Deep brain stimulation of the subthalamic nucleus for Parkinson's disease: methodologic aspects and clinical criteria.

The technique of deep brain stimulation (DBS) for the treatment of Parkinson's disease (PD) is evolving very rapidly. The subthalamic nucleus (STN) has become the preferred target in the past few years since our group demonstrated that high-frequency stimulation in this nucleus improves all cardinal features of PD, including resting tremor. This benefit in the parkinsonian symptoms allows a drastic reduction in daily levodopa requirements. Dyskinesias become drastically attenuated, possibly as a consequence of reduced dopaminergic medication but also because STN DBS may stabilize basal ganglia output activity, thus avoiding the problems associated with standard levodopa replacement therapy. DBS of the STN is associated with a marked improvement of motor function even in patients with advanced PD. Such a large degree of benefit in parkinsonian features relies on two crucial points that must be taken into consideration for achieving the best possible results with this technique: proper selection of patients and accuracy in targeting the STN. From a neurosurgical point of view, we believe that the most precise localization of the STN is obtained by using ventriculography to determine the stereotactic coordinates of the STN. This is complemented with intraoperative neuronal microrecording to define physiologically the sensorimotor region of the nucleus. Future advances in neuroimaging techniques may well lead to modifications of our current methodology.