A 16-year-old patient presents with a history of severe pain in her R leg that persists several months after twisting her ankle during basketball. She reports pain in her right foot without allodynia, hyperalgesia, temperature or skin changes, but with significant swelling and motor impairment. She is walking with a crutch as she is unable to weight-bear on her right leg. She is seen by the multidisciplinary pain clinic and undergoes a unilateral lumbar sympathetic block under general anesthesia. After receiving the block and waking up from anesthesia, her pain is resolved, but now she states that she can’t feel or move either of her legs. She gets an MRI, is evaluated by neurology, and is diagnosed with Functional Neurological Symptom Disorder. What is the definition of FNSD and how might you describe it to a patient?