THE SUBTHALAMIC NUCLEUS IN PARKINSONS-DISEASE AND PROGRESSIVE SUPRANUCLEAR PALSY

The subthalamus has become a promising target for the neurosurgical tr eatment of parkinsonian symptoms. We have used unbiased counting techn iques to quantify the neuronal populations of the subthalamic nucleus in patients with idiopathic Parkinson's disease and progressive supran uclear palsy. Tn addition, the type of calcium binding proteins contai ned within these subthalamic neurons was established using immunohisto chemistry Most of the 550,000 subthalamic neurons contain either parva lbumin or calretinin calcium binding proteins, and patients with idiop athic Parkinson's disease sustained no damage to this nucleus. This is consistent with current theories of basal ganglia circuitry, which po stulate that overstimulation of this excitatory nucleus contributes to the inhibition of the motor thalamus via the activation of inhibitory relays. In contrast, we found that there was substantial cell loss in the subthalamus in progressive supranuclear palsy (45 to 85% neuronal reduction) and that both cell types were equally affected. Extracellu lar neurofibrillary tangles as well as tau-positive glia were observed in the subthalamus of these cases. As the patients with Parkinson's d isease and progressive supranuclear palsy all had overlapping parkinso nian symptoms, the loss of subthalamic stimulation within the basal ga nglia of progressive supranuclear palsy cases is puzzling, unless thei r parkinsonian symptoms were generated by an alternate mechanism.