Surgical and hardware complications in subthalamic nucleus deep brain stimulation

Deep brain stimulation: Challenges at the tissue-electrode interface and current solutions

Deep brain stimulation (DBS) is used to treat the motor symptoms of Parkinson's disease patients by stimulating the subthalamic nucleus. However, optimization of DBS is still needed since the performance of the neural electrodes is limited by the body's response to the implant. This review discusses the issues with DBS, such as placement of electrodes, foreign body response, and electrode degradation. The current solutions to these technical issues include modifications to electrode material, coatings, and geometry.

Deep Brain Stimulation-Related Surgical Site Infections: A Systematic Review and Meta-Analysis

BACKGROUND

Over the last decades, the increased use of deep brain stimulation (DBS) has raised concerns about the potential adverse health effects of the treatment. Surgical site infections (SSIs) following an elective surgery remain a major challenge for neurosurgeons. Few studies have examined the prevalence and risk factors of DBS-related complications, particularly focusing on SSIs.

OBJECTIVES

We systematically searched published literature, up to June 2020, with no language restrictions.

MATERIALS AND METHODS

Eligible were studies that examined the prevalence of DBS-related SSIs, as well as studies that examined risk and preventive factors in relation to SSIs. We extracted information on study characteristics, follow-up, exposure and outcome assessment, effect estimate and sample size. Summary odds ratios (sOR) and 95% confidence intervals (CI) were calculated from random-effects meta-analyses; heterogeneity and small-study effects were also assessed.

RESULTS

We identified 66 eligible studies that included 12,258 participants from 27 countries. The summary prevalence of SSIs was estimated at 5.0% (95% CI: 4.0%-6.0%) with higher rates for dystonia (6.5%), as well as for newer indications of DBS, such as epilepsy (9.5%), Tourette syndrome (5.9%) and OCD (4.5%). Similar prevalence rates were found between early-onset and late-onset hardware infections. Among risk and preventive factors, the perioperative implementation of intra-wound vancomycin was associated with statistically significantly lower risk of SSIs (sOR: 0.26, 95% CI: 0.09-0.74). Heterogeneity was nonsignificant in most meta-analyses.

CONCLUSION

The present study confirms the still high prevalence of SSIs, especially for newer indications of DBS and provides evidence that preventive measures, such as the implementation of topical vancomycin, seem promising in reducing the risk of DBS-related SSIs. Large clinical trials are needed to confirm the efficacy and safety of such measures.

Role of deep brain stimulation therapy in the magnetic resonance-guided high-frequency focused ultrasound era: current situation and future prospects

Introduction: Deep brain stimulation (DBS) is a well-established treatment of movement disorders; but recently there has been an increasing trend toward the ablative procedure magnetic resonance-guided focused ultrasound (MRgFU). DBS is an efficient neuromodulatory technique but associated with surgical complications. MRIgFUS is an incision-free method that allows thermal lesioning, with fewer surgical complications but irreversible effects.Areas covered: We look at current and prospective aspects of both techniques. In DBS, appropriate patient selection, improvement in surgical expertise, target accuracy (preoperative and intraoperative imaging), neurophysiological recordings, and novel segmented leads need to be considered. However, increased number of older patients with higher comorbidities and risk of DBS complications (mainly intracranial hemorrhage, but also infections, hardware complications) make them not eligible for surgery. With MRgFUS, hemorrhage risks are virtually nonexistent, infection or hardware malfunction are eliminated, while irreversible side effects can appear.Expert commentary: Comparison of the efficacy and risks associated with these techniques, in combination with a growing aged population in developed countries with higher comorbidities and a preference for less invasive treatments, necessitates a review of the indications for movement disorders and the most appropriate treatment modalities.

Towards unambiguous reporting of complications related to deep brain stimulation surgery: A retrospective single-center analysis and systematic review of the literature

Background and objective

To determine rates of adverse events (AEs) related to deep brain stimulation (DBS) surgery or implanted devices from a large series from a single institution. Sound comparisons with the literature require the definition of unambiguous categories, since there is no consensus on the reporting of such AEs.

Patients and methods

123 consecutive patients (median age 63 yrs; female 45.5%) treated with DBS in the subthalamic nucleus (78 patients), ventrolateral thalamus (24), internal pallidum (20), and centre médian-parafascicular nucleus (1) were analyzed retrospectively. Both mean and median follow-up time was 4.7 years (578 patient-years). AEs were assessed according to three unambiguous categories: (i) hemorrhages including other intracranial complications because these might lead to neurological deficits or death, (ii) infections and similar AEs necessitating the explantation of hardware components as this results in the interruption of DBS therapy, and (iii) lead revisions for various reasons since this involves an additional intracranial procedure. For a systematic review of the literature AE rates were calculated based on primary data presented in 103 publications. Heterogeneity between studies was assessed with the I² statistic and analyzed further by a random effects meta-regression. Publication bias was analyzed with funnel plots.

Results

Surgery- or hardware-related AEs (23) affected 18 of 123 patients (14.6%) and resolved without permanent sequelae in all instances. In 2 patients (1.6%), small hemorrhages in the striatum were associated with transient neurological deficits. In 4 patients (3.3%; 0.7% per patient-year) impulse generators were removed due to infection. In 2 patients electrodes were revised (1.6%; 0.3% per patient-year). There was no lead migration or surgical revision because of lead misplacement. Age was not statistically significant different (p>0.05) between patients affected by AEs or not. AE rates did not decline over time and similar incidences were found among all patients (423) implanted with DBS systems at our institution until December 2016. A systematic literature review revealed that exact AE rates could not be determined from many studies, which could not be attributed to study designs. Average rates for intracranial complications were 3.8% among studies (per-study analysis) and 3.4% for pooled analysis of patients from different studies (per-patient analysis). Annual hardware removal rates were 3.6 and 2.4% for per-study and per-patient analysis, respectively, and lead revision rates were 4.1 and 2.6%, respectively. There was significant heterogeneity between studies (I² ranged between 77% and 91% for the three categories; p< 0.0001). For hardware removal heterogeneity (I² = 87.4%) was reduced by taking study size (p< 0.0001) and publication year (p< 0.01) into account, although a significant degree of heterogeneity remained (I² = 80.0%; p< 0.0001). Based on comparisons with health care-related databases there appears to be publication bias with lower rates for hardware-related AEs in published patient cohorts.

Conclusions

The proposed categories are suited for an unequivocal assessment of AEs even in a retrospective manner and useful for benchmarking. AE rates in the present cohorts from our institution compare favorable with the literature.

Bilateral stereotactic lesions and chronic stimulation of the anterior thalamic nuclei for treatment of pharmacoresistant epilepsy

Background:

The use of the anterior nucleus of thalamus (ANT) as a target for treatment of pharmacoresistant epilepsy is based on its crucial role in seizure propagation. We describe results of chronic bilateral ANT stimulation and bilateral ANT lesions in 31 patients with refractory epilepsy.

Methods:

ANT DBS was performed in 12 patients (group I) and bilateral stereotactic radiofrequency lesions of ANT were performed in 19 patients (group II). Targeting was based on stereotactic atlas information with correction of the final coordinates according to the location of anatomical landmarks and intraoperative microelectrode recording data.

Results:

Both groups were similar in age, gender, seizures frequency, and duration of disease. The median x, y, and z coordinates of ANT were found to be 2.9, 5, and 11 mm anterior, lateral, and superior to the mid-commissural point, respectively. Mean seizures reduction reached 80.3% in group of patients with ANT DBS with two nonresponders and 91.2% in group of patients with lesions. Five patients from group I and three patients from group II became seizure-free. The morbidity rate was low in both groups.

Conclusions:

Stereotactic anterior thalamotomy and chronic ANT stimulation are both effective for seizure control in epilepsy originated from frontal and temporal lobes. ANT lesions and stimulation were more effective for secondary-generalized seizures compared to simple partial seizures.

An Analysis of the Use of Multichannel Microelectrode Recording During Deep Brain Stimulation Surgeries at a Single Center

BACKGROUND

Microelectrode recording (MER) can be used to map out the target nucleus and identify ideal lead placement.

OBJECTIVE

To assess the use of multichannel MER to increase the efficiency of lead placement without compromising patient safety.

METHODS

Analysis of a single center's technique for utilizing multichannel MER with 3 consistent anterior-to-posterior simultaneous passes that include an evaluation of the location of final lead placement, patient diagnosis, target nuclei, and additional work involved for refinement of targeting. Lead revision rates and rate of hemorrhage are also assessed.

RESULTS

There were a total of 237 lead placements in 123 patients over a 4-yr period. In 4.2% of lead placements, additional planning was required, while only 2.5% required additional MER. The lead placement matched 51.3% of the time in bilateral placements and was consistent regardless of target nuclei. In 84.8% of cases, the final lead placement was within the initial 3 MER passes. An additional 11.3% could be placed without the need for an additional pass. There were 2 lead revisions and no hemorrhage or stroke complications.

CONCLUSION

This series demonstrates that our technique of multichannel MER leads to accurate and efficient lead placement maintaining its safety profile.

Changing of the guard: reducing infection when replacing neural pacemakers

OBJECTIVE

Infection of deep brain stimulation (DBS) hardware has a significant impact on patient morbidity. Previous experience suggests that infection rates appear to be higher after implantable pulse generator (IPG) replacement surgery than after the de novo DBS procedure. In this study the authors examine the effect of a change in practice during DBS IPG replacements at their institution.

METHODS

Starting in January 2012, patient screening for methicillin-resistant Staphylococcus aureus (MRSA) and, and where necessary, eradication was performed prior to elective DBS IPG change. Moreover, topical vancomycin was placed in the IPG pocket during surgery. The authors then prospectively examined the infection rate in patients undergoing DBS IPG replacement at their center over a 3-year period with at least 9 months of follow-up.

RESULTS

The total incidence of infection in this prospective consecutive series of 101 IPG replacement procedures was 0%, with a mean follow-up duration of 24 ± 11 months. This was significantly lower than the authors' previously published historical control group, prior to implementing the change in practice, where the infection rate for IPG replacement was 8.5% (8/94 procedures; p = 0.003).

CONCLUSIONS

This study suggests that a change in clinical practice can significantly lower infection rates in patients undergoing DBS IPG replacement. These simple measures can minimize unnecessary surgery, loss of benefit from chronic stimulation, and costly hardware replacement, further improving the cost efficacy of DBS therapies.

An Analysis of Scalp Thickness and Other Novel Risk Factors for Deep Brain Stimulator Infections

Introduction: Deep brain stimulator (DBS) infections are a persistent problem for patients undergoing this procedure. They may require further surgery, treatment with antibiotics, or even removal of the device. To date, no consensus exists on the best practices to avoid DBS infections or what factors predispose patients to an eventual infection. The goal of this study was to examine several patient factors for association with DBS infection.

Methods: A single-center, single-surgeon quality improvement database was queried. All patients who experienced an infection were identified. The primary variable analyzed was scalp thickness. Other pre-specified, secondary variables included routine intraoperative cultures, operative time, diagnosis, and age.

Results: None of the independent variables examined were significantly associated with DBS infections. Only two of the 46 infections qualified as surgical site infections as defined by the Centers for Disease Control.

Conclusion: DBS infections are independent of all of the predictor variables analyzed. Surgical site infections, according to traditional definitions, are not the optimal definition for evaluating DBS infections/erosions. New studies must examine new variables that are not routinely gathered in this population. Also, because of the rare event rates and difficulty in randomizing patients to exposures, a large, multicenter registry may be the optimal study design to solve this clinical problem.

Intra-operative micro-electrode recording in functional neurosurgery: Past, present, future

The field of functional neurosurgery has experienced a rise, fall and lastly a renaissance over the past 75years. Micro-electrode recording (MER) played a key role during this eventful journey. However, as the intra-operative MRI continues to evolve, a pertinent question about the utility of MER has been raised in recent years. In this article, we critically review these current controversies. The English literature is reviewed and the complex technique of MER is discussed in a simplified manner. The improvement of neuroimaging and its application in functional neurosurgery, especially in deep brain stimulation, is discussed. Finally, the current controversies and technical advances which can direct the future are reviewed. The results of existing meta-analyses addressing the controversies are summarized. Wide variations of pre-operative and intra-operative targeting methods have been described in the literature. Though functional neurosurgery is generally safe, complications do occur and multiple passes during MER can certainly add to the risk of inadvertent hemorrhage and infection. Additionally, the recent introduction of newer MRI modalities has ensured better delineation of the target. However, MER is still useful to address brain shift, for mapping of newer targets, for ablative surgeries and in centers without an intra-operative imaging facility. In the current scenario, it is nearly impossible to conduct a prospective study to decide the utility of MER. The importance of MER may further diminish in the future as a routine procedure, but its role as a gold standard procedure may still persist.

Chronological Changes of C-Reactive Protein Levels Following Uncomplicated, Two-Staged, Bilateral Deep Brain Stimulation

Objective

The occurrence of acute cerebral infection following deep brain stimulation (DBS) is currently being reported with elevation of C-reactive protein (CRP) level. The aim of the present study was to establish normal range of the magnitude and time-course of CRP increases following routine DBS procedures in the absence of clinical and laboratory signs of infection.

Methods

A retrospective evaluation of serial changes of plasma CRP levels in 46 patients undergoing bilateral, two-staged DBS was performed. Because DBS was performed as a two-staged procedure involving; implantation of lead and internal pulse generator (IPG), CRP was measured preoperatively and postoperatively every 2 days until normalization of CRP (post-lead implantation day 2 and 4, post-IPG implantation day 2, 4, and 6).

Results

Compared with preoperative CRP levels (0.12±0.17 mg/dL, n=46), mean CRP levels were significantly elevated after lead insertion day 2 and 4 (1.68±1.83 mg/dL, n=46 and 0.76±0.38 mg/dL, n=16, respectively, p<0.001). The mean CRP levels at post-lead implantation day 2 were further elevated at post-IPG implantation day 2 (3.41±2.56 mg/dL, n=46, respectively, p<0.01). This elevation in post-IPG day 2 rapidly declined in day 4 (1.24±1.29 mg/dL, n=46, p<0.05) and normalized to preoperative value at day 6 (0.42±0.33 mg/dL, n=46, p>0.05). Mean CRP levels after IPG implantation were significantly higher in patients whose IPGs were implanted at post-lead day 3 than those at post-lead day 5-6 (3.99±2.80 mg/dL, n=30, and 2.31±1.56 mg/dL, n=16, respectively, p<0.05). However, there was no difference in post-IPG day 2 and 4 between them (p>0.05).

Conclusion

The mean postoperative CRP levels were highest on post-IPG insertion day 2 and decreased rapidly, returning to the normal range on post-IPG implantation day 6. The duration of post-lead implantation period influenced the magnitude of CRP elevation at post-IPG insertion day 2. Information about the normal response of CRP following DBS could help to avoid unnecessary diagnostic and therapeutic efforts.

A groove technique for securing an electrode connector on the cranial bone: case analysis of efficacy

Objective

A groove technique for securing an electrode connector was described as an alternative surgical technique in deep brain stimulation (DBS) surgery to avoid electrode connector-related complications, such as skin erosion, infection, and migration.

Methods

We retrospectively reviewed 109 patients undergoing one of two techniques; the standard technique (52 patients using 104 electrodes) and the groove technique (57 patients using 109 electrodes) for securing the electrode connector in DBS surgery, regardless of patient disease. In the standard percutaneous tunneling technique, the connector was placed on the vertex of the cranial surface. The other technique, so called the groove technique, created a groove (about 4 cm long, 8 mm wide) in the cranial bone at the posterior parietal area. Wound erosion and migration related to the connectors were compared between the two techniques.

Results

The mean follow-up period was 73 months for the standard method and 46 months for the groove technique. Connector-related complications were observed in three patients with the groove technique and in seven patients with the standard technique. Wound erosion at the connector sites per electrode was one (0.9%) with the groove technique and six (5.8%) with the standard technique. This difference was statistically significant. The electrode connector was migrated in two patients with the groove technique and in one patient with the standard technique.

Conclusions

The groove technique, which involves securing an electrode using a groove in the cranial bone at the posterior parietal area, offers an effective and safe method to avoid electrode connector-related complications during DBS surgery.

Acute brain reaction to DBS electrodes after deep brain stimulation: chronological observation

BACKGROUND

As increasing numbers of deep brain stimulation (DBS) procedures are performed, rare abnormal findings on postoperative images that are not attributable to well-known complications are reported. Between 2005 and 2012, we encountered several symptomatic patients with transient abnormal low-attenuation lesions on postoperative computed tomography (CT) scans. The aim of this study was to clarify this rare phenomenon using chronological observations and to suggest a feasible mechanism.

RESULTS

In this period, seven (3.2 %) patients displayed transient increased low-attenuation signals, circumferentially surrounding the DBS electrodes and extending into the subcortical white matter. All these patients suffered from unexpected but transient neurological symptoms during the postoperative period. The abnormal low-attenuation lesions only disappeared completely a considerable time after the clinical symptoms had disappeared, without treatment in most patients.

CONCLUSIONS

We report here our chronological observations of acute brain reactions after DBS procedures, which we believe are neither infectious nor vascular, but are possibly caused by the mechanical breakdown of the blood-brain barrier by microelectrode recordings or by anchored DBS electrodes. These lesions are thought to constitute a self-limiting disorder requiring no further treatment.

Continuous perioperative apomorphine in deep brain stimulation surgery for Parkinson's disease

BACKGROUND

Patients with Parkinson's disease (PD) deprived of dopaminergic medication to facilitate awake testing during the deep brain stimulation (DBS) procedure are at increased risk of neurologic deterioration.. The aim of this survey was to demonstrate the safety of subcutaneous apomorphine treatment for reducing surgery-related neurologic deterioration in patients undergoing DBS surgery for PD.

METHODS

Ninety-two patients who underwent DBS surgery for PD between 11/2007 and 10/2011 in our department were retrospectively analyzed for this survey. Demographic data, apomorphine dosage, side-effects and need of ICU/IMC stay were collected and analyzed.

RESULTS

Seventy-two out of 92 patients (78.3%) received apomorphine treatment; main reason for omission of treatment was intolerable nausea (16/92, 17.3%). Apomorphine treatment was well tolerated and the most common side effect was nodular panniculitis. No severe complications were observed. No patient required ICU/IMC stay related to dopaminergic deprivation.

CONCLUSIONS

Perioperative withdrawal of dopaminergic medication in PD patients leads to an increased risk of neurologic and respiratory deterioration during DBS procedures. These complications can likely be tempered using perioperative subcutaneous apomorphine as a substitute. Our 5-year experience indicates a reduction in postoperative neurologic deterioration and ICU/IMC stay need. We consider perioperative apomorphine safe during DBS surgery for PD.

One-step tunneling of DBS extensions--a technical note

BACKGROUND

Infection constitutes a serious adverse event in deep brain stimulation (DBS) surgery, being responsible for difficult therapeutic decisions that may ultimately involve the removal of implanted material. Some cases begin with skin erosion and wound dehiscence of the retroauricular incision, which is one of the most fragile points. Several techniques of rotation flaps and skin reconstruction, as well as prolonged antibiotic regimens, have been proposed as therapeutic options. To prevent the onset of this complication, the authors propose a one-step tunneling technique of DBS extensions, avoiding the opening of the retroauricular space.

METHODS

We describe a surgical technique of a one-step tunneling of DBS extensions in 20 patients submitted to subthalamic DBS for Parkinson's disease, avoiding the opening of the retroauricular space.

RESULTS

After implantation of the extensions using this technique, we had no erosions of the retroauricular skin, with a consequent reduction in the number of infections.

CONCLUSIONS

The authors describe an easy surgical technique that allows reduction of wound and erosion complications, with great benefits for DBS patients.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Diagnosis and treatment of complications related to deep brain stimulation hardware

Deep brain stimulation is a therapeutic technique increasingly used in the treatment of a variety of neurological, psychiatric, and pain disorders. Although beneficial, it carries the immediate and long-term risks associated with implanted hardware in the brain parenchyma and subcutaneous tissue. The most common hardware complications include electrode migrations or misplacements, wire fractures, skin erosion, infections, and device malfunction. We systematically reviewed the literature on deep brain stimulation-related complications and propose a diagnostic and therapeutic algorithm. Our aim is to provide a guide for clinicians and medical staff involved in the treatment of patients with deep brain stimulation for rapid recognition and efficient management of these complications.

Tourette syndrome (TS) bears a higher rate of inflammatory complications at the implanted hardware in deep brain stimulation (DBS)

BACKGROUND

Deep brain stimulation (DBS) is a commonly performed surgical technique for the treatment of movement disorders, and recent surgical trials concerning the treatment of a wider range of disorders have recently been published. Despite DBS being non-ablative and minimally invasive, numerous complications and side effects have been recorded. In particular, concerning the growing interest in novel indications for DBS, an enthusiastic approach has put neurosurgeons at risk of underestimating some of the complications that might be associated with specific characters of the treated disease.

OBJECTIVE

Our objective was to evaluate hardware failures and rates of infective complications in correlation to the different indications to DBS, in order to ascertain whether DBS in Tourette syndrome (TS) is characterized by specific risks and pitfalls.

METHODS

We retrospectively reviewed our experience of 531 procedures on 272 patients treated for various movement disorders, among which 39 patients were treated for conservative treatmentrefractory TS.

RESULTS

A statistically significant association of infective complications was found with the TS subgroup.

CONCLUSIONS

It is our belief that specific behavioral characters of the TS patients may be put into association with this specific complication and need to be considered carefully when indicating DBS as treatment of choice for these patients.

Surgical and hardware complications of deep brain stimulation. A seven-year experience and review of the literature

PURPOSE

Deep brain stimulation (DBS) has been established as a safe and efficient method for the treatment of various movement disorders. As the emerging applications continue to expand and more centers become eligible for the procedure, complication rates and complication avoidance become increasingly important. Our aim was to report the DBS-related complication in our department over the last 7 years, compare our rates with those reported in the literature, and highlight those practices that will aid complications avoidance.

PATIENTS AND METHODS

Since 2003, 106 patients underwent DBS for various pathologies in our department. There were 38 (36%) females and 68 (64%) males with a mean age of 57 years. Preoperative diagnoses included Parkinson's disease (n = 88), dystonia (n = 12), tremor (n = 3), epilepsy (n = 1), obsessive-compulsive disorder (n = 1), and central pain syndrome (n = 1). Surgical and hardware-related complications, their treatment, and outcome were recorded and compared with those reported in the literature.

RESULTS

There were 12 procedure-related complications (11.3% of patients, 5.7% of the procedures). These included death (n = 1), aborted procedure (n = 1), postoperative respiratory distress (n = 3), intracranial hemorrhage (n = 2), epilepsy (n = 1), postoperative confusion or agitation (n = 3), and malignant neuroleptic syndrome (n = 1). Hardware-related complications presented in 4.3% of the procedures and included infection (five patients, 4.7%), electrode breakage (0.94%), lead migration or misplacement (0.94%), and stricture formation (two patients, 1.9%).

CONCLUSIONS

Complication rates after DBS surgery remain low, proving that DBS is not only effective but also safe. Certain strategies do exist in order to minimize complications.

DBS-relevant electric fields increase hydraulic conductivity of in vitro endothelial monolayers

Deep brain stimulation (DBS) achieves therapeutic outcome through generation of electric fields (EF) in the vicinity of energized electrodes. Targeted brain regions are highly vascularized, and it remains unknown if DBS electric fields modulate blood-brain barrier (BBB) function, either through electroporation of individual endothelial cells or electro-permeation of barrier tight junctions. In our study, we calculated the intensities of EF generated around energized Medtronic 3387 and 3389 DBS leads by using a finite element model. Then we designed a novel stimulation system to study the effects of such fields with DBS-relevant waveforms and intensities on bovine aortic endothelial cell (BAEC) monolayers, which were used as a basic analog for the blood-brain barrier endothelium. Following 5 min of stimulation, we observed a transient increase in endothelial hydraulic conductivity (Lp) that could be related to the disruption of the tight junctions (TJ) between cells, as suggested by zonula occludens-1 (ZO-1) protein staining. This 'electro-permeation' occurred in the absence of cell death or single cell electroporation, as indicated by propidium iodide staining and cytosolic calcein uptake. Our in vitro results, using uniform fields and BAEC monolayers, thus suggest that electro-permeation of the BBB may occur at electric field intensities below those inducing electroporation and within intensities generated near DBS electrodes. Further studies are necessary to address potential BBB disruption during clinical studies, with safety and efficacy implications.

Reoperation for suboptimal outcomes after deep brain stimulation surgery

OBJECTIVE

To examine a case series of reoperations for deep brain stimulation (DBS) leads in which clinical scenarios revealed suboptimal outcome from a previous operation. Suboptimally placed DBS leads are one potential reason for unsatisfactory results after surgery for Parkinson's disease (PD), essential tremor (ET), or dystonia. In a previous study of patients who experienced suboptimal results, 19 of 41 patients had misplaced leads. Similarly, another report commented that lead placement beyond a 2- to 3-mm window resulted in inadequate clinical benefit, and, in 1 patient, revision improved outcome. The goal of the current study was to perform an unblinded retrospective chart review of DBS patients with unsatisfactory outcomes who presented for reoperation.

METHODS

Patients who had DBS lead replacements after reoperation were assessed with the use of a retrospective review of an institutional review board-approved movement disorders database. Cases of reoperation for suboptimal clinical benefit were included, and cases of replacement of DBS leads caused by infection or hardware malfunction were excluded. Data points studied included age, disease duration, diagnosis, motor outcomes (the Unified Parkinson Disease Rating Scale III in PD, the Tremor Rating Scale in ET, and the Unified Dystonia Rating Scale in dystonia), quality of life (Parkinson's Disease Questionnaire-39 in PD), and the Clinician Global Impression scale. The data from before and after reoperation were examined to determine the estimated impact of repeat surgery.

RESULTS

There were 11 patients with PD, 7 with ET, and 4 with dystonia. The average age of the PD group was 52 years, the disease duration was 10 years, and the average vector distance of the location of the active DBS contact was adjusted 5.5 mm. Six patients (54%) with PD had preoperative off medication on DBS Unified Parkinson Disease Rating Scale scores that could be compared with postoperative off medication on DBS scores. The average improvement across this group of patients was 24.4%. The Parkinson's Disease Questionnaire-39 improved in the areas of mobility (28.18), activities of daily living (14.77), emotion (14.72), stigma (17.61), and discomfort (17.42). The average age of the ET group was 66 years, the disease duration was 29 years, and the average adjusted distance was 6.1 mm. Five ET patients (83.3%) in the cohort had a prereplacement on DBS Tremor Rating Scale and a postreplacement on DBS Tremor Rating Scale with the average improvement of 60.4%. The average age of the dystonia group was 39 years, the average disease duration was 7 years, and the average adjusted lead distance was 6.7 mm. Three patients (75%) with dystonia had prereplacement on DBS Unified Dystonia Rating Scale and postreplacement on DBS Unified Dystonia Rating Scale scores. Across these 3 dystonia patients, the improvement was 12.8%. Clinician Global Impression scale scores (1, very much improved; 2, much improved; 3, minimally improved; 4, no change; 5, minimally worse; 6, much worse; 7, very much worse) after replacement revealed the following results in patients with PD: 1, 7 patients; 2, 3 patients; 3, 1 patient); with ET (1, 4 patients; 2, 3 patients); and with dystonia (1, 1 patient; 2, 2 patients; 3, 1 patient). The latency from original lead placement to reoperation (repositioning/revision) overall was 28.9 months (range, 2-104 mo); however, in leads referred from outside institutions (n = 11 patients), this latency was 48 months (range, 12-104 mo) compared with leads implanted by surgeons from the University of Florida (n = 11 patients), which was 9.7 months (range, 2-19 mo). The most common clinical history was failure to achieve a perceived outcome; however, history of an asymmetric benefit was present in 4 (18.2%) of 22 patients, and lead migration was present in 3 (13.6%) of 22 patients.

CONCLUSION

There are many potential causes of suboptimal benefit after DBS. Timely identification of suboptimal lead placements followed by reoperation and repositioning/replacement in a subset of patients may improve outcomes.