Deep brain stimulation for treatment of refractory Tourette syndrome: long-term follow-up

Centromedian-parafascicular deep brain stimulation induces differential functional inhibition of the motor, associative, and limbic circuits in large animals

BACKGROUND

Deep brain stimulation (DBS) of the centromedian-parafascicular (CM-Pf) thalamic nuclei has been considered an option for treating Tourette syndrome. Using a large animal DBS model, this study was designed to explore the network effects of CM-Pf DBS.

METHODS

The combination of DBS and functional magnetic resonance imaging is a powerful means of tracing brain circuitry and testing the modulatory effects of electrical stimulation on a neuronal network in vivo. With a within-subjects design, we tested the proportional effects of CM and Pf DBS by manipulating current spread and varying stimulation contacts in healthy pigs (n = 5).

RESULTS

Our results suggests that CM-Pf DBS has an inhibitory modulating effect in areas that have been suggested as contributing to impaired sensory-motor and emotional processing. The results also help to define the differential neural circuitry effects of the CM and Pf with evidence of prominent sensorimotor/associative effects for CM DBS and prominent limbic/associative effects for Pf DBS.

CONCLUSIONS

Our results support the notion that stimulation of deep brain structures, such as the CM-Pf, modulates multiple networks with cortical effects. The networks affected by CM-Pf stimulation in this study reinforce the conceptualization of Tourette syndrome as a condition with psychiatric and motor symptoms and of CM-Pf DBS as a potentially effective tool for treating both types of symptoms.

Deep brain stimulation as a tool for improving cognitive functioning in Alzheimer's dementia: a systematic review

Deep brain stimulation (DBS) is an established, in selected cases therapeutically effective, non-lesional treatment method delivering current rectangular pulses into dysfunctional brain structures via chronically implanted stimulation electrodes. DBS is a recognized method applied in movement disorders and is increasingly evaluated as a possible therapeutic option for psychiatric diseases such as refractory obsessive-compulsive disorders, Gilles de la Tourette syndrome, major depression, and substance-related addiction. Latest research indicates that DBS may be a method for improving cognitive functions in Alzheimer's dementia (AD). Translational data in healthy and AD animals appear to support this notion. Nevertheless, many aspects remain unclear, particularly with regard to the optimal target structure. The objective of this review is to present a systematic overview regarding published research on DBS and cognitive functioning in animal and human studies as well as to provide a systematic overview of the feasibility and efficacy of the treatment. We describe three studies investigating the effects of DBS in patients with dementia, using either the fornix or the nucleus basalis of Meynert (NBM) as a target. In total, we identified 25 animal studies with 10 brain structures being targeted: fornix, NBM, anterior caudate nucleus, dorsal striatum, anterior thalamic nucleus, midline thalamic nuclei, central thalamus, lateral hypothalamus, hippocampus (entorhinal cortex, perforant path), and amygdala. Considering the wide and diverse spectrum of targets, we add to this review a supposition about possible underlying mechanisms of operation and recommendations for further research.

Lessons Learned from Open-label Deep Brain Stimulation for Tourette Syndrome: Eight Cases over 7 Years

Background

Deep brain stimulation (DBS) remains an experimental but promising treatment for patients with severe refractory Gilles de la Tourette syndrome (TS). Controversial issues include the selection of patients (age and clinical presentation), the choice of brain targets to obtain optimal patient-specific outcomes, and the risk of surgery- and stimulation-related serious adverse events.

Methods

This report describes our open-label experience with eight patients with severe refractory malignant TS treated with DBS. The electrodes were placed in the midline thalamic nuclei or globus pallidus, pars internus, or both. Tics were clinically assessed in all patients pre- and postoperatively using the Modified Rush Video Protocol and the Yale Global Tic Severity Scale (YGTSS).

Results

Although three patients had marked postoperative improvement in their tics (>50% improvement on the YGTSS), the majority did not reach this level of clinical improvement. Two patients had to have their DBS leads removed (one because of postoperative infection and another because of lack of benefit).

Discussion

Our clinical experience supports the urgent need for more data and refinements in interventions and outcome measurements for severe, malignant, and medication-refractory TS. Because TS is not an etiologically homogenous clinical entity, the inclusion criteria for DBS patients and the choice of brain targets will require more refinement.

Deep brain stimulation (DBS) at the interface of neurology and psychiatry

Deep brain stimulation (DBS) is an emerging interventional therapy for well-screened patients with specific treatment-resistant neuropsychiatric diseases. Some neuropsychiatric conditions, such as Parkinson disease, have available and reasonable guideline and efficacy data, while other conditions, such as major depressive disorder and Tourette syndrome, have more limited, but promising results. This review summarizes both the efficacy and the neuroanatomical targets for DBS in four common neuropsychiatric conditions: Parkinson disease, Tourette syndrome, major depressive disorder, and obsessive-compulsive disorder. Based on emerging new research, we summarize novel approaches to optimization of stimulation for each neuropsychiatric disease and we review the potential positive and negative effects that may be observed following DBS. Finally, we summarize the likely future innovations in the field of electrical neural-network modulation.

Deep brain stimulation for Tourette syndrome

Gilles de la Tourette syndrome is a movement disorder characterized by repetitive stereotyped motor and phonic movements with varying degrees of psychiatric comorbidity. Deep brain stimulation (DBS) has emerged as a novel therapeutic intervention for patients with refractory Tourette syndrome. Since 1999, more than 100 patients have undergone DBS at various targets within the corticostriatothalamocortical network thought to be implicated in the underlying pathophysiology of Tourette syndrome. Future multicenter clinical trials and the use of a centralized online database to compare the results are necessary to determine the efficacy of DBS for Tourette syndrome.

Deep brain electrophysiological recordings provide clues to the pathophysiology of Tourette syndrome

Although ample evidence suggests that high-frequency deep brain stimulation (DBS) is an effective therapy in patients with Tourette syndrome (TS), its pathophysiology and the neurophysiological mechanisms underlying these benefits remain unclear. The DBS targets mainly used to date in TS are located within the basal ganglia-thalamo-cortical circuit compromised in this syndrome: the medial and ventral thalamic nuclei, which are way stations within the circuit, the globus pallidus and the nucleus accumbens. Neuronal activity can be electrophysiologically recorded from deep brain structures during DBS surgery (intraoperative microrecordings) or within few days after DBS electrode implantation (local field potentials, LFPs). Recordings from the thalamus in patients with TS showed that the power in low-frequency oscillations (2-15 Hz) was higher than power in high frequency oscillations (<45 Hz) and that activity in gamma band (25-45 Hz) increases when patients' clinical status improved. Effective thalamic DBS for tic reduction seems to increase high frequency band oscillations (25-45 Hz). The same oscillatory pattern persists after DBS for 1 year, therefore showing that in TS DBS does not induce persistent neuroplastic changes in the neural activity in the stimulated structures. Neurophysiological recordings from deep brain structures suggest that tics originate not from the cortex but from neuronal dysfunction in deep brain structures such as the thalamus and globus pallidus. In conclusion, DBS can induce its beneficial effects in TS by modulating specific neural rhythms in the cortico-basal ganglia thalamic network. DBS could reduce tics related increased low-frequency activity by shifting the basal ganglia-thalamic oscillation power to higher frequencies.