Functional neurological symptom disorder (FNSD), also referred to as dissociative neurological symptom disorder (DNSD), is a condition in which patients experience neurological symptoms such as weakness, movement problems, sensory symptoms, and convulsions. As a functional disorder, there is, by definition, no known disease process affecting the structure of the body, yet the person experiences symptoms relating to their body function. Symptoms of functional neurological disorders are clinically recognisable, but are not categorically associated with a definable organic disease.
The intended contrast is with an organic brain syndrome, where a pathology (disease process) which affects the body's physiology can be identified. The diagnosis is made based on positive signs and symptoms in the history and examination during consultation of a neurologist.
Physiotherapy is particularly helpful for patients with motor symptoms (e.g., weakness, problems with gait, movement disorders) and tailored cognitive behavioral therapy has the best evidence in patients with non-epileptic seizures.