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While the effectiveness of deep brain stimulation in alleviating essential tremor is well-established, the underlying mechanisms of the treatment are unclear. Essential tremor, as characterized by tremor during action, is proposed to be driven by a dysfunction in the cerebello-thalamo-cerebral circuit that is evident not only during motor actions but also during rest. Stimulation effects on resting-state functional connectivity were investigated by functional MRI in 16 essential tremor patients with fully implanted deep brain stimulation in the caudal zona incerta during On-and-Off therapeutic stimulation, in a counterbalanced design. Functional connectivity was calculated between different constellations of sensorimotor as well as non-sensorimotor regions (as derived from seed-based and data-driven approaches), and compared between On and Off stimulation. We found that deep brain stimulation did not modulate resting-state functional connectivity. The lack of modulation by deep brain stimulation during resting-state, in combination with previously demonstrated effects on the cerebello-thalamo-cerebral circuit during motor tasks, suggests an action-dependent modulation of the stimulation in essential tremor.

Background: The advent of deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease 30 years ago has ushered a global breakthrough of DBS as a universal method for therapy and research in wide areas of neurology and psychiatry. The literature of the last three decades has described numerous concepts and practices of DBS, often branded as novelties or discoveries. However, reading the contemporary publications often elicits a sense of déjà vu in relation to several methods, attributes, and practices of DBS. Here, we review various applications and techniques of the modern-era DBS and compare them with practices of the past. Summary: Compared with modern literature, publications of the old-era functional stereotactic neurosurgery, including old-era DBS, show that from the very beginning multidisciplinarity and teamwork were often prevalent and insisted upon, ethical concerns were recognized, brain circuitries and rational for brain targets were discussed, surgical indications were similar, closed-loop stimulation was attempted, evaluations of surgical results were debated, and controversies were common. Thus, it appears that virtually everything done today in the field of DBS bears resemblance to old-Time practices, or has been done before, albeit with partly other tools and techniques. Movement disorders remain the main indications for modern DBS as was the case for lesional surgery and old-era DBS. The novelties today consist of the STN as the dominant target for DBS, the tremendous advances in computerized brain imaging, the sophistication and versatility of implantable DBS hardware, and the large potential for research. Key Messages: Many aspects of contemporary DBS bear strong resemblance to practices of the past. The dominant clinical indications remain movement disorders with virtually the same brain targets as in the past, with one exception: The STN. Other novel brain targets-that are so far subject to DBS trials-are the pedunculop

Introduction: Deep brain stimulation (DBS) is an established treatment for Parkinson’s disease (PD) and other movement disorders. The ventral intermediate nucleus of the thalamus (Vim) is considered as the target of choice for tremor disorders, including tremor-dominant PD not suitable for DBS in the subthalamic nucleus (STN). In the last decade, several studies have shown promising results on tremor from DBS in the posterior subthalamic area (PSA), including the caudal zona incerta (cZi) located postero-medial to the STN. The aim of this study was to evaluate the long-term effect of unilateral cZi/PSA-DBS in patients with tremor-dominant Parkinson’s disease. Methods: Thirteen patients with PD with medically refractory tremor were included. The patients were evaluated using the motor part of the Unified Parkinson Disease Rating Scale (UPDRS) off/on medication before surgery and off/on medication and stimulation 1-2 years (short-term) after surgery and at a minimum of 3 years after surgery (long-term). Results: At short-term follow-up DBS improved contralateral tremor by 88% in the off-medication state. This improvement persisted after a mean of 62 months. Contralateral bradykinesia was improved by 40% at short-term and 20% at long-term follow-up and the total UPDRS-III by 33% at short-term and by 22% at long-term follow-up with stimulation alone. Conclusions: Unilateral cZi/PSA-DBS seems to remain an effective treatment for patients with severe Parkinsonian tremor several years after surgery. There was also a modest improvement on bradykinesia.

Probabilistic stimulation maps of deep brain stimulation (DBS) effect based on voxel-wise statistics (p-maps) have increased in literature over the last decade. These p-maps require correction for Type-1 errors due to multiple testing based on the same data. Some analyses do not reach overall significance, and this study aims to evaluate the impact of sample size on p-map computation. A dataset of 61 essential tremor patients treated with DBS was used for the investigation. Each patient contributed with four stimulation settings, one for each contact. From the dataset, 5 to 61 patients were randomly sampled with replacement for computation of p-maps and extraction of high- and low-improvement volumes. For each sample size, the process was iterated 20 times with new samples generating in total 1140 maps. The overall p-value corrected for multiple comparisons, significance volumes, and dice coefficients (DC) of the volumes within each sample size were evaluated. With less than 30 patients (120 simulations) in the sample, the variation in overall significance was larger and the median significance volumes increased with sample size. Above 120 simulations, the trends stabilize but present some variations in cluster location, with a highest median DC of 0.73 for n = 57. The variation in location was mainly related to the region between the high- and low-improvement clusters. In conclusion, p-maps created with small sample sizes should be evaluated with caution, and above 120 simulations in single-center studies are probably required for stable results., Funding Agencies|Swedish Foundation for Strategic Research [SSF BD15-0032]; Swedish Research Council [VR 2016-03564]

Background: Long-term data on the effects of deep brain stimulation (DBS) for essential tremor (ET) is scarce, especially regarding DBS in the caudal Zona incerta (cZi) and the posterior subthalamic area (PSA). Objectives: The aim of this prospective study was to evaluate the effect of cZi/PSA DBS in ET at 10 years after surgery. Methods: Thirty-four patients were included. All patients received cZi/PSA DBS (5 bilateral/29 unilateral) and were evaluated at regular intervals using the essential tremor rating scale (ETRS). Results: One year after surgery, there was a 66.4% improvement of total ETRS and 70.7% improvement of tremor (items 1–9) compared with the preoperative baseline. Ten years after surgery, 14 patients had died and 3 were lost to follow-up. In the remaining 17 patients, a significant improvement was maintained (50.8% for total ETRS and 55.8% for tremor items). On the treated side the scores of hand function (items 11–14) had improved by 82.6% at 1 year after surgery, and by 66.1% after 10 years. Since off-stimulation scores did not differ between year 1 and 10, this 20% deterioration of on-DBS scores was interpreted as a habituation. There was no significant increase in stimulation parameters beyond the first year. Conclusions: This 10 year follow up study, found cZi/PSA DBS for ET to be a safe procedure with a mostly retained effect on tremor, compared to 1 year after surgery, and in the absence of increase in stimulation parameters. The modest deterioration of effect of DBS on tremor was interpreted as habituation.

Background: The year 2023 marks the 30th anniversary of deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson’s disease (PD). This procedure prompted a universal interest in DBS for various brain disorders and resulted in a unique expansion of clinical and scientific collaboration between many disciplines, with impact on many aspects of society. Objective: To study the anthropology of DBS, that is, its ethno-geographic origins, its evolution, its impact on clinicians and scientists, and its influence on society at large. Material and Methods: The authors scrutinized the geo-ethnic origins of the pioneers of modern DBS, and they evaluated, based on the literature and on a long-term praxis, the development of DBS and its impact on clinicians, on healthcare, and on society. Results: Scientists and clinicians from various geo-ethnic origins pioneered modern DBS, leading to worldwide spread of this procedure and to the establishment of large multidisciplinary teams in many centers. Neurologists became actively involved in surgery and took on new laborious tasks of programming ever more complicated DBS systems. Publications sky-rocketed and the global spread of DBS impacted positively on several aspects of society, including healthcare, awareness of neurological diseases, interdisciplinary relations, conferences, patient organizations, unemployment, industry, etc. Conclusions: STN DBS has boosted the field of deep brain electrotherapy for many neurological and psychiatric illnesses, and DBS has generated a global benefit on many aspects of society, well beyond its clinical benefits on symptoms of diseases. With the ever-increasing indications for DBS, more positive global impact is expected.

Background: Deep brain stimulation has become an established technology for the treatment of patients with a wide variety of conditions, including movement disorders, psychiatric disorders, epilepsy, and pain. Surgery for implantation of DBS devices has enhanced our understanding of human physiology, which in turn has led to advances in DBS technology. Our group has previously published on these advances, proposed future developments, and examined evolving indications for DBS. Summary: The crucial roles of structural MR imaging pre-, intra-, and post-DBS procedure in target visualization and confirmation of targeting are described, with discussion of new MR sequences and higher field strength MRI enabling direct visualization of brain targets. The incorporation of functional and connectivity imaging in procedural workup and their contribution to anatomical modelling is reviewed. Various tools for targeting and implanting electrodes, including frame-based, frameless, and robot-assisted, are surveyed, and their pros and cons are described. Updates on brain atlases and various software used for planning target coordinates and trajectories are presented. The pros and cons of asleep versus awake surgery are discussed. The role and value of microelectrode recording and local field potentials are described, as well as the role of intraoperative stimulation. Technical aspects of novel electrode designs and implantable pulse generators are presented and compared.

Funktionell neurokirurgi är ett samlingsnamn för en bred arsenal av neurokirurgiska metoder för att lindra besvär vid olika neurogena tillstånd. Syftet är genomgående att förbättra livskvalitet, och verksamheterna präglas av ett uttalat multidisciplinärt och tvärprofessionellt samarbete. Detta underlättar en god patientselektion, vilket är helt avgörande för att uppnå ett lyckat resultat. Med rätt urval och uppföljning erbjuder dessa ingrepp säker och effektiv lindring eller till och med bot för notoriskt svårbehandlade och ofta starkt funktionsnedsättande tillstånd.

BACKGROUND: Essential tremor (ET) is the most common adult movement disorder. For the relatively large group of patients who do not respond adequately to pharmacological therapy, deep brain stimulation (DBS) is a well-established treatment option. Most ET patients will have bilateral symptoms, and many of them receive bilateral DBS. Unilateral DBS is however still the most common procedure, and some papers suggest an ipsilateral effect in these patients. OBJECTIVES: The aim of this study was to analyze if there is an ipsilateral effect of DBS for ET. METHOD: We retrospectively analyzed our patient cohort with DBS surgery from 1996 to 2017, selecting patients with ET that underwent surgery with unilateral DBS without previous DBS or lesional surgery. A total number of 68 patients (39 males, 29 females) were identified. The patients were evaluated twice: first, at a mean time of 12 months after surgery defined as short-term follow-up and then again at a mean time of 49 months after surgery defined as long-term follow-up, using the clinical rating scale for tremor (CRST). RESULTS: The total CRST score was reduced from mean 49.5 points at baseline before surgery to 20.2 (p < 0.001) at short-term and 28.3 (p < 0.001) at long-term follow-up. Contralateral tremor was reduced from mean 6.1 to 0.4 (p < 0.001) and 1.2 (p < 0.001), respectively. Contralateral hand function was reduced from 11.5 to 2.6 (p < 0.001) and 4.6 (p < 0.001), respectively. Ipsilateral hand function scored 9 at baseline, 8.3 at 1 year, and then again 9.4 at long-term follow-up. Ipsilateral tremor scored 4.0 at baseline, 3.7 at 1 year, and 4.3 at long-term follow-up. Neither ipsilateral hand function nor ipsilateral tremor showed significant difference. CONCLUSIONS: There was no difference in severity of ipsilateral tremor, neither at 1 year nor in the long term. We believe ipsilateral effects of DBS for ET merits limited consideration regarding decision-making or patient counseling bef

Recently, a series of historical reports portrayed the first women neurosurgeons in various countries. One such woman, a pioneer on many levels, remained unrecognized: Judith Balkányi-Lepintre. She was the first woman neurosurgeon in France, the first woman war neurosurgeon for the French Army, and the first woman pediatric neurosurgeon in France. Born in 1912 to a Hungarian Jewish family, she graduated with honors from medical school in Budapest in 1935, then moved to Paris where she started neurosurgical training in 1937 at L’Hôpital de la Pitié under the mentorship of Clovis Vincent, the founder of French neurosurgery. Shortly after marrying a French colleague in 1940, she had to escape the Geheime Staatspolizei (Gestapo) in Paris and ended up in Algeria, where she joined the French Army of De Gaulle. As a neurosurgeon, she participated in the campaigns of Italy and France between 1943 and 1945. After the war, she returned to work at La Pitié Hospital. In 1947, she defended her doctoral thesis, “Treatment of cranio-cerebral wounds by projectiles and their early complications.” Soon thereafter, she joined Europe’s first dedicated children’s hospital, Hôpital Necker-Enfants Malades in Paris, and contributed to the establishment of pediatric neurosurgery in France. She remained clinically and academically active at Necker until her death in 1982 but was never promoted.

Background: Group analysis of patients with deep brain stimulation (DBS) has the potential to help understand and optimize the treatment of patients with movement disorders. Probabilistic stimulation maps (PSM) are commonly used to analyze the correlation between tissue stimulation and symptomatic effect but are applied with different methodological variations. Objective: To compute a group-specific MRI template and PSMs for investigating the impact of PSM model parameters. Methods: Improvement and occurrence of dizziness in 68 essential tremor patients implanted in caudal zona incerta were analyzed. The input data includes the best parameters for each electrode contact (screening), and the clinically used settings. Patient-specific electric field simulations (n = 488) were computed for all DBS settings. The electric fields were transformed to a group-specific MRI template for analysis and visualization. The different comparisons were based on PSMs representing occurrence (N-map), mean improvement (M-map), weighted mean improvement (wM-map), and voxel-wise t-statistics (p-map). These maps were used to investigate the impact from input data (clinical/screening settings), clustering methods, sampling resolution, and weighting function. Results: Screening or clinical settings showed the largest impacts on the PSMs. The average differences of wM-maps were 12.4 and 18.2% points for the left and right sides respectively. Extracting clusters based on wM-map or p-map showed notable variation in volumes, while positioning was similar. The impact on the PSMs was small from weighting functions, except for a clear shift in the positioning of the wM-map clusters. Conclusion: The distribution of the input data and the clustering method are most important to consider when creating PSMs for studying the relationship between anatomy and DBS outcome.

Background: Serendipity and observations have a noble tradition in medicine, including neurology, and are responsible for many medical treatments (carbamazepine for tic douloureux, amantadine for Parkinson's disease, gabapentin for restless legs...). We aimed at examining the contribution of serendipity and observations to functional neurosurgery. Scholarly publications relevant to the history of functional neurosurgery for movement and psychiatric disorders were reviewed, starting from the pre-stereotactic era. The documents were scrutinized with respect to indications for surgery, surgical methods, and brain targets, in view of determining whether serendipitous discoveries and other observations contributed to various functional neurosurgical procedures. Summary: James Parkinson's observation that tremors disappeared in the arm of a person with shaking palsy after a hemiparetic stroke encouraged neurosurgeons in the first half of the 20th century to perform ablative procedures on central motor pathways. Following a lobotomy performed by Browder that extended too far medially in a psychiatric patient with coexisting Parkinson's disease (PD), it was noted that the Parkinsonian signs improved. This encouraged Russel Meyers to carry out open surgery on the caudate nucleus and basal ganglia in PD. Cooper introduced ligation of the anterior choroidal artery as a treatment for PD following a surgical accident during a pedunculotomy. Cooper later started to perform stereotactic surgery on the ventrolateral thalamus following the pathological finding that an intended pallidal lesion had in fact targeted the thalamus. Leksell discovered the ideal location of a pallidal lesion being in the posteroventral area empirically, long before the advent of the basal ganglia model of PD. Modern Deep Brain Stimulation (DBS) that started in the thalamus for tremor was the result of an observation by Benabid that intraoperative high-frequency stimulation during a thalamotomy reduced trem

Purpose: The aim of this study was to evaluate cognitive effects 12 months after Deep Brain Stimulation (DBS) of the Bed Nucleus of Stria Terminalis (BNST) in patients with refractory Obsessive–Compulsive Disorder (OCD). Methods: Eight patients (5 female; mean ± SD age 36 ± 15) with OCD were included. A neuropsychological test battery covering verbal and spatial episodic memory, executive function, and attention was administered preoperatively and 12 months after surgery. Medical records were used as a source for descriptive data to probe for any changes not covered by standardized checklists and the Yale-Brown Obsessive Compulsive Scale (Y-BOCS), the primary outcome measure. Results: At 12 months, seven patients showed response to DBS: three were full responders (i.e., Y-BOCS ≥ 35% improvement), and four were partial responders (Y-BOCS 25–34% improvement). Relative to baseline, there was a slight decline on visuo-spatial learning (p = 0.027), and improved performance on the Color-Word Interference inhibition/switching subtest (p = 0.041), suggesting improvement in cognitive flexibility. Conclusions: DBS in the BNST for treatment refractory OCD generates very few adverse cognitive effects and improves cognitive flexibility after 12 months of stimulation. The improvement in Y-BOCS and the absence of major cognitive side effects support the BNST as a potential target for DBS in severe OCD.

Parkinson's disease (PD) is a progressive neurodegenerative illness with both motor and nonmotor symptoms. Deep brain stimulation (DBS) is an established safe neurosurgical symptomatic therapy for eligible patients with advanced disease in whom medical treatment fails to provide adequate symptom control and good quality of life, or in whom dopaminergic medications induce severe side effects such as dyskinesias. DBS can be tailored to the patient's symptoms and targeted to various nodes along the basal ganglia-thalamus circuitry, which mediates the various symptoms of the illness; DBS in the thalamus is most efficient for tremors, and DBS in the pallidum most efficient for rigidity and dyskinesias, whereas DBS in the subthalamic nucleus (STN) can treat both tremors, akinesia, rigidity and dyskinesias, and allows for decrease in doses of medications even in patients with advanced stages of the disease, which makes it the preferred target for DBS. However, DBS in the STN assumes that the patient is not too old, with no cognitive decline or relevant depression, and does not exhibit severe and medically resistant axial symptoms such as balance and gait disturbances, and falls. Dysarthria is the most common side effect of DBS, regardless of the brain target. DBS has a long-lasting effect on appendicular symptoms, but with progression of disease, nondopaminergic axial features become less responsive to DBS. DBS for PD is highly specialised; to enable adequate selection and follow-up of patients, DBS requires dedicated multidisciplinary teams of movement disorder neurologists, functional neurosurgeons, specialised DBS nurses and neuropsychologists.