Functional Neurological Symptom Disorder

Functional neurological symptom disorder (conversion disorder, FND) is genuine neurological symptoms (weakness, movement disorder, seizures, sensory loss, gait disorder) incompatible with recognised neurological disease and diagnosed by positive clinical signs.

• Incidence 4 to 12 per 100,000; women 2 to 3 times more affected; onset in young adults.
• Pathophysiology: abnormal attention, predictive coding, limbic and sensorimotor network dysfunction; triggers include injury, illness, stress, panic and dissociation.
• Common in neurology clinics (about 15%) and coexists with epilepsy in 10 to 20% of functional seizure patients.
• Disability and quality of life impairment equal to structural neurological disease.

• Functional limb weakness, tremor (variable, entrainable), dystonia, gait disorder (dragging monoplegic gait, astasia abasia), non epileptic seizures (long duration, eye closure, rare injury), speech and visual symptoms.
• Pain, fatigue, dissociation common; la belle indifference is not discriminating.
• Fluctuating, distractible deficits.

• Positive signs: Hoover sign, hip abductor sign, give way weakness, tremor entrainment and distractibility, midline splitting, drift without pronation.
• Functional seizures: video EEG showing no epileptiform activity during typical events; normal prolactin is not diagnostic.
• Appropriate investigation (MRI) to exclude comorbid disease; avoid over testing.
• Screen for depression, anxiety, trauma and dissociation.

• Clear, positive explanation of the diagnosis (real, common, reversible), with written information, is the first step.
• Specialist physiotherapy (retraining automatic movement, distraction) for motor disorders, occupational therapy and speech therapy.
• Psychotherapy: CBT based, tailored to functional seizures (reduces frequency).
• Treat comorbid anxiety, depression or PTSD with SSRIs (sertraline 50 to 200 mg); antiseizure drugs not indicated unless epilepsy coexists, with gradual withdrawal.
• Avoid unnecessary hospital admissions; emergency plan for seizures.
• Multidisciplinary care and follow up.