Functional correlates of pallidal stimulation for Parkinson's disease

We measured regional cerebral blood flow with (H2O)-O-15 and positron emiss ion tomography (PET) scanning at rest and during a motor task to study the mechanism of motor improvement induced by deep brain stimulation of the int ernal globus pallidus in Parkinson's disease. Six right-handed patients wit h Parkinson's disease were scanned while performing a predictable paced seq uence of reaching movements and while observing the same screen displays an d tones. PET studies were performed ON and OFF stimulation in a medication- free state. Internal globus pallidus deep brain stimulation improved off-st ate United Parkinson's Disease Rating Scale motor ratings (37%, P < 0.002) and reduced timing errors (movement onset time, 55%, p < 0.01) as well as s patial errors (10%, p < 0.02). Concurrent regional cerebral blood flow reco rdings revealed a significant enhancement of motor activation responses in the left sensorimotor cortex (Brodmann area [BA] 4), bilaterally in the sup plementary motor area (BA 6), and in the right anterior cingulate cortex (B A 24/32). Significant correlations were evident between the improvement in motor performance and the regional cerebral blood flow changes mediated by stimulation. With internal globus pallidus deep brain stimulation, improved movement initiation correlated with regional cerebral blood flow increases in the left sensorimotor cortex and ventrolateral thalamus and in the cont ralateral cerebellum. By contrast, improved spatial accuracy correlated wit h regional cerebral blood flow increases in both cerebellar hemispheres and in the left sensorimotor cortex. These results suggest that internal globu s pallidus deep brain stimulation may selectively improve different aspects of motor performance. Multiple, overlapping neural pathways may be modulat ed by this intervention.