Deep brain stimulation for dystonia confirming a somatotopic organization in the globus pallidus internus.

OBJECT: In patients with dystonia, symptoms vary greatly in their extent and severity. The efficacy of pallidal stimulation is now established, but an interindividual variability in the responses to this treatment exists. A retrospective analysis of postoperative magnetic resonance (MR) images demonstrated millimetric variations in the positions of electrode contacts inside the posterolateroventral portion of the globus pallidus internus (GPi). It therefore seemed very likely that there is a somatotopic organization within the GPi. The goal of this study was to examine the positions of specific electrode contacts according to patients' clinical evolution, so that a somatotopic organization within the GPi could be defined. METHODS: This study included 19 patients (17 of whom were right handed) with generalized dystonia who were treated by bilateral stimulation of the GPi. Patients were examined pre- and postoperatively by using the Burke-Fahn-Marsden Dystonia Rating Scale. Dividing the patient's body into three parts--cervicoaxial area, superior limb, and inferior limb--we determined the following: 1) where the dystonic symptoms started; 2) where symptoms predominated at the time of surgery; and 3) where the highest postoperative improvement was observed. Variations in clinical response were correlated to the positions of the electrode contacts. All activated electrode contacts were in the posterolateroventral portion of the GPi (Laitinen target). A correlation between the contact location measured longitudinally and the part of the body in which the highest improvement was observed (three different areas; p = 0.004) showed that a location more anterior for the inferior limb and one more posterior for the superior limb were delineated for the right side, but not for the left side. CONCLUSIONS: Inside the posterolateroventral subvolume of the GPi on the right side, three statistically different locations of electrode contacts were determined to be primary deep brain stimulation treatment sites for particular body parts in cases of dystonia.

Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results.

OBJECT: Primary generalized dystonia (PGD) is a medically refractory disease of the brain causing twisting or spasmodic movements and abnormal postures. In more than 30% of cases it is associated with the autosomal DYT1 mutation. Continuous electrical stimulation of the globus pallidus internus (GPi) has been used successfully in the treatment of PGD. The aim of this study was to examine the long-term efficacy and safety of deep brain stimulation (DBS) in the treatment of PGD in children and adults with and without the DYT1 mutation. METHODS: Thirty-one patients with PGD were selected for surgery. Electrodes were bilaterally implanted under stereotactic guidance and connected to neurostimulators that were inserted subcutaneously. Efficacy was evaluated by comparing scores on the clinical and functional Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) before and after implantation. The efficacy of stimulation improved with time. After 2 years, compared with preoperative values, the mean (+/- standard deviation) clinical and functional BFMDRS scores had improved by 79 +/- 19% and 65 +/- 33%, respectively. At the 2-year follow-up examination the improvement was comparable in patients with and without the DYT1 mutation in both the functional (p = 0.12) and clinical (p = 0.33) scores. Children displayed greater improvements in the clinical score than adult patients (p = 0.04) at 2 years of follow up. In contrast, there was no significant difference in functional scores between children and adults (p = 0.95). CONCLUSIONS: Electrical stimulation of the GPi is an effective, reversible, and adaptable treatment for PGD and should be considered for conditions refractory to pharmaceutical therapies.

Evolution of brain impedance in dystonic patients treated by GPI electrical stimulation.

Deep Brain Stimulation is an effective treatment of generalized dystonia. Optimal stimulation parameters vary between patients. This article investigates the influence of electrical brain impedance and delivered current on the brain response to stimulation. Twenty-four patients were bilaterally stimulated in the globus pallidus internus through two implanted four-contact electrodes. The variation of brain impedance and current measurements was correlated with stimulation parameters, time course, and clinical outcome. When a contact was activated, a statistically significant and reversible decrease of brain impedance was found. Impedance and current values and their variations with time significantly differed between patients. The absolute impedance did not significantly correlate with the final outcome. We conclude that the reversible decrease of impedance reflects an adaptive long-term mechanism, which could be due to a plasticity phenomenon, but has no prognostic value. Impedance and current measurements give new complementary information for parameter adjustment and trouble shooting and should therefore be included in all patients' follow-up.

Comparison of atlas- and magnetic resonance imaging-based stereotactic targeting of the globus pallidus internus in the performance of deep brain stimulation for treatment of dystonia.

OBJECT: To assess the validity of relying on atlases during stereotactic neurosurgery, the authors compared target coordinates in the globus pallidus internus (GPi) obtained using magnetic resonance (MR) imaging with those determined using an atlas. The targets were used in deep brain stimulation (DBS) for the treatment of generalized dystonia. METHODS: Thirty-five patients, who were treated using bilateral DBS of the GPi, were included in this study. The target was selected on three-dimensional MR images by direct visual recognition of the GPi. The coordinates were automatically recorded using dedicated software. They were translated into the anterior commissure-posterior commissure (AC-PC) coordinate system by using a matrix transformation process. The same GPi target was defined, based on the locations of brain structures shown in the atlases of Schaltenbrand and Talairach. Magnetic resonance imaging-based GPi target coordinates were statistically compared with the corresponding atlas-based coordinates by applying the Student t-test. A significant difference (p < 0.001) was demonstrated in x, y, and z directions between MR imaging-based and Schaltenbrand atlas-derived target coordinates. The comparison with normalized Talairach atlas coordinates demonstrated a significant difference (p < 0.01) in the y and z directions, although not in the x direction (p = 0.12). No significant correlation existed between MR imaging-based target coordinates and patient age (p > 0.1). No significant correlation was observed between MR imaging-based target coordinates and patient sex in the y and z directions (p > 0.9), although it was significant in the x direction (p < 0.05). A significant variation in coordinates and the length of the AC-PC line was revealed only in the y direction (p < 0.005). CONCLUSIONS: A significant difference was found between target coordinates obtained by direct visual targeting on MR images (validated by postoperative clinical results) and those obtained by indirect targeting based on atlases.

Deep brain stimulation for dystonia. Surgical technique.

Stimulation electrodes are implanted under general anesthesia, without intra-operative electrophysiology or clinical testing, based only on stereotactic MRI and direct anatomical localization of the postero-ventro-basal GPi. We retrospectively analyzed the surgical procedure that has been designed and implemented in our center, using the Leksell G frame, for initiating deep brain stimulation in 65 dystonic patients. We report the surgical technique and the hardware and software complications. We recommend immediate postoperative stereotactic MRI under general anesthesia as a prerequisite to check the reliability of MR acquisition (magnet stability) and the exact localization of each electrode. This technique allowed us to reduce the duration of the operation to 4 h, including general anesthesia, frame fixation, MRI acquisition, implantation of two electrodes under radioscopic control, immediate postoperative stereotactic MRI and frame removal. Surgery-related morbidity was very low with a 0% hemorrhage rate and three delayed unilateral infections re-operated 6 months later. Hardware and software complications were rare. The advances in 3D-MR imaging permit the electrode implantation for deep brain stimulation without resorting to intraoperative localization techniques, which is especially helpful in children and for treating dystonia. The maximum follow-up period is 58 months (first case: November 1996). GPi stimulation has proven to be an effective treatment for most dystonic syndromes with particular efficacy in the disease due to the DYT1 mutation.