Subthalamic stimulation in Parkinson's disease. Preliminary results

Microelectrode recording duration and spatial density constraints for automatic targeting of the subthalamic nucleus

BACKGROUND

Accurate detection of the boundaries of the subthalamic nucleus (STN) in deep brain stimulation (DBS) surgery using microelectrode recording (MER) is considered to refine localization and may therefore improve clinical outcome. However, MER tends to extend operation time and its cost-utility balance has been debated.

OBJECTIVES

To quantify the tradeoff between accuracy of STN localization and the spatial and temporal parameters of MER that effect the operation time using an automated detection method.

METHODS

We retrospectively estimated the accuracy of STN detection on data from 100 microelectrode trajectories. Our dense (average step = 0.12 mm) and long (average duration = 22.5 s) MER data was downsampled in the spatial and temporal domains. Then, the STN borders were detected automatically on both the downsampled and original data and compared to each other.

RESULTS

With a recording duration of 16 s, average accuracy for detecting STN entry ranged from 0.06 mm for a 0.1-mm step to 0.51 mm for a 1.0-mm step. Smaller effects were found along the temporal axis. For example, a 0.1-mm recording step yielded an STN entry average accuracy ranging from 0.06 mm for a 16-second recording duration to 0.16 mm for 0.1 s.

CONCLUSIONS

STN entry detection error was about half of the step size. Sampling duration of STN activity can be minimized to 1 s/record without compromising accuracy. We conclude that bilateral DBS surgery time utilizing MER may be significantly shortened without compromising targeting accuracy.

Surgery for movement disorders

Movement disorders, such as Parkinson's disease, tremor, and dystonia, are among the most common neurological conditions and affect millions of patients. Although medications are the mainstay of therapy for movement disorders, neurosurgery has played an important role in their management for the past 50 years. Surgery is now a viable and safe option for patients with medically intractable Parkinson's disease, essential tremor, and dystonia. In this article, we provide a review of the history, neurocircuitry, indication, technical aspects, outcomes, complications, and emerging neurosurgical approaches for the treatment of movement disorders.

Single electrode and multiple electrode guided electrical stimulation of the subthalamic nucleus in advanced Parkinson's disease

OBJECTIVE

It is still debated to what extent intraoperative electrophysiological techniques contribute to the outcome of subthalamic nucleus (STN) deep brain stimulation (DBS). Intraoperative electrophysiological recordings for identification of the STN can be made with one electrode or with multiple, simultaneously implanted electrodes. The latter provide more detailed information about the electrophysiological boundaries of the STN; however, implantation of several electrodes at one time might increase the risk of bleeding. Here we report the results of a study of patients with advanced Parkinson's disease, in which one group of patients underwent bilateral STN DBS with electrophysiological recordings from a single electrode, and the other group received STN DBS with multiple (five or fewer) simultaneously implanted electrodes.

PATIENTS AND METHODS

Fifty-five patients suffering from advanced Parkinson's disease who underwent bilateral STN stimulation were included in this study. Thirty-two patients underwent STN DBS guided by a single semi-microelectrode, and 23 patients underwent STN DBS guided with simultaneously implanted multiple microelectrodes. All patients were examined preoperatively and 3 and 12 months postoperatively with regard to activities of daily living, motor functions, and neuropsychological functions.

RESULTS

We found that the simultaneous implantation of multiple electrodes does not increase the risk of bleeding or any other major intracranial complication. The use of multiple electrodes resulted in better motor results when compared with patients who underwent STN DBS guided with a single recording electrode. There were significantly more improvements in patients' tremor and rigidity, and as a consequence, a better total Unified Parkinson Disease Rating Scale, Part III score was identified during the medication-off phase. Despite better motor effects, patients treated with multiple electrodes showed subtle deterioration in neuropsychological functions, particularly in memory function.

CONCLUSION

STN DBS performed with multiple electrophysiological recording electrodes resulted in better motor outcome but induced specific mild declines in neuropsychological functions.

Electrical stimulation devices in the treatment of epilepsy

Over the last ten years there has been a progressively increasing interest in the research and clinical application of implantable electrical brain stimulation devices in the treatment of drug-resistant epilepsy. The concept is not new, but the efforts were strengthened and accelerated after the efficacy of vagus nerve stimulation in controlling epilepsy was first demonstrated in the early 1990s and gained subsequently the approval of the USA Food and Drug Administration in 1997. This chapter reviews the progress made in this field. Special emphasis is given to the most important available evidence from animal and human studies, the neuroanatomical pathways and the role of the relevant neurotransmitters, the stimulation devices and the significance of correct programming of the stimulation parameters. The chapter also examines the antiepileptic efficacy of stimulation in all the known targets including vagus nerve, cerebellum, thalamus, subthalamic nucleus, locus ceruleus, and epileptogenic cortex. On the basis of the current evidence, the future directions of this exciting field are described.

Targets for deep brain stimulation in Parkinson's disease

The use of stimulation electrodes implanted in the brain to control severely disabling neurological and psychiatric conditions is an exciting and fast emerging area of neuroscience. An excellent example is Parkinson's disease (PD), in which tens of thousands of patients have now been implanted with stimulation electrodes. Patients with PD underwent deep brain stimulation (DBS) at the level of the thalamus, globus pallidus internus, subthalamic nucleus, pedunculopontine nucleus and prelemniscal radiation. The results of these interventions revealed that each target has its own specific stimulation-related positive and negative effects. Clinicians can choose their DBS target based on the situation of their individual PD patients. In the authors' opinion, patient-specific targeting should be preferred over disease-specific targeting. In this review, the authors give an overview of the targets that have been used for DBS in PD and discuss patient-specific targeting.

Behavioural changes after bilateral subthalamic stimulation in advanced Parkinson disease: a systematic review

INTRODUCTION

The long-lasting beneficial effects of subthalamic nucleus (STN) deep brain stimulation (DBS) on motor function have now largely been acknowledged. Whereas behavioural changes have been demonstrated in certain case reports and small case series, some authors have not observed behavioural changes at all. The extent to which these changes occur has not yet been established. The aim of the present study was to systematically analyse behavioural changes of bilateral STN DBS.

MATERIALS AND METHODS

A structured Medline search was conducted using previously described methods. Studies were selected according to specific in- and exclusion criteria. Data on patients, surgical technique, outcome and complications were collected and pooled.

RESULTS

In total 1,398 patients who underwent bilateral STN DBS were included. The total cumulative follow-up period was 1,480 patient-years. Cognitive problems were seen in 41%, depression in 8%, and (hypo)mania in 4% of the patients. Anxiety disorders were observed in less than 2%, and personality changes, hypersexuality, apathy, anxiety, and aggressiveness were observed in less than 0.5% of the group studied. About half of the patients did not experience behavioural changes.

CONCLUSION

Caregivers should be aware of the extent of these behavioural changes and a risk/benefit evaluation should be performed for individual patients.

The functional role of the subthalamic nucleus in cognitive and limbic circuits

Once it was believed that the subthalamic nucleus (STN) was no more than a relay station serving as a "gate" for ascending basal ganglia-thalamocortical circuits. Nowadays, the STN is considered to be one of the main regulators of motor function related to the basal ganglia. The role of the STN in the regulation of associative and limbic functions related to the basal ganglia has generally received little attention. In the present review, the functional role of the STN in the control of cortico-basal ganglia-thalamocortical associative and limbic circuits is discussed. In the past 20 years the concepts about the functional role of the STN have changed dramatically: from being an inhibitory nucleus to a potent excitatory nucleus, and from being involved in hyperkinesias to hypokinesias. However, it has been demonstrated only recently, mainly by reports on the behavioral (side-) effects of STN deep brain stimulation (DBS), which is a popular surgical technique in the treatment of patients suffering from advanced Parkinson Disease (PD), that the STN is clinically involved in associative and limbic functions. These findings were confirmed by results from animal studies. Experimental studies applying STN DBS or STN lesions to investigate the neuronal mechanisms involved in these procedures found profound effects on cognitive and motivational parameters. The anatomical, electrophysiological and behavioral data presented in this review point towards a potent regulatory function of the STN in the processing of associative and limbic information towards cortical and subcortical regions. In conclusion, it can be stated that the STN has anatomically a central position within the basal ganglia thalamocortical associative and limbic circuits and is functionally a potent regulator of these pathways.

Dopaminergic reinnervation of the globus pallidus by fetal nigral grafts in the rodent model of Parkinson's disease

The current neural transplantation strategy for Parkinson's disease (PD) involves the dopaminergic reinnervation of the striatum (STR). Although up to 85% reinnervation of the STR has been attained by neural transplantation, functional recovery in animal models and transplanted patients is incomplete. This limitation may be due to an incomplete restoration of the dopaminergic input to other basal ganglia structures such as the external segment of the globus pallidus (GPe, homologue of the rodent GP), which normally receives dopaminergic input from the substantia nigra (SN). As part of our investigation into a multiple grafting strategy for PD, we have explored the effects of dopaminergic grafts in the GP of rodents with unilateral 6-hydroxydopamine (6-OHDA) lesions. In this experiment, lesioned rats received either 300,000 fetal ventral mesencephalic (FVM) cells or a sham injection into the GP. Functional assessment consisted of rotational behavior at 3 and 6 weeks posttransplantation. A fluorogold tracer study was conducted to rule out any behavioral improvement due to striatal outgrowth of the GP graft. Sections were stained for glial fibrillary acidic protein (GFAP) to assess the degree of trauma in the GP by the graft in comparison to the sham injection. Immunohistochemistry for tyrosine hydroxylase (TH) was performed after transplantation to assess graft survival. Animals with GP grafts demonstrated a significant improvement in rotational behavior at 3 and 6 weeks posttransplantation (p < 0.05) while sham control animals did not improve. All animals receiving FVM cells showed TH-immunoreactive grafts in the GP posttransplantation. TH-positive neurons in the GP showed no double labeling with an intrastriatal injection of fluorogold, indicating that behavioral improvement was not due to striatal innervation by the GP graft. These observations suggest that functional recovery was the result of dopaminergic reinnervation of the GP and that this nucleus may be a potential target for neural transplantation in clinical PD.

Surgery for Parkinson disease in the United States, 1996 to 2000: practice patterns, short-term outcomes, and hospital charges in a nationwide sample

Object. The surgical treatment of Parkinson disease (PD) has undergone a dramatic shift, from stereotactic ablative procedures toward deep brain stimulaion (DBS). The authors studied this process by investigating practice patterns, mortality and morbidity rates, and hospital charges as reflected in the records of a representative sample of US hospitals between 1996 and 2000.

Methods. The authors conducted a retrospective cohort study by using the Nationwide Inpatient Sample database; 1761 operations at 71 hospitals were studied. Projected to the US population, there were 1650 inpatient procedures performed for PD per year (pallidotomies, thalamotomies, and DBS), with no significant change in the annual number of procedures during the study period. The in-hospital mortality rate was 0.2%, discharge other than to home was 8.1%, and the rate of neurological complications was 1.8%, with no significant differences between procedures. In multivariate analyses, hospitals with larger annual caseloads had lower mortality rates (p = 0.002) and better outcomes at hospital discharge (p = 0.007).

Placement of deep brain stimulators comprised 0% of operations in 1996 and 88% in 2000. Factors predicting placement of these devices in analyses adjusted for year of surgery included younger age, Caucasian race, private insurance, residence in higher-income areas, hospital teaching status, and smaller annual hospital caseload. In multivariate analysis, total hospital charges were 2.2 times higher for DBS (median $36,000 compared with $12,000, p < 0.001), whereas charges were lower at higher-volume hospitals (p < 0.001).

Conclusions. Surgical treatment of PD in the US changed significantly between 1996 and 2000. Larger-volume hospitals had superior short-term outcomes and lower charges. Future studies should address long-term functional end points, cost/benefit comparisons, and inequities in access to care.

Pathophysiology of pediatric movement disorders

Pediatric movement disorders constitute a relatively small cluster of symptoms that can be associated with many different underlying diseases. To provide effective treatment, it is essential to understand the relationship between etiology and clinical expression. This article reviews the recent literature on several common pediatric movement disorders, including spasticity, dystonia, chorea, myoclonus, bradykinesia, and tics, and it discusses current models of physiology that may help link the cellular pathology of specific diseases to the expression of clinical symptoms.

Neuropsychological sequelae of subthalamic nucleus deep brain stimulation in Parkinson's disease: a critical review

Neuropsychologists are increasingly involved in surgical candidacy evaluations and postoperative neurobehavioral assessments of patients with movement disorders, most notably those with Parkinson's disease (PD). We review here the initial studies regarding neuropsychological outcomes of deep brain stimulation (DBS) within the subthalamic nucleus (STN) for treatment of PD. Overall, these initial investigations provide preliminary support for the cognitive and neurobehavioral safety of STN DBS. Improvements in self-reported symptoms of depression and diminished verbal fluency were the most common findings, whereas changes in global cognitive abilities, memory, attention, and frontal/executive functions were inconsistent and most often described as nominal and/or transient. The generalizability of this literature is hindered by several methodological limitations, including small samples and the absence of appropriate control participants. The clinical and theoretical implications of these initial studies are highlighted and recommendations are offered to guide future research.

Complications of deep brain stimulation surgery

Currently, DBS is a commonly performed surgery for treatment of movement disorders, especially Parkinson's disease. Although nonablative and minimally invasive, this procedure may give rise to many complications and side effects, some of which are neither reversible nor adaptable. This study reviews the potential complications of DBS along the entire path of this procedure, from patient selection through the postoperative period. Although intraoperative complications such as paralysis and hematoma are rare, other serious complications due to the hardware, such as lead fracture, dislocation, and infection, are not uncommon. Complications or side effects as a result of chronic stimulation itself may be the most common. It is concluded that every member of the surgical team, including the referring neurologist, has an important role in the avoidance of such complications. Proper and careful patient selection, matching each patient to the specific DBS procedure appropriate for his/her symptom profile and suitable for his/her social and cognitive condition, along with experienced and careful intraoperative surgical routine, may be the best way to prevent the complications of DBS procedures.

Results of chronic subthalamic nucleus stimulation for Parkinson's disease: a 1-year follow-up study

BACKGROUND

Deep brain stimulation (DBS) has been established as an alternative approach for the treatment of advanced Parkinson's disease (PD). Recently, the subthalamic nucleus (STN) has been identified as the optimal target for DBS.

METHODS

Thirty-eight patients have undergone surgery for advanced PD since 1996. They include 12 females and 26 males with a mean age of 55.6 years. The mean stage on the Hoehn and Yahr Scale was 3.5 (off condition). Electrodes (Medtronic DBS 31389) were stereotactically implanted into the STN bilaterally. Targeting was performed using computerized tomography (CT) scans and ventriculography (VG). After 4 days of external stimulation, permanent neurostimulators were implanted. Patients were evaluated preoperatively and 1, 6, and 12 months postoperatively. Evaluations were performed in defined on and off states using the Unified Parkinson's Disease Rating Scale (UPDRS) as well as the Hoehn and Yahr Scale, the dyskinesia scale, and the Activities of Daily Living (ADL) Scale.

RESULTS

Significant improvement of all motor symptoms was found in all patients (UPDRS motor score 32/48 preoperatively versus 15/30 at 12-month follow-up, p < 0.001). Daily off-times were reduced by 35%. Dyskinesias also improved markedly (UPDRS IV: 3.2/3.1 [on/off] vs. 0.9/1.3 at 12 months follow-up). Postoperative L-dopa medication was adjusted (mean reduction: 53%). Complications occurred in two patients (5%) who developed infections, leading to system removal. Systems were replaced after 6 months. Two patients (5%) had a permanent worsening of a previously known depressive state and developed progressive dementia.

CONCLUSIONS

TN stimulation is a relatively safe procedure for treating advanced PD. The possibility of readjusting the stimulation parameters postoperatively improves the therapeutic outcome and reduces side effects in comparison to ablative methods.

The process and development of image-guided procedures

Medical imaging has been used primarily for diagnosis. In the past 15 years there has been an emergence of the use of images for the guidance of therapy. This process requires three-dimensional localization devices, the ability to register medical images to physical space, and the ability to display position and trajectory on those images. This paper examines the development and state of the art in those processes.

Neurosurgical intervention for Parkinson's disease: an update

For patients with advanced Parkinson's disease who do not respond to levodopa anymore, neurosurgical intervention is the only option. Cell transplantation has not met expectations as yet. Deep brain stimulation is gaining ground and currently seems to be the most efficient, flexible, and safe procedure.