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

Central motor conduction studies and diagnostic magnetic resonance imaging in children with severe primary and secondary dystonia

AIM

Dystonia in childhood has many causes. Imaging may suggest corticospinal tract dysfunction with or without coexistent basal ganglia damage. There are very few published neurophysiological studies on children with dystonia; one previous study has focused on primary dystonia. We investigated central motor conduction in 62 children (34 males, 28 females; age range 3-19y, mean age 10y 8mo, SD 4y 8mo) with severe dystonia to evaluate corticospinal tract integrity before consideration for deep brain stimulation.

METHOD

Distal motor and F-wave latencies were measured in the ulnar and/or posterior tibial nerves. Transcranial magnetic stimulation was applied over the motor cortex and motor-evoked potentials were recorded in the activated abductor digiti minimi and/or abductor hallucis muscles. Central motor conduction time (CMCT) was calculated using the F-wave method.

RESULTS

CMCT was normal in 50 out of 62 patients; 12 patients showed prolonged CMCT to upper and/or lower limbs. Most children with severe primary and secondary dystonia had normal CMCT, indicating corticospinal tract integrity despite abnormal imaging in 42 out of 50 patients. Abnormal CMCT was found in two out of 12 patients with normal imaging.

INTERPRETATION

This study provides new CMCT data for children with severe primary and secondary dystonia. Over 50% of children with evidence of periventricular white-matter damage from magnetic resonance imaging had normal CMCT, challenging traditional pathophysiological models. This is consistent with recent diffusion tensor imaging in children with periventricular white-matter damage, showing disruption of sensory connections rather than corticospinal tract damage. CMCT helps refine our understanding of imaging changes in complex motor disorders of childhood.

Early-onset primary dystonia

"Dystonia" is the term used to describe abnormal movements consisting of sustained muscle contractions frequently causing twisting and repetitive movements or abnormal postures. Dystonia is classified partly by age at onset because this helps guide the diagnostic work-up and treatment decisions. This chapter focuses on early-onset (<26 years old) primary dystonia. The history, clinical features, genetics, pathophysiology, diagnosis, and treatment of early-onset primary dystonia are discussed. Special emphasis is placed on DYT1 dystonia, the most common, autosomal-dominant, early-onset, primary dystonia. A diagnostic algorithm is proposed for gene-negative early-onset dystonia, and treatment recommendations for generalized, early-onset dystonia are made.

Deep-Brain Stimulation for Basal Ganglia Disorders

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

EFNS guidelines on diagnosis and treatment of primary dystonias

OBJECTIVES

to provide a revised version of earlier guidelines published in 2006.

BACKGROUND

primary dystonias are chronic and often disabling conditions with a widespread spectrum mainly in young people.

DIAGNOSIS

primary dystonias are classified as pure dystonia, dystonia plus or paroxysmal dystonia syndromes. Assessment should be performed using a validated rating scale for dystonia. Genetic testing may be performed after establishing the clinical diagnosis. DYT1 testing is recommended for patients with primary dystonia with limb onset before age 30, and in those with an affected relative with early-onset dystonia. DYT6 testing is recommended in early-onset or familial cases with cranio-cervical dystonia or after exclusion of DYT1. Individuals with early-onset myoclonus should be tested for mutations in the DYT11 gene. If direct sequencing of the DYT11 gene is negative, additional gene dosage is required to improve the proportion of mutations detected. A levodopa trial is warranted in every patient with early-onset primary dystonia without an alternative diagnosis. In patients with idiopathic dystonia, neurophysiological tests can help with describing the pathophysiological mechanisms underlying the disorder.

TREATMENT

botulinum toxin (BoNT) type A is the first-line treatment for primary cranial (excluding oromandibular) or cervical dystonia; it is also effective on writing dystonia. BoNT/B is not inferior to BoNT/A in cervical dystonia. Pallidal deep brain stimulation (DBS) is considered a good option, particularly for primary generalized or cervical dystonia, after medication or BoNT have failed. DBS is less effective in secondary dystonia. This treatment requires a specialized expertise and a multidisciplinary team.

Dystonia due to cerebral palsy responds to deep brain stimulation of the globus pallidus internus

BACKGROUND

Cerebral palsy is the most common cause of pediatric-onset dystonia. Deep brain stimulation is gaining acceptance for treating dystonias in children. There is minimal reported experience regarding the efficacy of deep brain stimulation in cerebral palsy.

METHODS

Fourteen patients, including 8 younger than 16 years, received bilateral implants (13 patients) or a unilateral implant (1 patient) of the internal globus pallidus and were observed in a noncontrolled, nonblinded study for at least 6 months. Motor function was assessed using the Burke-Fahn-Marsden Dystonia Movement and Disability scales and the Barry Albright Dystonia Scale.

RESULTS

By 6 months, significant improvement was observed in the Burke-Fahn-Marsden Dystonia Movement scale (P=.004), the Burke-Fahn-Marsden Dystonia Disability scale (P=.027), and the Barry Albright Dystonia Scale (P=.029) for the whole cohort (n=14) and in the patients treated before skeletal maturity (group 1; n=8): Burke-Fahn-Marsden Dystonia Movement scale, P=.012; Burke-Fahn-Marsden Dystonia Disability scale, P=.020; and Barry Albright Dystonia Scale, P=.027.

CONCLUSIONS

Deep brain stimulation may offer an effective treatment option for cerebral palsy-related dystonia, especially in those treated before skeletal maturity.

Pallidal Deep Brain Stimulation for Primary Dystonia in Children

BACKGROUND:

Deep brain stimulation (DBS) at the internal globus pallidus (GPi) has replaced ablative procedures for the treatment of primary generalized dystonia (PGD) because it is adjustable, reversible, and yields robust clinical improvement that appears to be long lasting.

OBJECTIVE:

To describe the long-term responses to pallidal DBS of a consecutive series of 22 pediatric patients with PGD.

METHODS:

Retrospective chart review of 22 consecutive PGD patients, ≤21 years of age treated by one DBS team over an 8-year period. The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was used to evaluate symptom severity and functional disability, pre- and post-operatively. Adverse events and medication changes were also noted.

RESULTS:

The median follow-up was 2 years (range, 1-8 years). All 22 patients reached 1-year follow-up; 14 reached 2 years, and 11 reached 3 years. The BFMDRS motor subscores were improved 84%, 93%, and 94% (median) at these time points. These motor responses were matched by equivalent improvements in function, and the response to DBS resulted in significant reductions in oral and intrathecal medication requirements after 12 and 24 months of stimulation. There were no hemorrhages or neurological complications related to surgery and no adverse effects from stimulation. Significant hardware-related complications were noted, in particular, infection (14%), which delayed clinical improvement.

CONCLUSION:

Pallidal DBS is a safe and effective treatment for PGD in patients &lt;21 years of age. The improvement appears durable. Improvement in device design should reduce hardware-related complications over time.

An Overview of Surgical Therapy for Movement Disorders

Surgical treatments are an important consideration in the management of many movement disorders, particularly for patients refractory to medications. Increasing number of published reports have demonstrated an overall improvement in motor function, activities of daily living and quality of life particularly with deep brain stimulation. In addition the procedure is also relatively safe. In this article, we review the various types of movement disorders that may benefit from surgical intervention.

Early globus pallidus internus stimulation in pediatric patients with generalized primary dystonia: long-term efficacy and safety

Primary generalized dystonia presents mainly at a young age and commonly is severely disabling. The authors report the long-term follow-up (mean, 73 months; range, 50-101 months) of 5 pediatric patients (mean age at surgery 13 years; range, 8-16 years) undergoing globus pallidus internus deep brain stimulation. Mean improvement in the Burke-Fahn-Marsden movement score was 67.4% (range, 47.0%-87.5%), 75.4% (range, 61.5%-91.7%), and 83.5% (range, 72.0%-93.3%) at 3 months, 12 months, and long-term follow-up (>36 months), respectively. Hardware problems (electrode dislocation/breakage of extension cable, and imminent perforation of extension cable) were observed in 2 patients (operative revision without sequelae). Except for mild dysarthria in 2 patients, no other therapy-related morbidity was observed. The authors found globus pallidus internus stimulation to offer a very effective and safe therapy in pediatric patients with primary dystonia. Early neurosurgical intervention seems to be crucial to prevent irreversible impairment of motor function.

Stimulation of the globus pallidus internus in a patient with DYT1-positive primary generalized dystonia: a 10-year follow-up

The authors report the case of DYT1-positive primary generalized dystonia refractory to medical management that was successfully treated with continuous deep brain stimulation of the internal segment of the globus pallidus. Prior studies have shown that neuromusculoskeletal deficits can remain permanent if early surgical intervention is not undertaken. The authors report prolonged efficacy and safety over a 10-year period in a 28-year-old man.

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.

Restoration of erect posture by deep brain stimulation of the globus pallidus in disabling dystonic spinal hyperextension

Dystonia is a movement disorder notoriously difficult to treat. While primary dystonia is classically considered to respond well to deep brain stimulation (DBS), treatment of secondary dystonia yields variable results. Patient selection should be done on a case-by-case basis. Clearly, there is a need to accumulate additional information with regard to prognostic factors that may aid neurosurgeons in selecting those patients in whom the disorder is most likely to respond favorably to pallidal DBS.

The authors report the case of a 29-year-old man with secondary dystonia due to perinatal hypoxia. The most prominent symptom was what we have termed ectatocormia—that is, severe, fixed truncal hyperextension and retrocollis, exacerbated by phasic, twisting movements of the trunk and head. This made it impossible for the patient to maintain a normal upright posture or to walk. The patient underwent bilateral DBS of the globus pallidus internus (GPi), and the authors observed impressive improvement in motor abilities and function. The patient's body adopted the normal upright posture and he became able to walk again, 4 months after the commencement of GPi stimulation.

This report, along with others, emphasizes that the GPi as an ideal target for alleviating axial tonic symptoms. The presence of normal MR imaging findings, a phenotypical purity of predominantly dystonic symptoms, and a younger age seem to favor a positive outcome.

Regional cerebral blood flow changes induced by deep brain stimulation in secondary dystonia

PURPOSE

The purpose of the present study is to investigate the effect of deep brain stimulation (DBS) on regional cerebral blood flow (rCBF) in cases of secondary dystonia as well as to correlate the rCBF changes with clinical outcomes.

METHODS

Six patients with medically intractable secondary dystonia who underwent DBS surgery were included in this study. Burke-Fahn-Mardsen Dystonia Rating Scale (BFMDRS) was used for the assessment of dystonia, before and after surgery. Single photon emission computed tomography (SPECT) of the brain was performed postoperatively in the two stimulation states (ON-DBS and OFF-DBS) and the changes of rCBF in the three following brain regions of interest (ROIs): primary motor cortex, premotor and supplementary motor cortex, and prefrontal cortex were evaluated.

RESULTS

Two patients exhibited excellent response to DBS, two patients got moderate benefit after the procedure, and in two patients, no clinical improvement was achieved. A mean improvement of 49.1% (0-90.7%) in BFMDRS total scores was found postoperatively. Brain SPECT data analysis revealed an overall decrease in rCBF in the investigated ROIs, during the ON-DBS state. Clinical improvement was significantly correlated with the observed decrease in rCBF in the presence of DBS.

CONCLUSIONS

When conservative treatment fails to relieve severely disabled patients suffering from secondary dystonia, DBS may be a promising therapeutic alternative. Moreover, this study indicates a putative role of brain SPECT imaging as a postoperative indicator of clinical responsiveness to DBS.

Bilateral pallidal stimulation in children and adolescents with primary generalized dystonia--report of six patients and literature-based analysis of predictive outcomes variables

INTRODUCTION

Primary generalized dystonia is a rare movement disorder. Medical treatment rarely relieves symptoms. The aim of this study was to investigate the efficacy and safety of bilateral pallidal stimulation in 6 children and adolescents with primary generalized dystonia. In addition, we strived to find predictors for treatment outcome by review and analysis of previously published studies.

METHODS

Six patients with primary generalized dystonia underwent chronic bilateral stimulation of the globus pallidus internus. A PubMed and MEDLINE search was performed in order to identify children and adolescents who underwent deep brain stimulation for primary generalized dystonia. The primary efficacy endpoint was the relative change of the Burke-Fahn-Marsden-Dystonia-Rating-Scale (movement score) after surgery.

RESULTS

Forty-four patients were found to meet the inclusion criteria. The mean age at onset of the disease was 7.8+/-2.8years and the mean age at surgery was 14.2+/-3.5years. The mean Burke-Fahn-Marsden-Dystonia-Rating-Scale (movement score) was 56.9+/-22.7 before surgery and 23.7+/-23.2 at a mean follow up of 13.0+/-4.8months (p<0.001). The improvement in the DYT1-positive group was significantly higher compared to the DYT1-negative group (77%+/-24% and 44%+/-30%, respectively, p<0.001). A positive correlation between the movement score before and after surgery was found in both the DYT1-positive and DYT1-negative cohort (rs=0.624, p<0.001 and rs=0.734, p<0.001, respectively).

CONCLUSION

DBS is an effective treatment in children and adolescents with primary generalized dystonia. Predictive factors for a better treatment outcome are DYT1-positive status and minor motor impairment before surgery.

Meige's syndrome: A cranial dystonia treated with bilateral pallidal deep brain stimulation

BACKGROUND

Meige's syndrome is a rare form of segmental dystonia characterized by blepharospasm and oromandibular dystonia. Medical treatment including botulinum toxin injections usually present disappointing results. The experience on Deep Brain Stimulation (DBS) in the treatment of Meige's syndrome and other segmental dystonias is still limited. At the moment, only a few cases of pallidal DBS have been reported to improve this rare form of dystonia.

CASE DESCRIPTION

We report on a case of a woman with a 7-year history of Meige's syndrome, which rendered her functionally blind. The treatment with botulinum toxin injections failed to improve her symptoms, whereas stereotactic bilateral DBS of the pallidum led to a dramatic clinical improvement. Clinical assessment using the Burke-Fahn-Mardsen Dystonia Rating Scale (BFMDRS) in a double-blind manner, showed an improvement of 70% in the Movement score and 93.33% in the Disability score (84% reduction of the total score) on the 3 and 6 month follow-up.

CONCLUSIONS

Stereotactic pallidal DBS might be considered as a potential treatment in the management of Meige's syndrome.

A family with a hereditary form of torsion dystonia from northern Sweden treated with bilateral pallidal deep brain stimulation

To evaluate pallidal DBS in a non-DYT1 form of hereditary dystonia. We present the results of pallidal DBS in a family with non-DYT1 dystonia where DYT5 to 17 was excluded. The dystonia is following an autosomal dominant pattern. Ten members had definite dystonia and five had dystonia with minor symptoms. Four patients received bilateral pallidal DBS. Mean age was 47 years. The patients were evaluated before surgery, and "on" stimulation after a mean of 2.5 years (range 1-3) using the Burke-Fahn-Marsden scale (BFM). Mean BFM score decreased by 79 % on stimulation, from 42.5 +/- 24 to 9 +/- 6.5 at the last evaluation. Cervical involvement improved by 89%. The 2 patients with oromandibular dystonia and blepharospasm demonstrated a reduction of 95% regarding these symptoms. The present study confirms the effectiveness of pallidal DBS in a new family with hereditary primary segmental and generalized dystonia.

Magnetic Resonance-Based Deep Brain Stimulation Technique: A Series of 478 Consecutive Implanted Electrodes With No Perioperative Intracerebral Hemorrhage

Objective:

The aim of this study was to determine the safety of a deep brain stimulation technique consisting of a combination of routine general anesthesia, magnetic resonance imaging direct targeting, and a single penetration technique in a large population of patients undergoing operation for movement disorders.

Methods:

One hundred ninety-four patients treated with deep brain stimulation between 1996 and 2007 were assessed via a computerized database for intra- and perioperative events. Most patients were young; only 62 of them were older than 40 years (mean age, 31.1 years). General anesthesia was induced in all cases before placement of a magnetic resonance imaging-compatible stereotactic frame. Electrode implantation was done under radioscopic control via a rigid immobile cannula using a single cerebral perforation. No perioperative microelectrode recording or neurostimulation testing was used. Systematic postoperative magnetic resonance imaging was performed before frame removal.

Results:

A total of 478 electrodes were implanted in 220 procedures: 426 for d ystonic-dyskinetic syndromes and 52 for Parkinson disease. The mean number of parenchymal penetrations per patient was 2.5 for the dystonic-dyskinetic syndrome group and 2.08 for the Parkinson disease group. Postimplantation magnetic resonance imaging detected no perioperative intraparenchymal hemorrhages.

Conclusion:

We consider that the risk of hemorrhagic complication is multifactorial but closely related to the chosen technique.

Early onset primary dystonia

Dystonia is a syndrome characterized by sustained muscle contractions, frequently causing twisting and repetitive movements or abnormal postures. It is classified by age at onset, by distribution, and by aetiology. The aetiological classification distinguishes the following categories: primary, dystonia plus, secondary, heredo-degenerative and psychogenic dystonia. Primary dystonia is defined as clinical condition characterized by dystonia as the only neurological abnormality apart from tremor. Different genetic alterations and gene loci have been mapped in familial and sporadic patients. Early onset-primary dystonia (EO-PD) is the most severe form of primary dystonia, with clinical and genetic heterogeneity. It usually starts in one body part, subsequently spreads to involve other body regions with frequent generalization. DYT1 dystonia is transmitted as an autosomal dominant trait with reduced penetrance. The unique underlying mutation is a GAG deletion in the coding region of the TOR1A gene, located at chromosome 9q34. DYT16 dystonia is a novel recessive form of EO-PD, recently described in few patients, caused by mutations in the PRKRA gene located at chromosome 2q31. At least other two loci have been mapped, but there remains a large number of patients with EO-PD in whom no genetic alteration is discovered.

Neuroimaging and deep brain stimulation

Deep brain stimulation (DBS) is a new neurosurgical method principally used for the treatment of Parkinson disease (PD). Many new applications of DBS are under development, including the treatment of intractable psychiatric diseases. Brain imaging is used for the selection of patients for DBS, to localize the target nucleus, to detect complications, and to evaluate the final electrode contact position. In patients with implanted DBS systems, there is a risk of electrode heating when MR imaging is performed. This contraindicates MR imaging unless specific precautions are taken. Involvement of neuroradiologists in DBS procedures is essential to optimize presurgical evaluation, targeting, and postoperative anatomic results. The precision of the neuroradiologic correlation with anatomic data and clinical outcomes in DBS promises to yield significant basic science and clinical advances in the future.

Factors predicting improvement in primary generalized dystonia treated by pallidal deep brain stimulation

Despite the beneficial effects of Globus Pallidus internus (GPi) deep brain stimulation (DBS) in patients with primary generalized dystonia (PGD), the degree of improvement varies from one patient to another. The objective of this study was to examine the effects of clinical, anatomical (volume of the GPi), and electrical variables on the postoperative Burke-Fahn-Marsden Dystonia rating scale (BFMDRS) motor score to identify which factors may be predictive of the degree of improvement. We reviewed retrospectively the clinical records of 40 steady-state patients with PGD who had been treated by bilateral GPi lead implantation. The follow-up period was 2 to 8 years. The correlation between the electrical parameters (voltage, impedance, and current) and the clinical outcome was studied. An analysis of covariance was performed to identify factors predictive of the magnitude of improvement. The most influential factors according to the model are as follows: the preoperative BFMDRS score (P < 0.0001); age at surgery (P < 0.0001); the right GPi volume (P = 0.002); the left stimulated GPi volume (P = 0.005). No significant correlation was found between the electrical parameters used and the mean motor scores in steady state.

Avoiding the ventricle: a simple step to improve accuracy of anatomical targeting during deep brain stimulation

OBJECT

The authors examined the accuracy of anatomical targeting during electrode implantation for deep brain stimulation in functional neurosurgical procedures. Special attention was focused on the impact that ventricular involvement of the electrode trajectory had on targeting accuracy.

METHODS

The targeting error during electrode placement was assessed in 162 electrodes implanted in 109 patients at 2 centers. The targeting error was calculated as the shortest distance from the intended stereotactic coordinates to the final electrode trajectory as defined on postoperative stereotactic imaging. The trajectory of these electrodes in relation to the lateral ventricles was also analyzed on postoperative images.

RESULTS

The trajectory of 68 electrodes involved the ventricle. The targeting error for all electrodes was calculated: the mean +/- SD and the 95% CI of the mean was 1.5 +/- 1.0 and 0.1 mm, respectively. The same calculations for targeting error for electrode trajectories that did not involve the ventricle were 1.2 +/- 0.7 and 0.1 mm. A significantly larger targeting error was seen in trajectories that involved the ventricle (1.9 +/- 1.1 and 0.3 mm; p < 0.001). Thirty electrodes (19%) required multiple passes before final electrode implantation on the basis of physiological and/or clinical observations. There was a significant association between an increased requirement for multiple brain passes and ventricular involvement in the trajectory (p < 0.01).

CONCLUSIONS

Planning an electrode trajectory that avoids the ventricles is a simple precaution that significantly improves the accuracy of anatomical targeting during electrode placement for deep brain stimulation. Avoidance of the ventricles appears to reduce the need for multiple passes through the brain to reach the desired target as defined by clinical and physiological observations.

A novel hereditary spastic paraplegia with dystonia linked to chromosome 2q24-2q31

Spastic paraplegias (HSPs) and dystonias (DYTs) typically localize to different neuroanatomic systems. We report clinical and genetic data from large Ohio kindred with autosomal dominant (AD) HSP and DYT. Single and multipoint linkage using microsatellite and single nucleotide polymorphism array genotyping were performed on a large, multigenerational family with a novel, AD, highly penetrant neurological disease causing spasticity and DYT. Age of onset of spasticity and weakness is from the first year to the sixth decade, and age of onset of DYT from the first to third decade. There is no ataxia or apparent cognitive involvement. Neuroimaging and peripheral neurophysiology are normal. Generalized DYT improved markedly with deep brain stimulation in 1 child. The disease locus was mapped to a region on chromosome 2q 24-31, flanked by markers rs1424937-rs1559510, proximal to SPG13, in a region where there are no known HSP or DYT genes. A secondary analysis for candidate genes segregating with the DYT phenotype revealed two candidate regions with parametric lod scores above 2.0. On the basis of clinical presentation and linkage results, we conclude that this disease is a novel neurological disorder. Identifying the causative gene may elucidate an important pathway for pyramidal and extrapyramidal disorders.

Deep brain stimulation: current and future perspectives

Deep brain stimulation (DBS) has been used to treat various neurological and psychiatric disorders. Over the years, the most suitable surgical candidates and targets for some of these conditions have been characterized and the benefits of DBS well demonstrated in double-blinded randomized trials. This review will discuss some of the areas of current investigation and potential new applications of DBS.

Pallidal stimulation in cervical dystonia: clinical implications of acute changes in stimulation parameters

BACKGROUND AND PURPOSE

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is successful in dystonia, but the role of each electrical parameters of stimulation is unclear. We studied the clinical effects of acute changes of different parameters of GPi-DBS in cervical dystonia (CD).

METHODS

Eight CD patients with bilateral GPi-DBS at 28.6 +/- 19.2 (mean +/- SD) months after surgery were recruited. Mean improvement in the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) severity score was 54.5% compared to before surgery. Ten settings, including a combination of a wide range of pulse widths (PWs), low and high frequencies and voltage, were administered in a randomized double blinded fashion. Clinical benefit was assessed by two raters using the TWSTRS and by the patients using an analogue rating scale.

RESULTS

The TWSTRS severity scores were reduced by 56.7% with stimulation at the best settings. Improvement was significantly associated with high frequency (> or = 60 Hz) and high voltage. Stimulation at 130 Hz showed the best clinical improvement. Increasing PWs (from 60 to 450 micros) did not result in a significant improvement.

CONCLUSION

Frequency and amplitude appear to be the most important factors in the acute anti-dystonic effects in GPi-DBS patients with CD.

Deep brain stimulation for pediatric movement disorders

Deep brain stimulation (DBS) has been used for the treatment of tremor and dystonia in adults since 1997. With more than 50,000 treated adults, it has become part of the standard care for pharmacoresistant tremor, Parkinson disease, and dystonias. Dystonias are a heterogeneous group of disorders with intrinsic (genetic) and extrinsic etiologic factors. In children and adults, DBS has been used for the treatment of both primary and secondary dystonias. Pediatric use has been more limited, with only a few experienced centers worldwide. Awake surgery can be safely performed with a dedicated multidisciplinary team approach to help ensure appropriate lead placement. It is incumbent upon us, as physicians, to advise patients and payers on the appropriate use of this technology. Neuromodulation of other disorders, including epilepsy, Tourette syndrome, obsessive-compulsive disorder, and depression, by DBS is under active investigation. Pediatric DBS is still in its early stages; experience will help us refine the indications and techniques for applying this complex technology to our most vulnerable patients, which should lead to our common goal of improving quality of life for our patients and their families. We review the role of DBS and our experience with establishing a dedicated pediatric DBS program.

Deep brain stimulation for secondary dystonia: results in 8 patients

BACKGROUND

Dystonia is a medically intractable condition characterized by involuntary twisting movements and/or abnormal postures. Deep Brain Stimulation (DBS) has been used successfully in various forms of dystonia. In the present study, we report on eight patients with secondary dystonia, treated with DBS in our clinic.

METHOD

Eight patients (five males, three females) underwent DBS for secondary dystonia. The etiology of dystonia was cerebral palsy (n = 2), drug-induced (n = 1), post encephalitis (n = 2) and postanoxic dystonia (n = 3). The functional capacity was evaluated before and after surgery with the use of Burke-Fahn-Mardsen Dystonia Rating Scale (BFM scale), both movement and disability scale (MS and DS, respectively). The target for DBS was the globus pallidus internus (GPi) in 7 patients and in one patient, with postanoxic damaged pallidum, the ventralis oralis anterior (Voa) nucleus. Brain perfusion scintigraphy using Single Photon Emission Computed Tomography (SPECT) was performed in two separate studies for each patient, one in the "off-DBS" and the other in the "on-DBS" state.

FINDINGS

Postoperative both MS and DS scores were found to be significantly lower compared to preoperative scores (p = 0.018 and p = 0.039, respectively). Mean improvement rate after DBS was 41.4% (0-94.3) and 29.5% (0-84.2) in MS and DS scores, respectively. The SPECT Scan, during the "on-DBS" state, showed a decrease in regional cerebral blood flow (rCBF), compared to the "off-DBS" state.

CONCLUSIONS

Our results seem promising in the field of secondary dystonia treatment. More studies with greater number of patients and longer follow-up periods are necessary in order to establish the role of DBS in the management of secondary dystonia. Finally, the significance of brain SPECT imaging in the investigation of dystonia and functional effects of DBS should be further evaluated.

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

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

Prognostic value of globus pallidus internus volume in primary dystonia treated by deep brain stimulation

Object

Given that improvement is variable from one patient to another, the authors analyzed the impact of globus pallidus internus (GPi) volume on the result of deep brain stimulation (DBS) by comparing highly and less improved patients with primary dystonodyskinetic syndromes.

Methods

A stereotactic model was developed to visualize and quantify the relationship between the isofield lines generated by the DBS lead and GPi target. The model was used in 30 right-handed selected patients with primary dystonodyskinetic syndromes who had been treated using bilateral stimulation of the sensorimotor GPi. Ten healthy control individuals were also included in the study. First, the authors compared the GPi volumes between patients and healthy controls. Second, the stimulated GPi volumes, that is, the intersection between the volume of each isofield value and the GPi volumes, were compared between less improved and highly improved patients.

Results

Improvement in the Burke-Fahn-Marsden Dystonia Rating Scale's motor score was rated > 90% in 20 patients (97 ± 4.6%) and < 60% in 10 patients (56.9 ± 6%). The mean volume of the right (461.8 ± 81.8 mm3) and left (406.6 ± 113.2 mm3) GPi in patients showing less response to DBS was significantly smaller than the GPi volume of patients who responded well (right 539.9 ± 86.6 mm3, left 510.6 ± 88.7 mm3) and healthy controls (right 557.8 ± 109.1 mm3, left 525.1 ± 40.8 mm3).

Conclusions

On the left side, the mean stimulated volumes (isofield line range 0.2–1 V/mm) were significantly larger in highly improved than in less improved patients. In this model, the threshold for functional effect was calculated at 0.2 V/mm.

Induction of bradykinesia with pallidal deep brain stimulation in patients with cranial-cervical dystonia

BACKGROUND

Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective and well-tolerated treatment for idiopathic generalized dystonia. More recently, it has been applied as a treatment for focal and segmental dystonias. This patient population offers an opportunity to study the effects of alteration of pallidal outflow on previously normal limb function.

METHODS

We sought to retrospectively characterize the extent of novel GPi DBS-induced adverse motor effects in patients with adult-onset cervical and cranial-cervical dystonia using a questionnaire, and compared the findings to dystonia improvement as measured by standard scales.

RESULTS

Despite significant improvement in dystonia (65% in mean Burke-Fahn-MarsdenDystonia Rating Scale motor score, p < 0.005, and 59% in mean Toronto Western Spasmodic Torticollis Rating Scale score, p < 0.008), slowing and difficulty with normal motor function was reported in previously nondystonic extremities in 10 of 11 patients. Symptoms were common in both upper and lower extremities and included new difficulties with handwriting (82%), getting up from a chair or in/out of a car (73%), and walking (45%), and were not associated with aberrant lead placement near the internal capsule.

CONCLUSION

Although GPi DBS was shown to be effective in these patients, the influence of GPi DBS on nondystonic body regions deserves further investigation.

Research priorities in spasmodic dysphonia

OBJECTIVE

To identify research priorities to increase understanding of the pathogenesis, diagnosis, and improved treatment of spasmodic dysphonia.

STUDY DESIGN AND SETTING

A multidisciplinary working group was formed that included both scientists and clinicians from multiple disciplines (otolaryngology, neurology, speech pathology, genetics, and neuroscience) to review currently available information on spasmodic dysphonia and to identify research priorities.

RESULTS

Operational definitions for spasmodic dysphonia at different levels of certainty were recommended for diagnosis and recommendations made for a multicenter multidisciplinary validation study.

CONCLUSIONS

The highest priority is to characterize the disorder and identify risk factors that may contribute to its onset. Future research should compare and contrast spasmodic dysphonia with other forms of focal dystonia. Development of animal models is recommended to explore hypotheses related to pathogenesis. Improved understanding of the pathophysiology of spasmodic dysphonia should provide the basis for developing new treatment options and exploratory clinical trials.

SIGNIFICANCE

This document should foster future research to improve the care of patients with this chronic debilitating voice and speech disorder by otolaryngology, neurology, and speech pathology.