A three-dimensional histological atlas of the human basal ganglia. II. Atlas deformation strategy and evaluation in deep brain stimulation for Parkinson disease

Processing of emotional information in the human subthalamic nucleus

BACKGROUND

The subthalamic nucleus (STN) is an efficient target for treating patients with Parkinson's disease as well as patients with obsessive-compulsive disorder (OCD) using high frequency stimulation (HFS). In both Parkinson's disease and OCD patients, STN-HFS can trigger abnormal behaviours, such as hypomania and impulsivity.

METHODS

To investigate if this structure processes emotional information, and whether it depends on motor demands, we recorded subthalamic local field potentials in 16 patients with Parkinson's disease using deep brain stimulation electrodes. Recordings were made with and without dopaminergic treatment while patients performed an emotional categorisation paradigm in which the response varied according to stimulus valence (pleasant, unpleasant and neutral) and to the instruction given (motor, non-motor and passive).

RESULTS

Pleasant, unpleasant and neutral stimuli evoked an event related potential (ERP). Without dopamine medication, ERP amplitudes were significantly larger for unpleasant compared with neutral pictures, whatever the response triggered by the stimuli; and the magnitude of this effect was maximal in the ventral part of the STN. No significant difference in ERP amplitude was observed for pleasant pictures. With dopamine medication, ERP amplitudes were significantly increased for pleasant compared with neutral pictures whatever the response triggered by the stimuli, while ERP amplitudes to unpleasant pictures were not modified.

CONCLUSIONS

These results demonstrate that the ventral part of the STN processes the emotional valence of stimuli independently of the motor context and that dopamine enhances processing of pleasant information. These findings confirm the specific involvement of the STN in emotional processes in human, which may underlie the behavioural changes observed in patients with deep brain stimulation.

High-level gait and balance disorders in the elderly: a midbrain disease?

The pathophysiology of gait and balance disorders in elderly people with ‘higher level gait disorders’ (HLGD) is poorly understood. In this study, we aimed to identify the brain networks involved in this disorder. Standardised clinical scores, biomechanical parameters of gait initiation and brain imaging data, including deep white matter lesions (DWML) and brain voxel-based morphometry analyses, were assessed in 20 HLGD patients in comparison to 20 age-matched controls. In comparison to controls, HLGD patients presented a near-normal preparatory phase of gait initiation, but a severe alteration of both locomotor and postural parameters of first-step execution, which was related to ‘axial’ hypokinetic-rigid signs. HLGD patients showed a significant grey matter reduction in the mesencephalic locomotor region (MLR) and the left primary motor cortex. This midbrain atrophy was related to the severity of clinical and neurophysiologically determined balance deficits. HLGD patients also showed a reduction in speed of gait, related to ‘appendicular’ hypokinetic-rigid signs and frontal-lobe-like cognitive deficits. These last two symptoms were correlated with the severity of DWML, found in 12/20 HLGD patients. In conclusion, these data suggest that the gait and balance deficits in HLGD mainly result from the lesion or dysfunction of the network linking the primary motor cortex and the MLR, brain regions known to be involved in the control of gait and balance, whereas cognitive and ‘appendicular’ hypokinetic-rigid signs mainly result from DWML that could be responsible for a dysfunction of the frontal cortico-basal ganglia loops.

Histology-derived volumetric annotation of the human hippocampal subfields in postmortem MRI

Recently, there has been a growing effort to analyze the morphometry of hippocampal subfields using both in vivo and postmortem magnetic resonance imaging (MRI). However, given that boundaries between subregions of the hippocampal formation (HF) are conventionally defined on the basis of microscopic features that often lack discernible signature in MRI, subfield delineation in MRI literature has largely relied on heuristic geometric rules, the validity of which with respect to the underlying anatomy is largely unknown. The development and evaluation of such rules are challenged by the limited availability of data linking MRI appearance to microscopic hippocampal anatomy, particularly in three dimensions (3D). The present paper, for the first time, demonstrates the feasibility of labeling hippocampal subfields in a high resolution volumetric MRI dataset based directly on microscopic features extracted from histology. It uses a combination of computational techniques and manual post-processing to map subfield boundaries from a stack of histology images (obtained with 200μm spacing and 5μm slice thickness; stained using the Kluver-Barrera method) onto a postmortem 9.4Tesla MRI scan of the intact, whole hippocampal formation acquired with 160μm isotropic resolution. The histology reconstruction procedure consists of sequential application of a graph-theoretic slice stacking algorithm that mitigates the effects of distorted slices, followed by iterative affine and diffeomorphic co-registration to postmortem MRI scans of approximately 1cm-thick tissue sub-blocks acquired with 200μm isotropic resolution. These 1cm blocks are subsequently co-registered to the MRI of the whole HF. Reconstruction accuracy is evaluated as the average displacement error between boundaries manually delineated in both the histology and MRI following the sequential stages of reconstruction. The methods presented and evaluated in this single-subject study can potentially be applied to multiple hippocampal tissue samples in order to construct a histologically informed MRI atlas of the hippocampal formation.

A systematic review of studies on anatomical position of electrode contacts used for chronic subthalamic stimulation in Parkinson's disease

BACKGROUND

The dorso-lateral part of the subthalamic nucleus (STN) is considered as the usual target of deep brain stimulation for Parkinson's disease. Nevertheless, the exact anatomical location of the electrode contacts used for chronic stimulation is still a matter of debate. The aim of this study was to perform a systematic review of the existing literature on this issue.

METHOD

We searched for studies on the anatomical location of active contacts published until December 2012.

RESULTS

We identified 13 studies, published between 2002 and 2010, including 260 patients and 466 electrodes. One hundred and sixty-four active contacts (35 %) were identified within the STN, 117 (25 %) at the interface between STN and the surrounding structures, 184 (40 %) above the STN and one within the substantia nigra. We observed great discrepancies between the different series. The contra-lateral improvement was between 37 and 78.5 % for contacts located within the STN, between 48.6 and 73 % outside the STN, between 65.3 and 66 % at the interface. The authors report no clear correlation between anatomical location and stimulation parameters.

CONCLUSIONS

Post-operative analysis of the anatomical location of active contacts is difficult, and all the methods used are debatable. The relationship between the anatomical location of active contacts and the clinical effectiveness of stimulation is unclear. It would be necessary to take into account the volume of the electrode contacts and the diffusion of the stimulation. We can nevertheless assume that the interface between dorso-lateral STN, zona incerta and Forel's fields could be directly involved in the effects of stimulation.

Stimulation sites in the subthalamic nucleus projected onto a mean 3-D atlas of the thalamus and basal ganglia

BACKGROUND

In patients with severe forms of Parkinson's disease (PD), deep brain stimulation (DBS) commonly targets the subthalamic nucleus (STN). Recently, the mean 3-D Morel-Atlas of the basal ganglia and the thalamus was introduced. It combines information contained in histological data from ten post-mortem brains. We were interested whether the Morel-Atlas is applicable for the visualization of stimulation sites.

METHODS

In a consecutive PD patient series, we documented preoperative MRI planning, intraoperative target adjustment based on electrophysiological and neurological testing, and perioperative CT target reconstruction. The localization of the DBS electrodes and the optimal stimulation sites were projected onto the Morel-Atlas.

RESULTS

We included 20 patients (median age 62 years). The active contact had mean coordinates Xlat = ±12.1 mm, Yap = -1.8 mm, Zvert = -3.2 mm. There was a significant difference between the initially planned site and the coordinates of the postoperative active contact site (median 2.2 mm). The stimulation site was, on average, more anterior and more dorsal. The electrode contact used for optimal stimulation was found within the STN of the atlas in 38/40 (95 %) of implantations.

CONCLUSIONS

The cluster of stimulation sites in individual patients-as deduced from preoperative MR, intraoperative electrophysiology and neurological testing-showed a high degree of congruence with the atlas. The mean 3D Morel Atlas is thus a useful tool for postoperative target visualization. This represents the first clinical evaluation of the recently created atlas.

Functional magnetic resonance imaging suggests automatization of the cortical response to inspiratory threshold loading in humans

Inspiratory threshold loading (ITL) induces cortical activation. It is sustained over time and is resistant to distraction, suggesting automaticity. We hypothesized that ITL-induced changes in cerebral activation may differ between single-breath ITL and continuous ITL, with differences resembling those observed after cortical automatization of motor tasks. We analyzed the brain blood oxygen level dependent (BOLD) signal of 11 naive healthy volunteers during 5 min of random, single-breath ITL and 5 min of continuous ITL. Single-breath ITL increased BOLD in many areas (premotor cortices, bilateral insula, cerebellum, reticular formation of the lateral mesencephalon) and decreased BOLD in regions co-localizing with the default mode network. Continuous ITL induced signal changes in a limited number of areas (supplementary motor area). These differences are comparable to those observed before and after overlearning of motor tasks. We conclude that the respiratory-related cortical activation observed in response to ITL is likely due to automated, attention-independent mechanisms. Also, ITL activates cortical circuits right from the first breath.

Anatomizing the “King of Neurosciences”

The human nucleus accumbens (NA), a major part of the ventral striatum, is the area of continuity between the putamen and head of the caudate nucleus. It consists of two parts, a shell laterally and a core medially. The first is mainly connected to the limbic system and the second to the extrapyramidal motor system. The NA, a major pleasure center of the human brain, acts as a limbic-motor interface and is involved in several cognitive, emotional and psychomotor functions. It has a modulating function in the amygdala-basal ganglia-prefrontal cortex circuit. It is considered as the neural interface between motivation and action. Further, it is a principal modulator of the reward circuits and supplies motor expression to emotional responses. Such a clinical significance could easily explain the intense work taking place in the respective field of basic research. Its exceptional clinical importance justifies the title of the “King of Neurosciences” for this nucleus. Purpose of this editorial is to review the “informational paths” left behind by the few researchers who tried to explore the architecture (gross anatomy) of this ‘kingdom’. The first anatomical study focused on this nucleus came from Neto et al. The most extensive study of the NA gross, imaging, stereotactic and neurosurgical anatomy so far, came from the research efforts of Mavridis et al.

Neurologist consistency in interpreting information provided by an interactive visualization software for deep brain stimulation postoperative programming assistance

INTRODUCTION

Postoperative programming in deep brain stimulation (DBS) therapy for movement disorders can be challenging and time consuming. Providing the neurologist with tools to visualize the electrode location relative to the patient's anatomy along with models of tissue activation and statistical data can therefore be very helpful. In this study, we evaluate the consistency between neurologists in interpreting and using such information provided by our DBS programming assistance software.

METHODS

Five neurologists experienced in DBS programming were each given a dataset of 29 leads implanted in 17 patients. For each patient, probabilistic maps of stimulation response, anatomical images, models of tissue activation volumes, and electrode positions were presented inside a software framework called CRAnialVault Explorer (CRAVE) developed in house. Consistency between neurologists in optimal contact selection using the software was measured.

RESULTS

With only the efficacy map, the average consistency among the five neurologists with respect to the mode and mean of their selections was 97% and 95%, respectively, while these numbers were 93% and 89%, respectively, when both efficacy and an adverse effect map were used simultaneously. Fleiss' kappa statistic also showed very strong agreement among the neurologists (0.87 when using one map and 0.72 when using two maps).

CONCLUSION

Our five neurologists demonstrated high consistency in interpreting information provided by the CRAVE interactive visualization software for DBS postoperative programming assistance. Three of our five neurologists had no prior experience with the software, which suggests that the software has a short learning curve and contact selection is not dependent on familiarity with the program tools.

Neuronal activity correlated with checking behaviour in the subthalamic nucleus of patients with obsessive-compulsive disorder

Doubt, and its behavioural correlate, checking, is a normal phenomenon of human cognition that is dramatically exacerbated in obsessive-compulsive disorder. We recently showed that deep brain stimulation in the associative-limbic area of the subthalamic nucleus, a central core of the basal ganglia, improved obsessive-compulsive disorder. To understand the physiological bases of symptoms in such patients, we recorded the activity of individual neurons in the therapeutic target during surgery while subjects performed a cognitive task that gave them the possibility of unrestricted repetitive checking after they had made a choice. We postulated that the activity of neurons in this region could be influenced by doubt and checking behaviour. Among the 63/87 task-related neurons recorded in 10 patients, 60% responded to various combinations of instructions, delay, movement or feedback, thus highlighting their role in the integration of different types of information. In addition, task-related activity directed towards decision-making increased during trials with checking in comparison with those without checking. These results suggest that the associative-limbic subthalamic nucleus plays a role in doubt-related repetitive thoughts. Overall, our results not only provide new insight into the role of the subthalamic nucleus in human cognition but also support the fact that subthalamic nucleus modulation by deep brain stimulation reduced compulsive behaviour in patients with obsessive-compulsive disorder.

A new atlas localization approach for subthalamic nucleus utilizing Chinese visible human head datasets

OBJECTIVE

To study the possibility of Chinese visible human (CVH) head datasets as brain atlas for locating the subthalamic nucleus (STN) before deep brain stimulation (DBS) surgery.

METHODS

Optimal head axial and coronal 3.0T, T2-weighted magnetic resonance images (MRI) of 30 patients were obtained. Cross-sectional head images of four CVH head datasets were chosen to establish an average CVH model. All MRI sequences were registered to the CVH model via fiducials in X-, Y-, and Z-direction, respectively, within the same stereotactic space. The correlations between red nucleus (RN) and fiducials, the accuracy of MRI-to-CVH registration, and the coordinate value differences of RN gravity center between MRI and CVH were tested.

RESULTS

The mean gravity center coordinate values and ranges of STN in CVH were measured; The X coordinate value of RN positively correlates with the most anterior point of putamen(PU-A), the lateral edges of putamens (PU-L), and width of the third ventricle, negatively correlated with the patients' age; The minimal mean errors were when no fiducials were used when locating RN between the MRI and the CVH average model; There were no significant differences of RN in X- and Y-direction between MRI sequences and CVH.

CONCLUSION

CVH head datasets can be used as brain atlas for Chinese STN localization. Moreover, average coordinate values of the gravity center and the ranges of STN in CVH can be considered as references for locating STN.

Multimodal imaging and image analysis techniques for neuromodulation

Functional neurosurgical procedures used to treat the debilitating motor symptoms of Parkinson's disease and that target small subcortical structures have typically relied on semi-qualitative manual approaches that rely upon the establishing qualitative between volumetric imaging data and print atlases. This chapter reviews many new high -precision and -accuracy techniques that can be used for the full automated localization of these targets. These techniques rely on the a priori development of neuroanatomical atlases derived from magnetic resonance imaging data, high-resolution identification of subcortical structures from histology, and spatially localized data bases of intra-operative recordings and successful surgical outcomes. Other novel structural and functional MRI techniques that allow for the direct visualization of thalamic sub nuclei are also reviewed.

Limbic and motor function comparison of deep brain stimulation of the zona incerta and subthalamic nucleus

BACKGROUND

Psychiatric and neuropsychological side effects of subthalamic nucleus (STN) stimulation have been increasingly recognized. Most programming regimens focus on contacts 0 and 1, whereas contact 3, which often is located near or in the zona incerta (ZI), is usually not used. The question of whether ZI stimulation may limit limbic effects has not been answered.

OBJECTIVE

To examine the effects of short-term stimulation near or in the ZI (contact 3) compared with stimulation of the STN using standard trajectories and targeting as measured by limbic and motor functions.

METHODS

Motor and limbic functions of 11 patients with STN DBS were assessed with the Unified Parkinson Disease Rating Scale-3, structured gait video analysis, Visual Analog Scale mood scales, task testing of impulsivity, and facial recognition under routine STN programming and under stimulation in or near the ZI. Postoperative magnetic resonance imaging confirmed the location of contact 3 near or in the ZI.

RESULTS

Data analysis with repeated-measures analysis of variance revealed that motor scores remained stable with both stimulation settings, with specific improvements in finger taps (P = .02) and rapid alternating movements (P = .03) in ZI stimulation. Stimulation near or in the ZI led to a decrease in self- reported anxiety and depression (P = .03 for both) and an improvement in fear recognition (P = .02).

CONCLUSION

We provide preliminary evidence that stimulation in or near the ZI results in maintained motor function while improving self-reported depression and anxiety in patients with bilateral STN DBS. Stimulation in or near the ZI may provide a useful programming setting for patients prone to psychiatric side effects.

Functional parcellation of the lateral mesencephalus

The mesencephalic locomotor region (MLR), which includes the pedunculopontine nucleus (PPN) and the cuneiform nucleus (CN), has been recently identified as a key structure for locomotion and gait control in mammals. However, the function and the precise anatomy of the MLR remain unclear in humans. To study the lateral mesencephalus, we used fMRI in 15 right-handed healthy volunteers performing two tasks: imagine walking in a hallway and imagine an object moving along the same hallway. Both tasks were performed at two different speeds: normal and 30% faster. We identified two distinct networks of cortical activation: one involving motor/premotor cortices and the cerebellum for the walking task and the other involving posterior parietal and dorsolateral prefrontal cortices for the object moving task. In the lateral mesencephalus, we found that two different but anatomically connected parts of the MLR were activated during the fast condition of each task. The CN and the dorsal part of the PPN were activated during the fast imaginary walking task, whereas the ventral part of the PPN and the ventral part of the reticular formation were activated while subjects were imagining the object moving fast. Our data suggest that the lateral mesencephalus participates in different aspects of gait in humans, with the CN and dorsal PPN controlling motor aspects of locomotion and the ventral PPN being involved in integrating sensory information.

Does unilateral basal ganglia activity functionally influence the contralateral side? What we can learn from STN stimulation in patients with Parkinson's disease

In humans, the control of voluntary movement, in which the corticobasal ganglia (BG) circuitry participates, is mainly lateralized. However, several studies have suggested that both the contralateral and ipsilateral BG systems are implicated during unilateral movement. Bilateral improvement of motor signs in patients with Parkinson's disease (PD) has been reported with unilateral lesion or high-frequency stimulation (HFS) of the internal part of the globus pallidus or the subthalamic nucleus (STN-HFS). To decipher the mechanisms of production of ipsilateral movements induced by the modulation of unilateral BG circuitry activity, we recorded left STN neuronal activity during right STN-HFS in PD patients operated for bilateral deep brain stimulation. Left STN single cells were recorded in the operating room during right STN-HFS while patients experienced, or did not experience, right stimulation-induced dyskinesias. Most of the left-side STN neurons (64%) associated with the presence of right dyskinesias were inhibited, with a significant decrease in burst and intraburst frequencies. In contrast, left STN neurons not associated with right dyskinesias were mainly activated (48%), with a predominant increase 4–5 ms after the stimulation pulse and a decrease in oscillatory activity. This suggests that unilateral neuronal STN modulation is associated with changes in the activity of the contralateral STN. The fact that one side of the BG system can influence the functioning of the other could explain the occurrence of bilateral dyskinesias and motor improvement observed in PD patients during unilateral STN-HFS, as a result of a bilateral disruption of the pathological activity in the corticosubcortical circuitry.

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.

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.

Creation of Computerized 3D MRI-Integrated Atlases of the Human Basal Ganglia and Thalamus

Functional brain imaging and neurosurgery in subcortical areas often requires visualization of brain nuclei beyond the resolution of current magnetic resonance imaging (MRI) methods. We present techniques used to create: (1) a lower resolution 3D atlas, based on the Schaltenbrand and Wahren print atlas, which was integrated into a stereotactic neurosurgery planning and visualization platform (VIPER); and (2) a higher resolution 3D atlas derived from a single set of manually segmented histological slices containing nuclei of the basal ganglia, thalamus, basal forebrain, and medial temporal lobe. Both atlases were integrated to a canonical MRI (Colin27) from a young male participant by manually identifying homologous landmarks. The lower resolution atlas was then warped to fit the MRI based on the identified landmarks. A pseudo-MRI representation of the high-resolution atlas was created, and a non-linear transformation was calculated in order to match the atlas to the template MRI. The atlas can then be warped to match the anatomy of Parkinson's disease surgical candidates by using 3D automated non-linear deformation methods. By way of functional validation of the atlas, the location of the sensory thalamus was correlated with stereotactic intraoperative physiological data. The position of subthalamic electrode positions in patients with Parkinson's disease was also evaluated in the atlas-integrated MRI space. Finally, probabilistic maps of subthalamic stimulation electrodes were developed, in order to allow group analysis of the location of contacts associated with the best motor outcomes. We have therefore developed, and are continuing to validate, a high-resolution computerized MRI-integrated 3D histological atlas, which is useful in functional neurosurgery, and for functional and anatomical studies of the human basal ganglia, thalamus, and basal forebrain.

Magnetic resonance imaging techniques for visualization of the subthalamic nucleus

The authors reviewed 70 publications on MR imaging-based targeting techniques for identifying the subthalamic nucleus (STN) for deep brain stimulation in patients with Parkinson disease. Of these 70 publications, 33 presented quantitatively validated results. There is still no consensus on which targeting technique to use for surgery planning; methods vary greatly between centers. Some groups apply indirect methods involving anatomical landmarks, or atlases incorporating anatomical or functional data. Others perform direct visualization on MR imaging, using T2-weighted spin echo or inversion recovery protocols. The combined studies do not offer a straightforward conclusion on the best targeting protocol. Indirect methods are not patient specific, leading to varying results between cases. On the other hand, direct targeting on MR imaging suffers from lack of contrast within the subthalamic region, resulting in a poor delineation of the STN. These deficiencies result in a need for intraoperative adaptation of the original target based on test stimulation with or without microelectrode recording. It is expected that future advances in MR imaging technology will lead to improvements in direct targeting. The use of new MR imaging modalities such as diffusion MR imaging might even lead to the specific identification of the different functional parts of the STN, such as the dorsolateral sensorimotor part, the target for deep brain stimulation.

Basal ganglia dysfunction in OCD: subthalamic neuronal activity correlates with symptoms severity and predicts high-frequency stimulation efficacy

Functional and connectivity changes in corticostriatal systems have been reported in the brains of patients with obsessive-compulsive disorder (OCD); however, the relationship between basal ganglia activity and OCD severity has never been adequately established. We recently showed that deep brain stimulation of the subthalamic nucleus (STN), a central basal ganglia nucleus, improves OCD. Here, single-unit subthalamic neuronal activity was analysed in 12 OCD patients, in relation to the severity of obsessions and compulsions and response to STN stimulation, and compared with that obtained in 12 patients with Parkinson's disease (PD). STN neurons in OCD patients had lower discharge frequency than those in PD patients, with a similar proportion of burst-type activity (69 vs 67%). Oscillatory activity was present in 46 and 68% of neurons in OCD and PD patients, respectively, predominantly in the low-frequency band (1-8 Hz). In OCD patients, the bursty and oscillatory subthalamic neuronal activity was mainly located in the associative-limbic part. Both OCD severity and clinical improvement following STN stimulation were related to the STN neuronal activity. In patients with the most severe OCD, STN neurons exhibited bursts with shorter duration and interburst interval, but higher intraburst frequency, and more oscillations in the low-frequency bands. In patients with best clinical outcome with STN stimulation, STN neurons displayed higher mean discharge, burst and intraburst frequencies, and lower interburst interval. These findings are consistent with the hypothesis of a dysfunction in the associative-limbic subdivision of the basal ganglia circuitry in OCD's pathophysiology.

Anatomy of the human nucleus accumbens: a combined morphometric study

PURPOSE

The human nucleus accumbens (NA), which belongs to the basal ganglia of the brain, is the main part of the ventral striatum. The purpose of our clinically oriented anatomical-radiologic study was to provide anatomical and imaging data of the human NA, primarily useful to neurosurgeons.

METHODS

For our imaging study, we used cerebral magnetic resonance images (MRIs) from 26 neurosurgical patients (52 NAs). The material for our anatomic study consisted of 32 cerebral hemispheres (32 NAs) from 18 normal human brains which we have in our department (Department of Anatomy) from cadaver donors. We measured and analyzed the dimensions of the NA at specific clinically important transverse, coronal and sagittal levels.

RESULTS

The human NA suffers from age-related but no side- or sex-related morphometric changes. In surgically important stereotactic levels this nucleus is easily identifiable on MRIs.

CONCLUSIONS

We present an anatomic guide of the NA from carefully measured data of our extensive and combined study and we hope that our work will be really helpful to neuroscientists interested in the NA.

Decrease of prefrontal metabolism after subthalamic stimulation in obsessive-compulsive disorder: a positron emission tomography study

BACKGROUND

High-frequency bilateral subthalamic nucleus (STN) deep brain stimulation (DBS) is a promising treatment in refractory obsessive-compulsive disorder (OCD).

METHOD

Using the crossover, randomized, and double-blind procedure adopted by the STOC study, 10 patients treated with high-frequency bilateral STN DBS underwent am 18-fluorodeoxyglucose positron emission tomography (PET) investigation to highlight the neural substratum of this therapeutic approach.

RESULTS

The median Yale-Brown Obsessive Compulsive Scale (Y-BOCS) scores for all 10 patients were 31 (minimum = 18, maximum = 36) with "Off-Stimulation" status and 19 (minimum = 0, maximum = 30) with "On-Stimulation" status (p = .05). The OCD patients in Off-Stimulation status showed a hypermetabolism in the right frontal middle and superior gyri, right parietal lobe, postcentral gyrus, and bilateral putamen compared with healthy control subjects. A significant decrease in cerebral metabolism was observed in the left cingulate gyrus and the left frontal medial gyrus in On-Stimulation conditions compared with Off-Stimulation conditions. In addition, the improvement assessed by Y-BOCS scores during the On-Stimulation conditions was positively correlated with PET signal changes at the boundary of the orbitofrontal cortex and the medial prefrontal cortex, between PET signal changes and the Y-BOCS scores modifications in On-Stimulation status.

CONCLUSION

This study suggests that the therapeutic effect of STN DBS is related to a decrease in prefrontal cortex metabolism.

Probabilistic analysis of activation volumes generated during deep brain stimulation

Deep brain stimulation (DBS) is an established therapy for the treatment of Parkinson's disease (PD) and shows great promise for the treatment of several other disorders. However, while the clinical analysis of DBS has received great attention, a relative paucity of quantitative techniques exists to define the optimal surgical target and most effective stimulation protocol for a given disorder. In this study we describe a methodology that represents an evolutionary addition to the concept of a probabilistic brain atlas, which we call a probabilistic stimulation atlas (PSA). We outline steps to combine quantitative clinical outcome measures with advanced computational models of DBS to identify regions where stimulation-induced activation could provide the best therapeutic improvement on a per-symptom basis. While this methodology is relevant to any form of DBS, we present example results from subthalamic nucleus (STN) DBS for PD. We constructed patient-specific computer models of the volume of tissue activated (VTA) for 163 different stimulation parameter settings which were tested in six patients. We then assigned clinical outcome scores to each VTA and compiled all of the VTAs into a PSA to identify stimulation-induced activation targets that maximized therapeutic response with minimal side effects. The results suggest that selection of both electrode placement and clinical stimulation parameter settings could be tailored to the patient's primary symptoms using patient-specific models and PSAs.

CranialVault and its CRAVE tools: a clinical computer assistance system for deep brain stimulation (DBS) therapy

A number of methods have been developed to assist surgeons at various stages of deep brain stimulation (DBS) therapy. These include construction of anatomical atlases, functional databases, and electrophysiological atlases and maps. But, a complete system that can be integrated into the clinical workflow has not been developed. In this paper we present a system designed to assist physicians in pre-operative target planning, intra-operative target refinement and implantation, and post-operative DBS lead programming. The purpose of this system is to centralize the data acquired a the various stages of the procedure, reduce the amount of time needed at each stage of the therapy, and maximize the efficiency of the entire process. The system consists of a central repository (CranialVault), of a suite of software modules called CRAnialVault Explorer (CRAVE) that permit data entry and data visualization at each stage of the therapy, and of a series of algorithms that permit the automatic processing of the data. The central repository contains image data for more than 400 patients with the related pre-operative plans and position of the final implants and about 10,550 electrophysiological data points (micro-electrode recordings or responses to stimulations) recorded from 222 of these patients. The system has reached the stage of a clinical prototype that is being evaluated clinically at our institution. A preliminary quantitative validation of the planning component of the system performed on 80 patients who underwent the procedure between January 2009 and December 2009 shows that the system provides both timely and valuable information.

Sleep induced by stimulation in the human pedunculopontine nucleus area

The pedunculopontine nucleus is part of the reticular ascending arousal system and is involved in locomotion and sleep. Two patients with Parkinson disease received electrodes that stimulated the pedunculopontine nucleus area to alleviate their severe gait impairment. Instead, we found that low-frequency stimulation of the pedunculopontine nucleus area increased alertness, whereas high-frequency stimulation induced non-rapid eye movement sleep. In addition, the sudden withdrawal of the low-frequency stimulation was consistently followed by rapid eye movement sleep episodes in 1 patient. These data have the potential to benefit patients who suffer from sleep disorders.

Effects of pedunculopontine nucleus area stimulation on gait disorders in Parkinson's disease

Gait disturbances are frequent and disabling in advanced Parkinson's disease. These symptoms respond poorly to usual medical and surgical treatments but were reported to be improved by stimulation of the pedunculopontine nucleus. We studied the effects of stimulating the pedunculopontine nucleus area in six patients with severe freezing of gait, unresponsive to levodopa and subthalamic nucleus stimulation. Electrodes were implanted bilaterally in the pedunculopontine nucleus area. Electrode placement was checked by postoperative magnetic resonance imaging. The primary outcome measures were a composite gait score, freezing of gait questionnaire score and duration of freezing episodes occurring during a walking protocol at baseline and one-year follow-up. A double-blind cross-over study was carried out from months 4 to 6 after surgery with or without pedunculopontine nucleus area stimulation. At one-year follow-up, the duration of freezing episodes under off-drug condition improved, as well as falls related to freezing. The other primary outcome measures did not significantly change, nor did the results during the double-blind evaluation. Individual results showed major improvement of all gait measures in one patient, moderate improvement of some tests in four patients and global worsening in one patient. Stimulation frequency ranged between 15 and 25 Hz. Oscillopsia and limb myoclonus could hinder voltage increase. No serious adverse events occurred. Although freezing of gait can be improved by low-frequency electrical stimulation of the pedunculopontine nucleus area in some patients with Parkinson's disease our overall results are disappointing compared to the high levels of expectation raised by previous open label studies. Further controlled studies are needed to determine whether optimization of patient selection, targeting and setting of stimulation parameters might improve the outcome to a point that could transform this experimental approach to a treatment with a reasonable risk-benefit ratio.

Automated optimization of subcortical cerebral MR imaging-atlas coregistration for improved postoperative electrode localization in deep brain stimulation

BACKGROUND AND PURPOSE

The efficacy of deep brain stimulation in treating movement disorders depends critically on electrode localization, which is conventionally described by using coordinates relative to the midcommissural point. This approach requires manual measurement and lacks spatial normalization of anatomic variances. Normalization is based on intersubject spatial alignment (coregistration) of corresponding brain structures by using different geometric transformations. Here, we have devised and evaluated a scheme for automated subcortical optimization of coregistration (ASOC), which maximizes patient-to-atlas normalization accuracy of postoperative structural MR imaging into the standard Montreal Neurologic Institute (MNI) space for the basal ganglia.

MATERIALS AND METHODS

Postoperative T2-weighted MR imaging data from 39 patients with Parkinson disease and 32 patients with dystonia were globally normalized, representing the standard registration (control). The global transformations were regionally refined by 2 successive linear registration stages (RSs) (ASOC-1 and 2), focusing progressively on the basal ganglia with 2 anatomically selective brain masks, which specify the reference volume (weighted cost function). Accuracy of the RSs was quantified by spatial dispersion of 16 anatomic landmarks and their root-mean-square errors (RMSEs) with respect to predefined MNI-based reference points. The effects of CSF volume, age, and sex on RMSEs were calculated.

RESULTS

Mean RMSEs differed significantly (P < .001) between the global control (4.2 +/- 2.0 mm), ASOC-1 (1.92 +/- 1.02 mm), and ASOC-2 (1.29 +/- 0.78 mm).

CONCLUSIONS

The present method improves the registration accuracy of postoperative structural MR imaging data into MNI space within the basal ganglia, allowing automated normalization with increased precision at stereotactic targets, and enables lead-contact localization in MNI coordinates for quantitative group analysis.

Effect of brain shift on the creation of functional atlases for deep brain stimulation surgery

PURPOSE

In the recent past many groups have tried to build functional atlases of the deep brain using intra-operatively acquired information such as stimulation responses or micro-electrode recordings. An underlying assumption in building such atlases is that anatomical structures do not move between pre-operative imaging and intra-operative recording. In this study, we present evidences that this assumption is not valid. We quantify the effect of brain shift between pre-operative imaging and intra-operative recording on the creation of functional atlases using intra-operative somatotopy recordings and stimulation response data.

METHODS

A total of 73 somatotopy points from 24 bilateral subthalamic nucleus (STN) implantations and 52 eye deviation stimulation response points from 17 bilateral STN implantations were used. These points were spatially normalized on a magnetic resonance imaging (MRI) atlas using a fully automatic non-rigid registration algorithm. Each implantation was categorized as having low, medium or large brain shift based on the amount of pneumocephalus visible on post-operative CT. The locations of somatotopy clusters and stimulation maps were analyzed for each category.

RESULTS

The centroid of the large brain shift cluster of the somatotopy data (posterior, lateral, inferior: 3.06, 11.27, 5.36 mm) was found posterior, medial and inferior to that of the medium cluster (2.90, 13.57, 4.53 mm) which was posterior, medial and inferior to that of the low shift cluster (1.94, 13.92, 3.20 mm). The coordinates are referenced with respect to the mid-commissural point. Euclidean distances between the centroids were 1.68, 2.44 and 3.59 mm, respectively for low-medium, medium-large and low-large shift clusters. We found similar trends for the positions of the stimulation maps. The Euclidian distance between the highest probability locations on the low and medium-large shift maps was 4.06 mm.

CONCLUSION

The effect of brain shift in deep brain stimulation (DBS) surgery has been demonstrated using intra-operative somatotopy recordings as well as stimulation response data. The results not only indicate that considerable brain shift happens before micro-electrode recordings in DBS but also that brain shift affects the creation of accurate functional atlases. Therefore, care must be taken when building and using such atlases of intra-operative data and also when using intra-operative data to validate anatomical atlases.

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.