Bilateral internal globus pallidus stimulation for the treatment of spasmodic torticollis

Deep Brain Stimulation for the Dystonias: Evidence, Knowledge Gaps, and Practical Considerations

BACKGROUND

Deep brain stimulation (DBS) of the globus pallidus internus (GPi-DBS) is among the most effective treatment options for dystonias. Because the term "dystonia" is defined by a characteristic phenomenology of involuntary muscle contractions, which may present with a large clinical and pathogenetic heterogeneity, decision making for or against GPi-DBS can be difficult in individual patients.

METHODS

A search of the PubMed database for research and review articles, focused on "deep brain stimulation" and "dystonia" was used to identify clinical trials and to determine current concepts in the surgical management of dystonia. Patient selection in previous studies was recategorized by the authors using the new dystonia classification put forward by a consensus committee of experts in dystonia research. The evidence and knowledge gaps are summarized and commented by the authors taking into account expert opinion and personal clinical experience for providing practical guidance in patient selection for DBS in dystonia.

RESULTS

The literature review shows that pallidal deep brain stimulation is most effective in patients with isolated dystonia irrespective of the underlying etiology. In contrast, patients with combined dystonias are less likely to benefit from DBS, because the associated neurological symptoms (e.g., hypotonia or ataxia), with the exception of myoclonus, do not respond to pallidal neurostimulation.

CONCLUSIONS

It is important to recognize the clinical features of dystonia, because the distinction between isolated and combined dystonia syndromes may predict the treatment response to pallidal deep brain stimulation. The aim of this review is to help guide clinicians with advising patients about deep brain stimulation therapy for dystonia and refering appropriate candidates to surgical centers.

Pallidal Deep Brain Stimulation in Cervical Dystonia: Clinical Outcome in Four Cases

Objective:

Report on the clinical results following bilateral globus pallidus interna deep brain stimulation in four patients (one female and three males) with severe cervical dystonia, mean age 48 years (range 37-67).

Methods:

All four patients had failed extensive medical and botulinum toxin treatment. The mean duration of the disease was nine years (range 4-15 years). Patients were assessed pre and postoperatively using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Preoperatively, the mean TWSTRS total score was 43.2 (range 28-60.5). Posteroventral pallidal deep brain stimulators were inserted using MRI and microelectrode recording guidance. Last follow-up was 15 months for the four patients.

Results:

Mean reduction in the TWSTRS total scores at last follow- up was 73% (range 61- 85%). Improvement in pain occurred soon after deep brain stimulation surgery. Motor improvement was delayed and prolonged over several months. Frequent adjustment in the stimulation parameters was necessary in the first three months.

Conclusion:

Bilateral pallidal stimulation is effective in management of selected cases of intractable cervical dystonia.

Deep brain stimulation for dystonia

Dystonia is a movement disorder characterized by involuntary muscular contractions that generate twisting and repetitive movements and/or abnormal postures. It can affect a few muscle groups (focal dystonia) or spread to most muscles in the body (generalized dystonia). While botulinum toxin injections can be successfully used to treat focal dystonias, medical options for generalized dystonia are very limited. Surgical therapies--and in particular deep brain stimulation (DBS)--are becoming the standard of care for medically intractable, disabling dystonias. Advantages of DBS include reversibility, adjustability and continued access to the therapeutic target. Initial reports describing the use of DBS in generalized dystonia have been very encouraging and experience in the use of DBS to treat various forms of dystonia is continuously growing. This article reviews the issues related to DBS treatment of dystonia, including proper patient selection, surgical approaches to target choice and device implant, a description of the stimulating device and its programming principles, clinical results - with a focus on different outcomes for primary versus secondary and generalized versus cervical dystonia - and complications.

Failure of chronic pallidal stimulation in dystonic patients is a medical emergency

Deep brain stimulation (DBS) therapy is a continually expanding field of functional neurosurgery for the treatment of movement disorders and neuropathic pain. However, occurrence of adverse events related to implanted hardware cannot be ignored, particularly in patients with dystonic conditions. We report on two such patients who required emergency hospital admission and pulse generator re-implantation following sudden and unexpected cessation of DBS effectiveness resulting from battery failure.

Therapeutic challenges in dystonia

Because dystonia can vary in clinical presentation and etiology, proper diagnosis and classification of these disorders are important in making therapeutic decisions. In primary dystonia, treatment is generally geared toward alleviating symptoms rather than curing the underlying condition, therefore severity of contractions, pain, and functional and social impact are also factors to consider in determining if and how to initiate therapy. On the other hand, if a secondary cause is identified, then it is often appropriate to direct treatment toward the underlying disorder. Treatment options include physical and occupational therapy, oral medications, botulinum toxin, and surgery. This article briefly reviews the clinical features, pathophysiology, and classification of dystonia before reviewing current therapeutic options.

Treatment recommendations and practical applications of botulinum toxin treatment of cervical dystonia

CD is a complex disorder that can have significant impact on a patient's quality of life and physical well-being. BoNTs are a very effective and well-tolerated first-line therapy in relieving CD symptoms over long-term treatment. BoNT treatment should be administered at the lowest effective dose with a minimum of 3 months between treatments. As the incidence of immunoresistance is low, a reassessment of muscle selection, dosing, and diagnosis should take place in the event of suboptimal patient response. Optimal treatment may involve a combination of oral pharmacologic treatment with BoNTs to maintain the use of lowest possible dosing and to extend effectiveness to the recommended 3-month dosing interval. Physical therapy in conjunction with BoNT treatment can also extend treatment efficacy as well. Comorbidities such as insomnia, depression, and anxiety can interfere with successful CD treatment and should be actively managed along with the symptoms of CD. Although our understanding of CD is incomplete, it is ever expanding. As a deeper understanding of disease pathophysiology and disease progression is gained, treatment efforts will be refined for optimal outcome and patient satisfaction.

The sensory and motor representation of synchronized oscillations in the globus pallidus in patients with primary dystonia

In 15 patients with primary dystonia (six cervical and nine generalized dystonias) who were treated with bilateral chronic pallidal stimulation, we investigated the sensorimotor modulation of the oscillatory local field potentials (LFPs) recorded from the pallidal electrodes. We correlated these with the surface electromyograms in the affected muscles. The effects of involuntary, passive and voluntary movement and muscle-tendon vibration on frequency ranges of 0-3 Hz, theta (3-8 Hz), alpha (8-12 Hz), low (12-20 Hz) and high beta (20-30 Hz), and low (30-60 Hz) and high gamma (60-90 Hz) power were recorded and compared between cervical and generalized dystonia groups. Significant decreases in LFP synchronization at 8-20 Hz occurred during the sensory modulation produced by voluntary or passive movement or vibration. Voluntary movement also caused increased gamma band activity (30-90 Hz). Dystonic involuntary muscle spasms were specifically associated with increased theta, alpha and low beta (3-18 Hz). Furthermore, the increase in the frequency range of 3-20 Hz correlated with the strength of the muscle spasms and preceded them by approximately 320 ms. Differences in modulation of pallidal oscillation between cervical and generalized dystonias were also revealed. This study yields new insights into the pathophysiological mechanisms of primary dystonias and their treatment using pallidal deep brain stimulation.

Effects of pulse width variations in pallidal stimulation for primary generalized dystonia

BACKGROUND

Various pulse widths (from 60-450 mus) have been used for bilateral pallidal stimulation in generalized dystonia but, to date, no comparison of this parameter's effects is available.

OBJECTIVE

To provide an analysis of the differential effects of bilateral short, medium and long stimulus pulse width (PW) on clinical improvement in primary generalized dystonia.

METHODS

The most effective therapeutic stimulation parameters were recorded in 22 patients using bilateral pallidal stimulation. Six months after surgery, the effects of bilateral pallidal short (60-90 micros), medium (120-150 micros) and long (450 micros) PWs were studied in 20 of those patients. The effect of the stimulation was assessed by reviewing videotaped sessions by an observer blinded to treatment status (Burke-Fahn-Marsden movement score). Patients were tested on separate days, in random order, for the stimulation conditions (acute effect with the stimulation condition lasting 10 hours). The same contact was used for each stimulation condition. All the electrodes were set at 130 Hz (monopolar stimulation) and the intensity was set individually 10% below the side effect threshold.

RESULTS

Median PWs of 60 (short), 120 (medium) and 450 micros (long) were compared,with a mean intensity of 4.46, 3.45 and 2.47 V, respectively. This study failed to demonstrate any significant difference in the movement scale dystonia mean scores depending on PW.

CONCLUSION

According to our findings, short duration stimulus PWs are as effective as longer ones during a 10 hour period of observation. Confirmation of this finding for chronic use could be of importance in saving stimulator energy. Moreover, the use of smaller stimulus pulse widths are said to reduce charge injection and increase the therapeutic window between therapeutic effects and side effects.

The management of cervical dystonia

Cervical dystonia (CD), also known as 'spasmodic torticollis', is the most common form of adult-onset focal dystonia. It is a chronic disorder for which there is no curative treatment. Proposed interventions only have a symptomatic effect that is directed at controlling the intensity of the dystonic contractions and their associated symptoms. Both serotypes of botulinum toxin (BtA and BtB) have shown efficacy for the treatment of CD, and they constitute the first-line therapy for CD. BtB constitutes the best medical treatment for secondary failures to BtA. The efficacy of all other proposed medications, including anticholinergics, should be considered unknown due to the lack of good-quality trials. This lack of evidence applies also to all physical rehabilitation treatments. Although the authors have concluded that all surgical procedures for CD should still be considered investigational, the best data supporting benefit of surgery comes from case series of selective peripheral denervation and pallidal deep brain stimulation.

Deep brain stimulation for treatment of cervical dystonia

Pallidal deep brain stimulation is an efficient treatment option in those patients with cervical dystonia who do not benefit from conservative treatment including local botulinum toxin injections. Given the fact that other surgical treatment options such as selective peripheral denervation are available, it may be considered third-line treatment in most instances. Chronic bilateral pallidal stimulation improves dystonic posture and movements, pain caused by dystonia and disability related to dystonia. Preliminary data on longterm follow-up confirm its beneficial effect in the majority of patients. Given the frequency of cervical dystonia, pallidal deep brain stimulation will play a major role in the future.

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.

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.

Dystonic Movement Disorders and Spinal Degenerative Disease

The occurrence of degenerative spinal disease subsequent to dystonic movement disorders has been neglected and has received more attention only recently. Spinal surgery is challenging with regard to continuous mechanical stress when treatment of the underlying movement disorder is insufficient. To characterize better the particular features of degenerative spinal disease in patients with dystonia and to analyze operative strategies, we reviewed the available published data. Epidemiologic studies reveal that degenerative spinal disorders in patients with dystonia and choreoathetosis occur much earlier than in the physiological aging process. Dystonic movement disorders more often affect the spine at higher cervical levels (C(2-5)), in contrast to spinal degeneration with age which manifests more frequently at the middle and lower cervical spine (C(5-7)). Degenerative changes of the cervical spine are more likely to occur on the side where the chin is rotated or tilted to. Various operative approaches for treatment of spinal pathologies have been advocated in patients with dystonic movement disorders. The available data do not allow making firm statements regarding the superiority of one approach over the other. Posterior approaches were first used for decompression, but additional anterior fusion became necessary in many instances. Anterior approaches with or without instrumented fusion yielded more favorable results, but drawbacks are pseudarthrosis and adjacent-level disease. Parallel to the development of posterior fusion techniques, circumferential surgery was suggested to provide a maximum degree of cord decompression and a higher fusion rate. Perioperative local injections of botulinum toxin were used initially to enhance patient comfort with halo immobilization, but they are also applied in patients without external fixation nowadays. Treatment algorithms directed at the underlying movement disorder itself, taking advantage of new techniques of functional neurosurgery, combined with spinal surgery have recently been introduced and show promising results.

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.

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.

Different mechanisms may generate sustained hypertonic and rhythmic bursting muscle activity in idiopathic dystonia

Despite that deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favored intervention for patients with medically intractable dystonia, the pathophysiological mechanisms of dystonia are largely unclear. In eight patients with primary dystonia who were treated with bilateral chronic pallidal stimulation, we correlated symptom-related electromyogram (EMG) activity of the most affected muscles with the local field potentials (LFPs) recorded from the globus pallidus electrodes. In 5 dystonic patients with mobile involuntary movements, rhythmic EMG bursts in the contralateral muscles were coherent with the oscillations in the pallidal LFPs at the burst frequency. In contrast, no significant coherence was seen between EMG and LFPs either for the sustained activity separated out from the compound EMGs in those 5 cases, or in the EMGs in 3 other cases without mobile involuntary movements and rhythmic EMG bursts. In comparison with the resting condition, in both active and passive movements, significant modulation in the GPi LFPs was seen in the range of 8-16 Hz. The finding of significant coherence between GPi oscillations and rhythmic EMG bursts but not sustained tonic EMG activity suggests that the synchronized pallidal activity may be directly related to the rhythmic involuntary movements. In contrast, the sustained hypertonic muscle activity may be represented by less synchronized activity in the pallidum. Thus, the pallidum may play different roles in generating different components of the dystonic symptom complex.

Levodopa can worsen tremor associated with dystonia

A patient with tremor associated with spasmodic dysphonia developed a marked exacerbation of her upper limb tremor whilst on co-careldopa (Sinemet CR) that improved when the drug was withdrawn.

Deep brain stimulation for dystonia

Dystonia refers to movement disorders characterized by sustained muscle contractions that produce abnormal postures, twisting movements, and other abnormal involuntary movements. A spectrum of etiologies underlies the various dystonia syndromes, ranging from genetic conditions to brain injury. First-line therapy for dystonia consists of pharmacologic agents of several classes and, particularly for focal dystonia, chemodenervation therapy with botulinum toxin. Many patients with dystonia realize an inadequate response to those treatments, and for such patients whose symptoms are sufficiently troublesome, surgical treatment can be used to reduce symptoms and improve function. Previously, the ablative procedures of thalamotomy and pallidotomy were used, in which a permanent destructive lesion was made in the motor territory of the thalamus or the globus pallidus. More recently, the device-based therapy of deep brain stimulation (DBS) has emerged as the preferred surgical treatment for dystonia and other movement disorders for most patients who require operative intervention. DBS uses a surgically implanted brain lead connected to an implanted neurostimulator to deliver chronic, high- frequency electrical stimulation to one of several deep nuclei. 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 safe manner. Use of DBS to treat dystonia is a rapidly evolving area, and preliminary evidence suggests that primary dystonia linked to genetic mutation, other primary dystonias, and tardive dystonic syndromes respond most dramatically to treatment with DBS, whereas secondary dystonia tends to be less responsive.

Senile chorea treated by deep brain stimulation: a clinical, neurophysiological and functional imaging study

We report on a patient with senile chorea, treated with deep brain stimulation of the left globus pallidus internus and subsequently the left ventralis oralis posterior nucleus of the thalamus. Deep brain field potential recordings and functional imaging using single photon emission tomography enabled us to suggest pathophysiological mechanisms for the symptoms.

Patient-based outcomes of cervical dystonia: A review of rating scales

Decisions on treatment choice for patients are based on trials and outcome studies that are wholly dependent upon the scientific quality of the rating scales used. This study reviewed rating scales used in cervical dystonia outcome research to determine the extent that they satisfy recommended criteria for rigorous measurement.

The Canadian multicenter trial of pallidal deep brain stimulation for cervical dystonia: preliminary results in three patients

OBJECT

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is beneficial for generalized dystonia and has been proposed as a treatment for cervical dystonia. The Canadian Stereotactic/Functional and Movement Disorders Groups designed a pilot project to investigate the following hypothesis: that bilateral DBS of the GPi will reduce the severity of cervical dystonia at 1 year of follow up, as scored in a blinded fashion by two neurologists using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). Secondary outcome measures included pain and disability subscores of the TWSTRS, Short Form-36 quality of life index, and the Beck Depression Inventory.

METHODS

Three patients have undergone surgery in Calgary with a follow-up duration of 7.4 +/- 5.9 months (mean +/- standard deviation). One patient underwent inadvertent ineffective stimulation for the first 3 months and did not experience a benefit until DBS programming was corrected. All three patients had rapid response to stimulation, with the muscles relaxing immediately and abnormal movements improving within days. Total TWSTRS scores improved by 79%, and severity subscores improved significantly, from 15.7 +/- 2.1 to 7.7 +/- 2.9 (paired t-test, p = 0.02). Pain and disability subscores improved from 25.5 +/- 4.1 to 3.3 +/- 3.1 (paired t-test, p = 0.002) and from 13.3 +/- 4.9 to 3.3 +/- 4.2 (paired t-test, p = 0.06), respectively.

CONCLUSIONS

Although it is too early to reach broad conclusions, this report of preliminary results confirms the efficacy of DBS of the GPi for cervical dystonia.

Deep brain stimulation in the treatment of dyskinesia and dystonia

Deep brain stimulation (DBS) has become a mainstay of treatment for patients with movement disorders. This modality is directed at modulating pathological activity within basal ganglia output structures by stimulating some of their nuclei, such as the subthalamic nucleus (STN) and the globus pallidus internus (GPi), without making permanent lesions. With the accumulation of experience, indications for the use of DBS have become clearer and the effectiveness and limitations of this form of therapy in different clinical conditions have been better appreciated. In this review the authors discuss the efficacy of DBS in the treatment of dystonia and levodopa-induced dyskinesias. The use of DBS of the STN and GPi is very effective for the treatment of movement disorders induced by levodopa. The relative benefits of using the GPi as opposed to the STN as a target are still being investigated. Bilateral GPi stimulation is gaining importance in the therapeutic armamentarium for the treatment of dystonia. The DYT1 forms of generalized dystonia and cervical dystonias respond to DBS better than secondary dystonia does. Discrimination between the diverse forms of dystonia and a better understanding of the pathophysiological features of this condition will serve as a platform for improved outcomes.

Functional Stereotactic Surgery for Treatment of Cervical Dystonia: Review of the Experience from the Lesional Era

BACKGROUND

Functional stereotactic neurosurgery has been rediscovered as a powerful tool to treat various manifestations of medically refractory dystonia. The purpose of this study was to provide the first systematic review of previous experience with thalamic and basal ganglia surgery in the treatment of cervical dystonia (CD).

METHODS

A comprehensive review of the literature published between 1950 and 1990 was performed. In addition, data from an unpublished doctoral thesis on 162 patients with CD operated on by Mundinger between 1972 and 1986 were analyzed.

RESULTS

Overall, there is published documentation of experience with more than 300 patients with CD who underwent functional stereotactic surgery between the late 1950s and the early 1980s. In general, amelioration of CD was achieved in about 50-70% of patients in most studies. Bilateral surgery generally provided better outcomes than unilateral surgery. Postoperative benefit was reported to become evident only after a delay in several studies. Some reports demonstrated sustained benefit after follow-up of more than 5 years. Bilateral procedures, in particular bilateral thalamotomies, were clearly associated with a higher rate of postoperative side effects, such as dysarthria, dysphagia and ataxia, ranging from 20 to 70%. In the first decade after its introduction, thalamotomy was the preferred procedure. Later, the subthalamic area was targeted more frequently in order to affect pallidal outflow. Experience with targeting the pallidum proper was limited. Functional stereotactic surgery for CD was abandoned in the late 1970s for several reasons, including the general decline in movement disorder surgery at that time, the introduction of selective peripheral denervation and the widespread and beneficial use of botulinum toxin soon thereafter.

CONCLUSIONS

Functional stereotactic surgery for treatment of CD has a rich history. There are several lessons to be learned from review of earlier experience. Contemporary techniques have led to a significant improvement in the benefit to risk ratio, in particular regarding bilateral surgery.

Primary Dystonia Is More Responsive than Secondary Dystonia to Pallidal Interventions: Outcome after Pallidotomy or Pallidal Deep Brain Stimulation

OBJECTIVE

The response of patients with dystonia to pallidal procedures is not well understood. In this study, we assessed the postoperative outcome of patients with primary and secondary dystonia undergoing pallidotomy or pallidal deep brain stimulation.

METHODS

Fifteen patients with dystonia had pallidal surgery (lesions or deep brain stimulation). These included nine patients with primary dystonia (generalized and cervical dystonias) and six with secondary dystonia (generalized, segmental, and hemidystonias). There were nine male patients and six female patients. The mean age at onset was 21 years for primary dystonia and 18 years for secondary dystonia. The primary outcome measure was a Global Outcome Scale score for dystonia at 6 months after surgery. Other outcome measures were the Burke-Fahn-Marsden Dystonia Rating Scale and Toronto Western Spasmodic Torticollis Rating Scale scores.

RESULTS

The mean Global Outcome Scale score at 6 months for patients with primary dystonia was 3 (improvement in both movement disorder and function). In contrast, patients with secondary dystonia had a mean score of 0.83 (mild or no improvement in movement disorder with no functional improvement). All patients with primary dystonia had normal brains by magnetic resonance imaging, whereas five of six patients with secondary dystonia had basal ganglia abnormalities on their magnetic resonance imaging scans.

CONCLUSION

This study indicates that primary dystonia responds much better than secondary dystonia to pallidal procedures. We could not distinguish a difference in efficacy between pallidotomy and pallidal deep brain stimulation. The presence of basal ganglia abnormalities on the preoperative magnetic resonance imaging scan is an indicator of a lesser response to pallidal interventions for dystonia.

Cognitive executive function in dystonia

Dystonia is a movement disorder considered to result from basal ganglia dysfunction. The aim of this study was to investigate the functional significance of frontal hyperactivity demonstrated in dystonia in imaging studies by examining executive function and working memory, in which the prefrontal cortex is known to be involved. We assessed 10 patients with idiopathic dystonia and 12 age- and IQ-matched normal controls. All subjects completed tests of first letter, category, and alternating category word fluency, the Wisconsin Card Sorting Test, the Stroop Colour Word Naming Test, the Missing Digit Test of working memory, a test of random number generation, a test requiring generation of self-ordered random number sequences, the Paced Serial Addition Test, a test of conditional associative learning, and finger tapping and peg insertion under unimanual, bimanual, and dual task conditions. The patients with dystonia did not differ significantly from controls on any measures of executive function or working memory used other than category word fluency and the extent of decline in tapping with one hand under dual task conditions when simultaneously inserting pegs with the other hand. For this small sample, the results suggest that unlike other movement disorders associated with fronto-striatal dysfunction such as Parkinson's disease or Huntington's disease, dystonia was not associated with deficits on the tests of executive function or working memory used. A more detailed investigation of cognitive function in a larger sample of patients is required.

Bilateral pallidal stimulation for cervical dystonia. An optimal paradigm from our experiences

We sought to identify optimal paradigms of bilateral globus pallidus internus (GPi) stimulation in 3 subsequent patients with severe cervical dystonia. At low frequency stimulation (50-60 Hz) with wide pulse width (500 micros) and high amplitude (4.5-8.0 V), we observed immediate and consistent improvement of dystonia and dystonia-associated pain. Stimulation of the posteroventral portion of the GPi led to pronounced alleviation of dystonia; stimulation of the anterodorsal portion or at the dorsal border of the GPi resulted in significant worsening of symptoms. The therapeutic benefit obtained by using the optimal stimulation parameters continues and has lasted for at least 1 year in each patient.

Surgical therapy for dystonia

Surgical treatments for dystonia have been available since the early 20th century, but have improved in their efficacy to adversity ratio through a combination of technologic advances and better understanding of the role of the basal ganglia in dystonia. The word "dystonia" describes a phenotype of involuntary movement that may manifest from a variety of conditions. Dystonia may affect only certain regions of the body or may be generalized. It appears to be critical to determine whether the etiology underlying the dystonia is "primary" (ie, occurring from a genetic or idiopathic origin) or "secondary" (ie, occurring as a result of structural, metabolic, or neurodegenerative disorders). Secondary dystonias are far more common than primary dystonias. Primary dystonias respond well to pallidotomy or deep brain stimulation of the internal segment of the globus pallidum, whereas secondary dystonias appear to respond partially at best. Limited historic and current data suggest that the thalamus may be a promising target for the treatment of secondary dystonias, but more careful, prospective, randomized studies are needed. Combinations of bilateral targets are possible with the current technology of DBS, but not widely used due to surgical morbidity and expense. This article reviews the surgical treatment of dystonia from past to present, with a focus on separating the outcomes for primary versus secondary and generalized versus cervical dystonia.

Basal ganglia neuronal discharge in primary and secondary dystonia in patients undergoing pallidotomy

OBJECTIVE

Basal ganglia neuronal activity in patients undergoing posteroventral pallidotomy (PVP) for the treatment of primary genetic, secondary, or idiopathic dystonia (DYS) was studied to gain a better understanding of the pathophysiology of DYS.

METHODS

Intraoperative neurophysiological data recorded from 15 DYS patients were compared with those from 78 patients with Parkinson's disease (PD) who underwent PVP.

RESULTS

Putamen neurons in both DYS and PD patients had low discharge rates. Globus pallidus externa (GPe) and globus pallidus interna (GPi) neurons in DYS patients had significantly lower discharge rates and more irregular discharge patterns than in PD patients. GPe and GPi neurons displayed similar discharge rates and patterns in DYS, whereas in PD, the discharge rate of GPe neurons was lower than that of the GPi neurons. The discharge rate and pattern of GPe and GPi neurons in patients whose DYS was ameliorated by PVP were similar to those in DYS patients who did not benefit from PVP. No significant differences in the rate or pattern of neuronal discharge in patients with DYS of different causes were discernible. PVP was most beneficial in patients with primary genetic DYS. Anesthesia with desflurane depressed the discharge rate of the GPe and GPi neurons, particularly in patients with PD.

CONCLUSION

Significant differences in the rates and patterns of discharge of GPe and GPi neurons exist in DYS and PD. The findings are discussed with reference to the current model of the functional connections of the basal ganglia.

Post-operative progress of dystonia patients following globus pallidus internus deep brain stimulation

In the current era of functional surgery for movement disorders, deep brain stimulation (DBS) of the globus pallidus internus (GPi) is emerging as the favoured intervention for patients with dystonia. Here we report our results in 20 patients with medically intractable dystonia treated with GPi stimulation. The series comprised 14 patients with generalized dystonia and six with spasmodic torticollis. Although comparisons were limited by differences in their respective neurological rating scales, chronic DBS clearly benefited both patient groups. Data conveying the rate of change in neurological function following intervention are also presented, demonstrating the gradual but progressive and sustained nature of improvement following stimulation of the GPi in dystonic patients.

Chronic stimulation of the globus pallidus internus for treatment of non-dYT1 generalized dystonia and choreoathetosis: 2-year follow up

OBJECT

The authors studied the long-term efficacy of deep brain stimulation (DBS) of the posteroventral lateral globus pallidus internus up to 2 years postoperatively in patients with primary non-DYT1 generalized dystonia or choreoathetosis. The results are briefly compared with those reported for DBS in DYT1 dystonia (Oppenheim dystonia), which is caused by the DYT1 gene.

METHODS

Enrollment in this prospective expanded pilot study was limited to adult patients with severely disabling, medically refractory non-DYT1 generalized dystonia or choreoathetosis. Six consecutive patients underwent follow-up examinations at defined intervals of 3 months, 1 year, and 2 years postsurgery. There were five women and one man, and their mean age at surgery was 45.5 years. Formal assessments included both the Burke-Fahn-Marsden dystonia scale and the recently developed Unified Dystonia Rating Scale. Two patients had primary generalized non-DYT1 dystonia, and four suffered from choreoathetosis secondary to infantile cerebral palsy. Bilateral quadripolar DBS electrodes were implanted in all instances, except in one patient with markedly asymmetrical symptoms. There were no adverse events related to surgery. The Burke-Fahn-Marsden scores in the two patients with generalized dystonia improved by 78 and 71% at 3 months, by 82 and 69% at 1 year, and by 78 and 70% at 2 years postoperatively. This was paralleled by marked amelioration of disability scores. The mean improvement in Burke-Fahn-Marsden scores in patients with choreoathetosis was 12% at 3 months, 29% at 1 year, and 23% at 2 years postoperatively, which was not significant. Two of these patients thought that they had achieved marked improvement at 2 years postoperatively, although results of objective evaluations were less impressive. In these two patients there was a minor but stable improvement in disability scores. All patients had an improvement in pain scores at the 2-year follow-up review. Medication was tapered off in both patients with generalized dystonia and reduced in two of the patients with choreoathetosis. All stimulation-induced side effects were reversible on adjustment of the DBS settings. Energy consumption of the batteries was considerably higher than in patients with Parkinson disease.

CONCLUSIONS

Chronic pallidal DBS is a safe and effective procedure in generalized non-DYT1 dystonia, and it may become the procedure of choice in patients with medically refractory dystonia. Postoperative improvement of choreoathetosis is more modest and varied, and subjective ratings of outcome may exceed objective evaluations.

Treatment of dystonia

Therapeutic strategies in the treatment of dystonia consist primarily of pharmacologic, surgical, and supportive approaches. Many recent advances have been made in the treatment of dystonia with newer medications, availability of different botulinum toxins, and surgical procedures. However, these treatment modalities all have limiting factors and varying levels of efficacy. Studies range from case reports and open-label trials to double-blind placebo-controlled trials. More research and larger studies are needed to explore these newer medications and surgical techniques for both primary focal and generalized dystonia. Studies in functional outcome and quality of life further support the importance of discovering safe and effective means to treat dystonia. An algorithmic approach may be useful to guide the physician along the various treatment choices.

Unilateral pallidal stimulation for segmental cervical and truncal dystonia: which side?

We present a 24-year-old man with idiopathic segmental cervical and truncal dystonia of juvenile onset. His condition improved after unilateral stimulation of the internal globus pallidus ipsilateral to the contracting sternocleidomastoid muscle.

Camptocormia treated with bilateral pallidal stimulation

The authors report the neurological, neurophysiological, and neuropsychological effects of using long-term bilateral pallidal high-frequency deep brain stimulation (DBS) in a case of disabling camptocormia. Deep brain stimulation electrodes were implanted stereotactically to target the globus pallidus internus (GPi) bilaterally. Local field potentials (FPs) were recorded using the DBS electrodes and concurrent abdominal flexor electromyography (EMG) potentials during camptocormic episodes. Videotaped assessments of the movement disorder and neuropsychological evaluations of the patient before implantation and 6 months after initiation of pallidal stimulation were recorded. There was significant functional improvement following long-term pallidal stimulation, and some improvement was noted in neuropsychological scores. A temporal correlation between the GPi FPs and EMG-recorded rectus abdominis potentials was evident. There were no treatment-related adverse effects. The authors have found that long-term pallidal stimulation was safe and offered functional benefit to a patient with this severely disabling condition. The physiological studies may help further the understanding of the pathophysiology of this rare entity.

Methods for programming and patient management with deep brain stimulation of the globus pallidus for the treatment of advanced Parkinson's disease and dystonia

Globus pallidus (GPi) deep brain stimulation can markedly improve severe medication-refractory Parkinson's disease (PD) and dystonia. Appropriate perioperative patient management can assist with electrode implantation. Optimizing stimulation settings and simultaneously adjusting medications (when appropriate) can substantially improve patient outcomes. Although there are a large number of possible stimulation settings, in clinical practice, a relatively narrow range of settings has been shown to be most efficacious. A systematic approach to determining those settings that maximally improve parkinsonism and suppress drug-induced dyskinesias is outlined following a clear algorithm that uses the observation that stimulation of the dorsal and ventral pallidum has been shown to have opposite motor effects in PD. Based on the available literature, recommendations are also made for the use of GPi deep brain stimulation in dystonia.

Results of deep brain stimulation for dystonia: a critical reappraisal

Deep brain stimulation for severe dystonia is still in the very first stage of development. Only single case reports or small case series have been reported to date. Best results have been obtained with pallidal stimulation in patients with primary generalised dystonia, especially in DYT1 mutation carriers. In secondary dystonia, conflicting results were reported. However, there is today enough promising evidence for a striking efficacy of pallidal stimulation in dystonia, supporting the need for further investigations in the field, with collaborative projects (regarding to the limited number of eligible patients); double-blind studies, including a consensus about surgical method; and a precise anatomic analysis of the position of the electrode. A careful assessment of the efficacy by using improved clinical scale is also warranted.

Involvement of the medial pallidum in focal myoclonic dystonia: A clinical and neurophysiological case study

We successfully treated a patient with familial myoclonic dystonia (FMD), which primarily affected his neck muscles, with bilateral deep brain stimulation (DBS) to the medial pallidum, and investigated the role of the medial pallidum in FMD. A patient with FMD underwent bilateral implantation of DBS electrodes during which field potentials (FPs) in the medial pallidum and electromyograms (EMGs) from the affected neck muscles were recorded. The effects of high-frequency DBS to the medial pallidum on the FMD were also assessed by recording EMGs during and immediately after implantation, as well as 6 days and 8 weeks postoperatively. During spontaneous myoclonic episodes, increased FPs oscillating at 4 and 8 Hz were recorded from the medial pallidum; these correlated strongly with phasic EMG activity at the same frequencies in the contralateral affected muscles. The EMG activity was suppressed by stimulating the contralateral medial pallidum at 100 Hz during the operation and continuous bilateral DBS from an implanted stimulator abolished myoclonic activity even more effectively postoperatively. The phasic pallidal activity correlated with and led the myoclonic muscle activity, and the myoclonus was suppressed by bilateral pallidal DBS, suggesting that the medial pallidum was involved in the generation of the myoclonic activity. High-frequency DBS may suppress the myoclonus by desynchronising abnormal pallidal oscillations. This case study has significant clinical implications, because at present, there is no effective treatment for focal myoclonic dystonia.

Pallidal deep brain stimulation in patients with cervical dystonia and severe cervical dyskinesias with cervical myelopathy

OBJECTIVES

Surgical treatment of complex cervical dystonia and of cervical dyskinesias associated with cervical myelopathy is challenging. In this prospective study, the long term effect of chronic pallidal stimulation in cervical dystonia and on combining the technique with spinal surgery in patients with severe cervical dyskinesias and secondary cervical myelopathy is described.

METHODS

Eight patients with a history of chronic dystonia who did not achieve adequate benefit from medical treatment or botulinum toxin injection participated in the study. Five patients had complex cervical dystonia with tonic postures and phasic movements. Three patients had rapidly progressive cervical myelopathy secondary to severe cervical dyskinesias and dystonia in the context of a generalised movement disorder. Quadripolar electrodes were implanted in the posteroventral lateral globus pallidus internus with stereotactic CT and microelectrode guidance. In the three patients with secondary cervical myelopathy, spinal surgery was performed within a few weeks and included multilevel laminectomies and a four level cervical corporectomy with spinal stabilisation.

RESULTS

Improvement of the movement disorder was noted early after pallidal surgery, but the full benefit could be appreciated only with a delay of several months during chronic stimulation. Three months after surgery, patients with cervical dystonia had improved by 38% in the severity score, by 54% in the disability score, and by 38% in the pain score of a modified version of the Toronto western spasmodic torticollis rating scale. At a mean follow up of 20 months, the severity score had improved by 63%, the disability score by 69%, and the pain score by 50% compared with preoperatively. There was also sustained amelioration of cervical dyskinesias in the three patients who underwent spinal surgery. Lead fractures occurred in two patients. The mean amplitude needed for chronic deep brain stimulation was 3.8 V at a mean pulse width of 210 micros, which is higher than that used for pallidal stimulation in Parkinson's disease.

CONCLUSIONS

Chronic pallidal stimulation is effective for complex cervical dystonia and it is a useful adjunct in patients with cervical dyskinesias and secondary cervical myelopathy who undergo spinal surgery.

Camptocormia treated with bilateral pallidal stimulation

The authors report the neurological, neurophysiological, and neuropsychological effects of using chronic bilateral pallidal high-frequency deep brain stimulation (DBS) in a case of disabling camptocormia.

Deep brain stimulation electrodes were implanted stereotactically to target the globus pallidus internus (GPi) bilaterally. Local field potentials (FPs) were recorded using the DBS electrodes and concurrent abdominal flexor elec-tromyography (EMG) potentials during camptocormic episodes. Videotaped assessments of the movement disorder and neuropsychological evaluation before implantation and at 6 months after initiation of pallidal stimulation were recorded.

There was significant functional improvement following chronic pallidal stimulation, and some improvement was noted in neuropsychological scores. The GPi FPs showed temporal correlation with EMG-recorded rectus abdominis potentials. There were no treatment-related adverse effects.

The authors have found that chronic pallidal stimulation was safe and offered functional benefit in this severely disabling condition. The physiological studies may help further the understanding of the pathophysiology of this rare entity.

Botulinum toxin for the treatment of cervical dystonia

Cervical dystonia (CD) manifests clinically through involuntary spasms of neck muscles, producing abnormal head and neck movements and postures, which is often associated with pain. CD is the most common form of focal dystonia presenting to movement disorders clinics. Chemodenervation with botulinum toxin (BTX) has become the first-line treatment for CD, producing satisfactory relief of symptoms in > 80% of cases. Unresolved issues that may impact on the overall results include the method of selection for injection sites (clinical vs. electromyography), dosing, dilution and the role and relative efficacy of the different BTX serotypes. A guiding therapeutic principle of BTX injections is to achieve optimal results with the lowest possible dosage and frequency of administration. This strategy is critical in order to keep the risk of immunoresistance at a minimum. Development of antibodies that block the effects of BTX, usually associated with frequent injections of high doses, is the main reason for secondary unresponsiveness to this treatment. Although the mechanism of denervation at the neuromuscular junction by BTX is relatively well understood, the role of changes in muscle spindles and myopathic pain mechanisms, as well as secondary changes at the level of the basal ganglia, thalamus and cortex and their role in response to BTX, all need further exploration.

Review of the functional surgical treatment of dystonia

A review of functional surgery for dystonia is presented. Recently renewed interest in stereotaxy for dystonia has followed the resurgence of pallidotomy and the introduction of deep brain stimulation (DBS) in Parkinson's disease (PD) in the early 1990s. However, even since the 1950s, small series of patients treated with ablative surgery have been carefully studied, providing useful information, notably regarding the tolerability of surgery. In the setting of dystonia, thalamotomy was first performed with substantial benefits, but some authors outlined the great variability in outcome, and the high incidence of operative side-effects. In the 'modern' era of functional surgery for movement disorders, the globus pallidus internus (GPi) has emerged to be currently the best target for dystonia, based on small series of patients published in the last few years. Both bilateral posteroventral pallidotomy (PVP) and bilateral pallidal stimulation, performed by several teams, have benefited a variety of patients with severe dystonia, the most dramatic improvements being seen in primary dystonia with a mutation in the DYT1 gene. Whereas patients with secondary dystonia have often shown a lesser degree of improvement, some publications have nevertheless reported major benefit. There is today a strong need for carefully controlled studies comparing secondary and primary dystonia, DYT1 and non-DYT1 dystonia, ablative surgery and DBS, with additional assessment of neuropsychological changes, especially in children treated with bilateral pallidal procedures.