Deep brain stimulation for movement disorders. Considerations on 276 consecutive patients

Prediction of pyramidal tract side effect threshold by intra-operative electromyography in subthalamic nucleus deep brain stimulation for patients with Parkinson's disease under general anaesthesia

Introduction

In DBS for patients with PD, STN is the most common DBS target with the sweet point located dorsal ipsilaterally adjacent to the pyramidal tract. During awake DBS lead implantation, macrostimulation is performed to test the clinical effects and side effects especially the pyramidal tract side effect (PTSE) threshold. A too low PTSE threshold will compromise the therapeutic stimulation window. When DBS lead implantation is performed under general anaesthesia (GA), there is a lack of real time feedback regarding the PTSE. In this study, we evaluated the macrostimulation-induced PTSE by electromyography (EMG) during DBS surgery under GA. Our aim is to investigate the prediction of post-operative programming PTSE threshold using EMG-based PTSE threshold, and its potential application to guide intra-operative lead implantation.

Methods

44 patients with advanced PD received STN DBS under GA were studied. Intra-operative macrostimulation via EMG was assessed from the contralateral upper limb. EMG signal activation was defined as the amplitude doubling or greater than the base line. In the first programming session at one month post-operation, the PTSE threshold was documented. All patients were followed up for one year to assess clinical outcome.

Results

All 44 cases (88 sides) demonstrated activations of limb EMG via increasing amplitude of macrostimulation the contralateral STN under GA. Revision tracts were explored in 7 patients due to a low EMG activation threshold (<= 2.5 mA). The mean intraoperative EMG-based PTSE threshold was 4.3 mA (SD 1.2 mA, Range 2.0-8.0 mA), programming PTSE threshold was 3.7 mA (SD 0.8 mA, Range 2.0-6.5 mA). Linear regression showed that EMG-based PTSE threshold was a statistically significant predictor variable for the programming PTSE threshold (p value <0.001). At one year, the mean improvement of UPDRS Part III score at medication-off/DBS-on was 54.0% (SD 12.7%) and the levodopa equivalent dose (LED) reduction was 59.5% (SD 23.5%).

Conclusion

During STN DBS lead implantation under GA, PTSE threshold can be tested by EMG through macrostimulation. It can provide real-time information on the laterality of the trajectory and serves as reference to guide intra-operative DBS lead placement.

Unilateral deep brain stimulation (DBS) of nucleus ventralis intermedius thalami (Vim) for the treatment of post-traumatic tremor in children: a multicentre experience

PURPOSE

Deep brain stimulation (DBS) of nucleus ventralis intermedius thalami (Vim) is a validated technique for the treatment of essential tremor (ET) in adults. Conversely, its use for post traumatic tremor (PTT) and in paediatric patients is still debated. We evaluated the efficacy of Vim-DBS for lesional tremor in three paediatric patients with drug-resistant post-traumatic unilateral tremor.

METHODS

We retrospectively collected data regarding three patients with unilateral tremor due to severe head injury, with no MRI evidence of basal ganglia lesions. The three patients underwent stereotactic frame-based robot-assisted DBS of Vim contralateral to the tremor side.

RESULTS

Mean follow-up was 48 months (range: 36-60 months). Tremor was reduced in all patients with a better control of voluntary movements and improvement of functional status (mean FIM scale improvement + 7 points). No surgical complications occurred.

CONCLUSION

Unilateral contralateral DBS of Vim could be efficacious in post-traumatic tremor, even in paediatric patients and should be offered in PTT drug-resistant patients.

Deep brain stimulation in posterior subthalamic area for Holmes tremor: Case reports with review of the literature

Background

Holmes tremor (HT) is a refractory tremor associated with cortico-basal ganglia loops and cerebellothalamic tract abnormalities. Various drug treatments have been attempted; however, no treatment method has yet been established. Historically, thalamic deep brain stimulation (DBS) has been performed in medically refractory cases. Recently, the posterior subthalamic area (PSA) has been used for HT. Here, we report cases of HT and review the effectiveness and safety of PSA-DBS for HT.

Cases

We conducted a retrospective chart review of two patients with HT who underwent PSA-DBS. Improvement in tremors was observed 1 year after surgery without apparent complications.

Literature review

We identified 12 patients who underwent PSA-DBS for HT, including our cases. In six patients, PSA was targeted alone; for the rest, the ventralis intermediate nucleus (Vim) of the thalamus and PSA were simultaneously targeted. The Fahn-Tolosa-Marin Tremor Rating Scale improvement rates were 56.8% (range, 33.9-82.1%; n = 6) and 77.8% (range, 42.6-100%; n = 5) for the PSA-DBS and PSA+Vim-DBS, respectively.

Conclusion

Reasonable improvements in HT were observed after PSA-DBS. PSA might be an appropriate target for improving the symptoms of HT. Long-term observations, accumulation of cases, and randomized studies are required in future.

Neurostimulation for Functional Recovery After Traumatic Brain Injury: Current Evidence and Future Directions for Invasive Surgical Approaches

We aim to provide a comprehensive review of the current scientific evidence supporting the use of invasive neurostimulation in the treatment of deficits associated with traumatic brain injury (TBI), as well as to identify future directions for research and highlight important questions that remain unaddressed. Neurostimulation is a treatment modality with expanding applications in modern medical practice. Targeted electrical stimulation of specific brain regions has been shown to increase synaptogenesis and enhance structural reorganization of neuronal networks. This underlying therapeutic effect might be of high value for patients suffering from TBI because it could modulate neuronal connectivity and function of areas that are partially or completely spared after injury. The current published literature exploring the application of invasive neurostimulation for the treatment of functional deficits associated with TBI is scarce but promising. Rodent models have shown that targeted stimulation of the hippocampus or connecting structures can result in significant cognitive recovery, while stimulation of the motor cortex and deep cerebellar nuclei is associated with motor improvements. Data from clinical studies are extremely limited; single-patient reports and case series found neurostimulation to be effective in relieving motor symptoms, improving visuospatial memory, and supporting emotional adjustment. Looking forward, it will be important to identify stimulation targets and paradigms that can maximize improvement over multiple functional domains. It will also be important to corroborate the observed behavioral improvements with histological, electrophysiological, and radiological evidence. Finally, the impact of biological variables such as sex and age on the treatment outcomes needs to be explored.

Consensus Paper: Experimental Neurostimulation of the Cerebellum

The cerebellum is best known for its role in controlling motor behaviors. However, recent work supports the view that it also influences non-motor behaviors. The contribution of the cerebellum towards different brain functions is underscored by its involvement in a diverse and increasing number of neurological and neuropsychiatric conditions including ataxia, dystonia, essential tremor, Parkinson's disease (PD), epilepsy, stroke, multiple sclerosis, autism spectrum disorders, dyslexia, attention deficit hyperactivity disorder (ADHD), and schizophrenia. Although there are no cures for these conditions, cerebellar stimulation is quickly gaining attention for symptomatic alleviation, as cerebellar circuitry has arisen as a promising target for invasive and non-invasive neuromodulation. This consensus paper brings together experts from the fields of neurophysiology, neurology, and neurosurgery to discuss recent efforts in using the cerebellum as a therapeutic intervention. We report on the most advanced techniques for manipulating cerebellar circuits in humans and animal models and define key hurdles and questions for moving forward.

Deep Brain Stimulation for Multiple Sclerosis Tremor: A Meta-Analysis

OBJECTIVES

To examine the effect of deep brain stimulation (DBS) on multiple sclerosis (MS)-tremor, as measured by a normalized scale of tremor severity, with a meta-analysis of the published literature.

METHODS

Medline and EBSCO Host (January, 1998 to June, 2018) were systematically reviewed with librarian guidance, using the keywords "Deep brain stimulation" and "multiple sclerosis." Bibliographies and experts in the field were also consulted to identify missed articles. All therapeutic studies on DBS for MS-tremor, reported in the English language, within the study period were included. Papers that reported outcomes without a measure of central tendency and/or distribution were excluded. The papers were read in their entirety and graded for risk of bias according to the American Academy of Neurology (AAN) standards. To maximize statistical power, papers using different stimulation targets were grouped together. Outcomes were reported with the Fahn-Tolosa-Marin scale (FTM), the Bain-Finchley scale (CRS) and 3- and 4-point tremor severity scales and normalized with a Hedges g.

RESULTS

The search produced 13 studies suitable for meta-analysis. The random-effects meta-analysis showed that DBS improved the Hedges standardized mean tremor score by 2.86 (95%CI 2.03-3.70, p < .00001). Heterogeneity was high, with an I² of 84%, suggesting that random effects model is more appropriate. Adverse event rates varied from 8% to 50%.

CONCLUSIONS

This meta-analysis provides level III evidence that DBS may improve MS-related tremor as measured by standardized tremor severity scales.

Is awake physiological confirmation necessary for DBS treatment of Parkinson's disease today? A comparison of intraoperative imaging, physiology, and physiology imaging-guided DBS in the past decade

BACKGROUND

Deep brain stimulation (DBS) is a well-established surgical therapy for Parkinson's disease (PD). Intraoperative imaging (IMG), intraoperative physiology (PHY) and their combination (COMB) are the three mainstream DBS guidance methods.

OBJECTIVE

To comprehensively compare the use of IMG-DBS, PHY-DBS and COMB-DBS in treating PD.

METHODS

PubMed, Embase, the Cochrane Library and OpenGrey were searched to identify PD-DBS studies reporting guidance techniques published between January 1, 2010, and May 1, 2018. We quantitatively compared the therapeutic effects, surgical time, target error and complication risk and qualitatively compared the patient experience, cost and technical prospects. A meta-regression analysis was also performed. This study is registered with PROSPERO, number CRD42018105995.

RESULTS

Fifty-nine cohorts were included in the main analysis. The three groups were equivalent in therapeutic effects and infection risks. IMG-DBS (p < 0.001) and COMB-DBS (p < 0.001) had a smaller target error than PHY-DBS. IMG-DBS had a shorter surgical time (p < 0.001 and p = 0.008, respectively) and a lower intracerebral hemorrhage (ICH) risk (p = 0.013 and p = 0.004, respectively) than PHY- and COMB-DBS. The use of intraoperative imaging and microelectrode recording correlated with a higher surgical accuracy (p = 0.018) and a higher risk of ICH (p = 0.049).

CONCLUSIONS

The comparison of COMB-DBS and PHY-DBS showed intraoperative imaging's superiority (higher surgical accuracy), while the comparison of COMB-DBS and IMG-DBS showed physiological confirmation's inferiority (longer surgical time and higher ICH risk). Combined with previous evidence, the use of intraoperative neuroimaging techniques should become a future trend.

Deep brain stimulation of the thalamic ventral intermediate nucleus for Benedikt's syndrome mainly present as tremor: a long-term case observation

Benedikt's syndrome (BS) is caused by the lesion in the midbrain and specifically manifests a series of symptoms, including ipsilateral third nerve palsy, contralateral tremor, hemiataxia, and hyperactive tendon reflexes. Deep brain stimulation (DBS) for BS emerges as a new approach and achieves successfully results. We report a successful case report of thalamic ventral intermediate (VIM) nucleus DBS for a patient with BS. During follow-up of 3 years, DBS successfully control the tremor and greatly improve his living and working quality. We consider that VIM DBS may have sustained benefit for refractory BS that mainly presents as tremor.

Speech and language adverse effects after thalamotomy and deep brain stimulation in patients with movement disorders: A meta-analysis

BACKGROUND

The thalamus has been a surgical target for the treatment of various movement disorders. Commonly used therapeutic modalities include ablative and nonablative procedures. A major clinical side effect of thalamic surgery is the appearance of speech problems.

OBJECTIVE

This review summarizes the data on the development of speech problems after thalamic surgery.

METHODS

A systematic review and meta-analysis was performed using nine databases, including Medline, Web of Science, and Cochrane Library. We also checked for articles by searching citing and cited articles. We retrieved studies between 1960 and September 2014.

RESULTS

Of a total of 2,320 patients, 19.8% (confidence interval: 14.8-25.9) had speech difficulty after thalamotomy. Speech difficulty occurred in 15% (confidence interval: 9.8-22.2) of those treated with a unilaterally and 40.6% (confidence interval: 29.5-52.8) of those treated bilaterally. Speech impairment was noticed 2- to 3-fold more commonly after left-sided procedures (40.7% vs. 15.2%). Of the 572 patients that underwent DBS, 19.4% (confidence interval: 13.1-27.8) experienced speech difficulty. Subgroup analysis revealed that this complication occurs in 10.2% (confidence interval: 7.4-13.9) of patients treated unilaterally and 34.6% (confidence interval: 21.6-50.4) treated bilaterally. After thalamotomy, the risk was higher in Parkinson's patients compared to patients with essential tremor: 19.8% versus 4.5% in the unilateral group and 42.5% versus 13.9% in the bilateral group. After DBS, this rate was higher in essential tremor patients.

CONCLUSION

Both lesioning and stimulation thalamic surgery produce adverse effects on speech. Left-sided and bilateral procedures are approximately 3-fold more likely to cause speech difficulty. This effect was higher after thalamotomy compared to DBS. In the thalamotomy group, the risk was higher in Parkinson's patients, whereas in the DBS group it was higher in patients with essential tremor. Understanding the pathophysiology of speech disturbance after thalamic procedures is a priority. © 2017 International Parkinson and Movement Disorder Society.

Meta-Analysis of the Relationship between Deep Brain Stimulation in Patients with Parkinson's Disease and Performance in Evaluation Tests for Executive Brain Functions

Parkinson's disease (PD) is a neurodegenerative condition, which compromises the motor functions and causes the alteration of some executive brain functions. The presence of changes in cognitive symptoms in PD could be due to the procedure of deep brain stimulation (DBS). We searched in several databases for studies that compared performance in executive function tests before and after the DBS procedure in PE and then performed a meta-analysis. After the initial search, there were 15 articles that specifically evaluated the functions of verbal fluency, working memory, cognitive flexibility, abstract thinking, and inhibition. It was found that there were differences in the evaluation of the cognitive functions in terms of the protocols, which generated heterogeneity in the results of the meta-analysis. Likewise, a tendency to diminish functions like verbal fluency and inhibition was found, being this consistent with similar studies. In the other functions evaluated, no difference was found between pre- and postsurgery scores. Monitoring of this type of function is recommended after the procedure.

Deep Brain Stimulation in Posttraumatic Tremor: A Series of Cases and Literature Review

BACKGROUND

Posttraumatic tremor (PTT) is the most frequent movement disorder secondary to cranioencephalic trauma and can be persistent and disabling.

OBJECTIVES

We review and assess the efficacy of deep brain stimulation (DBS) at the VIM/VOP/ZI (ventralis intermedius/ventrooralis posterior/zona incerta) complex level for the treatment of PTT.

METHODS

During the period from 1999 to 2014, 5 patients diagnosed with PTT were selected who had experienced a major deterioration in their quality of life without improvement during medical treatment for more than 1 year. They underwent surgery for DBS at the VIM/VOP/ZI complex level, and the modified tremor scale before and after surgery was used for their follow-up.

RESULTS

Each patient showed improvements in their symptoms after DBS compared with baseline, which was moderate (II) in 2 cases and marked (III) in the other cases. All of the improvements were maintained with chronic DBS, without tremor rebound.

CONCLUSIONS

Stimulation of the contralateral VIM/VOP/ZI complex resulted in a noticeable improvement in tremor and recovery of independence in basic daily activities in patients with PTT.

Deep Brain Stimulation for Status Dystonicus: A Case Series and Review of the Literature

BACKGROUND

Status dystonicus (SD) is a rare and potentially life-threatening complication of primary or secondary dystonia, characterized by acute worsening of dystonic movements. There is no consensus regarding optimal treatment, which may be medical and/or surgical.

METHODS

We present our experience with pallidal deep brain stimulation (DBS) in 5 DYT1-positive patients with SD and provide a review of the literature to examine optimal management.

RESULTS

Of the 5 patients treated with pallidal DBS, all experienced postoperative resolution of their dystonic crisis within a range of 1-21 days. Long-term follow-up resulted in 1 patient returning to preoperative baseline, 3 patients improving from baseline, and 1 patient making a complete recovery. Of the 28 SD patients (including our 5 patients) reported in the literature who were treated with DBS or ablative surgery, 26 experienced cessation of their dystonic crisis with a return to baseline function and, in most cases, clinical improvement.

CONCLUSION

DBS is an effective therapeutic modality for the treatment of SD. In addition to the long-term benefits of stimulation, early and aggressive treatment may improve the overall outcome.

Deep brain stimulation for the treatment of uncommon tremor syndromes

Introduction: Deep brain stimulation (DBS) has become a standard therapy for the treatment of select cases of medication refractory essential tremor and Parkinson’s disease however the effectiveness and long-term outcomes of DBS in other uncommon and complex tremor syndromes has not been well established. Traditionally, the ventralis intermedius nucleus (VIM) of the thalamus has been considered the main target for medically intractable tremors; however alternative brain regions and improvements in stereotactic techniques and hardware may soon change the horizon for treatment of complex tremors.

Areas covered: In this article, we conducted a PubMed search using different combinations between the terms ‘Uncommon tremors’, ‘Dystonic tremor’, ‘Holmes tremor’ ‘Midbrain tremor’, ‘Rubral tremor’, ‘Cerebellar tremor’, ‘outflow tremor’, ‘Multiple Sclerosis tremor’, ‘Post-traumatic tremor’, ‘Neuropathic tremor’, and ‘Deep Brain Stimulation/DBS’. Additionally, we examined and summarized the current state of evolving interventions for treatment of complex tremor syndromes.

Expertcommentary: Recently reported interventions for rare tremors include stimulation of the posterior subthalamic area, globus pallidus internus, ventralis oralis anterior/posterior thalamic subnuclei, and the use of dual lead stimulation in one or more of these targets. Treatment should be individualized and dictated by tremor phenomenology and associated clinical features.

Movement Disorders Following Cerebrovascular Lesions: Etiology, Treatment Options and Prognosis

Post-stroke movement disorders are uncommon, but comprise an important part of secondary movement disorders. These exert variable and heterogeneous clinical courses according to the stroke lesion and its temporal relationships. Moreover, the predominant stroke symptoms hinder a proper diagnosis in clinical practice. This article describes the etiology, treatment options and prognosis of post-stroke movement disorders.

Revision Surgery of Deep Brain Stimulation Leads

INTRODUCTION

Deep brain stimulation (DBS) is widely used for various movement disorders. DBS lead revisions are becoming more common as the indications and number of cases increases.

METHODS

Patients undergoing DBS lead revisions at a single institution were retrospectively analyzed based on diagnosis, reason for revision, where the lead was relocated, and surgical technique.

RESULTS

We reviewed 497 consecutive DBS lead placements and found that there was need for 25 DBS lead revisions with at least six months of follow-up. Loss of efficacy and development of adverse effects over time were the most common reasons for lead revision across all diagnosis. Lead malfunction was the least common. Ten patients requiring 19 DBS lead revisions that underwent their original surgery at another institution were also analyzed. Surgical technique dictated replacing with a new lead while maintaining brain position and tract with the old lead until final placement. Methods to seal exposed wire were developed.

CONCLUSION

Surgical technique, as well as variable options are important in lead revision and can be dictated based on reason for revision. Over time patients who have had adequate relief with DBS placement may experience loss of efficacy and development of adverse effects requiring revision of the DBS lead to maintain its effects.

Comparative analysis of explanted DBS electrodes

BACKGROUND

Hardware-related complications frequently occur in deep brain stimulation. Microscopy and spectroscopy techniques are effective methods for characterizing the morphological and chemical basis of malfunctioning DBS electrodes. A previous report by our team revealed the morphological and chemical alterations on a malfunctioning explanted electrode when it was compared to a new device. The aim of this preliminary study was to verify whether these morphological and chemical alterations in the materials were a direct result of the hardware malfunctioning or if the failure was correlated to a degradation process over time.

METHODS

Two DBS electrodes were removed from two patients for reasons other than DBS system impairment and were analyzed by a scanning electron microscope and by an energy-dispersive X-ray spectroscopy. The results were compared to a malfunctioning device and to a new device, previously analyzed by our group.

RESULTS

The analysis revealed that the wear of the polyurethane external part of all the electrodes was directly correlated with the duration of implantation period. Moreover, these alterations were independent from the electrodes functioning and from parameters used during therapy.

CONCLUSIONS

This is the first study done that demonstrates a time-related degradation in the external layer of DBS electrodes. The analyses of morphological and chemical properties of the implanted devices are relevant for predicting the possibility of hardware's impairment as well as to improve the bio-stability of DBS systems.

Dyskinésies tardives induites par les neuroleptiques : intérêt de la stimulation cérébrale profonde

Introduction

Les dyskinésies tardives induites par les antipsychotiques sont des mouvements anormaux pouvant survenir à partir de 3 mois de prise médicamenteuse. Leur incidence, estimée à 29,7 %, semble liée à une hypersensibilité des récepteurs à la dopamine. Des thérapies médicamenteuses permettent de juguler ces effets indésirables. Lorsque ces propositions thérapeutiques échouent à soulager efficacement le patient, l’indication de la stimulation cérébrale profonde se pose alors.

Objectifs

À la lumière d’un cas clinique exposant la situation d’un jeune homme traité par antipsychotiques chez lequel des dyskinésies tardives invalidantes sont diagnostiquées, nous mettrons en évidence l’intérêt de la stimulation cérébrale profonde bilatérale pallidale interne lorsque les autres alternatives thérapeutiques ne sont pas efficaces.

Méthodes

Un report de cas complété par une revue de la littérature étayeront nos propos.

Conclusion

L’identification de facteurs de risque de survenue de ces mouvements anormaux doit davantage être considérée par les prescripteurs, pouvant agir sur un axe préventif. La place de la stimulation cérébrale profonde dans le traitement curatif de ces mouvements anormaux est encore marginale du fait des pathologies psychiatriques dont sont atteints ces sujets. Cette technique est pourtant vectrice d’une amélioration conséquente des dyskinésies tardives induites par les antipsychotiques résistantes aux thérapies médicamenteuses.

Spatial topographies of unilateral subthalamic nucleus deep brain stimulation efficacy for ipsilateral, contralateral, midline, and total Parkinson disease motor symptoms

BACKGROUND

Subthalamic nucleus (STN) deep brain stimulation is a successful intervention for medically refractory Parkinson disease, although its efficacy depends on optimal electrode placement. Even though the predominant effect is observed contralaterally, modest improvements in ipsilateral and midline symptoms are also observed.

OBJECTIVE

To elucidate the role of contact location of unilateral deep brain stimulation on contralateral, ipsilateral, and axial subscores of Parkinson disease motor symptoms.

METHODS

Eighty-six patients receiving first deep brain stimulation STN electrode placements were identified, yielding 73 patients with 3-month follow-up. Total preoperative and postoperative Unified Parkinson Disease Rating Scale Part III scores were obtained and divided into contralateral, ipsilateral, and midline subscores. Contact location was determined on immediate postoperative magnetic resonance imaging. A 3-dimensional ordinary "kriging" algorithm generated spatial interpolations for total, ipsilateral, contralateral, and midline symptom categories. Interpolative reconstructions were performed in the axial planes (z = -0.5, -1.0, -1.5, -3.5, -4.5, -6.0) and a sagittal plane (x = 12.0). Interpolation error and significance were quantified by use of a cross-validation technique and quantile-quantile analysis.

RESULTS

There was an overall reduction in Unified Parkinson Disease Rating Scale Part III symptoms: total = 37.0 ± 24.11% (P < .05), ipsilateral = 15.9 ± 51.8%, contralateral = 56.2 ± 26.8% (P < .05), and midline = 26.5 ± 34.7%. Kriging interpolation was performed and cross-validated with quantile-quantile analysis with high correlation (R2 > 0.92) and demonstrated regions of efficacy for each symptom category. Contralateral symptoms demonstrated broad regions of efficacy across the peri-STN area. The ipsilateral and midline regions of efficacy were constrained and located along the dorsal STN and caudal zona incerta.

CONCLUSION

We provide evidence for a unique functional topographic window in which contralateral, ipsilateral, and midline structures may achieve the best efficacy. Although there are overlapping regions, laterality demonstrates distinct topographies. Surgical optimization should target the intersection of optimal regions for these symptom categories.

Internal Pulse Generators in Deep Brain Stimulation: Rechargeable or Not?

OBJECTIVE

Deep brain stimulation (DBS) is a cost-effective strategy for the treatment of different neurologic disorders. However, DBS procedures are associated with high costs of implantation and replacement of the internal pulse generator (IPG). Different manufacturers propose the use of rechargeable IPGs. The objective of this study is to compare the implantation costs of nonrechargeable IPGs versus the estimated costs of rechargeable IPGs in different categories of patients to evaluate if an economic advantage for the health care system could be derived.

METHODS

The study looked at 149 patients who underwent a surgical procedure for IPG replacement. In a hypothetical scenario, rechargeable IPGs were implanted instead of nonrechargeable IPGs at the time of DBS system implantation. Another scenario was outlined in a perspective period of time, corresponding to the patients' life expectancy. Costs were calculated, and inferential analysis was performed.

RESULTS

A savings of €234,194, including the cost of management of complications, was calculated during a follow-up period of 7.9 years. In a comprehensive life expectancy period of 47 years, a savings of €5,918,188 would be obtained (P < 0.05). Long-term group data point out that a relevant savings would be expected from implantation of rechargeable IPGs in dystonic patients (P < 0.05) and patients with Parkinson disease (P < 0.05), and a savings is projected to occur in other categories of patients (P < 0.05).

CONCLUSIONS

Implantation of rechargeable IPGs presents clinical advantages compared with nonrechargeable devices. A huge economic savings can be realized with the implantation of rechargeable IPGs in categories of patients implanted with IPGs for DBS.

Deep brain stimulation in critical care conditions

Some neurological conditions require admission to an intensive care unit (ICU) where deep sedation and mechanical ventilation are administered to improve the patient's condition. Nevertheless, these treatments are not always helpful in disease control. At this stage, deep brain stimulation (DBS) could become a viable alternative in the treatment of critical neurological conditions with long-lasting clinical benefit. The value of deep brain stimulation has been investigated in the treatment of patients who had undergone surgical electrode implants as an emergency procedure to treat acute life-threatening conditions requiring admission to neurological ICU (NICU). A before-and-after perspective study was examined of seven patients who were treated with DBS for status dystonicus (SD) and post-stroke severe hemiballismus. Bilateral globus pallidus internus (GPi) DBS was performed in five SD patients and unilateral ventralis oralis anterior and posterior (Voa/Vop) nucleus of the thalamus DBS in two post-stroke hemiballismus patients. Bilateral GPi-DBS allowed SD resolution in a time lapse varying from 1 week to 3 months. No clear improvements compared to the baseline clinical condition were observed. Unilateral Voa/Vop-DBS intervention controlled hemiballismus after 10 h, and the patient was discharged in 2 days. The other patient was transferred from the NICU to the neurosurgery ward after 13 days. No surgical complications were observed in any of the above procedures. Neurostimulation procedures could represent a valuable choice in critical care conditions, when involuntary movements are continuous, life-threatening and refractory to intensive care procedures. DBS is feasible, safe and effective in selected cases.

Movement disorders in cerebrovascular disease

Movement disorders can occur as primary (idiopathic) or genetic disease, as a manifestation of an underlying neurodegenerative disorder, or secondary to a wide range of neurological or systemic diseases. Cerebrovascular diseases represent up to 22% of secondary movement disorders, and involuntary movements develop after 1-4% of strokes. Post-stroke movement disorders can manifest in parkinsonism or a wide range of hyperkinetic movement disorders including chorea, ballism, athetosis, dystonia, tremor, myoclonus, stereotypies, and akathisia. Some of these disorders occur immediately after acute stroke, whereas others can develop later, and yet others represent delayed-onset progressive movement disorders. These movement disorders have been encountered in patients with ischaemic and haemorrhagic strokes, subarachnoid haemorrhage, cerebrovascular malformations, and dural arteriovenous fistula affecting the basal ganglia, their connections, or both.

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

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

Target identification for stereotactic thalamotomy using diffusion tractography

BACKGROUND

Stereotactic targets for thalamotomy are usually derived from population-based coordinates. Individual anatomy is used only to scale the coordinates based on the location of some internal guide points. While on conventional MR imaging the thalamic nuclei are indistinguishable, recently it has become possible to identify individual thalamic nuclei using different connectivity profiles, as defined by MR diffusion tractography.

METHODOLOGY AND PRINCIPAL FINDINGS

Here we investigated the inter-individual variation of the location of target nuclei for thalamotomy: the putative ventralis oralis posterior (Vop) and the ventral intermedius (Vim) nucleus as defined by probabilistic tractography. We showed that the mean inter-individual distance of the peak Vop location is 7.33 mm and 7.42 mm for Vim. The mean overlap between individual Vop nuclei was 40.2% and it was 31.8% for Vim nuclei. As a proof of concept, we also present a patient who underwent Vop thalamotomy for untreatable tremor caused by traumatic brain injury and another patient who underwent Vim thalamotomy for essential tremor. The probabilistic tractography indicated that the successful tremor control was achieved with lesions in the Vop and Vim respectively.

CONCLUSIONS

Our data call attention to the need for a better appreciation of the individual anatomy when planning stereotactic functional neurosurgery.