4

Clinical Impact and Burden

• Patients with FND experience high levels of distress and disability, leading to substantial disease burden, elevated unemployment rates, reduced quality of life, increased utilization of social care services, and added stigma. 5

Diagnostic Criteria and Clinical Features of Functional Neurological Disorder

Core Diagnostic Requirements (DSM‑5)

• The diagnosis of functional neurological disorder (FND) requires one or more symptoms of altered voluntary motor or sensory function that are incompatible with recognized neurological or medical conditions and that cause clinically significant distress or functional impairment. 8
• Presence of neurological symptoms affecting voluntary motor or sensory function is a mandatory criterion. 9
• Clinical examination must demonstrate findings that are incompatible with known neurological or medical diseases. 10
• The patient must experience clinically significant distress or functional impairment related to the symptoms. 9
• Symptoms must not be better explained by another neurological or medical condition. 8

Symptom Subtype Specification

• Motor manifestations – include weakness, movement disorders such as tremor, jerks, dystonia, and gait abnormalities. 10
• Sensory manifestations – include altered sensation, numbness, and pain. 10
• Non‑epileptic seizure‑like events – dissociative or psychogenic nonepileptic seizures. 10
• Speech and communication disturbances – dysphonia, dysarthria, and stuttering. 8
• Swallowing disturbances – functional dysphagia. 9
• Cognitive complaints – problems with memory, concentration, and word‑finding. 11
• Each subtype can be explicitly coded (e.g., “FND with speech symptoms” or “FND with swallowing symptoms”). 8

Essential Historical Elements for Diagnosis

• Detailed description of onset characteristics (how and when symptoms began and the patient’s perceived cause). 12
• Clarification of the temporal pattern (constant vs. intermittent, aggravating/relieving factors, any periods of complete resolution). 12
• Review of previous medical encounters (information conveyed by other providers and outcomes of prior treatments). 13
• Assessment of functional impact on daily activities, work, and relationships. 12
• Identification of precipitating context, especially recent physical triggers such as infection, injury, or head trauma. 8

Biopsychosocial Framework for Etiology

• Predisposing factors may be biological, psychological, or social vulnerabilities that increase susceptibility to FND. 10
• Precipitating factors are frequently physical events (e.g., infection, injury) rather than purely psychological stressors. 9
• Perpetuating factors include maladaptive illness beliefs, avoidance behaviours, and heightened attention to symptoms. 12
• The framework stresses aetiological neutrality, viewing FND as a disorder of function without implying exclusive psychological causation. 8

Diagnostic Pitfalls and Clarifications

• The absence of psychological stressors or psychiatric comorbidity does not rule out FND. 13
• Symptoms often arise after physical triggers (infection, injury, head trauma) rather than after psychological trauma. 13
• Repeatedly questioning patients about trauma when none is reported can damage the therapeutic relationship. 13
• Lack of identifiable adversity or distress should not be used as evidence against a functional diagnosis. 8

Specific Positive Feature for Functional Seizures

• Eyes closed during an event is a distinguishing sign that favors functional (non‑epileptic) seizures over epileptic seizures. 11