Chorea induced by globus pallidus externus stimulation in a dystonic patient

Bilateral high-frequency stimulation of the internal part of the pallidum has proven its efficacy in improving motor symptoms of dystonia. In Parkinson's disease, the stimulation of the external pallidum (GPe) can induce dyskinesias. This has never been described in dystonia. We report here a case of abnormal movements induced by the stimulation of GPe in a dystonic patient and discuss the pathophysiological mechanisms.

Impact of bilateral pallidal stimulation on DYT1-generalized dystonia in Japanese patients

Early-onset generalized dystonia attributable to a DYT1 gene mutation is a hyperkinetic movement disorder that responds poorly to pharmacotherapy. In this video brief, we show that continuous bilateral stimulation of the globus pallidus internus produced sustained and marked improvements in the motor symptoms and functional disabilities of Japanese patients with DYT1-generalized dystonia.

Use of surface electromyography to assess and select patients with idiopathic dystonia for bilateral pallidal stimulation

OBJECT

The object of this study was to identify a preoperative physiological index by using surface electromyography (EMG) signals that would correlate with clinical outcome in dystonic patients following bilateral pallidal stimulation.

METHODS

In 14 patients with spasmodic torticollis, generalized dystonia, and myoclonic dystonia, surface EMG signals were recorded from the most affected muscle groups. Although the dystonia affected different body segments, the EMG signals in all patients could be decomposed into bursting and sustained components. Subsequently, a ratio of the EMG amplitude was calculated between the two components and then correlated with clinical outcome. Patients who experienced rapid improvement following bilateral pallidal stimulation had a significantly higher EMG ratio compared with those who did not. Furthermore, a significant correlation was found between the EMG ratio and clinical improvement during the 12-month period following pallidal stimulation.

CONCLUSIONS

The authors concluded that surface EMG studies could be used to predict the clinical outcome of and to select patients for pallidal stimulation for dystonia.

[Deep brain stimulation in the treatment of dystonia]

Dystonia refers to movement disorders characterized by sustained muscle contractions that produce abnormal postures and twisting movements. First-line therapy for dystonia includes several classes of pharmacologic agents. Botulinum toxin injections are the treatment of choice for several forms of focal dystonia. Many patients with dystonia do not benefit from these treatments, and for those patients whose symptoms are sufficiently troublesome, surgical treatment can be used to reduce symptoms and to improve function. Formerly the ablative procedures of thalamotomy and pallidotomy were used. More recently, deep brain stimulation (DBS) has emerged not only as the preferred surgical treatment for advanced idiopathic form of Parkinson's disease and severe forms of essential tremor but also for dystonia. For dystonia, stimulation directed at the globus pallidus internus has been the most thoroughly studied to date. Advantages of DBS include its relatively non-destructive nature, its adjustability and reversibility, and its capacity to be used bilaterally in a single surgical session. Use of DBS to treat dystonia is a rapidly evolving area, and preliminary evidence suggests that primary dystonia linked to genetic mutation, especially DYT-1 positive generalized dystonia, and other primary dystonias respond most dramatically to treatment with DBS, whereas secondary dystonia tends to be less responsive.

Posttraumatic Peripherally-induced Dystonia and Multifocal Deep Brain Stimulation

OBJECTIVE:

We report on the effect of multifocal deep brain stimulation for the treatment of posttraumatic peripherally-induced dystonia.

CLINICAL PRESENTATION:

A 34-year-old woman presented with an 8-year history of painful tonic dystonia starting in her left leg after injury of the third metatarsal bone. She did not benefit from right-sided pallidal stimulation by an electrode misplaced in the globus pallidus externus in another hospital.

INTERVENTION:

Quadripolar deep brain stimulation electrodes were placed in the globus pallidus internus and the ventrolateral thalamus by computed tomographic-guided stereotactic surgery and microelectrode recording contralateral to the side of dystonia. The Burke-Fahn-Marsden motor score of 34 did not improve with chronic pallidal or thalamic stimulation.

CONCLUSION:

Although deep brain stimulation is received with great enthusiasm, it is important to identify its limitations in certain subtypes of dystonia.

A systematic review on the diagnosis and treatment of primary (idiopathic) dystonia and dystonia plus syndromes: report of an EFNS/MDS-ES Task Force

To review the literature on primary dystonia and dystonia plus and to provide evidence-based recommendations. Primary dystonia and dystonia plus are chronic and often disabling conditions with a widespread spectrum mainly in young people. Computerized MEDLINE and EMBASE literature reviews (1966-1967 February 2005) were conducted. The Cochrane Library was searched for relevant citations. Diagnosis and classification of dystonia are highly relevant for providing appropriate management and prognostic information, and genetic counselling. Expert observation is suggested. DYT-1 gene testing in conjunction with genetic counselling is recommended for patients with primary dystonia with onset before age 30 years and in those with an affected relative with early onset. Positive genetic testing for dystonia (e.g. DYT-1) is not sufficient to make diagnosis of dystonia. Individuals with myoclonus should be tested for the epsilon-sarcoglycan gene (DYT-11). A levodopa trial is warranted in every patient with early onset dystonia without an alternative diagnosis. Brain imaging is not routinely required when there is a confident diagnosis of primary dystonia in adult patients, whereas it is necessary in the paediatric population. Botulinum toxin (BoNT) type A (or type B if there is resistance to type A) can be regarded as first line treatment for primary cranial (excluding oromandibular) or cervical dystonia and can be effective in writing dystonia. Actual evidence is lacking on direct comparison of the clinical efficacy and safety of BoNT-A vs. BoNT-B. Pallidal deep brain stimulation (DBS) is considered a good option, particularly for generalized or cervical dystonia, after medication or BoNT have failed to provide adequate improvement. Selective peripheral denervation is a safe procedure that is indicated exclusively in cervical dystonia. Intrathecal baclofen can be indicated in patients where secondary dystonia is combined with spasticity. The absolute and comparative efficacy and tolerability of drugs in dystonia, including anticholinergic and antidopaminergic drugs, is poorly documented and no evidence-based recommendations can be made to guide prescribing.

A dominant bursting electromyograph pattern in dystonic conditions predicts an early response to pallidal stimulation

Although chronic pallidal deep brain stimulation (DBS) is effective in the treatment of medically intractable dystonia, there is no way of predicting the variations in clinical outcome, partly due to our limited understanding of the pathophysiological mechanisms underlying this condition. We recorded electromyographic (EMG) activity from the most severely affected muscle groups in seven dystonia patients before and after pallidal DBS. Patient EMG recordings could be classified into two groups: one consisting of patients who at rest demonstrated a dominant low frequency component of activity on power spectral analysis (ranging from 2 to 5 Hz), and one group in which this dominant pattern was absent. Early postoperative improvements (within 2-3 days) were observed in the former group, whereas the latter group benefited more gradually (over several months). Analysis of EMG activity may provide a sensitive means of identifying dystonic patients who are likely to be most responsive to functional neurosurgical intervention.

Treatment of dystonia

Dystonia may be a sign or symptom, that is comprised of complex abnormal and dynamic movements of different etiologies. A specific cause is identified in approximately 28% of patients, which only occasionally results in specific treatment. In most cases, treatment is symptomatic and designed to relieve involuntary movements, improve posture and function and reduce associated pain. Therapeutic options are dictated by clinical assessment of the topography of dystonia, severity of abnormal movements, functional impairment and progression of disease and consists of pharmacological, surgical and supportive approaches. Several advances have been made in treatment with newer medications, availability of different forms of botulinum toxin and globus pallidus deep brain stimulation (DBS). For patients with childhood-onset dystonia, the majority of whom later develop generalized dystonia, oral medication is the mainstay of therapy. Recently, DBS has emerged as an effective alternative therapy. Botulinum toxin is usually the treatment of choice for those with adult-onset primary dystonia in which dystonia usually remains focal. In patients with secondary dystonia, treatment is challenging and efficacy is typically incomplete and partially limited by side effects. Despite these treatment options, many patients with dystonia experience only partial benefit and continue to suffer significant disability. Therefore, more research is needed to better understand the underlying cause and pathophysiology of dystonia and to explore newer medications and surgical techniques for its treatment.

Surgery Insight: deep brain stimulation for movement disorders

Over the past two decades, deep brain stimulation (DBS) has supplanted lesioning techniques for the treatment of movement disorders, and has been shown to be safe and efficacious. The primary therapeutic indications for DBS are essential tremor, dystonia and Parkinson's disease. In the case of Parkinson's disease, DBS is effective for treating the primary symptoms--tremor, bradykinesia and rigidity--as well as the motor complications of drug treatment. Progress has been made in understanding the effects of stimulation at the neuronal level, and this knowledge should eventually improve the effectiveness of this therapy. Preliminary studies also indicate that DBS might be used to treat Tourette's syndrome, obsessive-compulsive disorder, depression and epilepsy. As we will discuss in this review, the success of DBS depends on an appropriate rationale for the procedure, and on collaborations between neurologists and neurosurgeons in defining outcomes.

Effect of GPi DBS on functional imaging of the brain in dystonia

Five patients with idiopathic dystonic conditions, treated successfully with deep brain stimulation (DBS) of the globus pallidus internus (GPi), were studied using single-photon emission tomography (SPET) in order to evaluate brain perfusion in the presence and absence of DBS. Comparison was made between the "on" and "off" DBS scans on an individual basis and also as part of a group analysis. Whilst the individual data suggested great regional variation in cerebral perfusion between individuals, the results of the group analysis revealed several topographically similar areas of the brain where relative hyperperfusion in the absence of DBS was common to all patients. Based on these results we postulate on possible mechanisms for this phenomenon.

Oscillatory pallidal local field potential activity correlates with involuntary EMG in dystonia

The pathophysiology of dystonia is unclear. The authors recorded local field potentials (LFPs) from deep brain stimulation electrodes implanted in the pallidum of 13 dystonic patients. LFP power correlated with the level of dystonic EMG in the sternocleidomastoid, with maximal positive correlations at the lower contacts of pallidal electrodes. The data suggest that the neuronal synchronization indexed by LFP oscillations in the globus pallidus may be mechanistically linked to dystonic EMG activity.

Microelectrode-guided implantation of deep brain stimulators into the globus pallidus internus for dystonia: techniques, electrode locations, and outcomes

OBJECT

Deep brain stimulation (DBS) of the globus pallidus internus (GPI) is a promising new procedure for the treatment of dystonia. The authors describe their technical approach for placing electrodes into the GPI in awake patients with dystonia, including methodology for electrophysiological mapping of the GPI in the dystonic state, clinical outcomes and complications, and the location of electrodes associated with optimal benefit.

METHODS

Twenty-three adult and pediatric patients with various forms of dystonia were included in this study. Baseline neurological status and DBS-related improvement in motor function were measured using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS). The implantation of DBS leads was performed using magnetic resonance (MR) imaging-based stereotaxy, single-cell microelectrode recording, and intraoperative test stimulation to determine thresholds for stimulation-induced adverse effects. Electrode locations were measured on computationally reformatted postoperative MR images according to a prospective protocol.

CONCLUSIONS

Physiologically guided implantation of DBS electrodes in patients with dystonia was technically feasible in the awake state in most patients, and the morbidity rate was low. Spontaneous discharge rates of GPI neurons in dystonia were similar to those of globus pallidus externus neurons, such that the two nuclei must be distinguished by neuronal discharge patterns rather than rates. Active electrode locations associated with robust improvement (> 70% decrease in BFMDRS score) were located near the intercommissural plane, at a mean distance from the pallidocapsular border of 3.6 mm.

Globus pallidus deep brain stimulation in dystonia

Globus pallidus deep brain stimulation (GPi-DBS) is a useful alternative in the treatment of dystonia. Patients selected for GPi-DBS were prospectively rated with the Unified Dystonia Rating Scale (UDRS). Also, "blinded" videotape assessments were performed. Eleven patients were identified. Compared with pre-DBS scores, there were improvements in mean total UDRS score (15.3%) and in the following subscores: neck (18.18%), trunk (32.9%), arm (17.9%), and leg (19.9%). One patient developed a skin infection and erosion requiring surgical debridement. GPi-DBS is a safe and effective treatment for generalized dystonia in patients who remained impaired, despite optimal medical therapy.

Pregnancy in dystonic women with in situ deep brain stimulators

In the past few years, an increasing number of dystonic patients, of both sexes, have undergone insertion of deep brain stimulators (DBS) with consistent improvement of their symptoms and enhancement of their quality of life. We describe 3 women with dystonia who, after insertion of bilateral globus pallidus internus stimulators, succeeded in conceiving and completing pregnancies, 2 of them having married. These histories illustrate the significant positive impact that DBS can have on women's social relationships. Based on this experience, we also provide an overview of some of the issues that might arise in pregnancy and during delivery in dystonic women with an in situ deep brain stimulator.

The effect of repetitive transcranial magnetic stimulation on dystonia: a clinical and pathophysiological approach

Dystonia is characterized by sustained muscle contraction, which frequently causes repetitive, twisting movements or abnormal posture. The precise pathophysiological mechanisms of dystonia are still unknown. Several studies did demonstrate that, although motor cortex hyperexcitability appears to be responsible for abnormal co-contraction and overflow to adjacent muscles, plasticity mechanisms and integrative sensorimotor processing are also likely to be involved in this condition. Current dystonia treatments are based on oral medication, injection of botulinum toxin and, in a low proportion of cases, bi-pallidal deep brain stimulation. However, treatment outcome is generally disappointing. A few researchers have reported the application of repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex or the premotor cortex, with the goal of decreasing motor cortex hyperexcitability. This article reviews all studies using this technique in dystonia and discusses rTMS therapeutic impact and its possible mechanisms of action in this indication. Currently, the premotor cortex seems to be the best target for rTMS in dystonia. Rather than merely reducing the hyperexcitability of the primary motor cortex, this technique's clinical benefit seems to result from modifications in plasticity and restoration of sensorimotor integration. The corollary technique for chronic rTMS is electrical cortical stimulation. Even though this new therapeutic tool may have therapeutic promise, more studies are required to confirm it. In particular, we need to broaden our knowledge of rTMS impact on the various forms of dystonia and to optimize target localization.

Effects of bilateral subthalamic nucleus stimulation on sleep, daytime sleepiness, and early morning dystonia in patients with Parkinson disease

Object

The aim of this study was to assess the long-term effects of bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson disease (PD) on sleep, daytime sleepiness, and early morning dystonia and to evaluate the relationship between total sleep time and motor function.

Methods

Patients who had undergone bilateral STN DBS and a follow-up evaluation of 6 months (89 patients), 12 months (83 patients), and 24 months (43 patients) were included in this study. The patients were preoperatively assessed using the Unified Parkinson’s Disease Rating Scale (UPDRS) in the medication-on and -off conditions, and they completed patient diaries. A subset of patients also completed the Epworth Sleepiness Scale. These assessments were repeated postoperatively with stimulation.

The UPDRS activities of daily living (ADL) and motor scores as well as total sleep hours were significantly improved at 6, 12, and 24 months poststimulation and with no medication compared with baseline values. Increased sleep time was significantly correlated with improvements in bradykinesia but not with tremor or rigidity. Patient-reported sleep problems and early morning dystonia were reduced after STN DBS. Antiparkinsonian medications were significantly reduced after STN DBS; however, there were no changes in excessive daytime sleepiness 6, 12, or 24 months after surgery.

Conclusions

Bilateral STN DBS increased total sleep time and reduced patient-reported sleep problems and early morning dystonia for up to 24 months posttreatment. These changes in sleep were related to improvements in functioning, specifically those affected by bradykinesia. Despite significant reductions in antiparkinsonian medications, STN DBS did not reduce excessive daytime sleepiness.

Acupuncture-induced cerebral blood flow responses in dystonia

OBJECTIVE

The effect of acupuncture (ACP) on regional cerebral blood flow (rCBF) is unclear. Single-photon emission computed tomography studies on three patients with dystonia were performed before and after ACP treatment to test the contention that ACP affects rCBF.

METHODS

Pre-ACP and post-ACP CBF study were performed on the same day; 99mTc ethyl cysteinate dimer was injected for each study. rCBF images were analyzed using a three-dimensional stereotaxic ROI template (3DSRT) to objectively measure rCBF. We evaluated rCBF bilaterally in five segments related to the pathophysiology of dystonia (1, superior frontal; 2, middle and inferior frontal; 3, primary sensorimotor; 4, lenticular nucleus; and 5, thalamus). More than 10% left-right asymmetry in rCBF over three continuous slices was defined as significant laterality. Post-ACP rCBF and laterality were evaluated with the pre-ACP rCBF study acting as a control in each subject.

RESULTS

The clinical effect of ACP was remarkable in all patients and rCBF increased in most segments. Pre-ACP rCBF exhibited significant laterality in eight segments of the three patients. Laterality reversed in seven of these segments and resolved in the remaining segment after ACP. Pre-ACP rCBF laterality was not preserved in any segment after ACP. The remaining five segments exhibited laterality only after ACP. In total, after ACP, 13 of 15 segments demonstrated a change in CBF that was greater unilaterally.

CONCLUSIONS

ACP results in an increase in CBF that is greater unilaterally. We think that unilateral change in CBF may be correlated with the action of ACP on the central nervous system in patients with dystonia.

Singer's dystonia: first report of a variant of spasmodic dysphonia

OBJECTIVES

We discuss the phonatory characteristics of a previously undescribed focal laryngeal dystonia present in the singing voice.

METHODS

We performed a retrospective chart review of 5 patients with singer's dystonia at a neurolaryngology referral center.

RESULTS

Four patients reviewed demonstrated phonatory characteristics consistent with adductor spasmodic dysphonia present in their singing voice. One patient demonstrated abductor spasmodic dysphonia in the singing voice. Each patient initially exhibited normal connected speech in conversational voicing. The treatment protocol and outcome are discussed, including the use of botulinum toxin.

CONCLUSIONS

Singer's dystonia is a previously undescribed neurologic disorder that should be understood by those who treat voice performers and voice disorders.

Dystonia

BACKGROUND

Dystonia refers to a syndrome of sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. Although age at onset, anatomic distribution, and family history are essential elements in the evaluation of dystonia, new classification increasingly relies on etiologic and genetic data. In recent years, much progress has been made on the genetics of various forms of dystonia and its pathophysiology underlying the clinical signs. The treatment of dystonia has continued to evolve to include newer medications, different forms of botulinum toxin, and various surgical procedures.

REVIEW SUMMARY

In this article, the author reviewed and summarized the history of dystonia, its evolving classification, and recent genetic data, as well as its clinical investigation and treatment.

CONCLUSIONS

Recent advances in molecular biology have led to the discovery of novel dystonia genes and loci, updating classification schemes, and better understanding of underlying pathophysiology. Treatment strategies for dystonia have significantly been updated with the introduction of different forms of botulinum toxin therapy, new pharmacologic agents, and most recently pallidal deep brain stimulation. A systematic approach to the diagnosis and treatment evaluation of dystonic patients provides optimal care for long-term management.

State of the art: deep brain stimulation in Parkinson's disease

Surgical therapy for Parkinson's disease has a long history beginning in the 1930s with empirical exploration of different brain targets, such as resection of the primary motor cortex or extirpation of the caudate. Recently, there has been a renaissance of functional neurosurgery for the treatment of advanced Parkinson's disease, particularly deep brain stimulation (DBS). To date, DBS of the globus pallidus interna and subthalamic nucleus has been reported to relieve motor symptoms and levodopa-induced dyskinesia in patients with advanced Parkinson's disease. DBS also has different advantages over pallidotomy and subthalamotomy, including reversibility, decreased risk of reoperation and decreased morbidity. In addition to well-experienced neurologists and neurosurgeons, a multidisciplinary team approach is fundamental and critical to ensure success in the DBS procedure in individual patients. With the advances in neuroimaging, neurophysiology and localization techniques, it is increasingly likely that there will be more surgical targets in the future that can also improve cardinal features of Parkinson's disease, or even nonmotor manifestations of this condition.