Diagnostic Features of Functional Neurological Disorder (FND)
Introduction to FND
- The American Academy of Neurology suggests that FND presents with genuine neurological symptoms that are internally inconsistent, disproportionate to examination findings, and demonstrate variability with attention, establishing the diagnosis rather than exclusion of other diseases 1, 2
Motor Symptoms
- Functional limb weakness manifests as weakness that improves during distraction, shows inconsistent patterns during examination, and demonstrates give-way weakness that differs from neurological patterns 3
- Movement disorders, including tremor that varies in amplitude with distraction, dystonia with abnormal postures that worsen with attention, and jerky movements that are distractible, are common in FND 3
Communication and Swallowing Symptoms
- Functional dysphonia presents as total or partial voice loss despite normal vocal fold structure and function on laryngoscopy, according to the American Academy of Otolaryngology 1, 2
- Speech disorders, including articulation problems, dysfluency, and functional foreign accent syndrome, where symptoms resolve or reduce during spontaneous conversation or when attention is diverted, are characteristic of FND 1, 7
Key Diagnostic Features
- Internal inconsistency, where symptoms vary in ways that don't follow recognized neurological patterns, is a key diagnostic feature of FND 1, 3
- Disproportionate severity, where symptom severity exceeds what would be expected from examination findings, imaging, or the nature of any precipitating injury, is also characteristic of FND 1, 2