Functional Neurological Symptom Disorder (Conversion Disorder) By Joel E Dimsdale, MD, University of California, San Diego Reviewed / Revised Aug 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Functional neurological symptom disorder, previously known as conversion disorder, consists of neurologic symptoms or deficits that develop unconsciously and nonvolitionally and usually involve motor or sensory function.