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

Deep brain stimulation improves quality of life in pantothenate kinase-associated neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) is an uncommon extrapyramidal movement disorder characterized by the progressive incapacitating dystonia. Medical management is often incapable of reversing the dystonic symptoms. In recent years, stereotactic procedure like deep brain stimulation has been found effective in resolving the disabling dystonia and improving the quality of life. There are few cases in the world literature highlighting the usefulness of this technique. We report a case of 10-year-old girl who underwent bilateral Globus pallidus internus stimulation for PKAN.

Accuracy of stimulating electrode placement in paediatric pallidal deep brain stimulation for primary and secondary dystonia

BACKGROUND

Accuracy of electrode placement is an important determinant of outcome following deep brain stimulation (DBS) surgery. Data on accuracy of electrode placement into the globus pallidum interna (GPi) in paediatric patients is limited, particularly those with non-primary dystonia who often have smaller GPi. Pallidal DBS is known to be more effective in the treatment of primary dystonia compared with secondary dystonia.

OBJECTIVES

We aimed to determine if accuracy of pallidal electrode placement differed between primary, secondary and NBIA (neuronal degeneration and brain iron accumulation) associated dystonia and how this related to motor outcome following surgery.

METHODS

A retrospective review of a consecutive cohort of children and young people undergoing DBS surgery in a single centre. Fused in frame preoperative planning magnetic resonance imaging (MRI) and postoperative computed tomography (CT) brain scans were used to determine the accuracy of placement of DBS electrode tip in Leskell stereotactic system compared with the planned target. The differences along X, Y, and Z coordinates were calculated, as was the Euclidean distance of electrode tip from the target. The relationship between proximity to target and change in Burke-Fahn-Marsden Dystonia Rating Scale at 1 year was also measured.

RESULTS

Data were collected from 88 electrodes placed in 42 patients (14 primary dystonia, 18 secondary dystonia and 10 NBIA associated dystonia). Median differences between planned target and actual position were: left-side X-axis 1.05 mm, Y-axis 0.85 mm, Z-axis 0.94 mm and Euclidean difference 2.04 mm; right-side X-axis 1.28 mm, Y-axis 0.70 mm, Z-axis 0.70 mm and Euclidean difference 2.45 mm. Accuracy did not differ between left and right-sided electrodes. No difference in accuracy was seen between primary, secondary or NBIA associated dystonia. Dystonia reduction at 1 year post surgery did not appear to relate to proximity of implanted electrode to surgical target across the cohort.

CONCLUSIONS

Accuracy of surgical placement did not differ between primary, secondary or NBIA associated dystonia. Decreased efficacy of pallidal DBS in secondary and NBIA associated dystonia is unlikely to be related to difficulties in achieving the planned electrode placement.

Morphological and chemical analysis of a deep brain stimulation electrode explanted from a dystonic patient

Deep brain stimulation is an effective treatment for different types of dystonia; nevertheless dystonic movements could provoke hardware-related complications, including fractures or electrodes displacement. This study focuses on a morphological and structural analysis of a malfunctioning electrode removed from a dystonic patient. In this case, high impedance values and worsening of symptoms were observed. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) were performed on the explanted electrode. The qualitative and quantitative data collected from the damaged electrode were compared with a new electrode, used as a control. The SEM analysis of the damaged electrode revealed fissurations and crack-like forms of the outer jacket tubing, degeneration of the internal core and wires stretching. The EDX analysis permitted to appreciate an increase of chemical elements, especially sodium, suggesting an alteration of the electrode-brain interface. This study shows the qualitative and quantitative alterations of a malfunctioning electrode and, to reduce the rate of hardware-related complications, it suggests the development of more reliable polymers.

The impact of multichannel microelectrode recording (MER) in deep brain stimulation of the basal ganglia

Deep brain stimulation (DBS) of the basal ganglia (Ncl. subthalamicus, Ncl. ventralis intermedius thalami, globus pallidus internus) has become an evidence-based and well-established treatment option in otherwise refractory movement disorders. The Ncl. subthalamicus (STN) is the target of choice in Parkinson's disease.However, a considerable discussion is currently ongoing with regard to the necessity for micro-electrode recording (MER) in DBS surgery.The present review provides an overview on deep brain stimulation and (MER) of the STN in patients with Parkinson's disease. Detailed description is given concerning the multichannel MER systems nowadays available for DBS of the basal ganglia, especially of the STN, as a useful tool for target refinement. Furthermore, an overview is given of the historical aspects, spatial mapping of the STN by MER, and its impact for accuracy and precision in current functional stereotactic neurosurgery.The pros concerning target refinement by MER means on the one hand, and cons including increased bleeding risk, increased operation time, local or general anesthesia, and single versus multichannel microelectrode recording are discussed in detail. Finally, the authors favor the use of MER with intraoperative testing combined with imaging to achieve a more precise electrode placement, aiming to ameliorate clinical outcome in therapy-resistant movement disorders.

Deep brain stimulation for dystonia

The few reported controlled studies show that bilateral stimulation of the globus pallidus interna (GPi) is a safe and effective long-term treatment for hyperkinetic disorders. However, the recently published data on deep brain stimulation (DBS) applied to different targets or patients (especially those with secondary dystonia) are mainly uncontrolled case reports, precluding a clear determination of its efficacy, and providing little guidance as to the choice of a "good" target in a "good" patient. This chapter reviews the literature on DBS in primary dystonia, paying particular attention to the risk:benefit ratio in focal and segmental dystonias (cervical dystonia, cranial dystonia) and to the predictive factors for a good outcome. The chapter also highlights recent data on the marked benefits of the technique in myoclonus dystonia (in which pallidal, as opposed to thalamic, stimulation is more effective) and in tardive dystonia-dyskinesia. Although, the decision to treat appears relatively straightforward in patients with primary dystonia, myoclonus-dystonia, and tardive dystonia who have a normal findings on magnetic resonance imaging and normal cognitive function, there are still no reliable tools to help predict the timescale of postoperative benefit. This chapter provides a comprehensive analysis of the use of the treatment in various types of secondary dystonia, with little to moderate benefit in most cases, based on single cases or small series. Beyond the reduction in the severity of dystonia, the global motor and functional outcome is difficult to determine owing to the paucity of adequate evaluation tools. Because of the large interpatient variability, different targets may be effective depending on the symptoms in each individual.

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

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

Surgical treatment for secondary dystonia

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

Shorter Disease Duration Correlates With Improved Long-term Deep Brain Stimulation Outcomes in Young-Onset DYT1 Dystonia

BACKGROUND:

Treatment with deep brain stimulation (DBS) of the globus pallidus internus in children with DYT1 primary torsion dystonia is highly effective; however, individual response to stimulation is variable, and a greater understanding of predictors of long-term outcome is needed.

OBJECTIVE:

To report the long-term outcomes of subjects with young-onset DYT1 primary torsion dystonia treated with bilateral globus pallidus DBS.

METHODS:

Fourteen subjects (7 male, 7 female) treated consecutively from 2000 to 2010 at our center were included in this retrospective study. The Burke-Fahn-Marsden Dystonia Rating Scale was performed at baseline and at 1, 2, and up to 6 years postoperatively.

RESULTS:

Pallidal DBS was well tolerated and highly effective, with mean Burke-Fahn-Marsden Dystonia Rating Scale movement scores improving from baseline by 61.5% (P < .001) at 1 year, 64.4% (P < .001) at 2 years, and 70.3% (P < .001) at the final follow-up visit (mean, 32 months; range, 7–77 months). Disability scores also improved significantly. Multiple linear regression analysis revealed a significant influence of duration of disease as a predictor of percent improvement in Burke-Fahn-Marsden Dystonia Rating Scale movement score at long-term follow-up (duration of disease, P < .05). Subjects with fixed orthopedic deformities (4) had less improvement in these regions. Location of the active DBS electrode used at final follow-up visit was not predictive of clinical outcome.

CONCLUSION:

Our findings highlight the sustained benefit from DBS and the importance of early referral for DBS in children with medically refractory DYT1 primary torsion dystonia, which can lead to improved long-term benefits.

Deep brain stimulation: Subthalamic nucleus electrophysiological activity in awake and anesthetized patients

OBJECTIVE

The purpose of this study was to evaluate changes in subthalamic nucleus (STN) neuronal activity in Parkinson's disease (PD) patients during deep brain stimulation (DBS) surgery under general anesthesia, and to compare these data with those recorded in the same subjects during previous surgery under local anesthesia.

METHODS

Five patients with advanced PD, who had previously undergone bilateral STN-DBS under local anesthesia, underwent re-implantation under general anesthesia (with an anesthetic protocol based on the intravenous infusion of remifentanyl and ketamine) owing to surgical device complications. The microelectrode recording (MER) data obtained were analyzed by an off-line spike-sorting software. Neurophysiological data (number of spikes detected, mean firing rate, pause index and burst index) obtained under local and general anesthesia were then evaluated and compared by means of statistical analysis.

RESULTS

We found no statistically significant difference between the first and second surgical procedures in any of the neurophysiological parameters analyzed.

CONCLUSIONS

Bilateral STN-DBS for advanced PD with MER guidance is possible and reliable under a ketamine-based anesthetic protocol.

SIGNIFICANCE

General anesthesia can be proposed for those patients who do not accept an "awake surgery" for clinical reasons, such as excessive fear, poor cooperation or severe "off"-medication effects.

An evaluation of hardware and surgical complications with deep brain stimulation based on diagnosis and lead location

INTRODUCTION

Deep brain stimulation is the most frequently performed neurosurgical procedure for movement disorders. This procedure is well tolerated, but not free of complications. Analysis of hardware complications based on patient diagnosis and lead location could prove valuable in recognizing potential pitfalls and patients at higher risk.

METHODS

This review analyzes the most common surgery-related complications that may occur based on diagnosis and lead location. Patients were categorized based on diagnosis - Parkinson's disease (PD), dystonia, and essential tremor (ET) - as well as by lead location - subthalamic nucleus (STN), globus pallidus interna (GPi), and ventral intermediate nucleus of the thalamus (Vim). It is a retrospective review of 326 patients undergoing 949 procedures over a 10-year period by one surgeon. Fisher's exact test and χ(2) test were employed and multivariate logistic regression analysis was performed to identify the significant variables of correlation.

RESULTS

Overall lead revision was observed at 5.7%, but was observed at 11.9% of GPi lead placements, and 10.7% of dystonia patients with only 4.6% of STN lead placements. Total extension revision was at 2.5%, but observed at 5.3% for dystonia patients and at only 1.4% for ET patients. Overall infection rate was at 1.9% with the highest rate observed in dystonia and ET patients. Postoperative complications with hardware, erosion, infection, and delayed stimulation failure were observed more often with ET and dystonia than with PD. This difference was statistically significant between dystonia and PD (p < 0.03) but not between the other disease entities (p > 0.05). On multivariate analysis, age and gender had no correlation with these complications. PD had significantly fewer complications on forward selection regression analysis (p = 0.004). Asymptomatic intracerebral hemorrhage was at 2.5% with the majority in Vim and none observed in GPi placements. There was only one symptomatic hemorrhage with a permanent deficit. Infarcts were observed at 0.8%. There were no mortalities.

CONCLUSION

This large series of patients and long-term follow-up demonstrate that risks of complications are not universal among movement disorder patients. Diagnosis and lead location are important risk stratification factors in determining complications.

Efficacy of zolpidem for dystonia: a study among different subtypes

Although there are some newly developed options to treat dystonia, its medical treatment is not always satisfactory. Zolpidem, an imidazopyridine agonist with a high affinity on benzodiazepine subtype receptor BZ1 (ω1), was found to improve clinical symptoms of dystonia in a limited number of case reports. To investigate what subtype of dystonia is responsive to the therapy, we conducted an open label study to assess the efficacy of zolpidem (5–20 mg) in 34 patients suffering from miscellaneous types of dystonia using the Burke–Fahn–Marsden Dystonia Rating Scale (BFMDRS). Patients were entered into the study if they had been refractory to other medications as evaluated by BFMDRS (no change in the previous two successive visits). After zolpidem therapy, the scores in the patients as a whole were decreased from 7.2 ± 7.9 to 5.5 ± 5.0 (P = 0.042). Patients with generalized dystonia, Meige syndrome/blepharospasm, and hand dystonia improved in the scale by 27.8, 17.8, and 31.0%, respectively, whereas no improvement was found in cervical dystonia patients. Overall response rate among patients were comparable to that of trihexyphenidyl. Zolpidem may be a therapeutic option for generalized dystonia, Meige syndrome, and hand dystonia including musician’s. Drowsiness was the dose-limiting factor.

Meige syndrome relieved by bilateral pallidal stimulation with cycling mode: case report

BACKGROUND AND IMPORTANCE

Deep brain stimulation (DBS) of the bilateral globus pallidus internus (GPi) has been used effectively to treat dystonia. We report a patient with severe Meige syndrome who received bilateral GPi DBS with good improvement in symptoms during the first 24-month stimulation therapy. To decrease energy consumption and to prolong battery life, the stimulation parameters of the replaced programmable pulse generator were adjusted to the cyclic mode and the stimulator was turned off during nighttime sleep. The patient achieved similar good treatment effect with extended battery life in the following years.

CLINICAL PRESENTATION

A 66-year-old woman with a 3-year history of severe cranial-cervical dystonia received stereotaxic surgery for bilateral GPi DBS therapy. The Burke-Fahn-Marsden dystonia score improved from 32 to 7.5. The effect lasted up to 24 months after therapy when the battery ran out of life. After careful evaluation, we adjusted the stimulation parameters of the second implantable pulse generator to the cyclic stimulation mode and programmed the stimulator to turn off automatically during nighttime sleep. The patient showed persistent good effect 36 months after starting use of the second implantable pulse generator.

CONCLUSION

To treat dystonic symptoms effectively, stimulation parameters with higher energy consumption are usually required. For reducing the discomfort of repeated battery replacement within a short time and decreasing energy consumption in implantable pulse generator, cyclic mode stimulation could be considered in dystonic patients receiving bilateral GPi DBS.

Deep brain stimulation in children: experience and technical pearls

OBJECT

Deep brain stimulation (DBS) is an established technique for the treatment of several movement disorders in adults. However, the technical approach, complications, and results of DBS in children have not been well documented.

METHODS

A database of DBS implantations performed at a single institution, prospectively established in 1998, was reviewed for patients who received DBS prior to the age of 18. Diagnoses, surgical technique, and complications were noted. Outcomes were assessed using standard rating scales of neurological function.

RESULTS

Of 815 patients undergoing DBS implantation over a 12-year period, 31 were children (mean age at surgery 13.2 years old, range 4-17 years old). Diagnoses included the following: DYT1 primary dystonia (autosomal dominant, Tor1AΔGAG mutation, 10 cases), non-DYT1 primary dystonia (3 cases), secondary dystonia (11 cases), neurodegeneration with brain iron accumulation (NBIA, 3 cases), levodopa-responsive parkinsonism (2 cases), Lesch-Nyhan disease (1 case), and glutaric aciduria Type 1 (1 case). Six children ages 15-17 years old underwent awake microelectrode-guided surgery. For 25 children operated under general anesthesia, the surgical technique evolved from microelectrode-guided surgery to image-guided surgeries using real-time intraoperative MR imaging or CT for lead location confirmation. Complications included 5 hardware infections, all in children younger than 10 years old. At 1 year after implantation, patients with DYT1 dystonia had a mean improvement in the Burke-Fahn-Marsden Dystonia Rating Scale movement subscore of 75%, while those with secondary dystonia had only small improvements. Outcomes in the 3 children with NBIA were disappointing.

CONCLUSIONS

Results of DBS in children with primary and secondary dystonias were similar to those in adults, with excellent results for DYT1 dystonia in children without fixed orthopedic deformity and much more modest results in secondary dystonia. In contrast to reported experience in adults with NBIA, these results in children with NBIA were poor. Infection risk was highest in the youngest patients.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Stereotactic biopsy with electrical monitoring for deep-seated brain tumors

OBJECTIVE

The stereotactic biopsy is widely integrated into clinical practice as an efficient and safe procedure for histologic diagnoses. However, the surgical risk increases when the lesions are close to the eloquence of the adjacent brain. The present report describes two patients with deep-seated brain tumors who underwent a stereotactic biopsy with electrical monitoring and demonstrates the importance of this technique.

METHODS

The tentative target and trajectory were determined on a stereotactic map from the Schaltenbrand and Wahren atlas. A Cosman-Roberts-Wells stereotactic frame was applied to the patient. Electrical recording along a single trajectory was used to identify the circumscribed neuronal structures, and electrical simulation was administered to the target. The biopsy point was decided when no adverse events were observed with a low electric current level.

RESULTS

A 34-year-old male patient with anaplastic astrocytoma in the putamen and thalamus and an 81-year-old female patient with malignant lymphoma in the midbrain underwent stereotactic biopsies with electrical monitoring. The biopsies were successfully performed without any resulting neurologic deficits.

CONCLUSIONS

This report describes two patients with deep-seated brain tumors who underwent stereotactic biopsies with electrical recording and stimulation. The electrical monitoring appears to be a useful technique to complement the ordinary image-guided biopsy.

Moving forward: advances in the treatment of movement disorders with deep brain stimulation

The modern era of stereotactic and functional neurosurgery has ushered in state of the art technologies for the treatment of movement disorders, particularly Parkinson's disease (PD), tremor, and dystonia. After years of experience with various surgical therapies, the eventual shortcomings of both medical and surgical treatments, and several serendipitous discoveries, deep brain stimulation (DBS) has risen to the forefront as a highly effective, safe, and reversible treatment for these conditions. Idiopathic advanced PD can be treated with thalamic, globus pallidus internus (GPi), or subthalamic nucleus (STN) DBS. Thalamic DBS primarily relieves tremor while GPi and STN DBS alleviate a wide range of Parkinsonian symptoms. Thalamic DBS is also used in the treatment of other types of tremor, particularly essential tremor, with excellent results. Both primary and various types of secondary dystonia can be treated very effectively with GPi DBS. The variety of anatomical targets for these movement disorders is indicative of the network-level dysfunction mediating these movement disturbances. Despite an increasing understanding of the clinical benefits of DBS, little is known about how DBS can create such wide sweeping neuromodulatory effects. The key to improving this therapeutic modality and discovering new ways to treat these and other neurologic conditions lies in better understanding the intricacies of DBS. Here we review the history and pertinent clinical data for DBS treatment of PD, tremor, and dystonia. While multiple regions of the brain have been targeted for DBS in the treatment of these movement disorders, this review article focuses on those that are most commonly used in current clinical practice. Our search criteria for PubMed included combinations of the following terms: DBS, neuromodulation, movement disorders, PD, tremor, dystonia, and history. Dates were not restricted.

Combined therapy of orthopedic surgery after deep brain stimulation in cerebral palsy mixed type - a case report -

Dystonia is a symptom defined by involuntary and irregular contractions of the muscles, which cause movement disorders and postural problems. Deep brain stimulation (DBS) in globus pallidus interna (GPi) is a good option for controlling dystonia. DBS has already been shown to have significant effects on primary dystonia as well as Parkinson's disease. Dystonia is very difficult to manage, as seen in cerebral palsy (CP) mixed with spasticity. As CP patients grow, their musculoskeletal problems may require orthopedic surgery. However, the outcome of orthopedic surgery is not usually suitable due to dystonia. Therefore, we attempted to control dystonia through DBS initially and perform orthopedic surgery to correct musculoskeletal deformities after treatment of dystonia. Herein, we report a case that showed remarkable improvement in terms of the dystonia rating scale and gait pattern after combined therapy of DBS and orthopedic surgery.

Stereotactic techniques and perioperative management of DBS in dystonia

This article reviews the available literature related to the surgical technique for implantation of deep brain stimulation (DBS) hardware for the treatment of dystonia. Topics covered include stereotactic targeting, selection of specific hardware components, site of placement of the cable connectors and pulse generators, and postoperative documentation of electrode location. Techniques in stereotactic neurosurgery are rapidly evolving, and there is no Class I evidence to unequivocally validate any specific technique described. Nevertheless, the guidelines provided may assist surgical teams in tailoring a rational approach to DBS implantation in dystonia.

Early postoperative management of DBS in dystonia: programming, response to stimulation, adverse events, medication changes, evaluations, and troubleshooting

Early postoperative management in deep brain stimulation-treated patients with dystonia differs from that of patients with essential tremor and Parkinson's disease, mainly due to the usually delayed effects of deep brain stimulation and the heterogenous clinical manifestation and etiologies of dystonia. The present chapter summarizes the available data about and concentrates on practical clinical aspects of early postoperative management in deep brain stimulation-treated patients with dystonia.

Intraoperative neurophysiology in DBS for dystonia

Deep brain stimulation (DBS) of the internal segment of the globus pallidus (GPi) has been demonstrated to be an effective therapy for the treatment of primary dystonia as well as tardive dystonia. Results for other forms of secondary dystonia have been less consistent. Although a number of target sites have been explored for the treatment of dystonia, most notably the motor thalamus, the target of choice remains the sensorimotor portion of the GPi. Although the optimal site within the GPi has not been determined, most centers agree that the optimal site involves the posteroventral lateral "sensorimotor" portion of the GPi. Microelectrode recording (MER) can be used to identify boundaries of the GPi and nearby white matter tracts, including the corticospinal tract and optic tract, and the sensorimotor GPi. However, whether or not the use of MER leads to improved outcomes compared with procedures performed without MER has not been determined. Currently, there is no evidence to support or refute the hypothesis that mapping structures with MER provides better short- or long-term outcomes. Centers using MER do not report a preference of one system over another, but there have not been any studies to compare the relative benefits or risks of using more than 1 electrode simultaneously. Comparison studies of different target structures and targeting techniques in dystonia have not been performed. Additional research, which includes comparative studies, is needed to advance our understanding and optimization of DBS targets, techniques, and approaches along with their relative benefits and risks in dystonia.

Long-Term management of DBS in dystonia: response to stimulation, adverse events, battery changes, and special considerations

Multiple independent case series have documented sustained benefit of bilateral pallidal deep brain stimulation (DBS) up to 3 years in patients with primary dystonia. Growing evidence exists for positive outcomes extending up to 10 years. The beneficial effects from DBS are usually reported to be stable, thus requiring little long-term modifications of the parameters of stimulation. Speech and swallowing abnormalities are less responsive than other dystonic symptoms. Symptom exacerbation after initial benefit has been reported in a few cases. It is not known whether this is related to potential tolerance or habituation to stimulation or to progression of the underlying disease. Failures of pallidal DBS, at least in primary dystonia patients, should not be accepted without further re-evaluation of each individual case, including possible revisions of the electrode location. Both hardware- and stimulation-related adverse effects, including insufficient relief of speech function, have been reported in the long-term. Despite early reports suggesting that hardware problems might be more frequent in dystonia, more recent studies did not confirm these observations. In patients with severe segmental (e.g., axial) or generalized dystonia, sudden cessation of stimulation may become a medical emergency and should be anticipated changing the neurostimulator before its natural end of life.

Transcranial sonographic localization of deep brain stimulation electrodes is safe, reliable and predicts clinical outcome

In patients with deep brain stimulation (DBS), poor postoperative outcome or unexpected clinical change require brain imaging to check the lead location. Here, we studied safety, reliability and prognostic value of transcranial sonography (TCS) for DBS lead localization applying predefined TCS criteria. After measuring thermal effects of TCS and imaging artefact sizes of DBS lead using a skull phantom, we prospectively enrolled 34 patients with DBS of globus pallidus internus, ventro-intermediate thalamic or subthalamic nucleus. TCS had no influence on lead temperature, electrical parameters of DBS device or clinical state of patients. TCS measures of lead coordinates agreed with MRI measures in anterior-posterior and medial-lateral axis. Lead dislocation requiring reinsertion was reliably detected. Only patients with optimal lead position on TCS had favorable clinical 12-month outcome (>50% improvement), whereas unfavorable outcome (<25% improvement) was associated with suboptimal lead position. TCS may therefore become a first-choice modality to monitor lead location.

Automatic computation of electrode trajectories for Deep Brain Stimulation: a hybrid symbolic and numerical approach

PURPOSE

The optimal electrode trajectory is needed to assist surgeons in planning Deep Brain Stimulation (DBS). A method for image-based trajectory planning was developed and tested.

METHODS

Rules governing the DBS surgical procedure were defined with geometric constraints. A formal geometric solver using multimodal brain images and a template built from 15 brain MRI scans were used to identify a space of possible solutions and select the optimal one. For validation, a retrospective study of 30 DBS electrode implantations from 18 patients was performed. A trajectory was computed in each case and compared with the trajectories of the electrodes that were actually implanted.

RESULTS

Computed trajectories had an average difference of 6.45° compared with reference trajectories and achieved a better overall score based on satisfaction of geometric constraints. Trajectories were computed in 2 min for each case.

CONCLUSION

A rule-based solver using pre-operative MR brain images can automatically compute relevant and accurate patient-specific DBS electrode trajectories.

Intraoperative computed tomography for deep brain stimulation surgery: technique and accuracy assessment

BACKGROUND

The efficacy of deep brain stimulation (DBS) is highly dependent on the accuracy of lead placement.

OBJECTIVE

To describe the use of intraoperative computed tomography (iCT) to confirm lead location before surgical closure and to study the accuracy of this technique.

METHODS

Fifteen patients underwent awake microelectrode-guided DBS surgery in a stereotactic frame. A portable iCT scanner (Medtronic O-arm) was positioned around the patient's head throughout the procedure and was used to confirm lead location before fixation of the lead to the skull. Images were computationally fused with preoperative magnetic resonance imaging (MRI), and lead tip coordinates with respect to the midpoint of the anterior commissure-posterior commissure line were measured. Tip coordinates were compared with those obtained from postoperative MRI.

RESULTS

iCT was integrated into standard frame-based microelectrode-guided DBS surgery with a minimal increase in surgical time or complexity. Technically adequate 2-dimensional and 3-dimensional images were obtained in all cases. Head positioning and fixation techniques that allow unobstructed imaging are described. Lead tip measurements on iCT fused with preoperative MRI were statistically indistinguishable from those obtained with postoperative MRI.

CONCLUSION

iCT can be easily incorporated into standard DBS surgery, replaces the need for C-arm fluoroscopy, and provides accurate intraoperative 3-dimensional confirmation of electrode tip locations relative to preoperative images and surgical plans. iCT fused to preoperative MRI may obviate the need for routine postoperative MRI in DBS surgery. Technical nuances that must be mastered for the efficient use of iCT during DBS implantation are described.

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.

Cortically evoked responses of human pallidal neurons recorded during stereotactic neurosurgery

Responses of neurons in the globus pallidus (GP) to cortical stimulation were recorded for the first time in humans. We performed microelectrode recordings of GP neurons in 10 Parkinson's disease (PD) patients and 1 cervical dystonia (CD) patient during surgeries to implant bilateral deep brain stimulation electrodes in the GP. To identify the motor territories in the external (GPe) and internal (GPi) segments of the GP, unitary responses evoked by stimulation of the primary motor cortex were observed by constructing peristimulus time histograms. Neurons in the motor territories of the GPe and GPi responded to cortical stimulation. Response patterns observed in the PD patients were combinations of an early excitation, an inhibition, and a late excitation. In addition, in the CD patient, a long-lasting inhibition was prominent, suggesting increased activity along the cortico-striato-GPe/GPi pathways. The firing rates of GPe and GPi neurons in the CD patient were lower than those in the PD patients. Many GPe and GPi neurons of the PD and CD patients showed burst or oscillatory burst activity. Effective cathodal contacts tended to be located close to the responding neurons. Such unitary responses induced by cortical stimulation may be of use to target motor territories of the GP for stereotactic functional neurosurgery. Future findings utilizing this method may give us new insights into understanding the pathophysiology of movement disorders.

Diffusion tensor imaging (DTI) and colored fractional anisotropy (FA) mapping of the subthalamic nucleus (STN) and the globus pallidus interna (GPi)

Introduction

The subthalamic nucleus (STN) and the globus pallidus internus (GPi) are the most common surgical targets for the treatment of Parkinson’s disease. We studied directionally colored fractional anisotropy (FA) and diffusion tensor imaging (DTI) sequences to better target these anatomical regions.

Methods

Four patients undergoing stereotactic surgery for movement disorders were studied. Stereotactic targets and fiber tractography were determined on MRIs using the Schaltenbrand–Wahren atlas for definition in the iPlan software. In addition, post-operative imaging was fused to preoperative FA sequences for end-result identification. Axial, sagittal, and coronal images of the FA sequence were studied. DTI parameters used ranged from 2 to 4 mm for voxel size in the x/y/z planes, fiber length was kept constant at 15 mm and FA threshold of 0.25.

Results

Colored FA maps resulted in a key signature in and around the STN and GPi. Regions identified include, but were not limited to: the internal capsule, nigral projections, the thalamic fasciculus, Forel’s fields H1 and H2, zona incerta, suthalamic fasciculus, tegmental tracts, and cerebello-rubro-thalamic tract.

Conclusions

Colored FA maps allow a potential method to identify the STN and GPi accurately. DTI has proven to be a powerful tool that can be used to augment identification of the STN nucleus and GPi used for stereotactic surgery.

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.

Bilateral deep brain stimulation for treatment of medically refractory paroxysmal nonkinesigenic dyskinesia

The authors present the case of a 26-year-old man with a 10-15-year history of worsening bilateral dystonia and baseline chorea occurring up to 20 times per day that was exacerbated by stress and anxiety and was refractory to medical management. Paroxysmal nonkinesigenic dyskinesia was diagnosed, which is a rare, hyperkinetic movement disorder that is episodic and does not respond to nonbenzodiazepine antiepileptics. The patient was significantly debilitated by his disease, lived in a group home, and suffered from frequent falls, necessitating the wearing of a protective helmet and face mask at all times. The patient underwent implantation of bilateral deep brain stimulation quadripolar electrodes in the globus pallidus internus with the aid of image-guided stereotactic neurosurgery and microelectrode recording without complication. At his 1-month postoperative follow-up, the patient reported a subjective 90% improvement in his symptoms; the only notable side effect was a slight increased slurring in his baseline dysarthria. Objective reporting and recording forms maintained by the patient's caretakers over the following 18 months suggested a significant and sustained improvement in his overall balance, ambulation, and gross motor function with a substantial decrease in the incidence of reported falls. The authors conclude that pallidal deep brain stimulation may be successfully applied to patients suffering from refractory paroxysmal nonkinesigenic dyskinesia with promising results. This treatment strategy deserves further prospective investigation, clinical consideration, and refinement.

Dystonia: a surgeon's perspective

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

Bilateral 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.

Deep brain stimulation of the subcallosal cingulate gyrus for depression: anatomical location of active contacts in clinical responders and a suggested guideline for targeting

OBJECT

Deep brain stimulation (DBS) of the subcallosal cingulate gyrus (SCG), including Brodmann area 25, is currently being investigated for the treatment of major depressive disorder (MDD). As a potential emerging therapy, optimal target selection within the SCG has still to be determined. The authors compared the location of the electrode contacts in responders and nonresponders to DBS of the SCG and correlated the results with clinical outcome to help in identifying the optimal target within the region. Based on the location of the active contacts used for long-term stimulation in responders, the authors suggest a standardized method of targeting the SCG in patients with MDD.

METHODS

Postoperative MR imaging studies of 20 patients with MDD treated with DBS of the SCG were analyzed. The authors assessed the location of the active contacts relative to the midcommissural point and in relation to anatomical landmarks within the medial aspect of the frontal lobe. For this, a grid with 2 main lines was designed, with 1 line in the anterior-posterior and 1 line in the dorsal-ventral axis. Each of these lines was divided into 100 units, and data were converted into percentages. The anterior-posterior line extended from the anterior commissure (AC) to the projection of the anterior aspect of the corpus callosum (CCa). The dorsal-ventral line extended from the inferior portion of the CC (CCi) to the most ventral aspect of the frontal lobe (abbreviated "Fr" for the formula).

RESULTS

Because the surgical technique did not vary across patients, differences in stereotactic coordinates between responders and nonresponders did not exceed 1.5 mm in any axis (x, y, or z). In patients who responded to the procedure, contacts used for long-term stimulation were in close approximation within the SCG. In the anterior-posterior line, these contacts were located within a 73.2 +/- 7.7 percentile distance from the AC (with the AC center being 0% and the line crossing the CCa being 100%). In the dorsal-ventral line, active contacts in responders were located within a 26.2 +/- 13.8 percentile distance from the CCi (with the CCi edge being 0% and the Fr inferior limit being 100%). In the medial-lateral plane, most electrode tips were in the transition between the gray and white matter of SCG.

CONCLUSIONS

Active contacts in patients who responded to DBS were relatively clustered within the SCG. Because of the anatomical variability in the size and shape of the SCG, the authors developed a method to standardize the targeting of this region.

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.

Deep brain stimulation of the internal globus pallidus in dystonia: target localisation under general anaesthesia

Deep brain stimulation (DBS) of the internal globus pallidus (Gpi) is an effective therapy for various types of dystonia. The authors describe their technical approach for securing appropriate placement of the stimulating electrodes within the Gpi under general anaesthesia, including MRI based individualised anatomical targeting combined with electrophysiological mapping of the Gpi using micro-recording (MER) as well as macrostimulation and report the subsequent clinical outcome and complications using this method.

METHOD

We studied 42 patients (male-female ratio 25:17; mean age 43.6 years, range 9 to 74 years) consecutively operated at the Department of Neurosurgery, University Hospital Schleswig-Holstein, Campus Kiel, between 2001 - 2006. One patient underwent unilateral implantation after a right-sided pallidotomy 30 years before and strictly unilateral symptoms; all other implantations were bilateral. Two patients had repeat surgery after temporary removal of uni- or bilateral implants secondary to infection. Overall, 86 DBS electrodes were implanted. In 97% of the implantations, at least three microelectrodes were inserted simultaneously for MER and test stimulation. Initial anatomical targeting was based on stereotactic atlas coordinates and individual adaptation by direct visualisation of the Gpi on the stereotactic T2 or inversion-recovery MR images. The permanent electrode was placed according to the results of MER and test stimulations for adverse effects.

FINDINGS

The average improvement from baseline in clinical ratings using either the Burke-Fahn-Marsden-Dystonia (BFMDRS) or Toronto-Western-Spasmodic-Torticollis (TWSTR) rating scale at the last post-operative follow-up (mean 16.4 ; range 3-48 months) was 64.72% (range 20.39 to 98.52%). The post-operative MRI showed asymptomatic infarctions of the corpus caudatus in three patients and asymptomatic small haemorrhages in the lateral basal ganglia in two patients. One patient died due to a recurrent haemorrhage which occurred three months after the operation. The electrodes were implanted as follows: central trajectory in 64%, medial trajectory in 20%, anterior in 9% and lateral dorsal trajectories in 3.5% each. The reduction in BFMDRS or TWSTR motor score did not differ between the group implanted in the anatomically defined (central) trajectory bilateral (-64.15%, SD 23.8) and the physiologically adopted target (uni- or bilateral) (-63.39%, SD 23.1) indicating that in both groups equally effective positions were chosen within Gpi for chronic stimulation (t-test, p > 0.4).

CONCLUSIONS

The described technique using stereotactic MRI for planning of the trajectory and direct visualisation of the target, intra-operative MER for delineating the boundaries of the target and macrostimulation for probing the distance to the internal capsule by identifying the threshold for stimulation induced tetanic contractions is effective in DBS electrode implantation in patients with dystonia operated under general anaesthesia. The central trajectory was chosen in only 64%, despite individual adaptation of the target due to direct visualisation of the Gpi in inversion recovery MRI in 43% of the patients, demonstrating the necessity of combining anatomical with neurophysiological information.

Bilateral pallidal deep brain stimulation for the treatment of patients with dystonia-choreoathetosis cerebral palsy: a prospective pilot study

BACKGROUND

Cerebral palsy (CP) with dystonia-choreoathetosis is a common cause of disability in children and in adults, and responds poorly to medical treatment. Bilateral pallidal deep brain stimulation (BP-DBS) of the globus pallidus internus (GPi) is an effective treatment for primary dystonia, but the effect of this reversible surgical procedure on dystonia-choreoathetosis CP, which is a subtype of secondary dystonia, is unknown. Our aim was to test the effectiveness of BP-DBS in adults with dystonia-choreoathetosis CP.

METHODS

We did a multicentre prospective pilot study of BP-DBS in 13 adults with dystonia-choreoathetosis CP who had no cognitive impairment, little spasticity, and only slight abnormalities of the basal ganglia on MRI. The primary endpoint was change in the severity of dystonia-choreoathetosis after 1 year of neurostimulation, as assessed with the Burke-Fahn-Marsden dystonia rating scale. The accuracy of surgical targeting to the GPi was assessed masked to the results of neurostimulation. Analysis was by intention to treat.

FINDINGS

The mean Burke-Fahn-Marsden dystonia rating scale movement score improved from 44.2 (SD 21.1) before surgery to 34.7 (21.9) at 1 year post-operatively (p=0.009; mean improvement 24.4 [21.1]%, 95% CI 11.6-37.1). Functional disability, pain, and mental health-related quality of life were significantly improved. There was no worsening of cognition or mood. Adverse events were related to stimulation (arrest of the stimulator in one patient, and an adjustment to the current intensity in four patients). The optimum therapeutic target was the posterolateroventral region of the GPi. Little improvement was seen when the neurostimulation diffused to adjacent structures (mainly to the globus pallidus externus [GPe]).

INTERPRETATION

Bilateral pallidal neurostimulation could be an effective treatment option for patients with dystonia-choreoathetosis CP. However, given the heterogeneity of motor outcomes and the small sample size, results should be interpreted with caution. The optimum placement of the leads seemed to be a crucial, but not exclusive, factor that could affect a good outcome.

FUNDING

National PHRC; Cerebral Palsy Foundation: Fondation Motrice/APETREIMC; French INSERM Dystonia National Network; Medtronic.

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.

Single unit "pauser" characteristics of the globus pallidus pars externa distinguish primary dystonia from secondary dystonia and Parkinson's disease

The presence of high frequency discharge neurons with long periods of silence or "pauses" in the globus pallidus pars externa (GPe) is a unique identifying feature of this nucleus. Prior studies have demonstrated that pause characteristics reflect synaptic inputs into GPe. We hypothesized that GPe pause characteristics should distinguish movement disorders whose basal ganglia network abnormalities are different. We examined pause characteristics in 224 GPe units in patients with primary generalized dystonia, Parkinson's disease (PD), and secondary dystonia, undergoing single unit microelectrode recording for DBS placement in the awake state. Pauses in neuronal discharge were identified using the Poisson surprise method. Mean pause length in primary dystonia (606.8373.3) was higher than in PD (557.4366.6) (p<0.05). Interpause interval (IPI) was lower in primary dystonia (2331.63874.1) than PD (3646.45894.5) (p<0.01), and mean pause frequency was higher in primary dystonia (0.140.10) than PD (0.070.12) (p<0.01). Comparison of pause characteristics in primary versus secondary generalized dystonia revealed a significantly longer mean pause length in primary (606.8373.3) than in secondary dystonia (495.6236.5) (p<0.01). IPI was shorter in primary (2331.6+/-3874.1) than in secondary dystonia (3484.5+/-3981.6) (p<0.01). The results show that pause characteristics recorded in the awake human GPe distinguish primary dystonia from Parkinson's disease and secondary dystonia. The differences may reflect increased phasic input from striatal D2 receptor positive cells in primary dystonia, and are consistent with a recent model proposing that GPe provides capacity scaling for cortical input.