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Postoperative management of subthalamic nucleus stimulation for Parkinson's disease

The postoperative neurologic management of patients with deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson' s disease is a complex dynamic process that involves a progressive increase in stimulation intensity and a parallel decrease in antiparkinsonian medication while assessing the interactions of both treatments. Neurologists responsible for postoperative management of patients receiving STN DBS must have expert knowledge of the electroanatomy of the subthalamic area and be familiar with the medical treatment of motor and nonmotor symptoms, including the management of long-term complications of levodopa treatment. Neurosurgeons who perform DBS need to understand the principles that guide the postoperative adaptation of treatment. This article defines guidelines for setting stimulation parameters, adapting drugs and managing adverse effects.

Bilateral high-frequency stimulation in the subthalamic nucleus for the treatment of Parkinson disease: correlation of therapeutic effect with anatomical electrode position

OBJECT

The goal of this study was to relate the degree of clinical improvement and that of energy consumption to the anatomical position of electrode poles used for long-term stimulation.

METHODS

The authors conducted a retrospective analysis of 15 consecutive patients in whom targeting of the subthalamic nucleus (STN) had been performed using ventriculography, three-dimensional (3D) magnetic resonance (MR) imaging, and 3D computerized tomography, together with macrostimulation and teleradiographic control of the electrode position. In these patients the follow-up period ranged from 6 to 12 months. Postoperative improvement in contralateral motor symptoms, which was assessed by assigning a lateralized motor subscore of the Unified Parkinson's Disease Rating Scale (UPDRS), and stimulus intensity required for optimal treatment results were correlated with the intracerebral position of the active electrode pole. Bilateral high-frequency stimulation of the STN improved the UPDRS motor score during the medication-off period by an average of 60.5% compared with that at baseline. Repeated transfer of stereotactic coordinates from postoperative teleradiography to treatment-planning MR images documented the proper localization of the most distal electrode pole (pole 0) in the targeted STN. Nevertheless, in most cases the best clinical improvement was achieved using electrode poles that were located several millimeters above the electrode tip. If the relative improvement in motor symptoms was correlated with the required electrical energy for chronic stimulation, the best coefficient was observed for active electrode poles projecting onto white matter dorsal to the STN.

CONCLUSIONS

This observation makes blocking or activation of large fiber connections arising in the STN or running nearby more likely than electrical interference with cell bodies inside the STN. Anatomical correlates may be the pallidothalamic bundle (including Field H of Forel and the thalamic fascicle), the pallidosubthalamic tract, and/or the zona incerta.

Does stimulation of the GPi control dyskinesia by activating inhibitory axons?

A 69-year-old woman with Parkinson's disease and levodopa-induced dyskinesias had a deep brain stimulation (DBS) electrode inserted into the right globus pallidus internus (GPi). During the operation, the GPi was mapped with dual microelectrode recordings. Stimulation through one microelectrode in GPi inhibited the firing of GPi neurons recorded with another microelectrode 600--1,000 microm distant. The inhibition could be obtained with pulse widths of 150 micros and intensities as low as 10 microA. Single stimuli inhibited GPi neurons for approximately 50 ms. Trains of 300 Hz stimuli inhibited GPi neuron firing almost completely. Postoperatively, stimulation through macroelectrode contacts located in the posterior ventral pallidum controlled the patient's dyskinesias. The effect could be obtained with pulse widths of 50 micros and frequencies as low as 70--80 Hz. We postulate stimulation of the ventral pallidum controls dyskinesias by activating large axons which inhibit GPi neurons.