PaUldotomy Increases Activity of Motor Association Cortex in Parkmson's Disease: A Positron Emission Tomographc Study

Stereotactic posteroventral pallidotomy can improve motor performance in Parkinson's disease. Interruption of inhibi-tory pallidal projections to ventrolateral thalamus, components of a cortical-basal ganglia motor loop allows for this clinical benefit. We hypothesized that pallidotomy would lead to increased movement related activity in motor cortical areas receiving projections from ventrolateral thalamus. This was tested in 6 Parkinson's disease patients who under-went stereotactic posteroventral pallidotomy. Each patient was imaged with positron emission tomography (:PET) measures of regional cerebral blood flow (rCBF) during performance of a simple prehension task and at rest. Scans were acquired before and 17 weeks after surgery. After pallidotomy, movement-related changes of rCBF increased significantly in both the supplementary motor area (SMA) and premotor cortex but not in primary motor cortex. The results demonstrate the importance of pallidothalamic circuitry for regulating volitional movements and confirni that disruption of inhibitory input to the ventrolateral thalamus can augment movement-related activity in motor associa-tion areas