Effect of pallidal deep brain stimulation on psychiatric symptoms in myoclonus-dystonia due to ε-sarcoglycan mutations

Long-term effects of pallidal and thalamic deep brain stimulation in myoclonus dystonia

OBJECTIVE

Observational study to evaluate long-term effects of deep brain stimulation (DBS) of the globus pallidus internus (GPi) and the ventral intermediate thalamic nucleus (VIM) on patients with medically refractory myoclonus dystonia (MD).

BACKGROUND

More recently, pallidal as well as thalamic DBS have been applied successfully in MD but long-term data are sparse.

METHODS

We retrospectively analyzed a cohort of seven MD patients with either separate (n = 1, VIM) or combined GPi- DBS and VIM-DBS (n = 6). Myoclonus, dystonia and disability were rated at baseline (BL), short-term (ST-FU) and long-term follow-up (LT-FU) using the United Myoclonus Rating Scale, Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Tsui rating scale, respectively. Quality of life (QoL) and mood were evaluated using the SF-36 and Beck Depression Inventory questionnaires, respectively.

RESULTS

Patients reached a significant reduction of myoclonus at ST-FU (62% ± 7.3%; mean ± SE) and LT-FU (68% ± 3.4%). While overall motor BFMDRS changes were not significant at LT-FU, patients with GPi-DBS alone responded better and predominant cervical dystonia ameliorated significantly up to 54% ± 9.7% at long-term. Mean disability scores significantly improved by 44% ± 11.4% at ST-FU and 58% ± 14.8% at LT-FU. Mood and QoL remained unchanged between 5 and up to 20 years postoperatively. No serious long-lasting stimulation-related adverse events were observed.

CONCLUSIONS

We present a cohort of MD patients with very long follow-up of pallidal and/or thalamic DBS that supports the GPi as the favourable stimulation target in MD with safe and sustaining effects on motor symptoms (myoclonus>dystonia) and disability.

Bilateral Pallidal Stimulation in a Family With Myoclonus Dystonia Syndrome Due to a Mutation in the Sarcoglycan Gene

OBJECTIVES

The study aimed to present a family with myoclonus dystonia (M-D) syndrome due to a mutation in the epsilon sarcoglycan gene (SGCE). Three members of the family suffered from treatment-refractory severe myoclonic jerks of the neck, trunk, and upper extremities. The mild dystonic symptoms recognized as cervical dystonia or truncal dystonia affected all individuals. The efficacy of pharmacotherapy, including anticholinergic, dopaminergic, and serotoninergic drugs, has failed. One individual developed an alcohol dependency and suffered from alcoholic epilepsy.

MATERIALS AND METHODS

The patients were referred for stereotactic surgery. All individuals underwent bilateral implantation of deep brain stimulation (DBS) leads into the posteroventrolateral segment of the globus pallidus internus (GPi). Surgeries were uneventful. The formal preoperative objective assessment included the Unified Myoclonus Rating Scale (UMRS) and the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). The postoperative UMRS and BFMDRS assessments were done only under continuous stimulation at 3, 6, and 12 months after the surgery and at the last available follow-up ranging from 6 to 15 months (mean, 10 months follow-up).

RESULTS

At the last follow-up visit, the rest and action parts of UMRS were improved by 93.3% and 88.2%, respectively, when compared to the baseline scores. The motor and disability scales of BFMDRS were improved by 77% and 43% at the last follow-up visit compared to the baseline BFMDRS scores. There were no hardware or stimulation-induced complications over the follow-up period. Positive social adjustment allowed two patients to regain jobs and one patient continued his education and hobbies.

CONCLUSION

Our experience gathered in three individuals in the family with a mutation in SGCE indicates that bilateral GPi DBS can be an effective and safe treatment for disabling pharmacological resistant, intractable M-D syndrome.

Pallidal Deep Brain Stimulation for Monogenic Dystonia: The Effect of Gene on Outcome

Globus pallidus internus deep brain stimulation (GPi DBS) is the most effective intervention for medically refractory segmental and generalized dystonia in both children and adults. Predictive factors for the degree of improvement after GPi DBS include shorter disease duration and dystonia subtype with idiopathic isolated dystonia usually responding better than acquired combined dystonias. Other factors contributing to variability in outcome may include body distribution, pattern of dystonia and DBS related factors such as lead placement and stimulation parameters. The responsiveness to DBS appears to vary between different monogenic forms of dystonia, with some improving more than others. The first observation in this regard was reports of superior DBS outcomes in DYT-TOR1A (DYT1) dystonia, although other studies have found no difference. Recently a subgroup with young onset DYT-TOR1A, more rapid progression and secondary worsening after effective GPi DBS, has been described. Myoclonus dystonia due to DYT-SCGE (DYT11) usually responds well to GPi DBS. Good outcomes following GPi DBS have also been documented in X-linked dystonia Parkinsonism (DYT3). In contrast, poorer, more variable DBS outcomes have been reported in DYT-THAP1 (DYT6) including a recent larger series. The outcome of GPi DBS in other monogenic isolated and combined dystonias including DYT-GNAL (DYT25), DYT-KMT2B (DYT28), DYT-ATP1A3 (DYT12), and DYT-ANO3 (DYT24) have been reported with varying results in smaller numbers of patients. In this article the available evidence for long term GPi DBS outcome between different genetic dystonias is reviewed to reappraise popular perceptions of expected outcomes and revisit whether genetic diagnosis may assist in predicting DBS outcome.

Medical management of myoclonus-dystonia and implications for underlying pathophysiology

Myoclonus-dystonia is an early onset genetic disorder characterised by subcortical myoclonus and less prominent dystonia. Its primary causative gene is the epsilon-sarcoglycan gene but the syndrome of "myoclonic dystonia" has been shown to be a heterogeneous group of genetic disorders. The underlying pathophysiology of myoclonus-dystonia is incompletely understood, although it may relate to dysfunction of striatal monoamine neurotransmission or disruption of cerebellothalamic networks (possibly via a GABAergic deficit of Purkinje cells). A broad range of oral medical therapies have been used in the treatment of myoclonus-dystonia with a varying response, and limited data relating to efficacy and tolerability, yet this condition responds dramatically to alcohol. Few well conducted randomized controlled trials have been undertaken leading to an empirical ad hoc approach for many patients. We review the current evidence for pharmacological therapies in myoclonus-dystonia, discuss implications for underlying pathogenesis of the condition and propose a treatment algorithm for these patients.

Deep brain stimulation for myoclonus dystonia syndrome: a meta-analysis with individual patient data

Good outcomes have been reported in deep brain stimulation (DBS) for myoclonus-dystonia syndrome (M-D), a heritable disease characterized by childhood-onset myoclonic jerks and dystonia in the upper body. This meta-analysis was to evaluate the clinical outcomes consecutively, compare the stimulation targets, and identify potential prognostic factors. A systematic literature search was performed on PubMed, Web of Science, and Embase. The primary outcome was the percent improvement in Burke-Fahn-Marsden Dystonia Rating Scale movement (BFMDRS-M) scores for dystonia and Unified Myoclonus Rating Scale (UMRS) scores for myoclonus at the last follow-up visit. BFMDRS-disability scores of the patients were also summarized. Pearson correlation analyses were performed to identify the myoclonus and dystonia outcome predictors. Thirty-one studies reporting 71 patients were included. There were significant improvements in BFMDRS-M and BFMDRS-disability scores in each time category and at the last follow-up visit. Mean improvement (%) in UMRS was 79.5 ± 18.2, and 94.1% of the patients showed > 50% improvement in UMRS scores at the last follow-up visit. There was a significant trend toward improved myoclonus outcome with older age at onset and shorter disease duration. Most of the adverse events were mild and transient, and pallidal stimulation seemed to be better with respect to fewer stimulation-induced events. Based on the current data, DBS is effective for even the severe M-D. Surgery at an early stage may predict a better outcome. Although targets do not serve as the outcome predictors, pallidal stimulation may be preferred due to fewer stimulation-induced events.

Twenty years on: Myoclonus-dystonia and ε-sarcoglycan - neurodevelopment, channel, and signaling dysfunction

Myoclonus-dystonia is a clinical syndrome characterized by a typical childhood onset of myoclonic jerks and dystonia involving the neck, trunk, and upper limbs. Psychiatric symptomatology, namely, alcohol dependence and phobic and obsessive-compulsive disorder, is also part of the clinical picture. Zonisamide has demonstrated effectiveness at reducing both myoclonus and dystonia, and deep brain stimulation seems to be an effective and long-lasting therapeutic option for medication-refractory cases. In a subset of patients, myoclonus-dystonia is associated with pathogenic variants in the epsilon-sarcoglycan gene, located on chromosome 7q21, and up to now, more than 100 different pathogenic variants of the epsilon-sarcoglycan gene have been described. In a few families with a clinical phenotype resembling myoclonus-dystonia associated with distinct clinical features, variants have been identified in genes involved in novel pathways such as calcium channel regulation and neurodevelopment. Because of phenotypic similarities with epsilon-sarcoglycan gene-related myoclonus-dystonia, these conditions can be collectively classified as "myoclonus-dystonia syndromes." In the present article, we present myoclonus-dystonia caused by epsilon-sarcoglycan gene mutations, with a focus on genetics and underlying disease mechanisms. Second, we review those conditions falling within the spectrum of myoclonus-dystonia syndromes, highlighting their genetic background and involved pathways. Finally, we critically discuss the normal and pathological function of the epsilon-sarcoglycan gene and its product, suggesting a role in the stabilization of the dopaminergic membrane via regulation of calcium homeostasis and in the neurodevelopmental process involving the cerebello-thalamo-pallido-cortical network. © 2019 International Parkinson and Movement Disorder Society.

Thalamus Stimulation for Myoclonus Dystonia Syndrome: Five Cases and Long-Term Follow-up

BACKGROUND

Myoclonic dystonia syndrome (MDS) is a rare inherited movement disorder characterized by the coexistence of myoclonic jerks and dystonia. Deep brain stimulation (DBS) is a promising treatment for patients with MDS that targets the globus pallidus internus or ventral intermediate nucleus (Vim) of the thalamus. However, there are few studies regarding the long-term effects of Vim DBS in patients with MDS and even fewer in those without gene mutations.

METHODS

Two positive and three negative SGCE mutation patients presenting with predominant myoclonus underwent Vim DBS. The Unified Myoclonus Rating Scale and the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) were assessed pre- and postoperation.

RESULTS

Over an average follow-up period of 50 months, the myoclonus improvement rate was 92.7%. The average improvement in the BFMDRS motor score was 71.4% and the average improvement in the BFMDRS disabling score was 75.8%.

CONCLUSIONS

This study suggests that Vim DBS can be a safe and effective treatment option for patients with MDS. Vim DBS alone may be preferable for patients with myoclonus-dominated MDS regardless of the identification of an SGCE mutation. Additional globus pallidus internus DBS may be used for progressive dystonia after Vim DBS.

Deep brain stimulation for myoclonus-dystonia syndrome with double mutations in DYT1 and DYT11

Myoclonus-dystonia syndrome (MDS) is a rare autosomal dominant inherited disorder characterized by the presentation of both myoclonic jerks and dystonia. Evidence is emerging that deep brain stimulation (DBS) may be a promising treatment for MDS. However, there are no studies reporting the effects of DBS on MDS with double mutations in DYT1 and DYT11. Two refractory MDS patients with double mutations were treated between 2011 and 2015 in our center. Genetic testing for DYT1 and DYT11 was performed through polymerase chain reaction amplification and direct sequencing of the specific exons of genes. For the first patient, initial bilateral ventral intermediate thalamus nucleus (Vim) DBS was performed. Because of worsening dystonia after initial improvement in symptoms, subsequent bilateral globus pallidus internus (GPi) DBS was offered at 43 months after initial surgery, which reversed the deterioration and restored the motor function. For the second patient, initial improvement in motor symptoms and quality of life was sustained at the follow-up 6 months after bilateral Vim DBS treatment. Thus, DBS may be an effective therapeutic option for MDS, even in patients with double mutations. Moreover, GPi DBS may be used as a supplementary treatment when initial Vim DBS fails to control MDS symptoms.

Bilateral pallidal deep brain stimulation in myoclonus-dystonia: our experience in three cases and their follow-up

BACKGROUND

Myoclonus-dystonia syndrome (MDS) is an autosomal dominant movement disorder caused by mutations in the SGCE gene. MDS is characterized by mild dystonia and myoclonic jerks, and a constellation of psychiatric manifestations. Deep brain stimulation (DBS) of bilateral internal globus pallidus (GPi) has recently been introduced as a new and beneficial technique to improve motor symptoms in MDS.

METHODS

We report three proven genetically MDS cases with successful response to DBS, and their clinical evolution over years.

RESULTS

DBS improves significantly the Unified Myoclonus Rating Scale and Burke-Fahn-Marsden Dystonia Rating Scale in all three patients. This improvement is sustained over the years and no major adverse events were recorded. DBS stimulation parameters employed are justified and compared with cases reported throughout the literature.

DISCUSSION

DBS of bilateral GPi is an effective and safe therapy to be considered in MDS refractory cases. Careful neuropsychological evaluation is essential inside the presurgery planning. Correct location of the DBS electrodes and individualized selection of stimulation parameters in each case are the main determinants of the best clinical response.

Improvement of Isolated Myoclonus Phenotype in Myoclonus Dystonia after Pallidal Deep Brain Stimulation

Background

Myoclonus–dystonia is a condition that manifests predominantly as myoclonic jerks with focal dystonia. It is genetically heterogeneous with most mutations in the epsilon sarcoglycan gene (SGCE). In medically refractory cases, deep brain stimulation (DBS) has been shown to provide marked sustainable clinical improvement, especially in SGCE-positive patients. We present two patients with myoclonus–dystonia (one SGCE positive and the other SGCE negative) who have the isolated myoclonus phenotype and had DBS leads implanted in the bilateral globus pallidus internus (GPi).

Methods

We review their longitudinal Unified Myoclonus Rating Scale scores along with their DBS programming parameters and compare them with published cases in the literature.

Results

Both patients demonstrated complete amelioration of all aspects of myoclonus within 6–12 months after surgery. The patient with the SGCE-negative mutation responded just as well as the patient who was SGCE positive. High-frequency stimulation (130 Hz) with amplitudes greater than 2.5 V provided therapeutic benefit.

Discussion

This case series demonstrates that high frequency GPi-DBS is effective in treating isolated myoclonus in myoclonus–dystonia, regardless of the presence of SGCE mutation.

Non-motor symptoms in genetically defined dystonia: Homogenous groups require systematic assessment

INTRODUCTION

Dystonia is a movement disorder involving sustained or intermittent muscle contractions resulting in abnormal movements and postures. Identification of disease causing genes has allowed examination of genetically homogenous groups. Unlike the motor symptoms, non-motor characteristics are less clearly defined, despite their impact on a patient's quality of life. This review aims to examine the evidence for non-motor symptoms, addressing cohort size and methods of assessment in each study.

METHODS

A systematic and standardised search strategy was used to identify the published literature relating to psychiatric symptoms, cognition, sleep disorders, sensory abnormalities and pain in each of the genetically determined dystonias. Studies were divided according to cohort size, method of assessment and whether comparison was made to an appropriate control group.

RESULTS

Ninety-five articles were identified including reported clinical histories (n = 42), case reports and smaller case series (n = 12), larger case series (n = 23) and case-control cohorts (n = 18). Psychiatric symptoms were the most frequently investigated with anxiety, depression and Obsessive-Compulsive disorder being most common. Cognitive impairment involved either global deficits or isolated difficulties in specific domains. Disturbances to sleep were most common in the dopa-responsive dystonias. Sensory testing in DYT1 cases identified an intermediate subclinical phenotype.

CONCLUSION

Non-motor symptoms form an integral component of the dystonia phenotype. However, future studies should involve a complete assessment of all symptom subtypes in order to understand the frequency and gene-specificity of these symptoms. This will enable early symptom identification, appropriate clinical management, and provide additional outcome measures in future clinical trials.

Long-term neuropsychiatric outcomes after pallidal stimulation in primary and secondary dystonia

OBJECTIVE

To evaluate changes in the diagnosis of Axis I psychiatric disorders in patients with primary and secondary dystonia after deep brain stimulation (DBS) of the globus pallidus internus (GPi).

METHODS

Structured Clinical Interviews for the DSM-IV, Axis I psychiatric disorders, were prospectively performed before and after surgery. Diagnoses were made based on DSM-IV criteria. Psychiatric disorders were grouped into 5 categories: mood, anxiety, addiction, obsessive-compulsive disorders, and psychosis. Patients could be stratified to more than one category. Rates for unchanged diagnoses, diagnoses in remission, and new-onset diagnoses after surgery for each category were calculated.

RESULTS

Fifty-seven patients with primary and secondary dystonia were included. Mean ± SD age at surgery and dystonia duration at time of surgery was 50.6 ± 13.8 and 19.0 ± 13.2 years, respectively. Preoperatively, 37 Axis I diagnoses were made in 25 patients, 43.8% of those presenting with at least 1 Axis I diagnosis (mostly mood and anxiety disorders). Mean ± SD duration of psychiatric follow-up was 24.4 ± 19.6 months. Overall, after surgery no significant changes (p = 0.16) were found in Axis I diagnoses (23 patients, 40.3%): 27 (73%) unchanged, 10 (27%) in complete remission, and 4 (12.9%) new-onset diagnoses.

CONCLUSIONS

Our results support the overall psychiatric stability of patients with primary and secondary dystonia treated with GPi DBS. However, considering the high psychiatric morbidity in the dystonia population, psychiatric assessments before and after surgery are strongly recommended.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that GPi DBS does not change Axis I psychiatric diagnoses in patients with primary and secondary dystonia.

Uncommon applications of deep brain stimulation in hyperkinetic movement disorders

Background

In addition to the established indications of tremor and dystonia, deep brain stimulation (DBS) has been utilized less commonly for several hyperkinetic movement disorders, including medication-refractory myoclonus, ballism, chorea, and Gilles de la Tourette (GTS) and tardive syndromes. Given the lack of adequate controlled trials, it is difficult to translate published reports into clinical use. We summarize the literature, draw conclusions regarding efficacy when possible, and highlight concerns and areas for future study.

Methods

A Pubmed search was performed for English-language articles between January 1980 and June 2014. Studies were selected if they focused primarily on DBS to treat the conditions of focus.

Results

We identified 49 cases of DBS for myoclonus-dystonia, 21 for Huntington's disease, 15 for choreacanthocytosis, 129 for GTS, and 73 for tardive syndromes. Bilateral globus pallidus interna (GPi) DBS was the most frequently utilized procedure for all conditions except GTS, in which medial thalamic DBS was more common. While the majority of cases demonstrate some improvement, there are also reports of no improvement or even worsening of symptoms in each condition. The few studies including functional or quality of life outcomes suggest benefit. A limited number of studies included blinded on/off testing. There have been two double-blind controlled trials performed in GTS and a single prospective double-blind, uncontrolled trial in tardive syndromes. Patient characteristics, surgical target, stimulation parameters, and duration of follow-up varied among studies.

Discussion

Despite these extensive limitations, the literature overall supports the efficacy of DBS in these conditions, in particular GTS and tardive syndromes. For other conditions, the preliminary evidence from small studies is promising and encourages further study.

Bilateral globus pallidus interna deep-brain stimulation in a patient with myoclonus-dystonia: a case report

OBJECTIVE

Myoclonus-dystonia is a movement disorder characterized by childhood onset of myoclonus and dystonia. We report a case of the epsilon-sarcoglycan mutation-negative myoclonus-dystonia patient who underwent bilateral globus pallidus interna deep-brain stimulation with subsequent improvement of both myoclonus and dystonia.

CASE REPORT

A 37-year-old woman with myoclonic jerks and dystonia affecting predominantly the lower limbs was treated with chronic bilateral globus pallidus interna deep-brain stimulation.

RESULTS

The movement subscore of the Burke-Fahns-Marsden Dystonia Rating Scale was 38 before surgery and improved to 7 after 3 years. The disability subscore of the Burke-Fahns-Marsden Dystonia Rating Scale improved from 7 to 2. The Unified Myoclonus Rating Scale also decreased significantly from 93 to 39. No hardware- or stimulation-related complications occurred during follow-up.

CONCLUSION

This report suggests that patients with myoclonus-dystonia may significantly benefit from bilateral globus pallidus interna deep-brain stimulation. Larger studies of this patient population are needed to confirm the optimal target.

Selective peripheral denervation: comparison with pallidal stimulation and literature review

Patients with cervical dystonia who are non-responders to Botulinum toxin qualify for surgery. Selective peripheral denervation (Bertrand's procedure, SPD) and deep brain stimulation of the globus pallidus (GPi-DBS) are available surgical options. Although peripheral denervation has potential advantages over DBS, the latter is nowadays more commonly performed. We describe the long-term outcome of selective peripheral denervation as compared with GPi-DBS, along with the findings of literature review. Twenty patients with selective peripheral denervation and 15 with GPi-DBS were included. Tsui scale, a visual analogue scale, and the global outcome score of the Toronto Western Spasmodic Torticollis Rating Scale were used to define a "combined global surgical outcome". The "combined global surgical outcome" for patients with selective peripheral denervation or pallidal stimulation was respectively "bad" for 65 and 13.3 %, "fair-to-good" for 30 and 26.7 %, and "marked" improvement for 5 and 60 % (p < 0.001). Improvement on visual analogue scale (p < 0.002), global outcome score (p < 0.002), and Tsui score (p < 0.000) was larger for the pallidal stimulation group. Seventy-five percent of patients with selective peripheral denervation and 60 % of patients with pallidal stimulation reported side effects. Seven patients with selective peripheral denervation successively underwent GPi-DBS, with a further significant improvement in the Tsui score (-48.6 ± 17.4 %). GPi-DBS is to be preferred to selective peripheral denervation for the treatment of cervical dystonia because it produces larger benefit, even if it can have more potentially severe complications. GPi-DBS is also a valid alternative in case of failure of SPD.

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.

Surgical treatment of myoclonus dystonia syndrome

Myoclonus dystonia (M-D) syndrome is a heritable movement disorder characterized by myoclonic jerks and dystonia primarily of the upper extremities. M-D remains poorly responsive to pharmacological treatment. Emerging reports suggest good response to DBS of the internal globus pallidus (GPi) and ventral intermediate nucleus (VIM) of the thalamus. This study aimed to appraise the value of these two DBS targets by evaluating reports available in the literature. A systematic search of published case reports and case series was performed on Medline and Embase. Responses to DBS were evaluated. Myoclonus was assessed with the Unified Myoclonus Rating Scale (UMRS) and dystonia by the Burke-Fahn-Marsden dystonia rating scale (BFMDRS). The primary outcome of interest was the relative improvements noted with GPi, compared to VIM stimulation. A total of 17 publications yielded 40 unique cases, with mean follow-up of 27.2 months. All patients demonstrated improvements in myoclonus scores, with 93.5% showing at least a 50% improvement in UMRS. The mean improvement in myoclonus scores was 72.6%. In contrast, dystonia scores were improved in 87.9% of patients, with 72.7% reporting at least a 50% improvement in BFMDRS. The mean improvement in dystonia scores was 52.6%. Improvements in myoclonus scores were similar for both GPi (75.7%) and VIM (70.4%; P = 0.27). However, the improvements in dystonia scores were greater with GPi (60.2%), compared to VIM (33.3%; P = 0.03). Although both targets achieve similar improvements in myoclonus, GPi stimulation may be a preferred target because it may achieve greater improvements in dystonia, compared to VIM stimulation.

Prominent psychiatric comorbidity in the dominantly inherited movement disorder myoclonus-dystonia

BACKGROUND

Neurological and psychiatric disorders show clinical overlap suggesting a shared pathophysiological background. We evaluated myoclonus-dystonia, a monogenic movement disorder as a disease model for inherited psychopathology.

METHOD

We investigated 12 SGCE mutation carriers using standardized neurological and psychiatric examinations to assign DSM-IV diagnoses. Furthermore, we analyzed all studies in the Medline database which included psychiatric information on SGCE mutation-positive patients.

RESULTS

Of our twelve SGCE mutation carriers, 10 were older than 16 years. Two of them (20%) reported psychiatric diagnoses before our examination, which resulted in at least one psychiatric diagnosis in seven (70%) patients, most frequently anxiety (60%), depression (30%) or both. Substance abuse was observed in 20%, whereas obsessive-compulsive disorders were absent. One mutation carrier showed Axis 2 features. In the literature analysis, the ten studies using standardized tools covering DSM-IV criteria reported prevalences similar to those in our sample. This was three times the frequency of psychiatric disorders detected in 13 studies using clinical history or patient report only.

CONCLUSION

About two thirds of SGCE mutation carriers develop psychiatric comorbidity and >80% are previously undiagnosed.

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.