Staged implantation of multiple electrodes in the internal globus pallidus in the treatment of primary generalized dystonia

Alternative Deep Brain Stimulation Targets in the Treatment of Isolated Dystonic Syndromes: A Multicenter Experience-Based Survey

BACKGROUND

The globus pallidus internus (GPi) is the traditional evidence-based deep brain stimulation (DBS) target for treating dystonia. Although patients with isolated "primary" dystonia respond best to GPi-DBS, some are primary or secondary nonresponders (improvement <25%), showing variability in clinical response.

OBJECTIVE

The aim was to survey current practices regarding alternative DBS targets for isolated dystonia patients with focus on nonresponders to GPi-DBS.

METHODS

A 42-question survey was emailed and distributed during a DBS conference to clinicians involved in DBS for dystonia. The survey covered (1) use of alternative DBS targets as primary or rescue options, (2) target selection based on dystonia phenomenology, (3) experience with secondary nonresponders to GPi-DBS, and (4) management of patients with additional DBS leads.

RESULTS

The response rate was 53.8%, including neurologists and neurosurgeons from 28 DBS centers in 13 countries; 89% of neurologists and 86% of neurosurgeons used alternative DBS targets to GPi, with subthalamic nucleus being the most common initial or rescue alternative to GPi. Patients with additional tremor received DBS in the ventral intermediate nucleus or caudal zona incerta. Individual experience ranged from 5 to 25 patients. Most patients were still receiving dual target stimulation at the last follow-up.

CONCLUSIONS

We show that more than 85% of surveyed clinicians use alternative DBS targets, mostly in some isolated dystonia patients not adequately responsive to GPi-DBS. More knowledge is needed to evaluate outcomes in alternative targets and establish the best strategies for managing insufficient GPi-DBS response in dystonia patients with diverse phenomenology. Our article contributes to establishing a clearer time frame and criteria for defining nonresponders in dystonia patients undergoing DBS.

The role of genetics in the treatment of dystonia with deep brain stimulation: Systematic review and Meta-analysis

BACKGROUND

Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions that lead to involuntary postures or repetitive movements. Genetic mutations are being increasingly recognized as a cause of dystonia. Deep brain stimulation (DBS) is one of the limited treatment options available. However, there are varying reports on its efficacy in genetic dystonias. This systematic review of the characteristics of genetic dystonias treated with DBS and their outcomes aims to aid in the evaluation of eligibility for such treatment.

METHODS

We performed a PUBMED search of all papers related to genetic dystonias and DBS up until April 2022. In addition to performing a systematic review, we also performed a meta-analysis to assess the role of the mutation on DBS response. We included cases that had a confirmed genetic mutation and DBS along with pre-and post-operative BFMDRS.

RESULTS

Ninety-one reports met our inclusion criteria and from them, 235 cases were analyzed. Based on our analysis DYT-TOR1A dystonia had the best evidence for DBS response and Rapid-Onset Dystonia Parkinsonism was among the least responsive to DBS.

CONCLUSION

While our report supports the role of genetics in DBS selection and response, it is limited by the rarity of the individual genetic conditions, the reliance on case reports and case series, and the limited ability to obtain genetic testing on a large scale in real-time as opposed to retrospectively as in many cases.

Globus pallidus internus activity increases during voluntary movement in children with dystonia

The rate model of basal ganglia function predicts that muscle activity in dystonia is due to disinhibition of thalamus resulting from decreased inhibitory input from pallidum. We seek to test this hypothesis in children with dyskinetic cerebral palsy undergoing evaluation for deep brain stimulation (DBS) to analyze movement-related activity in different brain regions. The results revealed prominent beta-band frequency peaks in the globus pallidus interna (GPi), ventral oralis anterior/posterior (VoaVop) subnuclei of the thalamus, and subthalamic nucleus (STN) during movement but not at rest. Connectivity analysis indicated stronger coupling between STN-VoaVop and STN-GPi compared to GPi-STN. These findings contradict the hypothesis of decreased thalamic inhibition in dystonia, suggesting that abnormal patterns of inhibition and disinhibition, rather than reduced GPi activity, contribute to the disorder. Additionally, the study implies that correcting abnormalities in GPi function may explain the effectiveness of DBS targeting the STN and GPi in treating dystonia.

Microendoscopic transventricular deep brain stimulation of the anterior nucleus of the thalamus as a safe treatment in intractable epilepsy: A feasibility study

INTRODUCTION

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is proposed in patients with severe intractable epilepsy. When used, the transventricular approach increases the risk of bleeding due the anatomy around the entry point in the thalamus. To avoid such a complication, we used a transventricular microendoscopic technique.

METHODS

We performed a retrospective study of nine adult patients who were surgically treated for refractory epilepsy between 2010 and 2019 by DBS of the anterior thalamic nucleus.

RESULTS

Endoscopy provides a direct visual control of the entry point of the lead in the thalamus through the ventricle by avoiding ependymal vessels. No hemorrhage was recorded and accuracy was systematically checked by intraoperative stereotactic MRI. We reported a responder rate improvement in 88.9% of patients at 1 year and in 87.5% at 2 years. We showed a significant decrease in global seizure count per month one year after DBS (68.1%; P=0.013) leading to an overall improvement in quality of life. No major adverse effect was recorded during the follow-up. ANT DBS showed a prominent significant effect with a decrease of the number of generalized seizures.

CONCLUSION

We aimed at a better ANT/lead collimation using a vertical transventricular approach under microendoscopic monitoring. This technique permitted to demonstrate the safety and the accuracy of the procedure.

Increased movement-related signals in both basal ganglia and cerebellar output pathways in two children with dystonia

The contribution of different brain regions to movement abnormalities in children with dystonia is unknown. Three awake subjects undergoing depth electrode implantation for assessments of potential deep brain recording targets performed a rhythmic figure-8 drawing task. Two subjects had dystonia, one was undergoing testing for treatment of Tourette Syndrome and had neither dystonia nor abnormal movements during testing. Movement-related signals were evaluated by determining the magnitude of task-related frequency components. Brain signals were recorded in globus pallidus internus (GPi), the ventral oralis anterior/posterior (VoaVop) and the ventral intermediate (Vim) nuclei of the thalamus. In comparison to the subject without dystonia, both children with dystonia showed increased task-related activity in GPi and Vim. This finding is consistent with a role of both basal ganglia and cerebellar outputs in the pathogenesis of dystonia. Our results further suggest that frequency analysis of brain recordings during cyclic movements may be a useful tool for analysis of the presence of movement-related signals in various brain regions.

Should the Globus Pallidus Targeting Be Refined in Dystonia?

BACKGROUND AND STUDY AIMS

 Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is a highly effective therapy for primary generalized and focal dystonias, but therapeutic success is compromised by a nonresponder rate of up to 20%. Variability in electrode placement and in tissue stimulated inside the GPi may explain in part different outcomes among patients. Refinement of the target within the pallidal area could be helpful for surgery planning and clinical outcomes. The objective of this study was to discuss current and potential methodological (somatotopy, neuroimaging, and neurophysiology) aspects that might assist neurosurgical targeting of the GPi, aiming to treat generalized or focal dystonia.

METHODS

 We selected published studies by searching electronic databases and scanning the reference lists for articles that examined the anatomical and electrophysiologic aspects of the GPi in patients with idiopathic/inherited dystonia who underwent functional neurosurgical procedures.

RESULTS

 The sensorimotor sector of the GPi was the best target to treat dystonic symptoms, and was localized at its lateral posteroventral portion. The effective volume of tissue activated (VTA) to treat dystonia had a mean volume of 153 mm³ in the posterior GPi area. Initial tractography studies evaluated the close relation between the electrode localization and pallidothalamic tract to control dystonic symptoms.Regarding the somatotopy, the more ventral, lateral, and posterior areas of the GPi are associated with orofacial and cervical representation. In contrast, the more dorsal, medial, and anterior areas are associated with the lower limbs; between those areas, there is the representation of the upper limb. Excessive pallidal synchronization has a peak at the theta band of 3 to 8 Hz, which might be responsible for generating dystonic symptoms.

CONCLUSIONS

 Somatotopy assessment of posteroventral GPi contributes to target-specific GPi sectors related to segmental body symptoms. Tractography delineates GPi output pathways that might guide electrode implants, and electrophysiology might assist in pointing out areas of excessive theta synchronization. Finally, the identification of oscillatory electrophysiologic features that correlate with symptoms might enable closed-loop approaches in the future.

Regulatory Mechanism for Absence Seizures in Bidirectional Interactive Thalamocortical Model via Different Targeted Therapy Schemes

Recent clinical practice has found that the spike-wave discharge (SWD) scopes of absence seizures change from small cortical region to large thalamocortical networks, which has also been proved by theoretical simulation. The best biophysics explanation is that there are interactions between coupled cortico-thalamic and thalamocortical circuits. To agree with experiment results and describe the phenomena better, we constructed a coupled thalamocortical model with bidirectional channel (CTMBC) to account for the causes of absence seizures which are connected by the principle of two-way communication of neural pathways. By adjusting the coupling strength of bidirectional pathways, the spike-wave discharges are reproduced. Regulatory mechanism for absence seizures is further applied to CTMBC via four different targeted therapy schemes, such as deep brain stimulation (DBS), charge-balanced biphasic pulse (CBBP), coordinated reset stimulation (CRS) 1 : 0, and (CRS) 3 : 2. The new CTMBC model shows that neurodiversity in bidirectional interactive channel could supply theory reference for the bidirectional communication mode of thalamocortical networks and the hypothesis validation of pathogenesis.

A practical guide to troubleshooting pallidal deep brain stimulation issues in patients with dystonia

High frequency deep brain stimulation (DBS) of the internal portion of the globus pallidus has, in the last two decades, become a mainstream therapy for the management of medically-refractory dystonia syndromes. Such increasing uptake places an onus on movement disorder physicians to become familiar with this treatment modality, in particular optimal patient selection for the procedure and how to troubleshoot problems relating to sub-optimal efficacy and therapy-related side effects. Deep brain stimulation for dystonic conditions presents some unique challenges. For example, the frequent lack of immediate change in clinical status following stimulation alterations means that programming often relies on personal experience and local practice rather than real-time indicators of efficacy. Further, dystonia is a highly heterogeneous disorder, making the development of unifying guidelines and programming algorithms for DBS in this population difficult. Consequently, physicians may feel less confident in managing DBS for dystonia as compared to other indications e.g. Parkinson's disease. In this review, we integrate our years of personal experience of the programming of DBS systems for dystonia with a critical appraisal of the literature to produce a practical guide for troubleshooting common issues encountered in patients with dystonia treated with DBS, in the hope of improving the care for these patients.

Secondary Worsening Following DYT1 Dystonia Deep Brain Stimulation: A Multi-country Cohort

Objective: To reveal clinical characteristics of suboptimal responses to deep brain stimulation (DBS) in a multi-country DYT1 dystonia cohort. Methods: In this multi-country multi-center retrospective study, we analyzed the clinical data of DYT1 patients who experienced suboptimal responses to DBS defined as <30% improvement in dystonia scales at the last follow-up compared with baseline. We used a literature-driven historical cohort of 112 DYT1 patients for comparison. Results: Approximately 8% of our study cohort (11 out of 132) experienced suboptimal responses to DBS. Compared with the historical cohort, the multi-country cohort with suboptimal responses had a significantly younger age at onset (mean, 7.0 vs. 8.4 years; p = 0.025) and younger age at DBS (mean, 12.0 vs. 18.6 years; p = 0.019). Additionally, cranial involvement was more common in the multi-country cohort (before DBS, 64% vs. 45%, p = 0.074; before or after DBS, 91% vs. 47%, p = 0.001). Mean motor improvement at the last follow-up from baseline were 0% and 66% for the multi-country and historical cohorts, respectively. All 11 patients of the multi-country cohort had generalization of dystonia within 2.5 years after disease onset. All patients experienced dystonia improvement of >30% postoperatively; however, secondary worsening of dystonia commenced between 6 months and 3 years following DBS. The improvement at the last follow-up was less than 30% despite optimally-placed leads, a trial of multiple programming settings, and additional DBS surgeries in all patients. The on-/off-stimulation comparison at the long-term follow-up demonstrated beneficial effects of DBS despite missing the threshold of 30% improvement over baseline. Conclusion: Approximately 8% of patients represent a more aggressive phenotype of DYT1 dystonia characterized by younger age at onset, faster disease progression, and cranial involvement, which seems to be associated with long-term suboptimal responses to DBS (e.g., secondary worsening). This information could be useful for both clinicians and patients in clinical decision making and patient counseling before and following DBS implantations. Patients with this phenotype may have different neuroplasticity, neurogenetics, or possibly distinct neurophysiology.

Closed-Loop Control of Absence Seizures Inspired by Feedback Modulation of Basal Ganglia to the Corticothalamic Circuit

Basal ganglia (BG) has been demonstrated to play the role of modulation for absence seizure generated in the corticothalamic (CT) circuit. But it is unknown what the principle of modulation is and how to improve the modulation if BG fails to hold back the absence seizures. Although neurostimulation has been surgically employed to improve the clinical symptom of patients with epilepsy, the mechanism underlying the neurostimulation regulation is still unclear. In addition, it is not clear what sort of the spatiotemporal patterned stimulation protocols can effectively abate absence seizures with less side effect and energy consumption. Here, we address these issues on the previously proposed BG-CT model. In particular, we develop a reduced corticothalamic (RCT) moldel by viewing BG as a 2I:3O feedback modulator. By calculating the mean firing rate (MFR) and triggering mean firing rate (TMFR), we find that absence seizures can be induced or abated using the neurostimulations through driving the MFRs of the related neurons to fall into or be kicked out of the regions bounded by the TMFRs. In particular, closed-loop m:n ON-OFF anodic-cathodic-cathodic (ACC) triphase coordinated resetting stimulation (CRS) applied on the CT circuit and designed with the TMFR of subthalamic nucleus (STN) in BG could achieve the satisfying abatement effects of absence seizures with the least current consumption.

Clinically applicable delineation of the pallidal sensorimotor region in patients with advanced Parkinson's disease: study of probabilistic and deterministic tractography

OBJECTIVE

Deep brain stimulation (DBS) is an effective procedure in improving motor symptoms for patients with advanced Parkinson's disease (PD) through the use of high-frequency stimulation. Although one of the most commonly used target sites for DBS, sensorimotor regions of the globus pallidus interna (GPi) have yet to be thoroughly described with advanced neuroimaging analysis in vivo for human subjects. Furthermore, many imaging studies to date have been performed in a research setting and bring into question the feasibility of their applications in a clinical setting, such as for surgical planning. This study compares two different tractography methods applied to clinically feasible acquisition sequences in identifying sensorimotor regions of the GPi and the subthalamic nucleus (STN) in patients with advanced PD selected to undergo DBS.

METHODS

Seven patients with refractory PD selected for DBS were examined by MRI. Diffusion images were acquired with an average acquisition time of 15 minutes. Probabilistic and deterministic tractography methods were applied to each diffusion-weighted data set using FSL and MRtrix, respectively. Fiber assignment was performed using combined sensorimotor areas as initiation seeds and the STN and GPi, separately, as inclusion masks. Corticospinal tracts were excluded by setting the cerebral peduncles as exclusion masks. Variability between proposed techniques was shown using center of gravity (CoG) coordinates.

RESULTS

Deterministic and probabilistic corticopallidal and corticosubthalamic pathways were successfully reconstructed for all subjects across all target sites (bilaterally). Both techniques displayed large connections between the sensorimotor cortex with the posterolateral aspect of the ipsilateral GPi and the posterosuperolateral aspect of the ipsilateral STN. The average variability was 2.67 mm, with the probabilistic method identifying the CoG consistently more posterior and more lateral than the deterministic method.

CONCLUSIONS

Successful delineation of the sensorimotor regions in both the GPi and STN is achievable within a clinically reasonable timeframe. The techniques described in this paper may enhance presurgical planning with increased accuracy and improvement of patient outcomes in patients undergoing DBS. The variability found between tracking techniques warrants the use of the probabilistic tractography method over the deterministic method for presurgical planning. Probabilistic tractography was found to have an advantage over deterministic tractography in its sensitivity, in accurately describing previously described tracts, and in its ability to detect a larger number of fibers.

Management of Pediatric Movement Disorders: Present and Future

Management of movement disorders in children is an evolving field. This article outlines the major categories of treatment options for pediatric movement disorders and general guidelines for their use. We review the evidence for existing therapies, which continue to lack large-scale controlled trials to guide treatment decisions. The field continues to rely on extrapolations from adult studies and lower quality evidence such as case reports and case series to guide treatment guidelines and consensus statements. Developments in new pharmaceuticals for rare diseases have begun to provide hope for those cases in which a genetic diagnosis can be made. Advances in surgical therapies such as deep brain stimulation as well as new modes of treatment such as gene therapy, epigenetic modulation, and stem cell therapy hold promise for improving outcomes in both primary and secondary causes of movement disorders. There is a critical need for larger, multicenter, controlled clinical trials to fully evaluate treatments for pediatric movement disorders.

Causes of failure of pallidal deep brain stimulation in cases with pre-operative diagnosis of isolated dystonia

INTRODUCTION

Pallidal deep brain stimulation (GPi-DBS) is an effective therapy for isolated dystonia, but 10-20% of patients show improvement below 25-30%. We here investigated causes of insufficient response to GPi-DBS in isolated dystonia in a cross-sectional study.

METHODS

Patients with isolated dystonia at time of surgery, and <30% improvement on the Burke-Fahn-Marsden dystonia-rating-scale (BFMDRS) after ≥6 months of continuous GPi-DBS were videotaped ON and OFF stimulation, and history, preoperative videos, brain MRI, medical records, stimulation settings, stimulation system integrity, lead location, and genetic information were obtained and reviewed by an expert panel.

RESULTS

22 patients from 11 centres were included (8 men, 14 women; 9 generalized, 9 segmental, 3 focal, 1 bibrachial dystonia; mean (range): age 48.7 (25-72) years, disease duration 22.0 (2-40) years, DBS duration 45.5 (6-131) months). Mean BFMDRS-score was 31.7 (4-93) preoperatively and 32.3 (5-101) postoperatively. Half of the patients (n = 11) had poor lead positioning alone or in combination with other problems (combined with: other disease n = 6, functional dystonia n = 1, other problems n = 2). Other problems were disease other than isolated inherited or idiopathic dystonia (n = 5), fixed deformities (n = 2), functional dystonia (n = 3), and other causes (n = 1). Excluding patients with poor lead location from further analysis, non-isolated dystonia accounted for 45.5%, functional dystonia for 27.3%, and fixed deformities for 18.2%. In patients with true isolated dystonia, lead location was the most frequent problem.

CONCLUSION

After exclusion of lead placement and stimulation programming issues, non-isolated dystonia, functional dystonia and fixed deformities account for the majority of GPi-DBS failures in dystonia.

Toward defining deep brain stimulation targets in MNI space: A subcortical atlas based on multimodal MRI, histology and structural connectivity

Three-dimensional atlases of subcortical brain structures are valuable tools to reference anatomy in neuroscience and neurology. For instance, they can be used to study the position and shape of the three most common deep brain stimulation (DBS) targets, the subthalamic nucleus (STN), internal part of the pallidum (GPi) and ventral intermediate nucleus of the thalamus (VIM) in spatial relationship to DBS electrodes. Here, we present a composite atlas based on manual segmentations of a multimodal high resolution brain template, histology and structural connectivity. In a first step, four key structures were defined on the template itself using a combination of multispectral image analysis and manual segmentation. Second, these structures were used as anchor points to coregister a detailed histological atlas into standard space. Results show that this approach significantly improved coregistration accuracy over previously published methods. Finally, a sub-segmentation of STN and GPi into functional zones was achieved based on structural connectivity. The result is a composite atlas that defines key nuclei on the template itself, fills the gaps between them using histology and further subdivides them using structural connectivity. We show that the atlas can be used to segment DBS targets in single subjects, yielding more accurate results compared to priorly published atlases. The atlas will be made publicly available and constitutes a resource to study DBS electrode localizations in combination with modern neuroimaging methods.

Historical developments in children's deep brain stimulation

BACKGROUND

Heterogeneous by the underlying pathobiology and clinical presentation, childhood onset dystonia is most frequently progressive, with related disability and limitations in functions of daily living. Consequently, there is an obvious need for efficient symptomatic therapies.

METHODS AND RESULTS

Following lesional surgery to basal ganglia (BG) and thalamus, deep brain stimulation (DBS) is a more conservative and adjustable intervention to and validated for internal segment of the globus pallidus (GPi), highly efficient in treating isolated "primary" dystonia and associated symptoms such as subcortical myoclonus. The role of DBS in acquired, neurometabolic and degenerative disorders with dystonia deserves further exploration to confirm as an efficient and lasting therapy. However, the pathobiological background with distribution of the sequellae over the central nervous system and related clinical features, will limit DBS efficacy in these conditions. Cumulative arguments propose DBS in severe life threatening dystonic conditions called status dystonicus as first line therapy, irrespective of the underlying cause. There are no currently available validated selection criteria for DBS in pediatric dystonia. Concurrent targets such as subthalamic nucleus (STN) and several motor nuclei of the thalamus are under exploration and only little information is available in children. DBS programming in paediatric population was adopted from experience in adults. The choice of neuromodulatory DBS parameters could influence not only the initial therapeutic outcome of dystonic symptoms but also its maintenance over time and potentially the occurrence of DBS related side effects.

CONCLUSION

DBS allows efficient symptomatic treatment of severe dystonia in children and advances pathophysiological knowledge about local and distributed abnormal neural activity over the motor cortical-subcortical networks in dystonia and other movement disorders.

Selective peripheral denervation for cervical dystonia: long-term follow-up

OBJECTIVE

61 procedures with selective peripheral denervation for cervical dystonia were retrospectively analysed concerning surgical results, pain, quality of life (QoL) and recurrences.

METHODS

The patients were assessed with the Tsui torticollis scale, Visual Analogue Scale (VAS) for pain and Fugl-Meyer scale for QoL. Evaluations were performed preoperatively, early postoperatively, at 6 months, then at a mean of 42 (13-165) months. All patients underwent electromyogram at baseline, which was repeated in cases who presented with recurrence of symptoms after surgery.

RESULTS

Six months of follow-up was available for 55 (90%) of the procedures and late follow-up for 34 (56%). The mean score of the Tsui scale was 10 preoperatively. It improved to 4.5 (p<0.001) at 6 months, and 5.3 (p<0.001) at late follow-up. VAS for pain improved from 6.5 preoperatively to 4.2 (p<0.001) at 6 months and 4 (p<0.01) at late follow-up. The Fugl-Meyer score for QoL improved from 43.3 to 46.6 (p<0.05) at 6 months, and to 51.1 (p<0.05) at late follow-up. Major reinnervation and/or change in the dystonic pattern occurred following 29% of the procedures, and led in 26% of patients to reoperation with either additional denervation or pallidal stimulation.

CONCLUSIONS

Selective peripheral denervation remains a surgical option in the treatment of cervical dystonia when conservative measures fail. Although the majority of patients experience a significant relief of symptoms, there is a substantial risk of reinnervation and/or change in the pattern of the cervical dystonia.

Dystonia--new advances in classification, genetics, pathophysiology and treatment

Dystonia is a heterogeneous movement disorder and has been defined as 'a syndrome of sustained muscle contractions, frequently causing twisted and repetitive movements, or abnormal postures'. The classification of dystonia has developed along with increasing knowledge, and different schemes have been suggested, including age at onset, body distribution, and etiology as the main differentiating factors. A revised definition and a new classification of dystonia have now been proposed by a group of leading dystonia experts and will be referred here. The discovery of the first two gene mutations causing primary generalized dystonia (DYT1-TOR1A and DYT6-THAP1) has facilitated studies on pathogenesis and pathophysiology of primary dystonias, by comparing neurophysiology between manifesting and non-manifesting carriers, and by studying the molecular biology of the mutant gene products. During recent years, several other gene mutations causing primary dystonia, dystonia-plus, and paroxysmal dystonia disorders have been discovered. Only during the last year, by the use of whole-exome sequencing techniques, mutations in three different genes in families with predominantly cervical dystonia were found, which may lead to improved insight into the pathogenesis also of the more frequent focal dystonias. Botulinum neurotoxin (BoNT) and deep brain stimulation (DBS) have revolutionized the symptomatic treatment for dystonia during the last two decades and continue to be refined to improve efficacy and expand their indications. Unfortunately, no progress has been made in the oral medication of dystonia. Current and future new insights into pathogenetic and pathophysiological mechanisms of dystonia will hopefully lead to improvement also in this area soon.

Pallidotomy for medically refractory status dystonicus in childhood

AIM

Status dystonicus is a rare and potentially fatal condition of continuous and generalized muscle contraction that can complicate dystonia. As status dystonicus is usually refractory to traditional pharmacological therapy, alternative and invasive strategies have been developed, but so far there are no guidelines on status dystonicus management. Pallidotomy has shown good results in status dystonicus treatment.

METHOD

We report indications, surgical strategy, and outcome of bilateral pallidotomy in four pediatric patients (four males; mean age at surgery 11y 5mo) with secondary dystonia, who developed refractory status dystonicus. Pallidotomy was performed in the area corresponding to the mid portion of the globus pallidus internus.

RESULTS

This procedure allowed patients to recover the pre-status dystonicus condition, controlling dystonic postures and movements of trunk and limbs. Moreover oromandibular dystonia, which is resistant to conservative approaches and deep brain stimulation, was significantly reduced. No postoperative complications were registered.

INTERPRETATION

Our study suggests pallidotomy as a feasible treatment in patients with secondary dystonia complicated by status dystonicus.

Dystonia rating scales: critique and recommendations

Many rating scales have been applied to the evaluation of dystonia, but only few have been assessed for clinimetric properties. The Movement Disorders Society commissioned this task force to critique existing dystonia rating scales and place them in the clinical and clinimetric context. A systematic literature review was conducted to identify rating scales that have either been validated or used in dystonia. Thirty-six potential scales were identified. Eight were excluded because they did not meet review criteria, leaving 28 scales that were critiqued and rated by the task force. Seven scales were found to meet criteria to be "recommended": the Blepharospasm Disability Index is recommended for rating blepharospasm; the Cervical Dystonia Impact Scale and the Toronto Western Spasmodic Torticollis Rating Scale for rating cervical dystonia; the Craniocervical Dystonia Questionnaire for blepharospasm and cervical dystonia; the Voice Handicap Index (VHI) and the Vocal Performance Questionnaire (VPQ) for laryngeal dystonia; and the Fahn-Marsden Dystonia Rating Scale for rating generalized dystonia. Two "recommended" scales (VHI and VPQ) are generic scales validated on few patients with laryngeal dystonia, whereas the others are disease-specific scales. Twelve scales met criteria for "suggested" and 7 scales met criteria for "listed." All the scales are individually reviewed in the online information. The task force recommends 5 specific dystonia scales and suggests to further validate 2 recommended generic voice-disorder scales in dystonia. Existing scales for oromandibular, arm, and task-specific dystonia should be refined and fully assessed. Scales should be developed for body regions for which no scales are available, such as lower limbs and trunk.

Deep brain stimulation in DYT1 dystonia: a 10-year experience

BACKGROUND

Globus Pallidus Interna (GPi) deep brain stimulation (DBS) is an effective treatment for DYT1-associated dystonia, but long-term results are lacking.

OBJECTIVE

To evaluate the long-term effects of GPi DBS in patients with DYT1 dystonia.

METHODS

A retrospective chart review (cohort study) of 47 consecutive DYT1+ patients treated by a single surgical team over a 10-year period and followed for up to 96 months (mean, 46 months) was performed. Symptom severity was quantified with the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) motor (M) and disability (D) sub-scores.

RESULTS

As measured with the BFMDRS (M), symptom severity was reduced to less than 20% of baseline after 2 years of DBS therapy (P = .001). The disability scores were reduced to <30% of baseline (P = .001). Symptomatic improvement was durable throughout available follow-up. Sixty-one percent of patients had discontinued all dystonia-related medications at their last follow-up. Ninety-one percent had discontinued at least 1 class of medication. Infections requiring removal and later reimplantation of hardware occurred in 4 of 47 patients (8.5%). Hardware malfunction including lead fractures occurred in 4 of 47 cases (8.5%). Lead revision to address poor clinical response was performed in 2 of 92 implanted leads (2.2%).

CONCLUSION

GPi DBS is an effective therapy for DYT1-associated torsion dystonia. Statistically significant efficacy is maintained for up to 7 years. Neurologic complications are rare, but long-term hardware-related complications can be significant.

Deep brain stimulation for dystonia

The few controlled studies that have been carried out have shown that bilateral internal globus pallidum stimulation is a safe and long-term effective treatment for hyperkinetic disorders. However, most recent published data on deep brain stimulation (DBS) for dystonia, applied to different targets and patients, are still mainly from uncontrolled case reports (especially for secondary dystonia). This precludes clear determination of the efficacy of this procedure and the choice of the 'good' target for the 'good' patient. We performed a literature analysis on DBS for dystonia according to the expected outcome. We separated those with good evidence of favourable outcome from those with less predictable outcome. In the former group, we review the main results for primary dystonia (generalised/focal) and highlight recent data on myoclonus-dystonia and tardive dystonia (as they share, with primary dystonia, a marked beneficial effect from pallidal stimulation with good risk/benefit ratio). In the latter group, poor or variable results have been obtained for secondary dystonia (with a focus on heredodegenerative and metabolic disorders). From this overview, the main results and limits for each subgroup of patients that may help in the selection of dystonic patients who will benefit from DBS are discussed.

Deep brain stimulation for dystonia

The few reported controlled studies show that bilateral stimulation of the globus pallidus interna (GPi) is a safe and effective long-term treatment for hyperkinetic disorders. However, the recently published data on deep brain stimulation (DBS) applied to different targets or patients (especially those with secondary dystonia) are mainly uncontrolled case reports, precluding a clear determination of its efficacy, and providing little guidance as to the choice of a "good" target in a "good" patient. This chapter reviews the literature on DBS in primary dystonia, paying particular attention to the risk:benefit ratio in focal and segmental dystonias (cervical dystonia, cranial dystonia) and to the predictive factors for a good outcome. The chapter also highlights recent data on the marked benefits of the technique in myoclonus dystonia (in which pallidal, as opposed to thalamic, stimulation is more effective) and in tardive dystonia-dyskinesia. Although, the decision to treat appears relatively straightforward in patients with primary dystonia, myoclonus-dystonia, and tardive dystonia who have a normal findings on magnetic resonance imaging and normal cognitive function, there are still no reliable tools to help predict the timescale of postoperative benefit. This chapter provides a comprehensive analysis of the use of the treatment in various types of secondary dystonia, with little to moderate benefit in most cases, based on single cases or small series. Beyond the reduction in the severity of dystonia, the global motor and functional outcome is difficult to determine owing to the paucity of adequate evaluation tools. Because of the large interpatient variability, different targets may be effective depending on the symptoms in each individual.

The influence of deep brain stimulation intensity and duration on symptoms evolution in an OFF stimulation dystonia study

BACKGROUND

Deep brain stimulation (DBS) of the internal globus pallidus (GPi) is an established therapy for primary generalized dystonia. However, the evolution of dystonia symptoms after DBS discontinuation after years of therapy has only rarely been reported. We therefore longitudinally studied the main physiological measurements known to be impaired in dystonia, with DBS ON and then again after termination of DBS, after at least five years of continuous DBS.

OBJECTIVE

We studied whether dystonia evolution after DBS discontinuation in patients benefiting from long-term GPi DBS is different from that observed in earlier stages of the therapy.

METHODS

In eleven DYT1 patients treated with bilateral GPi DBS for at least 5 years, dystonia was assessed ON-DBS, immediately after switch-off (OFF-DBS1) and 48 h after DBS termination (OFF-DBS2). We studied the influence of DBS intensity on dystonia when DBS was discontinued.

RESULTS

On average a significant difference in symptoms was measured only between ON-DBS and OFF-DBS1 conditions. Importantly, none of the patients returned to their preoperative dystonia severity, even 48 h after discontinuation. The amount of clinical deterioration in the OFF conditions positively correlated with higher stimulation current in the chronic ON-DBS condition.

CONCLUSIONS

The duration of DBS application influences symptom evolution after DBS termination. DBS intensity seems to have a prominent role on evolution of dystonic symptoms when DBS is discontinued. In conclusion, DBS induces changing modulation of the motor network with less worsening of symptoms after long term stimulation, when DBS is stopped.