Pathophysiology of Involuntary Movements and Volitional Disorders

National Institute Of Neurological Disorders And Stroke

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Abstract

The pathophysiology of psychogenic movement disorders (PMD) is very poorly understood. These disorders are common in the population, diagnosis is difficult and treatment typically ineffective. We are studying the mechanisms underlying these disorders using cognitive tasks, neurophysiological testing, psychiatric measures, and functional imaging. One functional imaging study is an fMRI investigation of patients with tremor, and results show abnormally reduced activation in the temporoparietal junction region. We have initiated similar studies in patients with psychogenic myoclonus. We are also looking for abnormal activations related to tasks that probe functions such as emotional expression and movement inhibition, and have shown abnormal activation in the amygdala. We have also investigated these patients for their sense of agency during fMRI studies, similar to the way we have studied normal subjects. The origin of tics is generally unknown, and we have been approaching physiology in several ways. Tourette syndrome patients report "premonitory urge" and other sensory abnormalities associated with the presence of tics. We have been studying tic genesis with functional neuroimaging and EEG, and intend a series of studies looking at the physiology of the sensory urge. We are also seeing if we can detect the urge with real time fMRI. For many years, we have been collecting families with essential tremor looking for possible genetic abnormalities, and in several families found an area suggestive of genetic linkage on chromosome 6 and 11. This work is being pursued with additional sequencing in conjunction with Drs. Lev Goldfarb and David Goldman.