Deep brain stimulation of the internal globus pallidus for refractory tardive dystonia

Deep Brain Stimulation in the Treatment of Tardive Dyskinesia

Tardive dyskinesia (TD) is a phenomenon observed following the predominantly long-term use of dopamine receptor blockers (antipsychotics) widely used in psychiatry. TD is a group of involuntary, irregular hyperkinetic movements, mainly in the muscles of the face, eyelid, lips, tongue, and cheeks, and less frequently in the limbs, neck, pelvis, and trunk. In some patients, TD takes on an extremely severe form, massively disrupting functioning and, moreover, causing stigmatization and suffering. Deep brain stimulation (DBS), a method used, among others, in Parkinson's disease, is also an effective treatment for TD and often becomes a method of last resort, especially in severe, drug-resistant forms. The group of TD patients who have undergone DBS is still very limited. The procedure is relatively new in TD, so the available reliable clinical studies are few and consist mainly of case reports. Unilateral and bilateral stimulation of two sites has proven efficacy in TD treatment. Most authors describe stimulation of the globus pallidus internus (GPi); less frequent descriptions involve the subthalamic nucleus (STN). In the present paper, we provide up-to-date information on the stimulation of both mentioned brain areas. We also compare the efficacy of the two methods by comparing the two available studies that included the largest groups of patients. Although GPi stimulation is more frequently described in literature, our analysis indicates comparable results (reduction of involuntary movements) with STN DBS.

Deep Brain Stimulation of the Globus Pallidus Internus for Secondary Dystonia: Clinical Cases and Systematic Review of the Literature Regarding the Effectiveness of Globus Pallidus Internus versus Subthalamic Nucleus

OBJECTIVE

Deep brain stimulation (DBS) is a frequently applied therapy in primary dystonia. For secondary dystonia, the effects can be less favorable. We share our long-term findings in 9 patients with severe secondary dystonia and discuss these findings in the light of the literature.

METHODS

Patients who had undergone globus pallidus internus (GPi)-DBS for secondary dystonia were included. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores, clinical improvement rates, follow-up periods, stimulation parameters and the need for internal pulse generator replacements were analyzed. The PubMed and Google Scholar databases were searched for articles describing GPi-DBS and subthalamic nucleus (STN)-DBS only for secondary dystonia cases. Keywords were "dystonia," "deep brain stimulation," "GPi," "dystonia," "deep brain stimulation," and "STN."

RESULTS

A total of 9 secondary dystonia patients (5 male, 4 female) had undergone GPi-DBS with microelectrode recording in our units. The mean follow-up period was 29 months. The average BFMDRS score was 58.2 before the surgery, whereas the mean value was 36.5 at the last follow-up of the patients (mean improvement, 39%; minimum, 9%; maximum, 63%). In the literature review, we identified 264 GPi-DBS cases (mean follow-up, 19 months) in 72 different articles about secondary dystonia. The mean BFMDRS improvement rate was 52%. In 146 secondary dystonia cases, reported in 19 articles, STN-DBS was performed. The average follow-up period was 20 months and the improvement in BFMDRS score was 66%.

CONCLUSIONS

Although GPi-DBS has favorable long-term efficacy and safety in the treatment of patients with secondary dystonia, STN seems a promising target for stimulation in patients with secondary dystonia. Further studies including a large number of patients, longer follow-up periods, and more homogenous patients are necessary to establish the optimal target for DBS in the management of secondary dystonias.

Globus Pallidus Internus Deep Brain Stimulation for Dystonic Opisthotonus in Adult-Onset Dystonia: A Personalized Approach

Introduction

Dystonic opisthotonus is defined as a backward arching of the neck and trunk, which ranges in severity from mild backward jerks to life-threatening prolonged severe muscular spasms. It can be associated with generalized dystonic syndromes or, rarely, present as a form of axial truncal dystonia. The etiologies vary from idiopathic, genetic, tardive, hereditary-degenerative, or associated with parkinsonism. We report clinical cases of dystonic opisthotonus associated with adult-onset dystonic syndromes, that benefitted from globus pallidus internus (GPi) deep brain stimulation (DBS).

Methods

Clinical data from patients with dystonic syndromes who underwent comprehensive medical review, multidisciplinary assessment, and tailored medical and neurosurgical managements were prospectively analyzed. Quantification of dystonia severity pre- and postoperatively was performed using the Burke-Fahn-Marsden Dystonia Rating Scale and quantification of overall pain severity was performed using the Visual Analog Scale.

Results

Three male patients, with age of onset of the dystonic symptoms ranging from 32 to 51 years old, were included. Tardive dystonia, adult-onset dystonia-parkinsonism and adult-onset idiopathic axial dystonia were the etiologies identified. Clinical investigation and management were tailored according to the complexity of the individual presentations. Although they shared common clinical features of adult-onset dystonia, disabling dystonic opisthotonus, refractory to medical management, was the main indication for GPi-DBS in all patients presented. The severity of axial dystonia ranged from disturbance of daily function to life-threatening truncal distortion. All three patients underwent bilateral GPi DBS at a mean age of 52 years (range 48–55 years), after mean duration of symptoms prior to DBS of 10.7 years (range 4–16 years). All patients showed a rapid and sustained clinical improvement of their symptoms, notably of the dystonic opisthotonos, at postoperative follow-up ranging from 20 to 175 months. In some, the ability to resume activities of daily living and reintegration into the society was remarkable.

Conclusion

Adult-onset dystonic syndromes predominantly presenting with dystonic opisthotonus are relatively rare. The specific nature of dystonic opisthotonus remains a treatment challenge, and thorough investigation of this highly disabling condition with varying etiologies is often necessary. Although patients may be refractory to medical management and botulinum toxin injection, Globus pallidus stimulation timed and tailored provided symptomatic control in this cohort and may be considered in other carefully selected cases.

Long-term follow-up of bilateral subthalamic deep brain stimulation for refractory tardive dystonia

BACKGROUND

No effective treatment for tardive dystonia (TD) has been well established. Deep brain stimulation (DBS) can ameliorate motor manifestations in primary dystonia, and may also be an effective approach for TD.

OBJECTIVES

This study aimed to illuminate the long-term efficacy and safety of subthalamic nucleus (STN)-DBS in treating TD.

METHODS

Ten patients with refractory TD underwent STN-DBS therapy and were assessed by the Burke-Fahn-Marsden dystonia rating scale (BFMDRS), Abnormal Involuntary Movement Scale (AIMS), Hamilton Depression Scale (HAMD), Hamilton Anxiety Scale (HAMA), and the Short Form (36) Health Survey (SF-36) at four time points: pre-operation, 1 week post-operation, 6 months post-operation, and at a final long-term postsurgical follow-up time point.

RESULTS

The mean follow-up time was 65.6 ± 30.4 months (range, 12-105 months). At the first follow-up, BFMDRS motor and disability scores had improved by 55.9± 28.3% and 62.6± 32.0%, respectively, while AIMS scores improved by 53.3± 26.7%. At the second follow-up, BFMDRS motor and disability scores improved further, by 87.3± 17.0% and 84.3% ± 22.9%, respectively, while AIMS scores improved by 88.4 ± 16.1%. At the last follow-up, this benefit was sustained and had plateaued. Quality of life was improved significantly at the long-term follow-up, and the HAMA and HAMD scores displayed a significant reduction that persisted after the first follow-up.

CONCLUSION

STN-DBS may be an effective and acceptable procedure for TD, leading to persistent and significant improvement in both movement and psychiatric symptoms.

Deep brain stimulation for intractable tardive dystonia: Literature overview

BACKGROUND

Tardive dystonia (TD) represents a side effect of prolonged intake of dopamine receptor blocking compounds. TD can be a disabling movement disorder persisting despite available medical treatment. Deep brain stimulation (DBS) has been reported successful in this condition although the number of treated patients with TD is still limited to small clinical studies or case reports. The aim of this study was to present the systematical overview of the existing literature regarding DBS for intractable TD.

METHODS AND RESULTS

A literature search was carried out in PudMed. Clinical case series or case reports describing the patients with TD after DBS treatment were included in the present overview. Literature search revealed 19 articles reporting 59 individuals operated for TD. GPi was the target in 55 patients, while subthalamic nucleus (STN) was the target in the remaining 4. In most studies the motor part of Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was improved by more than 80% when compared to preoperative BFMDRS scores.

CONCLUSIONS

The performed literature analysis indicates that bilateral GPi DBS is an effective treatment for disabling TD. The response of TD to bilateral GPi DBS may be very rapid and occurs within days/weeks after the procedure. The efficacy of bilateral GPi DBS in TD patients is comparable to results achieved in patients with primary generalized dystonia.

Therapeutic Perspective on Tardive Syndrome with Special Reference to Deep Brain Stimulation

Tardive syndrome (TDS) is a potentially permanent and irreversible hyperkinetic movement disorder caused by exposure to dopamine receptor blocking agents. Guidelines published by the American Academy of Neurology recommend pharmacological first-line treatment for TDS with clonazepam (level B), ginkgo biloba (level B), amantadine (level C), and tetrabenazine (level C). Recently, a class II study provided level C evidence for use of deep brain stimulation (DBS) of the globus pallidus internus (GPi) in patients with TDS. Although the precise pathogenesis of TDS remains to be elucidated, the beneficial effects of GPi-DBS in patients with TDS suggest that the disease may be a basal ganglia disorder. In addition to recent advances in understanding the pathophysiology of TDS, this article introduces the current use of DBS in the treatment of medically intractable TDS.

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.

Temporal profile of improvement of tardive dystonia after globus pallidus deep brain stimulation

BACKGROUND

Several case reports and small series have indicated that tardive dystonia is responsive to globus pallidus deep brain stimulation. Whether different subtypes or distributions of tardive dystonia are associated with different outcomes remains unknown.

METHODS

We assessed the outcomes and temporal profile of improvement of eight tardive dystonia patients who underwent globus pallidus deep brain stimulation over the past six years through record review. Due to the retrospective nature of this study, it was not blinded or placebo controlled.

RESULTS

Consistent with previous studies, deep brain stimulation improved the overall the Burke-Fahn-Marsden motor scores by 85.1 ± 13.5%. The distributions with best responses in descending order were upper face, lower face, larynx/pharynx, limbs, trunk, and neck. Patients with prominent cervical dystonia demonstrated improvement in the Toronto Western Spasmodic Torticollis Rating Scale but improvements took several months. In four patients the effects of deep brain stimulation on improvement in Burke Fahn Marsden score was rapid, while in four cases there was partial rapid response of neck and trunk dystonia followed by was gradual resolution of residual symptoms over 48 months.

CONCLUSION

Our retrospective analysis shows excellent resolution of tardive dystonia after globus pallidus deep brain stimulation. We found instantaneous response, except with neck and trunk dystonia where partial recovery was followed by further resolution at slower rate. Such outcome is encouraging for using deep brain stimulation in treatment of tardive dystonia.

Globus pallidus deep brain stimulation for adult-onset axial dystonia

INTRODUCTION

Generalized dystonia, both primary and secondary forms, and axial dystonias such as tardive dystonia, and idiopathic cervical dystonia are responsive to globus pallidus interna (GPi) DBS. There is a paucity of investigations probing the impact of DBS on adult-onset axial dystonia. We assessed the efficacy of GPi DBS in four patients with rare adult-onset axial dystonia.

METHODS

Primary outcome measure was improvement in the motor component of the Burke-Fahn-Marsden (BFM) rating scale. Secondary outcome measures were quality of life as determined by the SF-36 questionnaire, time to achieve best possible benefit and DBS parameters that accounted for the best response. In patients with prominent concomitant cervical dystonia we also used the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS).

RESULTS

GPi DBS improved BFM scores by 87.63 ± 11.46%. Improvement in total severity scale of TWSTRS was 71.5 ± 12.7%. Quality of life also remarkably improved as evidenced by 109.38 ± 82.97 and 7.05 ± 21.48% percent change in psychometrically-based physical component summary (PCS), and a mental component summary (MCS) score respectively.

CONCLUSIONS

GPi DBS is a very effective treatment for adult-onset axial dystonia. Considering its refractoriness to medical therapy and significant impact on quality of life DBS should be considered for this disorder.

Deep brain stimulation suppresses pallidal low frequency activity in patients with phasic dystonic movements

Deep brain stimulation of the globus pallidus internus alleviates involuntary movements in patients with dystonia. However, the mechanism is still not entirely understood. One hypothesis is that deep brain stimulation suppresses abnormally enhanced synchronized oscillatory activity within the motor cortico-basal ganglia network. Here, we explore deep brain stimulation-induced modulation of pathological low frequency (4-12 Hz) pallidal activity that has been described in local field potential recordings in patients with dystonia. Therefore, local field potentials were recorded from 16 hemispheres in 12 patients undergoing deep brain stimulation for severe dystonia using a specially designed amplifier allowing simultaneous high frequency stimulation at therapeutic parameter settings and local field potential recordings. For coherence analysis electroencephalographic activity (EEG) over motor areas and electromyographic activity (EMG) from affected neck muscles were recorded before and immediately after cessation of high frequency stimulation. High frequency stimulation led to a significant reduction of mean power in the 4-12 Hz band by 24.8 ± 7.0% in patients with predominantly phasic dystonia. A significant decrease of coherence between cortical EEG and pallidal local field potential activity in the 4-12 Hz range was revealed for the time period of 30 s after switching off high frequency stimulation. Coherence between EMG activity and pallidal activity was mainly found in patients with phasic dystonic movements where it was suppressed after high frequency stimulation. Our findings suggest that high frequency stimulation may suppress pathologically enhanced low frequency activity in patients with phasic dystonia. These dystonic features are the quickest to respond to high frequency stimulation and may thus directly relate to modulation of pathological basal ganglia activity, whereas improvement in tonic features may depend on long-term plastic changes within the motor network.

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.

Dystonia, facial dysmorphism, intellectual disability and breast cancer associated with a chromosome 13q34 duplication and overexpression of TFDP1: case report

Background

Dystonia is a movement disorder characterized by involuntary sustained muscle contractions causing twisting and repetitive movements or abnormal postures. Some cases of primary and neurodegenerative dystonia have been associated with mutations in individual genes critical to the G₁-S checkpoint pathway (THAP1, ATM, CIZ1 and TAF1). Secondary dystonia is also a relatively common clinical sign in many neurogenetic disorders. However, the contribution of structural variation in the genome to the etiopathogenesis of dystonia remains largely unexplored.

Case presentation

Cytogenetic analyses with the Affymetrix Genome-Wide Human SNP Array 6.0 identified a chromosome 13q34 duplication in a 36 year-old female with global developmental delay, facial dysmorphism, tall stature, breast cancer and dystonia, and her neurologically-normal father. Dystonia improved with bilateral globus pallidus interna (GPi) deep brain stimulation (DBS). Genomic breakpoint analysis, quantitative PCR (qPCR) and leukocyte gene expression were used to characterize the structural variant. The 218,345 bp duplication was found to include ADPRHL1, DCUN1D2, and TMCO3, and a 69 bp fragment from a long terminal repeat (LTR) located within Intron 3 of TFDP1. The 3' breakpoint was located within Exon 1 of a TFDP1 long non-coding RNA (NR_026580.1). In the affected subject and her father, gene expression was higher for all three genes located within the duplication. However, in comparison to her father, mother and neurologically-normal controls, the affected subject also showed marked overexpression (2×) of the transcription factor TFDP1 (NM_007111.4). Whole-exome sequencing identified an SGCE variant (c.1295G > A, p.Ser432His) that could possibly have contributed to the development of dystonia in the proband. No pathogenic mutations were identified in BRCA1 or BRCA2.

Conclusion

Overexpression of TFDP1 has been associated with breast cancer and may also be linked to the tall stature, dysmorphism and dystonia seen in our patient.

Dramatic improvement of truncal tardive dystonia following globus pallidus pars interna deep brain stimulation

Truncal predominant tardive dystonia is an uncommon presentation of dystonia, and may be associated with significant disability. We report a patient with near-complete resolution of severe, disabling truncal tardive dystonia following globus pallidus pars interna deep brain stimulation. Her unusual clinical presentation highlights the difficulties in diagnosing unusual forms of dystonia, and the therapeutic gains that can be achieved once the diagnosis is recognised.

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.

Globus pallidus interna deep brain stimulation for tardive dyskinesia: case report and review of the literature

Tardive dyskinesia (TD) can be a disabling condition and is frequently refractory to medical therapy. Over the past decade there have been many reports of TD patients experiencing significant benefit with deep brain stimulation (DBS) of the globus pallidus interna (GPi). The growing literature on this treatment option for TD consists predominantly of case reports and series. The reported benefit ranges widely, but the majority of cases experienced at least a 50% improvement in symptoms. The anatomical distribution of dyskinesias has not clearly influenced outcome, though fixed postures appear less likely to improve than phasic movements. Onset of benefit can be immediate or take months, and benefit is sustained in most cases, for at least 6 months and up to several years. A wide variety of voltages, frequencies, and pulse widths have demonstrated efficacy. A small number of reports which examined psychiatric symptoms before and after surgery did not find any decline, and in some cases revealed improvement in mood. However, these overall positive results should be interpreted with caution, as the majority of reports lacked blinded assessments, control groups, or standardized therapy parameters. Finally, we present an illustrative case of refractory tardive dyskinesia treated with GPi-DBS with 5 years of follow-up and 4 accompanying video segments.

Surgical treatment for secondary dystonia

Surgical therapy for the secondary dystonias is generally perceived to be less effective than for primary disease. However, a number of case reports and small open series have recently appeared describing quite favorable outcomes following surgery for some nonprimary dystonias. We discuss surgical treatment options for this group of diverse conditions, including tardive dystonia, dystonic cerebral palsy, and certain heredodegenerative diseases in which deep brain stimulation and ablative lesions of the posteroventral pallidum have been shown to be effective. Other types of secondary dystonia respond less well to pallidal surgery, particularly when anatomical lesions of the basal ganglia are prominent on preoperative imaging. For these conditions, central baclofen delivery and botulinum toxin denervation may be considered. With optimal medical and surgical care, some patients with secondary dystonia have achieved reductions in disability and pain that approach those documented for primary dystonia.

Treatment of secondary dystonia with a combined stereotactic procedure: long-term surgical outcomes

OBJECTIVE

There is some debate about the effects of pallidal deep brain stimulation (DBS) or lesioning on secondary dystonia. We applied a multimodal method to maximize the treatment effects of deep brain stimulation in patients with secondary dystonia.

METHODS

Between March 2003 and January 2009, four patients underwent bilateral globus pallidus internus (GPi) DBS and six patients underwent bilateral GPi DBS plus unilateral thalamotomy for treatment of cerebral palsy (CP). Among the patients with secondary dystonia without CP, five were also treated by DBS. We classified patients with generalized secondary dystonia with cerebral palsy into group I and patients with focal dystonia without CP into group II. Clinical outcome assessments were based on Burke-Fahn-Marsden Dystonia Rating Scale movement and disability scores. Heath-related quality of life was assessed with a 36-item short-form general health survey questionnaire preoperatively and at the last follow-up.

RESULTS

The movement and disability scores of group I-A had improved by 32.0% (P = 0.285) and 14.3% (P = 0.593), respectively, at the last follow-up compared with baseline. The movement and disability scores of group I-B had improved by 31.5% and 0.18% at the last follow-up compared with baseline, respectively. In comparison with patients in group I-A, patients in group I-B showed a significant improvement in movement scores for the contralateral arm (P = 0.042). Group II patients showed a marked improvement in movement and disability scores of 77.7% (P = 0.039) and 80.0% (P = 0.041), respectively.

CONCLUSIONS

We demonstrated that DBS plus unilateral ventralis oralis thalamotomy for CP patients with fixed states in the upper extremities is useful not only to treat secondary dystonic movement but also to improve quality of life. In group II patients with post-traumatic dystonia and tardive dyskinesia, we achieved excellent clinical outcomes using a stereotactic procedure.

Deep-Brain Stimulation for Basal Ganglia Disorders

The realization that medications used to treat movement disorders and psychiatric conditions of basal ganglia origin have significant shortcomings, as well as advances in the understanding of the functional organization of the brain, has led to a renaissance in functional neurosurgery, and particularly the use of deep brain stimulation (DBS). Movement disorders are now routinely being treated with DBS of 'motor' portions of the basal ganglia output nuclei, specifically the subthalamic nucleus and the internal pallidal segment. These procedures are highly effective and generally safe. Use of DBS is also being explored in the treatment of neuropsychiatric disorders, with targeting of the 'limbic' basal ganglia-thalamocortical circuitry. The results of these procedures are also encouraging, but many unanswered questions remain in this emerging field. This review summarizes the scientific rationale and practical aspects of using DBS for neurologic and neuropsychiatric disorders.

Nonprimary dystonias

Dystonias can be classified as primary or secondary, as dystonia-plus syndromes, and as heredodegenerative dystonias. Their prevalence is difficult to determine. In our experience 80-90% of all dystonias are primary. About 20-30% of those have a genetic background; 10-20% are secondary, with tardive dystonia and dystonia in cerebral palsy being the most common forms. If dystonia in spastic conditions is accepted as secondary dystonia, this is the most common form of all dystonia. In primary dystonias, the dystonic movements are the only symptoms. In secondary dystonias, dystonic movements result from exogenous processes directly or indirectly affecting brain parenchyma. They may be caused by focal and diffuse brain damage, drugs, chemical agents, physical interactions with the central nervous system, and indirect central nervous system effects. Dystonia-plus syndromes describe brain parenchyma processes producing predominantly dystonia together with other movement disorders. They include dopa-responsive dystonia and myoclonus-dystonia. Heredodegenerative dystonias are dystonic movements occurring in the context of other heredodegenerative disorders. They may be caused by impaired energy metabolism, impaired systemic metabolism, storage of noxious substances, oligonucleotid repeats and other processes. Pseudodystonias mimic dystonia and include psychogenic dystonia and various orthopedic, ophthalmologic, vestibular, and traumatic conditions. Unusual manifestations, unusual age of onset, suspect family history, suspect medical history, and additional signs may indicate nonprimary dystonia. If they are suspected, etiological clarification becomes necessary. Unfortunately, potential etiologies are legion. Diagnostic algorithms can be helpful. Treatment of nonprimary dystonias, with few exceptions, does not differ from treatment of primary dystonias. The most effective treatment for focal and segmental dystonias is local botulinum toxin injections. Deep brain stimulation of the globus pallidus internus is effective for generalized dystonia. Antidystonic drugs, including anticholinergics, tetrabenazine, clozapine, and gamma-aminobutyric acid receptor agonists, are less effective and often produce adverse effects. Dopamine is extremely effective in dopa-responsive dystonia. The Bertrand procedure can be effective in cervical dystonia. Other peripheral surgery, including myotomy, myectomy, neurotomy, rhizotomy, ramizectomy, and accessory nerve neurolysis, has largely been abandoned. Central surgery other than deep brain stimulation is obsolete. Adjuvant therapies, including orthoses, physiotherapy, ergotherapy, behavioral therapy, social support, and support groups, may be helpful. Analgesics should also be considered where appropriate.

Chronic deep brain stimulation in patients with tardive dystonia without a history of major psychosis

Tardive dystonia usually occurs with a delay after neuroleptic exposure in patients with major psychosis. A subgroup of patients, however, is given such medication for "mild depression" or "neurasthenia." Tardive dystonia, in general, may respond favorably to pallidal deep brain stimulation (DBS). Nevertheless, it remains unclear thus far whether or not similar beneficial outcome is achieved with pallidal DBS in different subgroups of patients with tardive dystonia. Four women (mean age 59 years at surgery) underwent stereotactic pallidal DBS in the frame of an observational study. Tardive dystonia occurred secondary to medication with fluspirilene and haloperidol, and injection of long-acting depot neuroleptics prescribed for mild depression or "nervousness." Assessment included the Burke-Fahn-Marsden (BFM) scale preoperatively and at 12 months follow-up. Extended follow-up was available at a mean of 27.3 months postoperatively (range 16-36 months). There were no surgically related complications. All 4 patients experienced sustained statistically significant benefit from pallidal DBS. Mean improvement at 12 months was 77% for the BFM motor score (range, 45-91%; P = 0.043), and 84% at the last available follow-up (range, 70-91%; P = 0.03). This was paralleled by improvement of the BFM disability score. Chronic pallidal DBS in patients with tardive dystonia without a history of major psychosis provides sustained improvement which is similar to that in other subgroups of patients with tardive dystonia. This effect is stable on extended follow-up for up to 3 years.

Deep brain stimulation for dystonia: patient selection and outcomes

In a literature survey, 341 patients with primary and 109 with secondary dystonias treated with deep brain stimulation (DBS) of the internal segment of the globus pallidus (GPi) were identified. In general, the outcomes for primary dystonias were more favourable compared to the secondary forms. For some secondary dystonias--like tardive dystonia, myoclonus-dystonia (M-D), NBIA (PANK2), the outcome was very good. Only for the primary generalized dystonias, the efficacy of GPi-DBS has been confirmed in randomised controlled trials. Predictors of outcome are the experience and dedication of the stereotactic team, the selection of patients--the diagnosis and pre-operative screening--and the quality of the post-operative care. Predictors of negative outcome are long duration of the disease--with contractures or scoliosis--and concomitant symptoms like spasticity and cerebellar dysfunction. More studies are required to establish the role of GPi-DBS in the treatment of secondary dystonias.

Dystonia: a surgeon's perspective

Surgery for dystonia has a history stretching back for centuries including myotomy and other procedures on the musculoskeletal system. In the last century lesional procedures, mainly involving the pallidum became popular. More recently, with the advent of deep brain stimulation, bilateral medial pallidal stimulation has become commonplace. This review describes the issues with patient selection, technical aspects of implantation and effects as well as complications of the technique. Some of the rarer types of dystonia that have also been treated with DBS are also described.

Bilateral deep brain stimulation of the globus pallidus internus in tardive dystonia

Tardive dystonia is a disabling movement disorder as a consequence of exposure to neuroleptic drugs. We followed 6 patients with medically refractory tardive dystonia treated by bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for 21 +/- 18 months. At last follow-up, the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) motor score improved by 86% +/- 14%, and the BFMDRS disability score improved by 80% +/- 12%. Bilateral GPi-DBS is a beneficial therapeutic option for the long-term relief of tardive dystonia.

Surgery for movement disorders

Movement disorders, such as Parkinson's disease, tremor, and dystonia, are among the most common neurological conditions and affect millions of patients. Although medications are the mainstay of therapy for movement disorders, neurosurgery has played an important role in their management for the past 50 years. Surgery is now a viable and safe option for patients with medically intractable Parkinson's disease, essential tremor, and dystonia. In this article, we provide a review of the history, neurocircuitry, indication, technical aspects, outcomes, complications, and emerging neurosurgical approaches for the treatment of movement disorders.