Botulinum Toxin and Deep Brain Stimulation in Dystonia.

Deep Brain Stimulation (DBS) is a recognized treatment for different dystonia subtypes and has been approved by the Food and Drug Administration (FDA) since 2003. The European Federation of Neurological Societies (EFNS) and the International Parkinson and Movement Disorders Society (MDS) recommend DBS for dystonia after failure of botulinum toxin (BoNT) and other oral medications for dystonia treatment. In addition, several long-term studies have demonstrated the continuous efficacy of DBS on motor and quality of life (QoL) scores. However, there are only a few reports comparing the overall impact of surgical treatment in BoNT protocols (e.g., dosage and number of selected muscles before and after surgery). This retrospective multicenter chart-review study analyzed botulinum toxin total dosage and dosage per muscle in 23 dystonic patients before and after DBS surgery. The study's primary outcome was to analyze whether there was a reduction in BoNT dosage after DBS surgery. The mean BoNT dosages difference between baseline and post-surgery was 293.4 units for 6 months, 292.6 units for 12 months, and 295.2 units at the last visit. The median total dose of BoNT in the preoperative period was 800 units (N = 23). At the last visit, the median was 700 units (p = 0.05). This represents a 12.5% reduction in BoNT median dosage. In conclusion, despite the limitations of this retrospective study, there was a significant reduction in BoNT doses after DBS surgery in patients with generalized dystonia.

Actigraph-based quantification of sleep in children with dystonia undergoing deep brain stimulation.

OBJECTIVE: Dystonia is among the most common pediatric movement disorders and can manifest with a range of debilitating symptoms, including sleep disruptions. The duration and quality of sleep are strongly associated with quality of life in these individuals and could serve as biomarkers of dystonia severity and the efficacy of interventions such as deep brain stimulation (DBS). Thus, this study investigated sleep duration and its relationship to disease severity and DBS response in pediatric dystonia. METHODS: Actigraphs (wearable three-axis accelerometers) were used to record multiday sleep data in 22 children with dystonia, including 6 patients before and after DBS implantation, and age- and sex- matched healthy controls. Data were preprocessed, and metrics of sleep duration and quality were extracted. Repeated-measures statistical analyses were used. RESULTS: Children with dystonia slept less than typically developing children (p = 0.009), and shorter sleep duration showed trending correlation with worse dystonia severity (r = -0.421, p = 0.073). Of 4 patients who underwent DBS and had good-quality data, 1 demonstrated significantly improved sleep (p < 0.001) postoperatively. Reduction in dystonia severity strongly correlated with increased sleep duration after DBS implantation (r = -0.965, p = 0.035). CONCLUSIONS: Sleep disturbances are an underrecognized marker of pediatric dystonia severity, as well as the effectiveness of interventions such as DBS. They can serve as objective biomarkers of disease burden and symptom progression after treatment.

POLR3A-related disorders: From spastic ataxia to generalised dystonia and long-term efficacy of deep brain stimulation.

While biallelic POLR3A loss-of-function variants are traditionally linked to hypomyelinating leukodystrophy, patients with a specific splice variant c.1909+22G>A manifest as adolescent-onset spastic ataxia without overt leukodystrophy. In this study, we reported eight new cases, POLR3A-related disorder with c.1909+22 variant. One of these patients showed expanded phenotypic spectrum of generalised dystonia and her sister remained asymptomatic except for hypodontia. Two patients with dystonic arm tremor responded to deep brain stimulation. In our systemic literature review, we found that POLR3A-related disorder with c.1909+22 variant has attenuated disease severity but frequency of dystonia and upper limb tremor did not differ among genotypes.

Deep brain stimulation for pediatric pantothenate kinase-associated neurodegeneration with status dystonicus: A case report and literature review.

BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is a type of inherited metabolic disorder caused by mutation in the PANK2 gene. The metabolic disorder mainly affects the basal ganglia region and eventually manifests as dystonia. For patients of dystonia, their dystonic symptom may progress to life-threatening emergency--status dystonicus. OBJECTIVE: We described a case of a child with PKAN who had developed status dystonicus and was successfully treated with deep brain stimulation (DBS). Based on this rare condition, we analysed the clinical features of PKAN with status dystonicus and reviewed the reasonable management process of this condition. CONCLUSION: This case confirmed the rationality of choosing DBS for the treatment of status dystonicus. Meanwhile, we found that children with classic PKAN have a cluster of risk factors for developing status dystonicus. Once children diagnosed with similar neurodegenerative diseases are under status dystonicus, DBS can be active considered because it has showed high control rate of this emergent condition.

Genetic Update and Treatment for Dystonia.

A neurological condition called dystonia results in abnormal, uncontrollable postures or movements because of sporadic or continuous muscular spasms. Several varieties of dystonia can impact people of all ages, leading to severe impairment and a decreased standard of living. The discovery of genes causing variations of single or mixed dystonia has improved our understanding of the disease's etiology. Genetic dystonias are linked to several genes, including pathogenic variations of VPS16, TOR1A, THAP1, GNAL, and ANO3. Diagnosis of dystonia is primarily based on clinical symptoms, which can be challenging due to overlapping symptoms with other neurological conditions, such as Parkinson's disease. This review aims to summarize recent advances in the genetic origins and management of focal dystonia.

Effect of Thalamic versus Pallidal Deep Brain Stimulation on Head Tremor in Dystonic and Essential Tremor Patients-A Retrospective Video-Blinded Study.

BACKGROUND: Head tremor is common in dystonia syndromes and difficult to treat. Deep brain stimulation (DBS) is a therapeutic option in medically-refractory cases. In most DBS-centers, the globus pallidus internus (GPi) is targeted in patients with predominant dystonia and the ventrointermediate nucleus of the thalamus (Vim) in predominant tremor. The aim of the study was to evaluate the effect of GPi- versus Vim-DBS in dystonic or essential head tremor. METHODS: All patients with dystonia or essential tremor (ET) (n = 381) who underwent DBS surgery at our institution between 1999 and 2020 were screened for head tremor in our database according to predefined selection criteria. Of the 33 patients meeting inclusion criteria tremor and dystonia severity were assessed at baseline, short- (mean 10 months) and long-term follow-up (41 months) by two blinded video-raters. RESULTS: Twenty-two patients with dystonic head tremor received either GPi- (n = 12) or Vim-stimulation (n = 10), according to the prevailing clinical phenotype. These two groups were compared with 11 patients with ET, treated with Vim-stimulation. The reduction in head tremor from baseline to short- and long-term follow-up was 60-70% and did not differ significantly between the three groups. CONCLUSIONS: GPi-DBS effectively and sustainably reduced head tremor in idiopathic dystonia. The effect was comparable to the effect of Vim-DBS on head tremor in dystonia patients with predominant limb tremor and to the effect of Vim-DBS on head tremor in ET.

Pallidal multifractal complexity is a new potential physiomarker of dystonia.

OBJECTIVE: Low-frequency 4-12 Hz pallidal oscillations are being considered as potential physiomarkers for dystonia. We suggest investigating the multifractal properties of pallidal activity as an additional marker. METHODS: We employed local field potentials (LFP) recordings from 23 patients with dystonia who were undergoing deep brain stimulation (DBS) surgery to explore the connection between disease severity and the multifractal characteristics of pallidal activity. Furthermore, we performed an analysis of LFP recordings from four patients, following the externalization of DBS lead electrodes, to investigate the impact of DBS and neck muscle vibration on multifractal parameters. RESULTS: Greater dystonia severity exhibited a correlation with a narrower multifractal spectrum width but higher multifractal spectral asymmetry. Both GPi DBS and muscle vibration in dystonia patients expanded the multifractal spectrum width while restoring multifractal spectral symmetry. Notably, the threshold peak intensities for an increase in multifractal spectrum width substantially overlapped with the optimal volume of tissue activated. A broader multifractal spectrum during DBS corresponded to more favorable clinical outcomes. CONCLUSIONS: Multifractal properties of pallidal neuronal activity serve as indicators of neural dysfunction in dystonia. SIGNIFICANCE: These findings suggest the potential of utilizing multifractal characteristics as predictive factors for the DBS outcome in dystonia.

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.

Brain Shift during Staged Deep Brain Stimulation for Movement Disorders.

INTRODUCTION: Deep brain stimulation (DBS) is a routine neurosurgical procedure utilized to treat various movement disorders including Parkinson's disease (PD), essential tremor (ET), and dystonia. Treatment efficacy is dependent on stereotactic accuracy of lead placement into the deep brain target of interest. However, brain shift attributed to pneumocephalus can introduce unpredictable inaccuracies during DBS lead placement. This study aimed to determine whether intracranial air is associated with brain shift in patients undergoing staged DBS surgery. METHODS: We retrospectively evaluated 46 patients who underwent staged DBS surgery for PD, ET, and dystonia. Due to the staged nature of DBS surgery at our institution, the first electrode placement is used as a concrete fiducial marker for movement in the target location. Postoperative computed tomography (CT) images after the first electrode implantation, as well as preoperative, and postoperative CT images after the second electrode implantation were collected. Images were analyzed in stereotactic targeting software (BrainLab); intracranial air was manually segmented, and electrode shift was measured in the x, y, and z plane, as well as a Euclidian distance on each set of merged CT scans. A Pearson correlation analysis was used to determine the relationship between intracranial air and brain shift, and student's t test was used to compare means between patients with and without radiographic evidence of intracranial air. RESULTS: Thirty-six patients had pneumocephalus after the first electrode implantation, while 35 had pneumocephalus after the second electrode implantation. Accumulation of intracranial air following the first electrode implantation (4.49 ± 6.05 cm3) was significantly correlated with brain shift along the y axis (0.04 ± 0.35 mm; r (34) = 0.36; p = 0.03), as well as the Euclidean distance of deviation (0.57 ± 0.33 mm; r (34) = 0.33; p = 0.05) indicating statistically significant shift on the ipsilateral side. However, there was no significant correlation between intracranial air and brain shift following the second electrode implantation, suggesting contralateral shift is minimal. Furthermore, there was no significant difference in brain shift between patients with and without radiographic evidence of intracranial air following both electrode implantation surgeries. CONCLUSION: Despite observing volumes as high as 22.0 cm3 in patients with radiographic evidence of pneumocephalus, there was no significant difference in brain shift when compared to patients without pneumocephalus. Furthermore, the mean magnitude of brain shift was <1.0 mm regardless of whether pneumocephalus was presenting, suggesting that intracranial air accumulation may not produce clinical significant brain shift in our patients.

Electrophysiological variability as marker of dystonia worsening under deep brain stimulation successive withdrawal and renewal effects.

DBS has been shown to be an effective intervention for neurological disorders. However, the intervention is complex and many aspects have not been understood. Various clinical situations have no solution and follow trial and error approaches. Dystonia is a movement disorder characterized by involuntary muscle contractions, which gives rise to abnormal movements and postures. Status dystonicus (SD) represents a life-threatening condition that requires urgent assessment and management. Electrophysiological markers for risk of symptom worsening and SD related patterns of evolution in patients treated with long-term deep brain stimulation (DBS), and specially under the effect of withdrawal and renewals of simulation are needed. To this end, we study the variability of neural synchronization as a mechanism for symptom generation under successive perturbations to a system, i.e. withdrawals and renewals of neuromodulation, through computational simulation of clinical profiles under different plasticity conditions. The simulation shows that the neuroplasticity makeup influences the variability of oscillation synchronization patterns in virtual "patients". The difference between the effect of different electrophysiological signatures is remarkable and under a certain condition (equal medium long term potentiation and long term depression) the situation resembles that of a stable equilibrium, putatively making the sudden worsening or change less likely. Stability of variability can only be observed in this condition and is clearly distinct from other scenarios. CONCLUSION: Our results demonstrate that the neuroplasticity makeup affects the variability of the oscillatory synchrony. This i) informs the shaping of the electrophysiological makeup and ii) might serve as a marker for clinical behavior.

Deep brain stimulation in dystonia: The added value of neuropsychological assessments.

Deep brain stimulation (DBS) of the internal globus pallidus (GPi) is a recognized treatment for medication-refractory dystonia. Problems in executive functions and social cognition can be part of dystonia phenotypes. The impact of pallidal DBS on cognition appears limited, but not all cognitive domains have been investigated yet. In the present study, we compare cognition before and after GPi DBS. Seventeen patients with dystonia of various aetiology completed pre- and post-DBS assessment (mean age 51 years; range 20-70 years). Neuropsychological assessment covered intelligence, verbal memory, attention and processing speed, executive functioning, social cognition, language and a depression questionnaire. Pre-DBS scores were compared with a healthy control group matched for age, gender and education, or with normative data. Patients were of average intelligence but performed significantly poorer than healthy peers on tests for planning and for information processing speed. Otherwise, they were cognitively unimpaired, including social cognition. DBS did not change the baseline neuropsychological scores. We confirmed previous reports of executive dysfunctions in adult dystonia patients with no significant influence of DBS on cognitive functioning in these patients. Pre-DBS neuropsychological assessments appear useful as they support clinicians in counselling their patients. Decisions about post-DBS neuropsychological evaluations should be made on a case-by-case basis.

Short-term stimulations of the entopeduncular nucleus induce cerebellar changes of c-Fos expression in an animal model of paroxysmal dystonia.

Deep brain stimulation (DBS) of the globus pallidus internus (entopeduncular nucleus, EPN, in rodents) is important for the treatment of drug-refractory dystonia. The pathophysiology of this movement disorder and the mechanisms of DBS are largely unknown. Insights into the mechanisms of DBS in animal models of dystonia can be helpful for optimization of DBS and add-on therapeutics. We recently found that short-term EPN-DBS with 130 Hz (50 µA, 60 µs) for 3 h improved dystonia in dtsz hamsters and reduced spontaneous excitatory cortico-striatal activity in brain slices of this model, indicating fast effects on synaptic plasticity. Therefore, in the present study, we examined if these effects are related to changes of c-Fos, a marker of neuronal activity, in brains derived from dtsz hamsters after these short-term DBS or sham stimulations. After DBS vs. sham, c-Fos intensity was increased around the electrode, but the number of c-Fos+ cells was not altered within the whole EPN and projection areas (habenula, thalamus). DBS did not induce changes in striatal and cortical c-Fos+ cells as GABAergic (GAD67+ and parvalbumin-reactive) neurons in motor cortex and striatum. Unexpectedly, c-Fos+ cells were decreased in deep cerebellar nuclei (DCN) after DBS, suggesting that cerebellar changes may be involved in antidystonic effects already during short-term DBS. However, the present results do not exclude functional changes within the basal ganglia-thalamo-cortical network, which will be further investigated by long-term EPN stimulations. The present study indicates that the cerebellum deserves attention in ongoing examinations on the mechanisms of DBS in dystonia.

Deep brain stimulation in pediatric dystonia: calls for therapeutic realism over nihilism.

PURPOSE: Pediatric dystonia (PD) has a significant negative impact on the growth and development of the child. This study was done retrospectively to analyze functional outcomes in pediatric patients with dystonia who underwent deep brain stimulation. METHODS: In this retrospective analytical study, all the patients of age less than 18 years undergoing deep brain stimulation (DBS) for dystonia between 2012 and 2020 in a single center were analyzed and their functional outcomes were measured by the Burke-Fahn-Marsden-dystonia-rating-scale (BFMDRS). RESULTS: A total of 10 pediatric patients were included with a mean age of onset, duration of disease, and age at surgery being 5.75 years, 7.36 years, and 13.11 years, respectively, with a mean follow-up of 23.22 months. The mean pre-DBS motor score was 75.44 ± 23.53 which improved significantly at 6-month and 12-month follow-up to 57.27 (p value 0.004) and 50.38 (p value < 0.001), respectively. Limbs sub-scores improved significantly at both the scheduled intervals. There was a significant improvement in disability at 1-year follow-up with significant improvement in feeding, dressing, and walking components. There was a 27.34% and 36.64% improvement in dystonia with a 17.37% and 28.86% reduction in disability at 6 months and 12 months, respectively. There was a positive correlation between the absolute reduction of the motor score and improvement in disability of the patients at 6 months (rho = 0.865, p value 0.003). CONCLUSIONS: DBS in PD has an enormous role in reducing disease burden and achieving a sustainable therapeutic goal.

Subthalamic nucleus deep brain stimulation in primary Meige syndrome: motor and non-motor outcomes.

BACKGROUND AND PURPOSE: Deep brain stimulation (DBS) has emerged as a promising treatment for movement disorders. This prospective study aims to evaluate the effects of bilateral subthalamic nucleus DBS (STN-DBS) on motor and non-motor symptoms in patients with primary Meige syndrome. METHODS: Thirty patients who underwent bilateral STN-DBS between April 2017 and June 2020 were included. Standardized and validated scales were utilized to assess the severity of dystonia, health-related quality of life, sleep, cognitive function and mental status at baseline and at 1 year and 3 years after neurostimulation. RESULTS: The Burke-Fahn-Marsden Dystonia Rating Scale movement scores showed a mean improvement of 63.0% and 66.8% at 1 year and 3 years, respectively, after neurostimulation. Similarly, the Burke-Fahn-Marsden Dystonia Rating Scale disability scores improved by 60.8% and 63.3% at the same time points. Postoperative quality of life demonstrated a significant and sustained improvement throughout the follow-up period. However, cognitive function, mental status, sleep quality and other neuropsychological functions did not change after 3 years of neurostimulation. Eight adverse events occurred in six patients, but no deaths or permanent sequelae were reported. CONCLUSIONS: Bilateral STN-DBS is a safe and effective alternative treatment for primary Meige syndrome, leading to improvements in motor function and quality of life. Nevertheless, it did not yield significant amelioration in cognitive, mental, sleep status and other neuropsychological functions after 3 years of neurostimulation.