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----------------------------------------------------------------------- Parkinson's Surgery Normalizes Cerebral Control Of Movement ----------------------------------------------------------------------- NEW ORLEANS, LA. -- October 27, 1997 -- Brain scans of persons whose symptoms improve significantly after surgery for Parkinson's disease show a clear reversal in aberrant patterns of brain activity, report Emory University researchers at this week's Society for Neuroscience meeting. "These results provide new insight into the brain mechanisms responsible for symptomatic improvement following surgery for Parkinson's disease," said Robert S. Turner, Ph.D., assistant professor of neurology at the Emory University School of Medicine. The researchers sought to determine via the brain imaging technique known as positron emission tomography (PET), whether pallidotomy surgery for Parkinson's disease has the predicted effect of restoring a normal pattern of movement-related brain activity. Indeed, improvements in physical symptoms after pallidotomy such as tremor and rigidity corresponded with improvements in brain activity, as the Emory University neurologists showed with PET scans. Activity increased in brain regions normally responsible for controlling movement and decreased in cerebral areas that showed abnormally high activation with the movement disorder. One of the next steps in this research will be to discover the significance of the unexpected increased activity observed in the brains of Parkinson's disease subjects, Dr. Turner explained. Are these activations evidence of compensatory neural mechanisms working to overcome the primary deficits of Parkinson's? Or are they part of the primary pathology of Parkinson's and as such actually cause some of the symptoms of Parkinson's? The fact clinically effective pallidotomy caused a marked reduction in these activations suggests, at least, these abnormal activations are closely linked to the pathological processes that give rise to the symptoms of Parkinson's disease, he said. Although brain imaging techniques have been used previously to study Parkinson's disease and the effects of pallidotomy on movement-related brain activity, the current study is unique in that the Emory team focused on activations correlated with speed of movement. One of the cardinal symptoms of Parkinson's disease is a marked slowness of movement. By focusing on brain areas involved in the control of movement speed, the team hoped to discover why this specific aspect of the control of movement is impaired in Parkinson's disease and why pallidotomy is an effective treatment. In addition, this approach allowed the group to identify changes in brain activity that might have actually caused the improvement in task performance after pallidotomy and distinguish those from changes in activity that were merely caused by changes in performance. Researchers have established Parkinson's disease is caused by degeneration of the dopamine neurons that innervate the basal ganglia (a group of interconnected brain areas that lie below the cerebral cortex) and this loss of dopamine causes output neurons of the basal ganglia to send excessive and abnormal inhibitory signals to large portions of the frontal cortex. Most, if not all, of the symptoms of Parkinson's, including slowness of movement, are thought to arise from the excessive inhibition of frontal cortical circuits. In support of this concept, a group at Emory headed by Mahlon DeLong, M.D., chairman of neurology at Emory, and Jerrold Vitek, M.D., Ph.D., director of the department’s functional neurosurgery section, along with groups at a number of other research centers has shown that most parkinsonian symptoms can be alleviated by pallidotomy -- a neurosurgical ablation of neurons in the globus pallidus, the main output nucleus of the basal ganglia. Pallidotomy is thought to work because it eliminates the source of abnormal inhibition of the frontal cortex, thereby allowing the patterns of neural activity needed to perform normal movements. Pallidotomy as a treatment for Parkinson's disease has gained a great deal of attention recently because of its potential for addressing some of the shortcomings of traditional therapies, Dr. Turner explained. The most common drug treatments for Parkinson's, which work by providing an artificial supply of dopamine to the basal ganglia, are usually very effective when first administered. After years of use, however, these drugs may lose their effectiveness and begin to produce serious side effects such as excessive unwanted movement and hallucinations. Copyright (c) 1997 P\S\L Consulting Group Inc. http://www.pslgroup.com/dg/3fd0a.htm ----------------------------------------------------------------------- janet paterson - 50/9 - sinemet/selegiline/prozac - [log in to unmask]