The neuropsychiatry of movement disorders
Purpose of review: Recent developments in the study of neuropsychiatric aspects of movement disorders, and the movement disorder seen in psychiatric disorders, are discussed. Recent findings: All of the movement disorders have associated psychiatric symptoms that are intimately associated with the onset or progression of the disorder. In Parkinson's disease, the close association with mood disorder is highlighted by the fluctuation of mental state with on and off motor periods, and the direct effect on mood of deep brain stimulation of the subthalamic nucleus area during treatment of the motor disorder. In Huntington's disease, specific psychiatric symptoms are seen: irritability is an early symptom often present well before any motor disorder, and apathy is a late symptom, indicative of fronto-striatal circuit involvement. The movement disorder seen in schizophrenia is seen as an integral part of the disorder, indicative of chronic disease and cognitive impairment, and not wholly attributable to medication. The overlap between movement disorder and psychiatry is particularly blurred for obsessive-compulsive disorder. The association with group A β-haemolytic streptococcal infection in children, and a shared model of development with Tourette's syndrome are exciting new advances in our understanding of the disorder. Summary: The neuropsychiatric features of movement disorders are a vital dimension of the understanding of the pathophysiology of the disorders, as well as of their clinical management. The close relationship between mood and motor cortico-striato-thalamic circuits in the brain makes the division of these aspects of brain functioning into the domains of separate specialities arbitrary and unhelpful.