Magnetic resonance imaging stereotactic target localization for deep brain stimulation in dystonic children

Intraoperative DBS targeting of the globus pallidus internus by using motor evoked potentials

OBJECTIVES

Target localization for deep brain stimulation (DBS) is a crucial step that influences the clinical benefit of the DBS procedure together with the reduction of side effects. In this work, we address the feasibility of DBS target localization in the globus pallidus internus (GPi) aided by intraoperative motor evoked potentials (MEP) with emphasis on the reduction of capsular side effects.

MATERIAL AND METHODS

Micro-macroelectrode recordings were performed intraoperatively on 20 patients that underwent DBS treatment of the GPi (GPi-DBS). MEP were elicited intraoperatively by microelectrode stimulation during stereotactic DBS surgery. We studied the relationship between MEP thresholds and the internal capsule (IC) proximity.

RESULTS

We found a significant correlation between intraoperative MEP thresholds and IC proximity.

CONCLUSIONS

We provide further evidence of the role of MEPs for DBS target localization in the GPi, which extends and confirms the usefulness of MEPs as previously reported by DBS target localization studies dealing with the subthalamic and thalamic nuclei. Our approach is advantageous in that it provides criteria to determine the DBS target without the need to rely on a patient's response while avoiding capsular effects.

Microendoscopic transventricular deep brain stimulation of the anterior nucleus of the thalamus as a safe treatment in intractable epilepsy: A feasibility study

INTRODUCTION

Deep brain stimulation (DBS) of the anterior nucleus of the thalamus (ANT) is proposed in patients with severe intractable epilepsy. When used, the transventricular approach increases the risk of bleeding due the anatomy around the entry point in the thalamus. To avoid such a complication, we used a transventricular microendoscopic technique.

METHODS

We performed a retrospective study of nine adult patients who were surgically treated for refractory epilepsy between 2010 and 2019 by DBS of the anterior thalamic nucleus.

RESULTS

Endoscopy provides a direct visual control of the entry point of the lead in the thalamus through the ventricle by avoiding ependymal vessels. No hemorrhage was recorded and accuracy was systematically checked by intraoperative stereotactic MRI. We reported a responder rate improvement in 88.9% of patients at 1 year and in 87.5% at 2 years. We showed a significant decrease in global seizure count per month one year after DBS (68.1%; P=0.013) leading to an overall improvement in quality of life. No major adverse effect was recorded during the follow-up. ANT DBS showed a prominent significant effect with a decrease of the number of generalized seizures.

CONCLUSION

We aimed at a better ANT/lead collimation using a vertical transventricular approach under microendoscopic monitoring. This technique permitted to demonstrate the safety and the accuracy of the procedure.

Deep Brain Stimulation and Hypoxemic Perinatal Encephalopathy: State of Art and Perspectives

Cerebral palsy (CP) is a heterogeneous group of non-progressive syndromes with lots of clinical variations due to the extent of brain damages and etiologies. CP is majorly defined by dystonia and spasticity. The treatment of acquired dystonia in CP is very difficult. Many pharmacological treatments have been tried and surgical treatment consists of deep brain stimulation (continuous electrical neuromodulation) of internal globus pallidus (GPi). A peculiar cause of CP is neonatal encephalopathy due to an anoxic event in the perinatal period. Many studies showed an improvement of dystonia in CP patients with bilateral GPi DBS. However, it remains a variability in the range of 1% to 50%. Published case-series concerned mainly small population with a majority of adult patients. Selection of patients according to the clinical pattern, to the brain lesions observed on classical imaging and to DTI is the key of a high success rate of DBS in children with perinatal hypoxemic encephalopathy. Only a large retrospective study with a high number of patients in a homogeneous pediatric population with a long-term follow-up or a prospective multicenter trial investigation could answer with a high degree of certitude of the real interest of this therapeutic in children with hypoxemic perinatal encephalopathy.

Deep brain stimulation for cerebral palsy: where are we now?

Cerebral palsy (CP) is a complex disorder and children frequently have multiple impairments. Dystonia is a particularly frustrating impairment that interferes with rehabilitation and function and is difficult to treat. Of the available treatments, deep brain stimulation (DBS) has emerged as an option with the potential for large effect size in a subgroup of children. While brain stimulation has been used in CP for more than 40 years, modern devices and targeting methods are improving both the safety and efficacy of the procedure. Successful use of DBS depends on appropriate selection of patients, identification of effective neuroanatomical targets in each patient, careful neurosurgical procedure, and detailed follow-up evaluation and programming. The use of functional neurosurgery for neuromodulation in CP remains a technology in its infancy, but improving experience and knowledge are likely to make this one of the safest and most effective interventions for children with moderate-to-severe motor disorders. This review summarizes the current procedures for patient and target selection, and surgical implantation of DBS electrodes for CP. The history of DBS and future directions when used in secondary dystonia are also examined. WHAT THIS PAPER ADDS: Selection of candidates for deep brain stimulation (DBS) requires understanding of dystonia in cerebral palsy . DBS could become a first-line treatment option in some children.

Intraoperative Localization of the Subthalamic Nucleus Using Long-Latency Somatosensory Evoked Potentials

BACKGROUND

Target localization for deep brain stimulation (DBS) is a challenging step that determines not only the correct placement of stimulation electrodes, but also influences the success of the DBS procedure as reflected in the desired clinical outcome of a patient.

OBJECTIVE

We report on the feasibility of DBS target localization in the subthalamic nucleus (STN) by long-latency somatosensory evoked potentials (LL-SSEPs) (>40 msec) in Parkinson's disease (PD) patients.

METHODS

Micro-macroelectrode recordings were performed intraoperatively on seven PD patients (eight STN hemispheres) who underwent DBS treatment. LL-SSEPs were elicited by ipsi- and contralateral median nerve stimulation to the wrist.

RESULTS

Four distinctive LL-SSEP components were elicited ("LL-complex" consisting of P80, N100, P140, and N200). The P80 appeared as the most visible and reliable intraoperative component. Localization of the "LL-complex" within the target was approved with typical microelectrode firing activity patterns, atlas visualization of recording electrodes, and postoperative CT-based visualization of final DBS electrodes.

CONCLUSIONS

LL-SSEPs represent a promising approach for DBS target localization in the STN, provided deeper understanding on their anesthesia effect is obtained. This approach is advantageous in that it does not require the patient's participation in an intraoperative setting.

A comparative historical and demographic study of the neuromodulation management techniques of deep brain stimulation for dystonia and cochlear implantation for sensorineural deafness in children

Cochlear implants for sensorineural deafness in children is one of the most successful neuromodulation techniques known to relieve early chronic neurodisability, improving activity and participation. In 2012 there were 324,000 recipients of cochlear implants globally.

AIM

To compare cochlear implant (CI) neuromodulation with deep brain stimulation (DBS) for dystonia in childhood and explore relations between age and duration of symptoms at implantation and outcome.

METHODS

Comparison of published annual UK CI figures for 1985-2009 with a retrospective cohort of the first 9 years of DBS for dystonia in children at a single-site Functional Neurosurgery unit from 2006 to 14.

RESULTS

From 2006 to 14, DBS neuromodulation of childhood dystonia increased by a factor of 3.8 to a total of 126 cases over the first 9 years, similar to the growth in cochlear implants which increased by a factor of 4.1 over a similar period in the 1980s rising to 527 children in 2009. The CI saw a dramatic shift in practice from implantation at >5 years of age at the start of the programme towards earlier implantation by the mid-1990s. Best language results were seen for implantation <5 years of age and duration of cochlear neuromodulation >4 years, hence implantation <1 year of age, indicating that severely deaf, pre-lingual children could benefit from cochlear neuromodulation if implanted early. Similar to initial CI use, the majority of children receiving DBS for dystonia in the first 9 years were 5-15 years of age, when the proportion of life lived with dystonia exceeds 90% thus limiting benefits.

CONCLUSION

Early DBS neuromodulation for acquired motor disorders should be explored to maximise the benefits of dystonia reduction in a period of maximal developmental plasticity before the onset of disability. Learning from cochlear implantation, DBS can become an accepted management option in children under the age of 5 years who have a reduced proportion of life lived with dystonia, and not viewed as a last resort reserved for only the most severe cases where benefits may be at their most limited.

Personalized mapping of the deep brain with a white matter attenuated inversion recovery (WAIR) sequence at 1.5-tesla: Experience based on a series of 156 patients

OBJECTIVE

Deep brain mapping has been proposed for direct targeting in stereotactic functional surgery, aiming to personalize electrode implantation according to individual MRI anatomy without atlas or statistical template. We report our clinical experience of direct targeting in a series of 156 patients operated on using a dedicated Inversion Recovery Turbo Spin Echo sequence at 1.5-tesla, called White Matter Attenuated Inversion Recovery (WAIR).

METHODS

After manual contouring of all pertinent structures and 3D planning of trajectories, 312 DBS electrodes were implanted. Detailed anatomy of close neighbouring structures, whether gray nuclei or white matter regions, was identified during each planning procedure. We gathered the experience of these 312 deep brain mappings and elaborated consistent procedures of anatomical MRI mapping for pallidal, subthalamic and ventral thalamic regions. We studied the number of times the central track anatomically optimized was selected for implantation of definitive electrodes.

RESULTS

WAIR sequence provided high-quality images of most common functional targets, successfully used for pure direct stereotactic targeting: the central track corresponding to the optimized primary anatomical trajectory was chosen for implantation of definitive electrodes in 90.38%.

CONCLUSION

WAIR sequence is anatomically reliable, enabling precise deep brain mapping and direct stereotactic targeting under routine clinical conditions.

Interventional MRI-guided deep brain stimulation in pediatric dystonia: first experience with the ClearPoint system

OBJECT

The placement of deep brain stimulation (DBS) leads in adults is traditionally performed using physiological confirmation of lead location in the awake patient. Most children are unable to tolerate awake surgery, which poses a challenge for intraoperative confirmation of lead location. The authors have developed an interventional MRI (iMRI)-guided procedure to allow for real-time anatomical imaging, with the goal of achieving very accurate lead placement in patients who are under general anesthesia.

METHODS

Six pediatric patients with primary dystonia were prospectively enrolled. Patients were candidates for surgery if they had marked disability and medical therapy had been ineffective. Five patients had the DYT1 mutation, and mean age at surgery was 11.0 ± 2.8 years. Patients underwent bilateral globus pallidus internus (GPi, n = 5) or sub-thalamic nucleus (STN, n = 1) DBS. The leads were implanted using a novel skull-mounted aiming device in conjunction with dedicated software (ClearPoint system), used within a 1.5-T diagnostic MRI unit in a radiology suite, without physiological testing. The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was used at baseline, 6 months, and 12 months postoperatively. Further measures included lead placement accuracy, quality of life, adverse events, and stimulation settings.

RESULTS

A single brain penetration was used for placement of all 12 leads. The mean difference (± SD) between the intended target location and the actual lead location, in the axial plane passing through the intended target, was 0.6 ± 0.5 mm, and the mean surgical time (leads only) was 190 ± 26 minutes. The mean percent improvement in the BFMDRS movement scores was 86.1% ± 12.5% at 6 months (n = 6, p = 0.028) and 87.6% ± 19.2% at 12 months (p = 0.028). The mean stimulation settings at 12 months were 3.0 V, 83 μsec, 135 Hz for GPi DBS, and 2.1 V, 60 μsec, 145 Hz for STN DBS). There were no serious adverse events.

CONCLUSIONS

Interventional MRI-guided DBS using the ClearPoint system was extremely accurate, provided real-time confirmation of DBS placement, and could be used in any diagnostic MRI suite. Clinical outcomes for pediatric dystonia are comparable with the best reported results using traditional frame-based stereotaxy. Clinical trial registration no.: NCT00792532 ( ClinicalTrials.gov ).

Deep brain stimulation in children and young adults with secondary dystonia: the Children's Hospital Los Angeles experience

Background

Dystonia is a movement disorder in which involuntary sustained or intermittent muscle contractions cause twisting and repetitive movements, abnormal postures, or both. It can be classified as primary or secondary. There is no cure for dystonia and the goal of treatment is to provide a better quality of life for the patient.

Surgical intervention is considered for patients in whom an adequate trial of medical treatment has failed. Deep brain stimulation (DBS), specifically of the globus pallidus interna (GPi), has been shown to be extremely effective in primary generalized dystonia. There is much less evidence for the use of DBS in patients with secondary dystonia. However, given the large number of patients with secondary dystonia, the significant burden on the patients and their families, and the potential for DBS to improve their functional status and comfort level, it is important to continue to investigate the use of DBS in the realm of secondary dystonia.

Object

The objective of this study is to review a series of cases involving patients with secondary dystonia who have been treated with pallidal DBS.

Methods

A retrospective review of 9 patients with secondary dystonia who received treatment with DBS between February 2011 and February 2013 was performed. Preoperative and postoperative videos were scored using the Barry-Albright Dystonia Scale (BADS) and Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) by a neurologist specializing in movement disorders. In addition, the patients' families completed a subjective questionnaire to assess the perceived benefit of DBS.

Results

The average age at DBS unit implantation was 15.1 years (range 6–20 years). The average time to follow-up for the BADS evaluation from battery implantation was 3.8 months (median 3 months). The average time to follow-up for the subjective benefit evaluation was 10.6 months (median 9.5 months). The mean BADS scores improved by 9% from 26.5 to 24 (p = 0.04), and the mean BFMDRS scores improved by 9.3% (p = 0.055). Of note, even in patients with minimal functional improvement, there seemed to be decreased contractures and spasms leading to improved comfort. There were no complications such as infections or hematoma in this case series. In the subjective benefit evaluation, 3 patients' families reported “good” benefit, 4 reported “minimal” benefit, and 1 reported no benefit.

Conclusions

These early results of GPi stimulation in a series of 9 patients suggest that DBS is useful in the treatment of secondary generalized dystonia in children and young adults. Objective improvements in BADS and BFMDRS scores are demonstrated in some patients with generalized secondary dystonia but not in others. Larger follow-up studies of DBS for secondary dystonia, focusing on patient age, history, etiology, and patterns of dystonia, are needed to learn which patients will respond best to DBS.

Deep brain stimulationfor movement disorders

Movement disorders remain the primary indication for the use of intracranial neurostimulation techniques. This review will discuss the history of this technology as well as the mechanisms of action, current clinical indications, and future prospects for the treatment of movement disorders.

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.

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.

Evolution of brain impedance in dystonic patients treated by GPI electrical stimulation

Deep Brain Stimulation is an effective treatment of generalized dystonia. Optimal stimulation parameters vary between patients. This article investigates the influence of electrical brain impedance and delivered current on the brain response to stimulation. Twenty-four patients were bilaterally stimulated in the globus pallidus internus through two implanted four-contact electrodes. The variation of brain impedance and current measurements was correlated with stimulation parameters, time course, and clinical outcome. When a contact was activated, a statistically significant and reversible decrease of brain impedance was found. Impedance and current values and their variations with time significantly differed between patients. The absolute impedance did not significantly correlate with the final outcome. We conclude that the reversible decrease of impedance reflects an adaptive long-term mechanism, which could be due to a plasticity phenomenon, but has no prognostic value. Impedance and current measurements give new complementary information for parameter adjustment and trouble shooting and should therefore be included in all patients' follow-up.

Staged implantation of multiple electrodes in the internal globus pallidus in the treatment of primary generalized dystonia

Object

Deep brain stimulation (DBS) is used for treating various types of dystonia. Multiple electrodes could be proposed to improve the therapeutic outcome enabling the targeting of specific neuronal populations not reached by the electrical field generated by the initially implanted electrode. The authors address the question of the feasibility and safety of staged multiple lead implantations in the sensorimotor internal globus pallidus (GPi) in primary generalized dystonia (PGD). Criteria for patient selection, surgical technique, target selection, electrical settings management, and clinical outcome are presented.

Methods

Sixteen patients (8 harbored the DYT1 gene mutation) presented with PGD and were enrolled in this study. Patients underwent clinical assessment using the Burke-Fahn-Marsden Dystonia Rating Scale preoperatively and during follow-up with DBS. Prior to the addition of electrodes, the authors confirmed, by turning off stimulation, that the patient was still benefiting from DBS and that DBS settings adjustment did not provide further improvement. The second target was defined according to the position of the first electrode, to the residual volume within the sensorimotor GPi, and according to residual symptoms. The second surgery followed the same protocol as the first and the new electrode were inserted using the same bur hole as the first electrode.

Results

The addition of a new pair of electrodes was followed by significant improvement in the whole population (p = 0.005), as well as in the DYT1-negative subgroup (p = 0.012) but not in the DYT1 subgroup (p = not significant). Nevertheless, some patients did not exhibit significant additional benefit. Seven hardware-related complications occurred during the entire follow-up, 3 prior to it, and 4 after the addition of the second pair of electrodes.

Conclusions

The addition of a second pair of electrodes in the GPi in patients with PGD with suboptimal or decaying benefit following the first surgery seems to be a safe procedure and is not followed by an increase in surgery-related complications. This staged procedure may provide further clinical improvement in patients with PGD in whom DBS effect is initially incomplete or when disease progression occurs over time. The position of the additional electrode within the GPi is determined by the available volume within the posteroventral GPi and by the distribution of the dystonic symptoms that need to be controlled.

Automated segmentation of basal ganglia and deep brain structures in MRI of Parkinson's disease

PURPOSE

Template-based segmentation techniques have been developed to facilitate the accurate targeting of deep brain structures in patients with movement disorders. Three template-based brain MRI segmentation techniques were compared to determine the best strategy for segmenting the deep brain structures of patients with Parkinson's disease.

METHODS

T1-weighted and T2-weighted magnetic resonance (MR) image templates were created by averaging MR images of 57 patients with Parkinson's disease. Twenty-four deep brain structures were manually segmented on the templates. To validate the template-based segmentation, 14 of the 24 deep brain structures from the templates were manually segmented on 10 MR scans of Parkinson's patients as a gold standard. We compared the manual segmentations with three methods of automated segmentation: two registration-based approaches, automatic nonlinear image matching and anatomical labeling (ANIMAL) and symmetric image normalization (SyN), and one patch-label fusion technique. The automated labels were then compared with the manual labels using a Dice-kappa metric and center of gravity. A Friedman test was used to compare the Dice-kappa values and paired t tests for the center of gravity.

RESULTS

The Friedman test showed a significant difference between the three methods for both thalami (p < 0.05) and not for the subthalamic nuclei. Registration with ANIMAL was better than with SyN for the left thalamus and was better than the patch-based method for the right thalamus.

CONCLUSION

Although template-based approaches are the most used techniques to segment basal ganglia by warping onto MR images, we found that the patch-based method provided similar results and was less time-consuming. Patch-based method may be preferable for the subthalamic nucleus segmentation in patients with Parkinson's disease.

Interventional loopless antenna at 7 T

The loopless antenna magnetic resonance imaging detector is comprised of a tuned coaxial cable with an extended central conductor that can be fabricated at submillimeter diameters for interventional use in guidewires, catheters, or needles. Prior work up to 4.7 T suggests a near-quadratic gain in signal-to-noise ratio with field strength and safe operation at 3 T. Here, for the first time, the signal-to-noise ratio performance and radiofrequency safety of the loopless antenna are investigated both theoretically, using the electromagnetic method-of-moments, and experimentally in a standard 7 T human scanner. The results are compared with equivalent 3 T devices. An absolute signal-to-noise ratio gain of 5.7 ± 1.5-fold was realized at 7 T vs. 3 T: more than 20-fold higher than at 1.5 T. The effective field-of-view area also increased approximately 10-fold compared with 3 T. Testing in a saline gel phantom suggested that safe operation is possible with maximum local 1-g average specific absorption rates of <12 W kg(-1) and temperature increases of <1.9°C, normalized to a 4 W kg(-1) radiofrequency field exposure at 7 T. The antenna did not affect the power applied to the scanner's transmit coil. The signal-to-noise ratio gain enabled magnetic resonance imaging microscopy at 40-50 μm resolution in diseased human arterial specimens, offering the potential of high-resolution large-field-of-view or endoscopic magnetic resonance imaging for targeted intervention in focal disease.

Improving targeting in image-guided frame-based deep brain stimulation

BACKGROUND

Deep brain stimulation (DBS) is commonly used in the treatment of movement disorders such as Parkinson disease (PD), dystonia, and other tremors.

OBJECTIVE

To examine systematic errors in image-guided DBS electrode placement and to explore a calibration strategy for stereotactic targeting.

METHODS

Pre- and postoperative stereotactic MR images were analyzed in 165 patients. The perpendicular error between planned target coordinates and electrode trajectory was calculated geometrically for all 312 DBS electrodes implanted. Improvement in motor unified PD rating scale III subscore was calculated for those patients with PD with at least 6 months of follow-up after bilateral subthalamic DBS.

RESULTS

Mean (standard deviation) scalar error of all electrodes was 1.4(0.9) mm with a significant difference between left and right hemispheres. Targeting error was significantly higher for electrodes with coronal approach angle (ARC) ≥10° (P < .001). Mean vector error was X: -0.6, Y: -0.7, and Z: -0.4 mm (medial, posterior, and superior directions, respectively). Targeting error was significantly improved by using a systematic calibration strategy based on ARC and target hemisphere (mean: 0.6 mm, P < .001) for 47 electrodes implanted in 24 patients. Retrospective theoretical calibration for all 312 electrodes would have reduced the mean (standard deviation) scalar error from 1.4(0.9) mm to 0.9(0.5) mm (36% improvement). With calibration, 97% of all electrodes would be within 2 mm of the intended target as opposed to 81% before calibration. There was no significant correlation between the degree of error and clinical outcome from bilateral subthalamic nucleus DBS (R = 0.07).

CONCLUSION

After calibration of a systematic targeting error an MR image-guided stereotactic approach would be expected to deliver 97% of all electrodes to within 2 mm of the intended target point with a single brain pass.

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.

Clinical safety of brain magnetic resonance imaging with implanted deep brain stimulation hardware: large case series and review of the literature

BACKGROUND

Over 75,000 patients have undergone deep brain stimulation (DBS) procedures worldwide. Magnetic resonance imaging (MRI) is an important clinical and research tool in analyzing electrode location, documenting postoperative complications, and investigating novel symptoms in DBS patients. Functional MRI may shed light on the mechanism of action of DBS. MRI safety in DBS patients is therefore an important consideration.

METHODS

We report our experience with MRI in patients with implanted DBS hardware and examine the literature for clinical reports on MRI safety with implanted DBS hardware.

RESULTS

A total of 262 MRI examinations were performed in 223 patients with intracranial DBS hardware, including 45 in patients with an implanted pulse generator. Only 1 temporary adverse event occurred related to patient agitation and movement during immediate postoperative MR imaging. Agitation resolved after a few hours, and an MRI obtained before implanted pulse generator implantation revealed edema around both electrodes. Over 4000 MRI examinations in patients with implanted DBS hardware have been reported in the literature. Only 4 led to adverse events, including 2 hardware failures, 1 temporary and 1 permanent neurological deficit. Adverse neurological events occurred in a unique set of circumstances where appropriate safety protocols were not followed. MRI guidelines provided by DBS hardware manufacturers are inconsistent and vary among devices.

CONCLUSIONS

The importance of MRI in modern medicine places pressure on industry to develop fully MRI-compatible DBS devices. Until then, the literature suggests that, when observing certain precautions, cranial MR images can be obtained with an extremely low risk in patients with implanted DBS hardware.

The role of imaging in the surgical treatment of movement disorders

Functional neurosurgery involves precise surgical targeting of anatomic structures to modulate neurologic function. From its conception, advances in the surgical treatment of movement disorders have been intertwined with developments in medical imaging, culminating in the use of stereotactic magnetic resonance imaging (MRI). Meticulous attention to detail during image acquisition, direct anatomic localization, and planning of the initial surgical trajectory allows the surgeon to reach the desired anatomic and functional target with the initial trajectory in most cases, thus reducing the need for multiple passes through the brain, and the associated risk of hemorrhage and functional deficit. This philosophy is of paramount importance in a procedure that is primarily aimed at improving quality of life. Documentation of electrode contact location by means of stereotactic imaging is essential to audit surgical targeting accuracy and to further the knowledge of structure-to-function relationships within the human brain.

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.

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.

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.

Treatment of dystonia with deep brain stimulation

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

COMPARISON OF TWO TECHNIQUES TO POSTOPERATIVELY LOCALIZE THE ELECTRODE CONTACTS USED FOR SUBTHALAMIC NUCLEUS STIMULATION

OBJECTIVE

Cerebral ventriculography (Vg) and magnetic resonance imaging (MRI) scanning are routine procedures to determine the implanted electrode placement into the subthalamic nucleus (STN) and are used in several centers that provide deep brain stimulation for Parkinson's disease patients. However, because of image distortion, MRI scan accuracy in determining electrode placement is still matter of debate. The objectives of this study were to verify the expected localization of the electrode contacts within the STN and to compare the stereotactic coordinates of these contacts determined intraoperatively by Vg with those calculated postoperatively by MRI scans. To our knowledge, this is the first study attempting to compare the "gold standard" of stereotactic accuracy (Vg) with the anatomic resolution provided by MRI scans.

METHODS

Images from 18 patients with Parkinson's disease who underwent bilateral operation were used in this study. Among the 36 chronically stimulated contacts, 28 contacts (78%) were localized in the dorsolateral part of the STN. The remaining eight contacts (22%) were located more dorsally in the zona incerta, close to the upper border of the STN.

RESULTS

Significant differences were found between Vg and MRI scans regarding the mediolateral x coordinate of the contacts for both left and right electrodes and regarding the right-sided anteroposterior y coordinate. No statistical difference was found for the left-sided y coordinate and the dorsoventral z coordinate for both sides.

CONCLUSION

If we assume that Vg is an imaging gold standard, our results suggest that postoperative MRI scanning may induce a slight image translation compared with Vg. However, MRI scans allowed localization of most of the contacts within the STN.

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

OBJECT

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

METHODS

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

CONCLUSIONS

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

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

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

Compatibility of glass-guided recording microelectrodes in the brain stem of squirrel monkeys with high-resolution 3D MRI

Knowledge of the precise position of recording microelectrodes within the brain of a non-human primate is essential for a reliable exploration of very small anatomic structures. This work demonstrates the compatibility of a newly developed glass-guided microelectrode design and microfeed equipment with high-resolution 3D magnetic resonance imaging (MRI). T1- and T2-weighted images allow for the non-invasive visualization of chronically implanted microelectrodes within the brain stem of squirrel monkeys in vivo. Neural extracellular multi-unit recordings proved the functionality of the microelectrode before and after the use of 3D MRI suggesting the preservation of normal brain tissue at the tip of the electrode. Because histology confirmed the absence of lesions attributable to MRI, the approach offers an interactive monitoring during the course of neuroethological experiments. Consequently, MRI may become an in vivo alternative to common histological post mortem verifications of electrode tracks and hence may avoid the early sacrificing of primates after only a small number of experiments.

Reliability of atlas-derived coordinates in deep brain stimulation

BACKGROUND

In deep brain stimulation the way to define and localize the optimal target for the individual patient is still under debate. The objective of our study was to investigate the reliability of atlas derived data by comparing them with direct targeting on MR images.

METHOD

We investigated 28 STN targets in 14 volunteers. The stereotactic coordinates of the dorso-lateral subthalamic nucleus (STN), were determined in 5 different ways for both STNs of each individual volunteer: 1. directly, on axial T2WI spin echo slices, 2. directly, on coronal T2WI spin echo slices and after fusion of data sets: 3. indirectly, on an axial atlas plate, 4. indirectly, on a coronal atlas plate, 5. indirectly, 12 mm lateral, 3 mm posterior and 3 mm inferior to mid-AC-PC.

FINDINGS

The differences between MRI derived targets on axial vs. coronal slices were not statistically significant. After detection of the atlas derived targets the resulting x-coordinates were found more lateral than after direct detection on both, axial and coronal T2-weighted images (p < 0.001). On axial images y-coordinates were located more anterior (p = 0.240) on atlas derived targets and more posterior when target localizations were compared on coronal slices (p < 0.001). z-Coordinates were more superior after atlas targeting compared to MRI targeting (p < 0.001). Differences up to 6.21 mm occurred.

CONCLUSIONS

Despite the limitations concerning image distortions and slice thickness, direct target planning on MRI, regarding our results, is more reliable than targeting solely based on atlas derived data. Only MRI gives us detailed information about the individual configurations of central structures in every single patient. However, targets, which are not detectable on MRI like the nucleus ventralis intermedius have to be planned using stereotactic atlas information. In these cases intra-operative micro-electrode recording might help to better define the target region.

Pallidal stimulation improves pantothenate kinase-associated neurodegeneration

Pantothenate kinase-associated neurodegeneration (PKAN) causes a progressive generalized dystonia which remains pharmacologically intractable. We performed bilateral internal globus pallidus stimulation in six patients with genetically confirmed PKAN who obtained a major and long-lasting improvement of their painful spasms, dystonia, and functional autonomy. This study shows the benefits of pallidal DBS for the dystonia of PKAN patients.

Deep brain stimulation in myoclonus-dystonia syndrome

Myoclonus-dystonia syndrome (MDS) is an autosomal dominant disorder characterized by bilateral myoclonic jerks. An 8-year-old boy presenting with early onset, medically intractable, MDS due to a mutation in the epsilon-sarcoglycan gene (SGCE) underwent chronic bilateral stimulation of the globus pallidus internus, which eliminates both myoclonus and dystonia. We conclude that deep brain stimulation can be an effective and safe treatment for MDS.

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

Object. Primary generalized dystonia (PGD) is a medically refractory disease of the brain causing twisting or spasmodic movements and abnormal postures. In more than 30% of cases it is associated with the autosomal DYT1 mutation. Continuous electrical stimulation of the globus pallidus internus (GPi) has been used successfully in the treatment of PGD. The aim of this study was to examine the long-term efficacy and safety of deep brain stimulation (DBS) in the treatment of PGD in children and adults with and without the DYT1 mutation.

Methods. Thirty-one patients with PGD were selected for surgery. Electrodes were bilaterally implanted under stereotactic guidance and connected to neurostimulators that were inserted subcutaneously. Efficacy was evaluated by comparing scores on the clinical and functional Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) before and after implantation.

The efficacy of stimulation improved with time. After 2 years, compared with preoperative values, the mean (± standard deviation) clinical and functional BFMDRS scores had improved by 79 ± 19% and 65 ± 33%, respectively. At the 2-year follow-up examination the improvement was comparable in patients with and without the DYT1 mutation in both the functional (p = 0.12) and clinical (p = 0.33) scores. Children displayed greater improvements in the clinical score than adult patients (p = 0.04) at 2 years of follow up. In contrast, there was no significant difference in functional scores between children and adults (p = 0.95).

Conclusions. Electrical stimulation of the GPi is an effective, reversible, and adaptable treatment for PGD and should be considered for conditions refractory to pharmaceutical therapies.

Deep brain stimulation for dystonia confirming a somatotopic organization in the globus pallidus internus

Object. In patients with dystonia, symptoms vary greatly in their extent and severity. The efficacy of pallidal stimulation is now established, but an interindividual variability in the responses to this treatment exists. A retrospective analysis of postoperative magnetic resonance (MR) images demonstrated millimetric variations in the positions of electrode contacts inside the posterolateroventral portion of the globus pallidus internus (GPi). It therefore seemed very likely that there is a somatotopic organization within the GPi. The goal of this study was to examine the positions of specific electrode contacts according to patients' clinical evolution, so that a somatotopic organization within the GPi could be defined.

Methods. This study included 19 patients (17 of whom were right handed) with generalized dystonia who were treated by bilateral stimulation of the GPi. Patients were examined pre- and postoperatively by using the Burke-Fahn-Marsden Dystonia Rating Scale. Dividing the patient's body into three parts—cervicoaxial area, superior limb, and inferior limb—we determined the following: 1) where the dystonic symptoms started; 2) where symptoms predominated at the time of surgery; and 3) where the highest postoperative improvement was observed.

Variations in clinical response were correlated to the positions of the electrode contacts. All activated electrode contacts were in the posterolateroventral portion of the GPi (Laitinen target). A correlation between the contact location measured longitudinally and the part of the body in which the highest improvement was observed (three different areas; p = 0.004) showed that a location more anterior for the inferior limb and one more posterior for the superior limb were delineated for the right side, but not for the left side.

Conclusions. Inside the posterolateroventral subvolume of the GPi on the right side, three statistically different locations of electrode contacts were determined to be primary deep brain stimulation treatment sites for particular body parts in cases of dystonia.

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

Object

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

Methods

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

Conclusions

Physiologically guided implantation of DBS electrodes in patients with dystonia is technically feasible in the awake state in most cases, with low morbidity rates. Spontaneous discharge rates of GPi neurons in dystonia are similar to those of globus pallidus externus neurons, such that the two nuclei must be distinguished by neuronal discharge patterns rather than by rates. Active electrode locations associated with robust improvement (> 50% decrease in BFMDRS score) were located near the intercommissural plane, at a mean distance of 3.7 mm from the pallidocapsular border. Patients with juvenile-onset primary dystonia and those with the tardive form benefited greatly from this procedure, whereas benefits for most secondary dystonias and the adult-onset craniocervical form of this disorder were more modest.

Deep brain stimulation in the treatment of dyskinesia and dystonia

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