Functional neurological disorder (FND) is a condition where there is a problem with how the brain and body communicate, rather than a structural problem. Symptoms can include seizures, paralysis, fatigue, pain, sensory issues, speech problems, and more. FND was previously called conversion disorder and is not related to neurological diseases like MS or epilepsy. It occurs when there is a disruption in how the brain processes and transmits messages to different parts of the body.