What clinical features should I look for to differentiate Functional Neurological Disorder (FND) from other neurological conditions?

Clinical features to differentiate Functional Neurological Disorder (FND) from other neurological conditions include:

• Positive physical signs: FND diagnosis is based on positive signs rather than exclusion, such as inconsistency of symptoms and signs that do not conform to known neurological disease patterns. For example, limb weakness that fluctuates or improves with distraction or specific maneuvers (e.g., a limb returning briefly to normal during examination) suggests FND rather than structural damage.
• Symptom variability and fluctuation: Symptoms in FND often fluctuate, evolve over time, and may worsen during times of stress, unlike many progressive neurological diseases.
• Discrepancy between voluntary and automatic movements: In FND, automatic movements may be preserved while voluntary movements are impaired, indicating a problem with brain signalling rather than structural damage.
• Functional seizures: These are characterized by sudden dissociative, trance-like states without epileptiform activity on EEG, differentiating them from epileptic seizures.
• Absence of structural abnormalities: Normal neuroimaging and neurophysiological tests support FND diagnosis, although some neurological conditions may also have normal imaging.
• Associated psychological symptoms: Anxiety, depression, and stress often coexist and may exacerbate symptoms, which is common in FND.
• Symptom patterns inconsistent with known neurological diseases: For example, dystonia in FND may show unusual features such as fixed postures that do not follow typical neurological patterns.

Referral to neurology specialists is recommended for confirmation and to exclude coexisting neurological conditions, as comorbid neurological disorders occur in about 20% of FND cases. The diagnosis should be explained as a brain network disorder affecting signal processing rather than structural damage, emphasizing that symptoms are genuine and potentially reversible with appropriate treatment ¹,².