DEFINITION

• Functional neurological symptom disorder (conversion disorder) is defined as the presence of neurological symptoms with no known structural basis. The diagnosis can be made once neurological symptoms such as weakness, abnormal movements, or seizure-like activity are shown to be incompatible with pathophysiology of known neurologic disease.
• Functional neurological symptom disorder (conversion disorder) is classified under the Somatic Symptom and Related Disorders section of the Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5).[1]Other diagnoses under this section include somatic symptom disorder, illness anxiety disorder, and factitious disorder.
• Known primarily in the 19th century as hysteria, and the 20th century as conversion disorder, functional neurologic symptoms have a rich and complex history with constantly shifting diagnostic labels, definitions, and theories of etiology. Other synonyms/related terms include psychosomatic, psychogenic, somatoform, and dissociative disorders. Debates are ongoing re: "functional" versus "psychogenic" as an optimal label.
• When considering this diagnosis, it is important to have a firm understanding of somatization.
  • Somatization is the expression of mental phenomena as physical (somatic) symptoms.
  • There is a continuum of unconscious/non-volitional display of symptoms (patient unaware of the non-physiologic nature of symptoms) to conscious/volitional display (patient aware of the non-physiologic nature of symptoms).
  • Also important is the difference between primary gain (positive internal motivations) vs. secondary gain (positive external motivations).
    
    • Primary gain example: A patient feels guilty about not being able to perform a task, but if there is a medical condition justifying this inability, the guilt diminishes.
    • Secondary gain example: A patient is allowed to miss work and gets financial compensation as the result of a medical condition.
    • Any given patient with conversion disorder will have primary and/or secondary gains associated. Patients may not be consciously aware of associations.