Functional Neurological Disorder (FND), also known as functional neurologic disorder or formerly conversion disorder, is a condition where the brain and nervous system do not function properly, despite no structural damage or known disease causing the symptoms. The disorder involves problems in how the brain sends and receives signals to the body, leading to a variety of neurological symptoms such as weakness, paralysis, seizures, abnormal movements, sensory changes, speech difficulties, and cognitive issues. These symptoms are real and can cause significant distress and impairment. FND is different from neurological diseases caused by structural damage (like stroke or epilepsy) because the brain itself is undamaged but malfunctions in its control of movement, sensation, or other functions. The exact cause of FND is not fully understood, but it may be linked to changes in brain networks that affect a person's control over their actions, often triggered or worsened by stress or trauma. Diagnosis is made through clinical evaluation since there is no single test for FND, and treatment typically involves a multidisciplinary approach including physical therapy, psychotherapy, and symptom management. In summary, FND is a functional disorder of the nervous system where symptoms arise from brain function abnormalities without structural brain damage, causing real and often disabling neurological symptoms.