Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results

A prospective blinded evaluation of deep brain stimulation for the treatment of secondary dystonia and primary torticollis syndromes

OBJECT

The aim of this study was to provide an objective assessment of deep brain stimulation (DBS) for groups of patients with mixed secondary dystonia and primary torticollis syndromes by a blinded evaluation of 13 consecutive patients who underwent ineffective medical treatment and botulinum toxin injections.

METHODS

Nine patients with secondary dystonia and 4 with cranial dystonia involving prominent spasmodic torticollis were selected for a DBS implant after they underwent unsuccessful medical treatment. Preoperative videos and neurological assessments were obtained and the DBS implant was inserted into the globus pallidus internus. Postoperatively, DBS parameters were adjusted to provide optimal benefit. Postoperative videotapes and quality of life scores were obtained. Blinded randomized evaluation of videotapes was performed by a neurologist specializing in movement disorders. Videos were scored using the Unified Dystonia Rating Scale, Toronto Western Spasmodic Torticollis Rating Scale, Burke-Fahn-Marsden Dystonia Rating Scale, or Abnormal Involuntary Movement Scale. Quality of life scoring was assessed using a standardized 7-point Global Rating Scale.

RESULTS

All 13 patients completed preoperative videotaping, medical assessment, and surgery. Optimal DBS programming was completed in 6.5 visits over 5.9 months. Seven patients reported marked improvement, 3 reported moderate improvement, 2 reported slight improvement or no change, and 1 was lost to follow-up. Examiner scores on the Global Rating Scale reflected patient self-reported scores.

CONCLUSIONS

Global subjective gains and notable objective improvement were observed in 11 of 13 patients. Although the benefits were variable and not fully predictable, they were of sufficient magnitude to justify offering the procedure when medications and botulinum toxin injections have failed.

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.

Pallidal deep brain stimulation in the treatment of Meige syndrome

BACKGROUND

Pallidal deep brain stimulation (DBS) of globus pallidus internus (Gpi) has emerged as an effective treatment for dystonia. The experience is however limited concerning focal dystonias and to date only a few cases of pallidal DBS in the treatment of Meige syndrome have been published.

METHODS/RESULTS

We here present a patient with Meige syndrome in whom unilateral pallidal DBS failed to improve the axial symptoms, but bilateral stimulation resulted in a major improvement. The Burke-Fahn-Marsden score (BFM) improved by 71.5% and the patient's blepharospasm was abolished.

CONCLUSIONS

The results suggest bilateral pallidal DBS may be an effective treatment for Meige syndrome.

Long-term follow-up of Huntington disease treated by bilateral deep brain stimulation of the internal globus pallidus

Deep brain stimulation is now accepted as a safe and efficient treatment for movement disorders including selected types of dystonia and dyskinesia. Very little, however, is known about its effect on other movement disorders, particularly for “choreic” movements. Huntington disease is a fatal autosomal-dominant neurodegenerative disorder characterized by movement disorders, progressive cognitive impairment, and psychiatric symptoms. Bilateral chronic stimulation of the internal globus pallidus was performed to control choreic movements in a 60-year-old man with a 10-year history of Huntington disease. Chronic deep brain stimulation resulted in remarkable improvement of choreic movements. Postoperative improvement was sustained after 4 years of follow-up with a marked improvement in daily quality of life.

Outcome predictors of pallidal stimulation in patients with primary dystonia: the role of disease duration

Pallidal deep brain stimulation (DBS) is currently the most effective treatment for advanced, medically refractory dystonia. However, factors predicting clinical outcome are not well defined. We reviewed the clinical records of 39 consecutive patients with medically refractory primary dystonia who underwent pallidal DBS implants. Thirty-five patients were implanted bilaterally and four unilaterally. Seven patients had fixed skeletal deformities (FSD). The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores at baseline, 3 and 12 months after DBS were used to evaluate clinical outcome. We investigated the outcome predictive role of several demographic and clinical factors. FSD patients had a significantly inferior outcome at 12 months, mostly affected by axial scores. All other patients (n = 32) showed a remarkable improvement (median BFMDRS percentage improvement = 87.8). Only disease duration showed a significant correlation with DBS outcome at 3 and 12 months. No other demographic and baseline clinical features predicted DBS outcome. This study confirms that patients with primary, medically refractory dystonia are generally outstanding candidates for pallidal DBS, with the possible exception of axial FSD. Patients with shorter duration of disease may expect a better general outcome. No particular predictive value should be assigned to age at onset, age at surgery, severity of disease, DYT1 status and the presence of phasic or tonic involuntary movements.

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.

Cortical evoked potentials from pallidal stimulation in patients with primary generalized dystonia

Deep brain stimulation (DBS) of globus pallidus internus (GPi) has emerged as an effective treatment for primary generalized dystonia. However, the physiological mechanisms of improvement are not fully understood. Cortical activity in response to pallidal stimulation was recorded in 6 patients with primary generalized dystonia >6 months after bilateral GPi DBS. Scalp electroencephalogram was recorded using 60 surface electrodes during 10 Hz bipolar pallidal DBS at each electrode contact pair. Anatomical position of the electrode contacts in relation to the GPi, medial medullary lamina and globus pallidus externus (GPe) was determined from the postoperative stereotactic MRI. In all six patients an evoked potential (EP) was observed with average onset latency of 10.9 ms +/- 0.77, peak latency 26.6 ms +/- 1.6, distributed mainly over the ipsilateral hemisphere, maximal centrally. The mean amplitude of this potential was larger with stimulation in posteroventral GPi than in GPe (3.36 microV vs. 0.50 microV, P < 0.0001). The EP was absent in one patient-side, ipsilateral to a previous thalamotomy. Low frequency GPi stimulation produces an EP distributed centrally over the ipsilateral hemisphere. The latency and distribution of the EP are consistent with stimulation of pallidothalamic neurons projecting to the sensorimotor cortex. Because the EP is larger and more consistently present with stimulation of posteroventral GPi than GPe, it may provide a physiological tool to identify contacts within the optimal surgical target.

Treatment of dystonia with deep brain stimulation

Pallidal deep brain stimulation (DBS) is an established treatment option for medically refractive dystonia. The mechanism by which globus pallidus pars interna (GPi) DBS improves dystonia is still unclear. Primary generalized dystonia usually responds well to this therapy, as recently confirmed in two well-designed, double-blind, controlled trials; however, predictors of outcome within this population are not well known. The role of GPi DBS in idiopathic cervical dystonia resistant to treatment with botulinum toxin, in tardive dystonia, and in some types of secondary dystonia are emerging as populations of patients who may also benefit, but outcomes are not well documented. Serious complications from this therapy are rare. Future research will likely continue to address the most appropriate programming settings for various populations of dystonia, the mechanism by which DBS affects dystonia, and the possibility of alternative brain targets that might have less associated side effects or greater efficacy than the GPi.

Opposite effects of internal globus pallidus stimulation on pallidal neurones activity

Besides clinical efficacy, the mechanisms of action of deep brain stimulation (DBS) are still debated. To shed light on this complex issue, we have taken the opportunity to record the response of globus pallidus internus (GPi) neurones to 100 Hz stimulations in a case of Lesch-Nyhan syndrome (LNS) where four pallidal electrodes were implanted. Three types of response were observed, 2/19 neurones were unaffected by DBS. About 7/19 neurones were inhibited during DBS stimulation and 10/19 neurones were excited during DBS stimulation. Both effects ceased when DBS was turned off. Inhibited neurones were situated lower that exited ones on the trajectory (1.25 and 4.65 mm above the center of GPi respectively). These observations suggest that locally DBS induces a reversible inhibition of neurone firing rate while at the same time distantly exciting the main afferents to and/or efferents from the GPi. Both actions would result in a strong GPi inhibition that does not preclude increased outflow from the GPi.

Location of Active Contacts in Patients with Primary Dystonia Treated with Globus Pallidus Deep Brain Stimulation

Objective:

Deep brain stimulation of the globus pallidus internus has been used for the treatment of various forms of dystonia, but the factors influencing postoperative outcomes remain unknown. We compared the location of the contacts being used for stimulation (active contacts) in patients with cervical dystonia, generalized dystonia, and Parkinson's disease and correlated the results with clinical outcome.

Methods:

Postoperative magnetic resonance scans of 13 patients with cervical dystonia, six patients with generalized dystonia, and five patients with Parkinson's disease who underwent globus pallidus internus deep brain stimulation were analyzed. We assessed the location of the active contacts relative to the midcommisural point and in relation to the anteroposterior and mediolateral boundaries of the pallidum. Postoperative outcome was measured with the Toronto Western Spasmodic Torticollis Rating Scale (for cervical dystonia) and the Burke-Fahn-Marsden Dystonia Rating Scale (for generalized dystonia) during the last follow-up.

Results:

We found that the location of the active contacts relative to the midcom-misural point and the internal boundaries of the pallidum was similar across the groups. In our series, the contacts used for stimulation were clustered in the posterolateral region of the pallidum. Within that region, we found no correlation between the location of the contacts and postoperative outcome.

Conclusion:

The location of the active contacts used for globus pallidus internus deep brain stimulation was similar in patients with cervical dystonia, generalized dystonia, and Parkinson's disease.

Modulation of food intake following deep brain stimulation of the ventromedial hypothalamus in the vervet monkey

Object

Deep brain stimulation (DBS) has become an effective therapy for an increasing number of brain disorders. Recently demonstrated DBS of the posterior hypothalamus as a safe treatment for chronic intractable cluster headaches has drawn attention to this target, which is involved in the regulation of diverse autonomic functions and feeding behavior through complex integrative mechanisms. In this study, the authors assessed the feasibility of ventromedial hypothalamus (VMH) DBS in freely moving vervet monkeys to modulate food intake as a model for the potential treatment of eating disorders.

Methods

Deep brain stimulation electrodes were bilaterally implanted into the VMH of 2 adult male vervet monkeys by using the stereotactic techniques utilized in DBS in humans. Stimulators were implanted subcutaneously on the upper back, allowing ready access to program stimulation parameters while the animal remained conscious and freely moving. In anesthetized animals, intraoperatively and 6–10 weeks postsurgery, VMH DBS parameters were selected according to minimal cardiovascular and autonomic nervous system responses. Thereafter, conscious animals were subjected to 2 cycles of VMH DBS for periods of 8 and 3 days, and food intake and behavior were monitored. Animals were then killed for histological verification of probe placement.

Results

During VMH DBS, total food consumption increased. The 3-month bilateral implant of electrodes and subsequent periods of high-frequency VMH stimulation did not result in significant adverse behavioral effects.

Conclusions

This is the first study in which techniques of hypothalamic DBS in humans have been applied in freely moving nonhuman primates. Future studies can now be conducted to determine whether VMH DBS can change hypothalamic responsivity to endocrine signals associated with adiposity for long-term modulation of food intake.

Thalamic deep brain stimulation for writer's cramp

OBJECT

Writer's cramp is a type of idiopathic focal hand dystonia characterized by muscle cramps that accompany execution of the writing task specifically. In this report, the authors describe the clinical outcome after thalamic deep brain stimulation (DBS) therapy in patients with writer's cramp and present an illustrative case with which they compare the effects of pallidal and thalamic stimulation. In addition to these results for the clinical effectiveness, they also examine the best point and pattern for therapeutic stimulation of the motor thalamus, including the nucleus ventrooralis (VO) and the ventralis intermedius nucleus (VIM), for writer's cramp.

METHODS

The authors applied thalamic DBS in five patients with writer's cramp. The inclusion criteria for the DBS trial in this disorder were a diagnosis of idiopathic writer's cramp and the absence of a positive response to medication. The exclusion criteria included significant cognitive dysfunction, active psychiatric symptoms, and evidence of other central nervous system diseases or other medical disorders. In one of the cases, DBS leads were implanted into both the globus pallidus internus and the VO/VIM, and test stimulation was performed for 1 week. The authors thus had an opportunity to compare the effects of pallidal and thalamic stimulation in this patient.

RESULTS

Immediately after the initiation of thalamic stimulation, the neurological deficits associated with writer's cramp were improved in all five cases. Postoperatively all preoperative scale scores indicating the seriousness of the writer's cramp were significantly lower (p < 0.001). In the patient in whom two DBS leads were implanted, the clinical effect of thalamic stimulation was better than that of pallidal stimulation. During the thalamic stimulation, the maximum effect was obtained when stimulation was applied to both the VO and the VIM widely, compared with being applied only within the VO.

CONCLUSIONS

The authors successfully treated patients with writer's cramp by thalamic DBS. Insofar as they are aware, this is the first series in which writer's cramp has been treated with DBS. Thalamic stimulation appears to be a safe and valuable therapeutic option for writer's cramp.

Effect of electrode contact location on clinical efficacy of pallidal deep brain stimulation in primary generalised dystonia

OBJECTIVES

To determine the effect of electrode contact location on efficacy of bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) for primary generalised dystonia (PGD).

SUBJECTS AND METHODS

A consecutive series of 15 patients with PGD (10 females, mean age 42 years, seven DYT1) who underwent bilateral GPi DBS, were assessed using the Burke-Fahn-Marsden (BFM) dystonia scale before and 6 months after surgery. The position of the stimulated electrode contact(s) was determined from the postoperative stereotactic MRI. Contralateral limb and total axial BFM subscores were compared with the location of the stimulated contact(s) within the GPi.

RESULTS

The mean total BFM score decreased from 38.9 preoperatively to 11.9 at 6 months, an improvement of 69.5% (p<0.00001). Cluster analysis of the stimulated contact coordinates identified two groups, distributed along an anterodorsal to posteroventral axis. Clinical improvement was greater for posteroventral than anterodorsal stimulation for the arm (86% vs 52%; p<0.05) and trunk (96% vs 65%; p<0.05) and inversely correlated with the y coordinate. For the leg, posteroventral and anterodorsal stimulation were of equivalent efficacy. Overall clinical improvement was maximal with posteroventral stimulation (89% vs 67%; p<0.05) and inversely correlated with the y (A-P) coordinate (r = -0.62, p<0.05).

CONCLUSION

GPi DBS is effective for PGD but outcome is dependent on contact location. Posteroventral GPi stimulation provides the best overall effect and is superior for the arm and trunk. These results may be explained by the functional anatomy of GPi and its outflow tracts.

Pearls in patient selection for deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) has emerged as an important treatment for medication refractory movement and neuropsychiatric disorders. General neurologists and even general practitioners may be called upon to screen potential candidates for DBS. The patient selection process plays an important role in this procedure.

REVIEW SUMMARY

In this article, we discuss "pearls" for the clinician who may be called upon to identify appropriate candidates for DBS. Additionally, we will discuss the important points that should be considered when referring patients for surgical intervention.

CONCLUSION

Diagnosis, response to levodopa, cognitive status, psychiatric status, access to care, and patient expectations are all essential elements of the patient selection process for DBS. These areas must be adequately addressed prior to any surgical procedure.

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.

Operative and hardware complications of deep brain stimulation for movement disorders

The objective of this investigation was to present the operative and hardware complications encountered during follow-up of patients with in situ deep brain stimulators. The study took the form of a retrospective chart review on a series of consecutive patients who were treated successfully with insertion of deep brain stimulators at a single centre by a single surgeon between 1999 and 2005. During the study period, a total of 60 patients underwent 96 procedures for implantation of unilateral or bilateral DBS electrodes. The mean follow-up period was 43.7 months (range 6-78 months) from the time of the first procedure. No patients were lost to follow-up or died. Eighteen patients (30%) developed 28 adverse events, requiring 28 electrodes to be replaced. Seven patients developed two adverse events and two patients developed three adverse events. The rate of adverse events per electrode-year was 8%. We observed a higher proportion of early complications (<6 months postoperatively) in patients with Parkinson's disease, while dystonic patients had more late complications (>6 months postoperatively) and no early complications. Thirty per cent of our patients developed an adverse event that could potentially lead to revision of the implanted hardware. In patients with Parkinson's disease most of the complications tend to occur during the first 6 months postoperatively, while in dystonic patients most occur between 12 and 24 months postoperatively.

Deep brain stimulation for torsion dystonia in children

INTRODUCTION

Deep brain stimulation (DBS) at the internal globus pallidus (GPi) is an effective treatment for some patients with medically refractory torsion dystonia. In this article, we review the results of pallidal DBS surgery in children with dystonia. Details of the DBS procedure and programming of the DBS devices are discussed.

DISCUSSION

Pallidal DBS is most effective in patients with primary generalized dystonia. Children and adolescents possessing the DYT1 gene mutation may respond best of all. The presence of static dystonic postures and/or fixed orthopedic contractures may limit the functional response to DBS and may require additional surgery.

CONCLUSION

As a group, patients with secondary dystonias respond less well to DBS than patients with primary dystonia. However, patients with dystonia secondary to anoxic brain injury who have grossly intact basal ganglia anatomy may represent a subpopulation for whom pallidal DBS is a viable option.

Surgery for other movement disorders: dystonia, tics

PURPOSE OF REVIEW

Various movement disorders are now treated with stereotactic procedures, particularly deep brain stimulation. We review the neurosurgical treatment of dystonias and tics, focusing mainly on the surgical aspects and outcome of deep brain stimulation.

RECENT FINDINGS

Pallidal stimulation is nowadays the mainstay surgical treatment for patients with dystonia, particularly generalized dystonia. Various well designed recent clinical trials support the efficacy of the procedure. Improvements of 40-80% have been reported in primary generalized, segmental and cervical dystonia. For secondary dystonia, a similar outcome has been described in patients with tardive dystonia and pantothenate kinase-associated neurodegeneration. In patients with Tourette's syndrome, the results of the first trials with thalamic and pallidal deep brain stimulation have been very promising. Improvements of 70-90% in the frequency of tics have been reported with surgery in both targets.

SUMMARY

Deep brain stimulation has become an established therapy for dystonia and is currently being used to treat Tourette's syndrome. With accumulation of experience, clinical features that are more responsive to surgery and the best surgical candidates will be revealed. This will likely improve even further the outcome of surgery for the treatment of these disorders.

The physiological effects of pallidal deep brain stimulation in dystonia

Dystonia is an involuntary movement disorder characterized by muscle contractions causing abnormal postures and spasms, affecting part or all of the body. Dystonia may be primary where an abnormal gene, most commonly DYT1, may be identified, or secondary to structural brain lesions or heredodegenerative disorders. The underlying defect is believed to be abnormal basal ganglia modulation of cortical motor pathways, and various motor and sensory physiological abnormalities have been demonstrated. The failure of medical treatment in many patients with the more severe and generalized forms of dystonia has led to renewed interest in neurosurgical treatment approaches. In recent years, deep brain stimulation (DBS) of globus pallidus internus (GPi) has emerged as an effective treatment for dystonia, particularly patients with primary generalized dystonia, where remarkable improvement may occur. In contrast to Parkinson's disease, the beneficial effects of DBS in dystonia are not immediate but progressive over weeks to months. Physiological and imaging studies in dystonia patients with GPi DBS have demonstrated both short and long-term effects of GPi DBS on motor cortex and subcortical circuits including progressive normalization of spinal and brainstem excitability after GPi DBS which correlate with clinical improvement. These effects, in light of existing physiological data in dystonia, suggest that GPi DBS acts primarily by major modification of basal ganglia output to brainstem, thalamus, and cortex resulting in neural reorganization, which may explain the characteristic progressive improvement in dystonia after GPi DBS.

Deep brain stimulation in childhood: an effective treatment for early onset idiopathic generalised dystonia

BACKGROUND

Early onset idiopathic generalised dystonia is a progressive and profoundly disabling condition. Medical treatment may ameliorate symptoms. However, many children have profound, intractable disability including the loss of ambulation and speech, and difficulties with feeding. Following the failure of medical management, deep brain stimulation (DBS) of the globus pallidus internus (GPi) has emerged as an alternative treatment for the disorder.

METHODS

We describe four children who presented with dystonia.

RESULTS

Following the failure of a range of medical therapies, DBS systems were implanted in the GPi in an attempt to ameliorate the children's disabilities. All children found dystonic movements to be less disabling following surgery. Compared with preoperative Burke, Fahn and Marsden Dystonia Rating Scale scores, postoperative scores at 6 months were improved.

CONCLUSIONS

DBS is effective in improving symptoms and function in children with idiopathic dystonia refractory to medical treatment. Whilst surgery is complex and can be associated with intraoperative and postoperative complications, this intervention should be considered following the failure of medical therapy.

Reliability of the Burke-Fahn-Marsden scale in a multicenter trial for dystonia

BACKGROUND

The multicenter SPIDY trial (pallidal stimulation for generalized, idiopathic dystonia) recently reported a marked improvement in dystonia which was assessed by the Burke-Fahn-Marsden (BFM) scale. However, the reliability of this tool has rarely been evaluated and its use in a multicenter study has never been assessed prospectively.

PURPOSE

To evaluate the concordance between three unblinded clinical raters and one single-blinded rater for 10 prospective series of ratings on the BFM scale in 22 dystonic patients of the SPIDY study.

METHODS

Ten assessments on the BFM scale were performed under various stimulation conditions at different time points (before surgery and 1, 3, 6, and 12 months afterwards). Patients were first evaluated by three unblinded clinical raters (one per center). All assessments were videotaped and sent to a blinded rater. Intra- and inter-rater reliability was assessed using intraclass correlation coefficients.

RESULTS

The intra-rater reliability at inclusion was better for the blinded rater than for the clinical raters. The inter-rater reliability (comparing the blinded rater with each clinical rater) was "very good" at inclusion, "fair" at month 1 and was "good" at month 3, month 6, and month 12.

CONCLUSION

Blinding (rather than video) is probably the key factor in better intra-rater reliability and can produce more accurate rating than clinical rating. Consequently, a blind procedure should be performed systematically in multicenter studies. As inter-rater reliability is good in trained unblinded raters, the BFM scale may also be used in the follow up of dystonic patients in movement disorders centers, in clinical practice.

Deep brain stimulation of globus pallidus internus for dystonia

Neuromodulation is the functional modification of neural structures through the use of electrical stimulation. Its most clinically applicable use is deep brain stimulation (DBS) of basal ganglia structures in Parkinson's disease (PD) and essential tremor (ET). More recently, it has been used as a means of treating dystonic movement disorders. The main target of DBS for dystonia is the posteroventral globus pallidus internus (GPi), although the thalamus has been used as an alternate target in a minority of cases. In comparison to the effects seen in PD, the improvement in dystonic postures appear to differ in several ways--delay of clinical benefit, higher voltage requirements, and varied stimulator settings. In this review, the authors discuss the clinical characteristics, pathophysiology, microelectrode recording (MER) signatures, optimal surgical targets, programming parameters and outcomes in dystonia.

Subthalamic nucleus deep brain stimulation for severe idiopathic dystonia: impact on severity, neuropsychological status, and quality of life

Object

Medically refractory dystonia has recently been treated using deep brain stimulation (DBS) targeting the globus pallidus internus (GPI). Outcomes have varied depending on the features of the dystonia. There has been limited literature regarding outcomes for refractory dystonia following DBS of the subthalamic nucleus (STN).

Methods

Four patients with medically refractory, predominantly cervical dystonia underwent STN DBS. Intraoperative assessments with the patients in a state of general anesthesia were performed to determine the extent of fixed deformities that might predict outcome. Patients were rated using the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) preoperatively and 3 and 12 months following surgery by a rater blinded to the study. Mean changes and standard errors of the mean in scores were calculated for each subscore of the two scales. Scores were also analyzed using analysis of variance and probability values were generated. Neuropsychological assessments and quality of life ratings using the 36-Item Short Form Health Survey (SF-36) were evaluated longitudinally.

Results

Significant improvements were seen in motor (p = 0.04), disability (p = 0.02), and total TWSTRS scores (p = 0.03). Better outcomes were seen in those patients who did not have fixed deformities. There was marked improvement in the mental component score of the SF-36. Neuropsychological function was not definitively impacted as a result of the surgery.

Conclusions

Deep brain stimulation of the STN is a novel target for dystonia and may be an alternative to GPI DBS. Further studies need to be performed to confirm these conclusions and to determine optimal candidates and stimulation parameters.

Pallidal stimulation modifies after-effects of paired associative stimulation on motor cortex excitability in primary generalised dystonia

OBJECTIVE

To determine the effect of globus pallidus internus (GPi) deep brain stimulation (DBS) on motor cortex plasticity in patients with primary generalised dystonia.

METHODS

We studied 10 patients with primary generalised dystonia (5 DYT1+, 5 idiopathic, 5 female, mean age 42) following GPi DBS and 10 healthy subjects. Motor cortex plasticity was assessed using transcranial magnetic stimulation (TMS) paired associative stimulation (PAS) of motor cortex and median nerve, a method which has been shown in healthy subjects to produce LTP-like effects. Thresholds and TMS intensity to produce a resting motor evoked potential (MEP) of 1 mV were determined. Resting MEP amplitude and stimulus response curves were recorded before and after PAS. Patients were recorded ON and OFF DBS in separate sessions.

RESULTS

The mean TMS intensity to produce a resting MEP of 1 mV was 54% of maximum stimulator output when OFF and 52% ON DBS. Fifteen minutes after PAS the resting MEP amplitude increased in patients OFF DBS and in control subjects whereas it decreased in patients ON DBS. Similarly, after PAS, the mean amplitude of the stimulus response curve increased OFF DBS, but this effect was abolished with DBS ON. Furthermore, patients who had the largest clinical response to chronic DBS also had the largest difference in the effect of PAS with DBS ON vs. OFF.

CONCLUSIONS

After PAS, patients with primary generalised dystonia showed a similar pattern of increased motor cortex excitability as healthy subjects when GPi DBS was OFF but not with GPi DBS ON. These results suggest that GPi DBS may reduce LTP-like motor cortex plasticity, which could contribute to its mechanism of action in dystonia.

Bone morphogenetic protein for salvage fusion in an infant with Down syndrome and craniovertebral instability. Case report

The authors describe the use of bone morphogenetic protein (BMP) to promote bone fusion in an infant with craniovertebral instability after two attempts at arthrodesis had failed. To their knowledge, this is the first such report. Management of craniovertebral instability remains challenging in infants with Down syndrome. Surgical treatment may result in nonunion in this patient population. The authors report on a 4-month-old boy with Down syndrome who suffered a high cervical spinal cord injury secondary to craniovertebral instability. Two attempts to fuse and stabilize the craniovertebral junction resulted in nonunion. Finally, the use of BMP led to a stable fusion construct within 6 months without encroachment on the spinal canal. At 4 years of follow up, the patient has a solid fusion mass. The case suggests a role for the use of BMP to promote fusion in this patient population.

Lower stimulation frequency can enhance tolerability and efficacy of pallidal deep brain stimulation for dystonia

We report the case of a patient with medically refractory primary dystonia who was treated with bilateral pallidal deep brain stimulation. Stimulation at 130 Hz or higher, by means of the more ventral contacts generated capsular side effects, which made their use impractical. Consequently, the patient was treated for 9 months at 130 to 185 Hz, by means of the more dorsal contacts, achieving modest results. By reducing the stimulation frequency to 80 Hz, we were able to activate the ventral contacts without inducing side effects. Within days, the patient experienced a dramatic improvement in function that has persisted for 1 year. A further reduction in stimulation frequency to 60 Hz resulted in a worsening of his symptoms. We conclude that chronic stimulation at frequencies of <100 Hz may be efficacious in dystonia and may enhance the tolerability of stimulation by means of contacts that are positioned posteroventrally within the internal globus pallidus, nearer the internal capsule.

Patterns of reoccurrence of segmental dystonia after discontinuation of deep brain stimulation

The pattern of reoccurrence of symptoms after discontinuation of deep brain stimulation (DBS) has not been systematically studied in dystonia. Eight patients (mean age (SD) 53.8 (14.4) years) with segmental dystonia at a mean follow-up of 11.3 (4.2) months were studied after implantation of bilateral DBS electrodes in the internal globus pallidus using a standard video protocol and clinical rating scales, immediately and at 2 and 4 h after switching off DBS. Dystonic signs returned sequentially, with a rapid worsening of phasic and a slower worsening of tonic dystonic components. In all patients, phasic dystonic features appeared within a few minutes, whereas the tonic elements of dystonia reoccurred with a more variable delay. Differential clinical effects when withdrawing DBS might reflect its influence on different pathophysiological mechanisms in dystonia.

Bilateral, pallidal, deep-brain stimulation in primary generalised dystonia: a prospective 3 year follow-up study

BACKGROUND

We have previously reported the efficacy and safety of bilateral pallidal stimulation for primary generalised dystonia in a prospective, controlled, multicentre study with 1 year of follow-up. Although long-term results have been reported by other groups, no controlled assessment of motor and non-motor results is available. In this prospective multicentre 3 year follow-up study, involving the same patients as those enrolled in the 1 year follow-up study, we assessed the effect of bilateral pallidal stimulation on motor impairment, disability, quality of life, cognitive performance, and mood.

METHODS

We studied 22 patients with primary generalised dystonia after 3 years of bilateral pallidal stimulation. We compared outcome at 3 years with their status preoperatively and after 1 year of treatment. Standardised video recordings were scored by an independent expert. Data were analysed on an intention-to-treat basis.

FINDINGS

Motor improvement observed at 1 year (51%) was maintained at 3 years (58%). The improvement in quality of life (SF-36 questionnaire) was similar to that observed at 1 year. Relative to baseline and to the 1 year assessment, cognition and mood were unchanged 3 years after surgery, but slight improvements were noted in concept formation, reasoning, and executive functions. Pallidal stimulation was stopped bilaterally in three patients because of lack of improvement, technical dysfunction, and infection, and unilaterally in two patients because of electrode breakage and stimulation-induced contracture. No permanent adverse effects were observed.

INTERPRETATION

Bilateral pallidal stimulation provides sustained motor benefit after 3 years. Mild long-term improvements in quality of life and attention were also observed.

Changes in blink reflex excitability after globus pallidus internus stimulation for dystonia

A pathophysiological feature of dystonia is reduced inhibition at various levels of the nervous system, which may be detected in clinically unaffected body parts. Chronic deep brain stimulation (DBS) of the globus pallidus internus (GPi) has emerged as an effective treatment for primary torsion dystonia (PTD), although its mechanism of action and impact on inhibitory abnormalities in dystonia are unknown. We sought to understand the effect of GPi DBS on brainstem excitability in patients with PTD. We measured the blink reflex from orbicularis oculi in response to paired electrical stimulation of the supraorbital nerve at interstimulus intervals of 500 and 1,000 milliseconds in 10 patients with PTD before and at intervals of 1, 3, and 6 months after bilateral GPi DBS and in 10 healthy subjects. Patients were clinically evaluated using the Burke-Fahn-Marsden dystonia rating scale. We found R2 inhibition was significantly decreased in PTD patients compared with control subjects and progressively increased after GPi DBS, which correlated with clinical improvement in dystonia. We conclude that GPi DBS for PTD results in functional reorganization of the nervous system, which includes a long-term increase in brainstem inhibition.

Deep brain stimulation in neurologic disorders

Deep brain stimulation (DBS) is an effective surgical therapy for well-selected patients with medically intractable Parkinson's disease (PD) and essential tremor (ET). The purpose of this review is to describe the success of DBS in these two disorders and its promising application in dystonia, Tourette Syndrome (TS) and epilepsy. In the last 10 years, numerous short- and intermediate-term outcome studies have demonstrated significant relief to patients with PD and ET. A few long-term follow-up studies have also reported sustained benefits. When successful, DBS greatly reduces most of parkinsonian motor symptoms and drug-induced dyskinesia, and it frequently improves patients' ability to perform activities of daily living with less encumbrance from motor fluctuations. Quality of life is enhanced and many patients are able to significantly reduce the amount of antiparkinsonian medications required to still get good pharmacological benefit. Overall, adverse effects associated with DBS tend to be transient, although device-related and other postoperative complications do occur. DBS should be considered the surgical procedure of choice for patients who meet strict criteria with medically intractable PD, ET and selected cases of dystonia.

Deep brain stimulation for torsion dystonia

Deep brain stimulation (DBS) at the globus pallidus pars internus (GPi) is an effective treatment for some patients with medically refractory torsion dystonia. In this chapter we review the classification and treatment of torsion dystonia including the current indications for DBS surgery. Details of the DBS procedure and programming of the DBS devices are discussed. Pallidal DBS is most effective in patients with primary generalized dystonia. Children and adolescents possessing the DYT1 gene mutation may respond best of all. Patients with cervical dystonia may also improve with pallidal DBS but definitive clinical evidence is lacking. As a group, patients with secondary dystonias respond less well to DBS than do patients with primary dystonia; however, patients with dystonia secondary to anoxic brain injury who have grossly intact basal ganglia anatomy, and patients with tardive dystonia may represent secondary dystonia subtypes for whom pallidal DBS is a viable option.

Surgical considerations in movement disorders: deep brain stimulation, ablation and transplantation

Surgical therapy for movement disorders has been practiced since the early 20th century, mostly for Parkinson's disease. At its onset, large destructive procedures like open resection of cortex, parts of the basal ganglia or its fibre connections produced variable, ill-documented results. With the introduction of the stereotactic operating technique in the second half of the century, ablative surgery became more refined, and more selective interventions became possible to alleviate the suffering of those patients for whom no other treatment modalities were yet available. However, the introduction of levodopa-based pharmacological therapy pushed surgical therapy almost completely to the background. In the past two decades, there has been a resurgence of interest in surgery for movement disorders, due to both limitations of long-term pharmacological therapy and the advent of the treatment modality of deep brain stimulation. The subject has now grown into a large field of clinical and scientific interest. Parkinson's disease is the most widespread surgical indication, but in other movement disorders considerable improvement can be achieved by surgery as well, most notably in dystonia. A short review of the surgical therapy for these disorders is presented.

Surgical management of Chiari malformation: analysis of 128 cases

OBJECTIVE

A variety of surgical interventions have been recommended for patients with Chiari malformations (CMs). In this study, we have evaluated the intraoperative findings and clinical outcome in different-aged patients with CMs undergoing posterior fossa decompression.

METHODS

Sixteen pediatric and 112 adult cases with CMs underwent suboccipital craniectomy and wide duraplasty as well as autogenous bone grafting in selected cases. The clinical outcome was assessed by evaluation of postoperative signs and symptoms and magnetic resonance imaging of the craniocervical junction.

RESULTS

The most striking intraoperative finding was the presence of a very thin membrane over the opening of the central canal; the occurrence of this membrane in pediatric patients was significantly higher than that in adults (94 and 43%, respectively; p < 0.05, Fisher's exact probability test). During the immediate postoperative period, 81% of pediatric CMs and 90% of adult CMs showed improved symptomatology and magnetic resonance imaging revealed favorable findings comprising syrinx collapse or reduction of the syrinx diameter in 14 (88%) pediatric and 92 (82%) adult CMs. During discharge from hospital, 103 (90%) patients with CMs type I and 11 (85%) with CMs type II achieved good results. However, there was a statistically significant difference in the occurrence of poor results between patients treated with bony fusion and those without fusion (24 vs. 6%;p < 0.05, Fisher's exact probability test). The incidence of vertebral instability was markedly augmented in pediatric CMs in comparison to adult CMs (19 vs. 2%; p < 0.01, Fisher's exact probability test).

CONCLUSIONS

Suboccipital decompression and duraplasty with autogenous bone grafts in selected cases are effective treatments for most patients with CMs. A higher incidence of a special membrane over the obex and atlantoaxial instability were closely associated with childhood CMs.

Electricity in the treatment of nervous system disease

Electricity has been used in medicine for almost two millenniums beginning with electrical chocks from the torpedo fish and ending with the implantation of neuromodulators and neuroprostheses. These implantable stimulators aim to improve functional independence and quality of life in various groups of disabled people. New indications for neuromodulation are still evolving and the field is rapidly advancing. Thanks to modern science and computer technology, electrotherapy has reached a degree of sophistication where it can be applied relatively safely and effectively in a variety of nervous system diseases, including pain, movement disorders, epilepsy, Tourette syndrome, psychiatric disease, addiction, coma, urinary incontinence, impotence, infertility, respiratory paralysis, tinnitus and blindness.

Deep brain stimulation for neurologic and neuropsychiatric disorders

In the 1960s, ablative stereotactic surgery was employed for a variety of movement disorders and psychiatric conditions. Although largely abandoned in the 1970s because of highly effective drugs, such as levodopa for Parkinson's disease (PD), and a reaction against psychosurgery, the field has undergone a virtual renaissance, guided by a better understanding of brain circuitry and the circuit abnormalities underlying movement disorders such as PD and neuropsychiatric conditions, such as obsessive compulsive disorder. High-frequency electrical deep brain stimulation (DBS) of specific targets, introduced in the early 1990s for tremor, has gained widespread acceptance because of its less invasive, reversible, and adjustable features and is now utilized for an increasing number of brain disorders. This review summarizes the rationale behind DBS and the use of this technique for a variety of movement disorders and neuropsychiatric diseases.

Quantification and Visualization of Three-Dimensional Inconsistency of the Globus Pallidus Internus in the Schaltenbrand-Wahren Brain Atlas

The major shortcomings of the Schaltenbrand-Wahren (SW) brain atlas include 3-dimensional (3D) inconsistency and spatial sparseness. This work quantifies and visualizes 3D inconsistency of the globus pallidus internus (GPi), a stereotactic target for the treatment of Parkinson's disease, dystonia and Huntington disease. The GPi 3D models 3D-A, 3D-C and 3D-S are reconstructed from the SW axial, coronal and sagittal microseries, respectively, by applying a shape-based (Nonuniform Rational B Splines) method. All three 3D models, placed in the SW coordinate system, are compared quantitatively in terms of location (centroids), size (volumes), shape (normalized eigen values), orientation (eigen vectors) and mutual spatial relationships (overlaps and inclusions). The analysis is done in 3D within each orientation and across them. The reconstructed 3D GPi models substantially differ in location, size and inclusion rate. The centroid of 3D-C is located more medially (15.6 mm) than those of 3D-A (17.5 mm) and 3D-S (18.2 mm), and that of 3D-A more ventrally (-2.3 mm) than those of 3D-C (-0.1 mm) and 3D-S (-0.4 mm). 3D-S has the smallest volume (347.3 mm3); 3D-A is 1.18 and 3D-C 1.85 times larger. The highest inclusion rate is for 3D-S (54.3 and 56.3%) and the lowest for 3D-C (28.8 and 30.6%). A smaller variability is observed in shape, orientation and overlap size (196.8, 196.1 and 185.5 mm3). To get a better correspondence between 3D-C and 3D-S, the coronal microseries were scaled laterally by 1.1667. This results in a substantial improvement of the inclusion rate of 3D-S (87.9%), though raising the volume mismatch to 2.16. The GPi in the SW atlas has a substantial 3D inaccuracy within each orientation and across them. Therefore, absolute and direct reliance on the original atlas is unsafe, and this atlas has to be used with great care and understanding of its limitations. As matching various SW microseries by global scaling is not feasible, we propose the target-dependent scaling based on structure centroid matching.

IMPLANTATION OF ELECTRODES FORDEEP BRAIN STIMULATION OF THE SUBTHALAMIC NUCLEUS IN ADVANCED PARKINSON'S DISEASE WITH THE AID OF INTRAOPERATIVE MICRORECORDING UNDERGENERAL ANESTHESIA

OBJECTIVE

Deep brain stimulation (DBS) is widely accepted in the treatment of advanced Parkinson's disease (PD) and other movement disorders. The standard implantation procedure is performed under local anesthesia (LA). Certain groups of patients may not be eligible for surgery under LA because of clinical reasons, such as massive fear, reduced cooperativity, or coughing attacks. Microrecording (MER) has been shown to be helpful in DBS surgery. The purpose of this study was to evaluate the feasibility of MERfor DBS surgery under general anesthesia (GA) and to compare the data of intraoperative MERas well as the clinical data with that of the current literature of patients undergoing operation under LA.

CLINICAL PRESENTATION

The data of nine patients with advanced PD (mean Hoehn and Yahr status, 4.2) who were operated with subthalamic nucleus (STN) DBS under GA, owing to certain clinical circumstances ruling out DBS under LA, were retrospectively analyzed. All operations were performed under analgosedation with propofol or remifentanil and intraoperative MER. For MER, remifentanil was ceased completely and propofol was lowered as far as possible.

INTERVENTION

The STN could be identified intraoperatively in all patients with MER. The typical bursting pattern was identified, whereas a widening of the baseline noise could not be as adequately detected as in patients under LA. The daily off phases of the patients were reduced from 50 to 17%, whereas the Unified Parkinson's Disease Rating Scale III score was reduced from 43 (preoperative, medication off) to 19 (stimulation on, medication off) and 12 (stimulation on, medication on). Two patients showed a transient neuropsychological deterioration after surgery, but both also had preexisting episodes of disorientation. One implantable pulse generator infection was noticed. No further significant clinical complications were observed.

CONCLUSION

STN surgery for advanced PD with MERguidance is possible with good clinical results under GA. Intraoperative MERof the STN region can be performed under GA with a special anesthesiological protocol. In this setting, the typical STN bursting pattern can be identified, whereas the typical widening of the background noise baseline while entering the STN region is obviously absent. This technique may enlarge the group of patients eligible for STN surgery. Although the clinical improvements and parameter settings in this study were within the range of the current literature, further randomized controlled studies are necessary to compare the results of STN DBS under GA and LA, respectively.

Treatment of dystonia

Dystonia, defined as a neurological syndrome characterised by involuntary, patterned, sustained, or repetitive muscle contractions of opposing muscles, causing twisting movements and abnormal postures, is one of the most disabling movement disorders. Although gene mutations and other causes are increasingly recognised, most patients have primary dystonia without a specific cause. Although pathogenesis-targeted treatment is still elusive, the currently available symptomatic treatment strategies are quite effective for some types of dystonia in relieving involuntary movements, correcting abnormal posture, preventing contractures, reducing pain, and improving function and quality of life. A small portion of patients have a known cause and respond to specific treatments, such as levodopa in dopa-responsive dystonia or drugs that prevent copper accumulation in Wilson's disease. Therapeutic options must be tailored to the needs of individual patients and include chemodenervation with botulinum toxin injections for patients with focal or segmental dystonia, and medical treatments or deep brain stimulation for patients with generalised dystonia.

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.

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.