Anatomical and biochemical basis of the extrapyramidal disorders

1. Degeneration of various components of the extrapyramidal system has been correlated with specific clinical syndromes. 2. In Parkinson's disease, loss of ascending nigrostriatal fibers is associated with reduction of presynaptic dopamine binding and increase of postsynaptic dopamine binding. The latter is reversed by treatment with dopamine agonists. 3. In Huntington's disease, multiple types of striatal neurons are lost, with their corresponding enzymes and receptors. 4. In tardive dyskinesias, there are no specific neuropathological findings, but increased amounts of striatal dopamine receptors. 5. Knowledge of the chemical nature of the pallidal outflow to the thalamus may be the next most important step in the pharmacological control of extrapyramidal function.