Movement disorders: neurodevelopment and neurobehavioural expression.

Braak and co-workers have recently shown that movement disorders such as Parkinson's disease develop progressively over years with early neuronal losses in brainstem regions caudal to the substantia nigra. The relevance of this finding to notions of comorbidity between movement disorders and psychiatric symptoms was recognised at the recent meeting concerning, "Implications of Comorbidity for the Etiology and Treatment of Neuropsychiatric Disorders" held in Oct. 2005 in Mazagon, Spain. The identification of stages in the early development of neurodegenerative disorders appeared to unify multiple, diverse findings. These included: novel therapeutic innovations for Parkinson's disease, Alzheimer's disease and depression in the aged; the neurochemical ontogeny of drug-induced oral dyskinesias; the types of chemical agents abused in neuropsychiatric states; postnatal iron overload effects upon the functional and interactive role of dopaminergic and noradrenergic pathways that contribute to the expression of movement disorders; and the spectrum of motor symptoms expressed in schizophrenia and attention deficit hyperactivity disorder and the eventual treatment of these disorders. A continued focus on a number of neuropsychiatric diseases as progressive disorders may lead to further advances in understanding their etiology and in developing better therapeutics.