Deep Brain Stimulation for Tourette Syndrome: Lessons Learned and Future Directions

Paediatric deep brain stimulation: ethical considerations in malignant Tourette syndrome

Gilles de la Tourette syndrome (TS) is a childhood neuropsychiatric disorder characterised by the presence of motor and vocal tics. Patients with malignant TS experience severe disease sequelae; risking morbidity and mortality due to tics, self-harm, psychiatric comorbidities and suicide. By definition, those cases termed 'malignant' are refractory to all conventional psychiatric and pharmacological regimens. In these instances, deep brain stimulation (DBS) may be efficacious. Current 2015 guidelines recommend a 6-month period absent of suicidal ideation before DBS is offered to patients with TS. We therefore wondered whether it may be ethically justifiable to offer DBS to a minor with malignant TS. We begin with a discussion of non-maleficence and beneficence. New evidence suggests that suicide risk in young patients with TS has been underestimated. In turn, DBS may represent an invaluable opportunity for children with malignant TS to secure future safety, independence and fulfilment. Postponing treatment is associated with additional risks. Ultimately, we assert this unique risk-benefit calculus justifies offering DBS to paediatric patients with malignant TS. A multidisciplinary team of clinicians must determine whether DBS is in the best interest of their individual patients. We conclude with a suggestion for future TS-DBS guidelines regarding suicidal ideation. The importance of informed consent and assent is underscored.

Anterior pallidal deep brain stimulation for Tourette's syndrome: a randomised, double-blind, controlled trial

BACKGROUND

Deep brain stimulation (DBS) has been proposed to treat patients with severe Tourette's syndrome, and open-label trials and two small double-blind trials have tested DBS of the posterior and the anterior internal globus pallidus (aGPi). We aimed to specifically assess the efficacy of aGPi DBS for severe Tourette's syndrome.

METHODS

In this randomised, double-blind, controlled trial, we recruited patients aged 18-60 years with severe and medically refractory Tourette's syndrome from eight hospitals specialised in movement disorders in France. Enrolled patients received surgery to implant bilateral electrodes for aGPi DBS; 3 months later they were randomly assigned (1:1 ratio with a block size of eight; computer-generated pairwise randomisation according to order of enrolment) to receive either active or sham stimulation for the subsequent 3 months in a double-blind fashion. All patients then received open-label active stimulation for the subsequent 6 months. Patients and clinicians assessing outcomes were masked to treatment allocation; an unmasked clinician was responsible for stimulation parameter programming, with intensity set below the side-effect threshold. The primary endpoint was difference in Yale Global Tic Severity Scale (YGTSS) score between the beginning and end of the 3 month double-blind period, as assessed with a Mann-Whitney-Wilcoxon test in all randomly allocated patients who received active or sham stimulation during the double-blind period. We assessed safety in all patients who were enrolled and received surgery for aGPi DBS. This trial is registered with ClinicalTrials.gov, number NCT00478842.

FINDINGS

Between Dec 6, 2007, and Dec 13, 2012, we enrolled 19 patients. We randomly assigned 17 (89%) patients, with 16 completing blinded assessments (seven [44%] in the active stimulation group and nine [56%] in the sham stimulation group). We noted no significant difference in YGTSS score change between the beginning and the end of the 3 month double-blind period between groups (active group median YGTSS score 68·5 [IQR 34·0 to 83·5] at the beginning and 62·5 [51·5 to 72·0] at the end, median change 1·1% [IQR -23·9 to 38·1]; sham group 73·0 [69·0 to 79·0] and 79·0 [59·0 to 81·5], median change 0·0% [-10·6 to 4·8]; p=0·39). 15 serious adverse events (three in patients who withdrew before stimulation and six each in the active and sham stimulation groups) occurred in 13 patients (three who withdrew before randomisation, four in the active group, and six in the sham group), with infections in DBS hardware in four patients (two who withdrew before randomisation, one in the sham stimulation group, and one in the active stimulation group). Other serious adverse events included one electrode misplacement (active stimulation group), one episode of depressive signs (active stimulation group), and three episodes of increased tic severity and anxiety (two in the sham stimulation group and one in the active stimulation group).

INTERPRETATION

3 months of aGPi DBS is insufficient to decrease tic severity for patients with Tourette's syndrome. Future research is needed to investigate the efficacy of aGPi DBS for patients over longer periods with optimal stimulation parameters and to identify potential predictors of the therapeutic response.

FUNDING

French Ministry of Health.

The Use of Deep Brain Stimulation in Tourette Syndrome

Tourette syndrome (TS) is a childhood neurobehavioural disorder, characterised by the presence of motor and vocal tics, typically starting in childhood but persisting in around 20% of patients into adulthood. In those patients who do not respond to pharmacological or behavioural therapy, deep brain stimulation (DBS) may be a suitable option for potential symptom improvement. This manuscript attempts to summarise the outcomes of DBS at different targets, explore the possible mechanisms of action of DBS in TS, as well as the potential of adaptive DBS. There will also be a focus on the future challenges faced in designing optimized trials.