Globus Pallidus Internus Deep Brain Stimulation for Tourette's syndrome
The purpose of a study was to investigate the role of Globus pallidus internus Deep Brain Stimulation (DBS) in dopamine and dopamine transporter metabolism, and to explore the regulatory role of DBS on dopaminergic neurons in Tourette's syndrome by constructing an autoimmune model.
Serum with high concentrations of antinuclear antibodies or PBS was injected into rats' striatum by stereotactic technique and micro-pump. Then, electrodes were planted into rats' globus pallidus internus. Concentration of dopamine and dopamine transporter in striatum was detected by ELISA, immunohistochemistry and Western Blot after 7 days high frequency stimulation (130Hz).
The tic behavior score of Tourette's syndrome group was higher than control group (P<0.01). After high frequency stimulation (130Hz), the scores of Tourette's syndrome model group and control group significantly decreased. The concentration of dopamine in Tourette's syndrome model group and control group also significantly decreased after electrical stimulation (P<0.05). In addition, immunohistochemically analysis and Western Blot test results were presented: Dopamine transporter in Tourette's syndrome model non-stimulation group was lower than the Tourette's syndrome model stimulation group, dopamine transporter in control non-stimulation group was lower than the control stimulation group (P<0.05).
The results of this study elucidated that the mechanism of GPi-DBS in the treatment of Tourette's syndrome involved monoamine neurotransmitters, especially dopamine system, which affected the metabolism and transport of corresponding neurotransmitters, played an important role in regulating the concentration of synaptic neurotransmitters, and changed the biological activity of basal ganglia nerve circuits 1).
A study of 15 patients with long-term amGPi DBS for severe TS investigated whether a specific anatomical site within the amGPi correlated with optimal clinical outcome for the measures of tics, obsessive compulsive behaviour (OCB), and mood.
Validated clinical assessments were used to measure tics, OCB, quality of life, anxiety, and depression before DBS and at the latest follow-up (17-82 months). Electric field simulations were created for each patient using information on electrode location and individual stimulation parameters. A subsequent regression analysis correlated these patient-specific simulations to percentage changes in outcome measures in order to identify any significant voxels related to clinical improvement.
A region within the ventral limbic GPi, specifically on the medial medullary lamina in the pallidum at the level of the AC-PC, was significantly associated with improved tics but not mood or OCB outcome.
This study adds further support to the application of DBS in a tic-related network, though factors such as patient sample size and clinical heterogeneity remain as limitations and replication is required 2).
Bilateral/unilateral GPi-DBS was performed in 24 patients with TS. They evaluated symptoms of tics and obsessive-compulsive disorder (OCD) through the Yale Global Tic Severity Scale (YGTSS) and Yale-Brown Obsessive-compulsive Scale (Y-BOCS). They used the Wechsler Adult Intelligence Scale-Revised in China (WAIS-RC) to evaluate the safety of the treatment. We conducted follow-up assessments of all patients for at least 12 months (12-99 months).
Symptoms of tics and OCD were significantly relieved at a 12-month follow-up assessment. The mean YGTSS score was 74.04 ± 11.52, 49.83 ± 10.91, 32.58 ± 7.97, and 31.21 ± 8.87 at baseline, 3, 6, and 12 months, respectively. The mean YGTSS scores obtained at the follow-up assessments were significantly different from the baseline (P < 0.05). The improvement in motor tics was superior to that in phonic tics. The mean Y-BOCS scores were 21.61 ± 4.97, 18 ± 4.58, 14.39 ± 3.99, and 13.78 ± 4.56 at baseline, 3, 6, and 12 months, respectively (P < 0.05). We observed a remarkable improvement in psychiatric comorbidities, such as OCD and attention-deficit hyperactivity disorder, after the procedure. WAIS-RC scores were comparable before and after the operation. There were no severe postoperative complications.
GPi-DBS appears to comprehensively alleviate tic symptoms and psychiatric comorbidities in patients with TS, thus significantly improving patients' quality of life 3).