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Efficacy of bilateral subthalamic nucleus (STN) stimulation in Parkinson's disease.

BACKGROUND: Deep brain stimulation (DBS) has, for the most part, replaced irreversible stereotactic coagulations in the surgical treatment of advanced Parkinson's disease. This study was undertaken to evaluate the benefits of bilateral STN stimulation related to its potential risks and side effects. METHOD: Twenty-nine consecutive Parkinsonian patients treated with STN-DBS were prospectively followed-up. Effects on Parkinsonian symptoms were evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS). The evaluation was performed preoperatively and included postoperative follow-up evaluations at one and twelve months. All evaluations were made during the patient's best on-medication phase and postoperative follow-ups were conducted under both stimulator-on and stimulator-off conditions by a blinded neurologist. A neuropsychologist also evaluated the patients at every visit. FINDINGS: Two patients were excluded from the analysis because of severe surgical complications and three for an infection demanding the removal of the stimulator material. Other complications and side effects were clearly milder and temporary. At twelve months after surgery dyskinesia scores in the UPDRS were 53% lower than preoperative values. The results of the UPDRS motor scores improved 31.4% and activities of daily living (ADL) scores increased 19% compared with the preoperative situation. Also, the daily levodopa dose was 22% lower. Neuropsychological changes were minor, except for some deterioration in verbal fluency. CONCLUSION: The majority of Parkinsonian patients experienced significant and long lasting relief from their motor symptoms and an improvement in ADL functions due to DBS-STN therapy when evaluated at the best on-medication phase.

Aged↗

Effect of high-frequency stimulation of the subthalamic nucleus on subthalamic neurons: an intracellular study.

BACKGROUND/AIMS: The precise mechanism of action of deep brain stimulation in the subthalamic nucleus (STN) for the treatment of Parkinson's disease and epilepsy is unknown. In the present study, the intracellular effects on STN neurons following high-frequency stimulation (HFS) of STN were examined to test the hypothesis that HFS results in either an increase or a decrease in neuronal action potential generation. METHODS: Intracellular electrophysiological recordings were made in the rat STN neurons in in vitro slice preparations. A concentric bipolar stimulating electrode was placed in the STN, and electrical stimulation (duration, 100-2000 ms; amplitude, 10-500 microA, and frequency, 10-200 Hz) was delivered while simultaneously recording intracellularly from a STN neuron using a sharp electrode. RESULTS: HFS of STN resulted in the generation of excitatory postsynaptic potentials and an increase in action potential firing during the stimulation period followed by a period of poststimulation inhibition of firing in STN neurons. The degree of increase in action potentials from HFS was critically dependent on the frequency of electrical stimulation, i.e. at approximately 100-140 Hz, maximal increase was obtained, but at 200 Hz, the activity was blocked. Interestingly, the duration of poststimulation inhibition of firing was dependent on the duration of stimulation, i.e. the longer the HFS, the longer the inhibition. CONCLUSIONS: These results suggest that the mechanism of action of deep brain stimulation involves initial excitation followed by later inhibition of STN neurons at a cellular level rather than primary inhibition, as previously hypothesized.

Action Potentials↗

Stimulation methods for neuropathic pain control.

Neurostimulation methods for control of chronic neuropathic pain have recently gained in popularity. The reasons for this are multifactorial. As opposed to nerve ablation, these methods are minimally invasive and reversible. The improvements in hardware design simplified implantation techniques and prolonged equipment longevity. Stimulation trials have become less invasive, allowing patients to test its effects before final implantation. Finally, the scientific evidence has shown good outcomes of neurostimulation methods for chronic neuropathic pain control. Recent research efforts have revealed new potential mechanisms of action of neurostimulation. Whereas its action was widely explained by gate control theory in the past, it seems that neuromodulation acts also by modulation of neurotransmitters in the central nervous system. Three neurostimulation methods are currently used in clinical practice: spinal cord stimulation (SCS), peripheral nerve stimulation (PNS), and deep brain stimulation (DBS). The SCS and PNS are excellent treatment choices for certain forms of neuropathic pain. The new indications for SCS are end-stage peripheral vascular disease and ischemic heart disease, whereas PNS is used for the treatment of occipital neuralgia and chronic pelvic pain. DBS is reserved for carefully selected patients in whom the other treatment modalities have failed. In a minority of patients the "tolerance" to neurostimulation develops after long-term use. Further research is needed to establish better outcome predictors to neurostimulation and possibly improve patient selection criteria.

Electric Stimulation Therapy↗

Electrical stimulation in the treatment of pain.

PURPOSE: To review the published literature concerning the treatment of painful conditions using devices that deliver electrical stimulation to nervous structures. The review briefly surveys the results obtained using surface electrodes ("TENS") as well as implanted devices. METHOD: The method used is a critical review of the important published literature up to mid-1999. References were obtained using Medline and the keywords "pain", together with "electrical", "stimulation", "neurostimulation" or "TENS". RESULTS: Electrical stimulation has been found to be of potential benefit in the management of a range of painful conditions. Adequately controlled trials of electrical stimulation are often difficult to achieve. Implanted devices tend to be used in the more severe intractable pain conditions. It is likely that there is more than one mechanism of action. The mechanisms of action are however still often poorly understood, even though historically theoretical and experimental advances in the understanding of pain mechanisms prompted the development of clinical systems and the institution of clinical studies. CONCLUSIONS: TENS has proved to be remarkably safe, and provides significant analgesia in about half of patients experiencing moderate predictable pain. Implanted devices can be more effective, but they carry a risk of device failure, implant infection or surgical complication, and are reserved for the more severe intractable chronic pains. The main implanted devices used clinically are the spinal cord stimulator and the deep brain stimulator.

Angina Pectoris↗

Pain management after lower extremity amputation.

Phantom pain may occur in up to 85% of patients after limb amputation. Although the pathophysiology of postamputation phantom pain is not well understood, it seems to be produced by a complex multifactorial interaction between the peripheral, sympathetic, and central nervous systems. The theoretical aspects of this are reviewed. Management of phantom limb pain may be both medical and surgical. Among the pharmacological agents proved effective against phantom pain are beta-blockers, tricyclic antidepressants, and anticonvulsants. Surgical management includes peripheral nerve stimulation, thermocontrolled coagulation of the spinal cord, spinal cord stimulation, transcutaneous nerve stimulation, and stereotactic deep brain stimulation.

Adrenergic beta-Antagonists↗

Neural stimulation for Parkinson's disease: current therapies and future directions.

Neural stimulation has rapidly become an integral tool in the treatment of Parkinson's disease and other movement disorders. Today it serves as an important adjunct to medical therapy that continues to gain applicability to patients in whom the disease has progressed significantly. Studies have demonstrated efficacy in several deep-brain targets, with prolonged benefit exceeding 5-year follow-up times. Continuing study is teaching us more about the mechanism of deep-brain stimulation effect. New targets, which may treat the disease more successfully, are being examined. In this review, the history of deep-brain stimulation, the rationale for the known targets of stimulation; the clinical evidence demonstrating their benefit and, finally, future perspectives on new treatments that are being investigated and may have an impact on the field are discussed.

Brain↗

Conventional MRI is inadequate to delineate the relationship between the red nucleus and subthalamic nucleus in Parkinson's disease.

BACKGROUND: An understanding of the relationships between the anterior commissure-posterior commissure line (AC-PC), the subthalamic nucleus (STN), and red nucleus (RN) is imperative if these structures are to be used for targeting in deep brain stimulation. Currently, these relationships are incompletely understood and difficult to assess using conventional MRI. We examined the location and relationships of the STN and the RN to the AC-PC line and to each other in order to provide a greater understanding of their utility when targeting the STN, and the consistency of these anatomic relationships when examined using conventional MRI. METHODS: A total of 52 STN and RN in 26 patients with Parkinson's disease were evaluated on T2-weighted MR images. The anterior and posterior commissures and the border coordinates of the STN and RN were derived using frame coordinates. The distances from the midcommissural point (mcp) to the centers of the STN and RN, the diameters for each nucleus, and the distances between the nuclei were calculated in the x-, y-, and z-axes. RESULTS: The mean AC-PC length was 26.1 +/- 1.3 mm. The distance from the mcp to the center of the STN was 10 +/- 0.7 mm in the x-axis, 0.2 +/- 0.7 mm in the y-axis, and 3.3 +/- 0.9 mm in the z-axis. The distance from the mcp to the center of the RN was 4.7 +/- 0.6 mm in the x-axis, -5.9 +/- 1.0 mm in the y-axis, and 6.1 +/- 1.3 mm in the z-axis. The distance between the STN and RN was 2.3 +/- 0.7 mm in the x-axis, 2.1 +/- 1.0 mm in the y-axis, and -0.2 +/- 1.3 mm in the z-axis. CONCLUSIONS: Although recent studies imply that the RN can be used as a relatively consistent marker for the position of the STN, the present data suggest otherwise. These data indicate that a single targeting method may be inadequate given the resolution of conventional MRI, and that it is imperative to use multiple anatomical measurements when targeting the STN for deep brain stimulation in Parkinson's disease.

Deep Brain Stimulation↗

[Treatment of severe Parkinson disease with electric stimulation of the subthalamic nuclei].

INTRODUCTION: Patients with Parkinson's disease suffering from severe fluctuations, i.e. dyskinesias and on-off periods and/or severe tremor, who cannot be improved by adjustment of the medical treatment, can be treated with deep brain stimulation via leads implanted bilaterally into the subthalamic nuclei. METHODS: Nine patients with advanced idiopathic Parkinson's disease were treated with stereotactic and bilateral implantation of leads into the subthalamic nuclei. All patients had levodopa responsive Parkinson's disease and levodopa induced fluctuations in the form of on-off periods and dyskinesias. The mean age was 61 years and the mean duration of disease 15 years. The patients were followed for 12 months and evaluated with the Unified Parkinson's Disease Rating Scale off and on medications before and after lead implantation. RESULTS: The Hoehn & Yahr stage fell from 3.9/2.8 before lead implantation and off/on medication to 3.0/2.3 with lead stimulation turned on and off/on medication. The activity of daily living (ADL) index was significantly improved and reduced from 27/13 before lead implantation and off/on medication to 12/7 with the stimulation turned on and off/on medication i.e. with 55%/46% on stimulation. The motor score was likewise significantly improved and reduced from 55/28 to 24/17 i.e. with 56%/39% on stimulation. The most important results of deep brain stimulation in the subthalamic nuclei is the significant reduction of the motor fluctuations. On stimulation off periods were reduced from 30% to 6% and the dyskinesias were significantly reduced from 47% to 14% of the daytime. The mean dose of levodopa equivalent medication was reduced with 26%. DISCUSSION: In conclusion, patients with advanced Parkinson's disease and levodopa induced fluctuations can be successfully treated with bilateral high frequency electric stimulation of leads implanted into the subthalamic nuclei.

Adult↗

Concepts and methods in chronic thalamic stimulation for treatment of tremor: technique and application.

OBJECTIVE: To rationalize the technique and reduce the costs associated with chronic deep brain stimulation of the thalamus for treatment of refractory tremor. METHODS: The efficacy and safety of a modification in surgical techniques was prospectively assessed in 94 patients with tremor. Bilateral electrodes were implanted in 29 patients, and 65 patients received unilateral implants. Forty-five patients had Parkinson's disease tremor, 42 patients had essential tremor, and 7 patients had kinetic tremors of different causes. In all instances, intraoperative stimulations to analyze the thresholds of intrinsic and extrinsic responses were performed directly with the implanted leads. The electrodes were repositioned until satisfactory results were achieved. The pulse generators were implanted directly after the first step in the same operative session. Patients were not subjected to interoperative test stimulation trials. RESULTS: Postoperative improvement of tremor at a mean follow-up of 11.9 months was rated as excellent in 47 patients (50%), marked in 37 patients (39%), moderate in 8 patients (9%), and minor in 2 patients (2%). There was no persistent morbidity related to surgery. In patients with Parkinson's disease, the symptomatic improvement of tremor was rated as excellent in 51% of patients, marked in 36%, moderate in 11%, and minor in 2%. In patients with essential tremor, symptomatic outcome was classified as excellent in 57% of patients, marked in 36%, moderate in 5%, and minor in 2%. Six of the seven patients with kinetic tremor achieved marked symptomatic improvement, and one patient experienced moderate improvement. Forty patients experienced stimulation-related side effects. Side effects were mild in general, and they were reversible with a change in electrical parameters. They occurred more frequently in patients who had bilateral stimulation. CONCLUSION: Excellent to marked improvement of tremor is achieved in the majority of patients with physiological target determination via implanted leads in thalamic deep brain stimulation. Interoperative test stimulation trials are unnecessary. Modifications in technique may help to reduce the costs of the related hospital stay.

Adult↗

Influence of chronic bilateral stimulation of the subthalamic nucleus on cognitive function in Parkinson's disease.

BACKGROUND: The clinical efficacy of chronic deep brain stimulation in the treatment of parkinsonian patients with severe levodopa-related motor adverse effects has been repeatedly shown. Bilateral subthalamic nucleus (STN) stimulation has been shown to present an advantage over pallidal stimulation as it induces a higher antiakinetic effect and has positive effects on all parkinsonian symptoms. The morbidity of such surgery is usually considered to be very low. However, few studies have extensively examined the effects of chronic STN stimulation on cognitive function. OBJECTIVE: The aim of the present study was to assess the effects of chronic bilateral STN stimulation on performance in an extensive battery of neuropsychological tests, three months and one year after surgery. METHODS: Nine patients with Parkinson's disease were selected for STN electrodes implantation. They underwent a neuropsychological evaluation at one month before and at three months after surgery. Six of them were examined again at one year after surgery. RESULTS: Before surgery, no patient showed cognitive decline. At three months after surgery, no modification was observed for most tasks. The information processing speed tended to improve. There was a significant reduction of the performance in a delayed free recall test and a trend toward a significant reduction of categorial word fluency. At one year after surgery, most task measures did not change. Slight impairment was observed for tasks evaluating executive function. Examination of individual results showed that some patients (30% at 3 months after surgery) showed an overall cognitive decline. Behavioural changes were also observed in 4 patients with overall cognitive decline in one of them. CONCLUSION: In general, STN deep brain stimulation can be considered as a significant contribution to the treatment of severe Parkinson's disease However, in some patients it can induce overall cognitive decline or behavioural changes.

Cognition Disorders↗

International diffusion of new health technologies: a ten-country analysis of six health technologies.

OBJECTIVES: The objective of this study was to examine and explain the differential international diffusion of six health innovations. METHODS: A retrospective diffusion study was undertaken of sildenafil, cyclooxygenase-II (COX II) inhibitors, beta interferon, verteporfin, deep brain stimulators, and drug-eluting coronary stents in ten countries-Australia, Canada, Denmark, France, The Netherlands, Norway, Spain, Sweden, Switzerland, and the United Kingdom. We plotted diffusion curves of daily defined doses per quarter, vials or implants per million population, and examined the association between diffusion and five key variables. RESULTS: Canada, Switzerland, and Sweden are generally high users of new technologies; Spain, Denmark, and particularly the United Kingdom are low users. Almost all countries experienced rapid adoption of sildenafil with diffusion to a similar level; there was variable adoption and diffusion of COX II inhibitors, verteporfin, and interferon beta; drug-eluting stents penetrated the market in a similar way in all but one country; and two countries had very different adoption patterns for deep brain stimulators. Above average health spending and the presence of health technology assessment (HTA) or other guidance reports are consistently associated with increased diffusion. Early warning activity and a national coverage decision being taken are more likely to be associated with a reduced diffusion. CONCLUSIONS: The significant differences in diffusion between different countries are not consistent with a neat evidence-based world. The tools available to policy makers to control diffusion (early warning systems, HTA, and a fourth hurdle) play some part in influencing diffusion but need close scrutiny of how successfully they operate.

Australia↗

Surgical treatment of Parkinson's disease.

Ablative surgery and deep brain stimulation for Parkinson's disease can be performed in the thalamus, the pallidum and the subthalamic nucleus. The efficacy and safety of unilateral pallidotomy is well established. Deep brain stimulation has a lower morbidity and is preferred for bilateral surgery. The subthalamic nucleus presently seems to be the most promising target in advanced stage Parkinson's disease.

Electric Stimulation↗

Pallidal stimulation in Parkinson's disease patients with a prior unilateral pallidotomy.

OBJECTIVE: To evaluate, in a double-blind fashion, the efficacy of deep brain stimulation of the internal segment of the globus pallidus (GPi) contralateral to a previous unilateral medial pallidotomy (MP). METHODS: This pilot study involved 4 patients with a previous MP and one previously unoperated patient unable to tolerate any antiparkinsonian drugs. One of the patients with a prior unilateral MP had two electrodes implanted in the contralateral side, one in GPi and one in Vim thalamus. Detailed neurologic assessments were performed after overnight drug withdrawal and in the drug "on" state at baseline, 1 week and 3 months (in all), and 9 and 12 months (one) with patients and evaluators blinded to the status of stimulation. RESULTS: GPi stimulation resulted in improvements in "off-period" contralateral bradykinesia, rigidity and tremor in all patients. Dyskinesias and freezing episodes were ameliorated in one patient each but dyskinesias were transiently induced in another. The patient with GPi + Vim electrodes had complete resolution of contralateral tremor with thalamic stimulation but less benefit from acute GPi stimulation. One patient experienced a single seizure one week post-op and no other surgical complications were observed. CONCLUSIONS: Deep brain stimulation can be applied safely and effectively in patients who have already had a pallidotomy on the contralateral side. The effect of stimulation at different sites on different symptom profiles and levodopa-induced dyskinesias requires further evaluation.

Adult↗

Dystonia in Parkinson's disease.

Dystonia can occasionally be found in idiopathic Parkinson's disease. It is very uncommon in untreated patients and is more frequently seen as a complication of its treatment. In this review, the various types of dystonia occurring in PD, the differential diagnosis with other parkinsonian syndromes associated with dystonia and treatments available are revised. Dystonia unrelated to treatment can be typical (blepharospasm, torticollis), atypical (parkinsonian writer's cramp, camptocormia, anismus), or occurring in earlyonset Parkinson disease (the so-called kinesigenic foot dystonia, considered a hallmark of early-onset Parkinson's disease). Early and prominent dystonia in untreated patients with parkinsonism should raise the suspicion of other entities other than Parkinson's disease, such as progressive supranuclear palsy, multiple system atrophy or corticobasal degeneration. In patients on chronic dopaminergic treatment, peak-dose dystonia, diphasic dystonia and off-dystonia can be seen. The later constitutes the major dystonic feature of chronic levodopa therapy, and a wide variety of strategies are available to manage this complication. Among them, deep brain stimulation of the subthalamic nucleus has proved to be the most effective one. Dystonic reactions (mainly involving oculomotor cranial nerves and limbs) in operated patients (especially carriers of deep brain stimulation (DBS) devices) are increasingly being reported, constituting a new type of dystonia in patients with Parkinson's disease: dystonia linked to surgical treatment.

Dystonia↗

Interventional therapies in the management of complex regional pain syndrome.

Invasive procedures have long held a place in the therapeutic armamentarium for the management of complex regional pain syndrome (CRPS). However, this has evolved considerably, particularly as research into the mechanisms of CRPS has called into question long-held presumptions about the key role of sympathetic dysfunction in the syndrome. This review summarizes some of the key information currently available about interventional treatments, including nerve blocks, spinal cord and peripheral nerve stimulation, chemical and surgical sympathectomies, and deep brain stimulation. The potential roles for these procedures in facilitating functional rehabilitation goals that are primary to the treatment of CRPS are emphasized.

Complex Regional Pain Syndromes↗

Treatment of Parkinson's disease.

The aim of current treatment of Parkinson's disease is to ameliorate the symptoms while seeking to lessen the potential development of late levodopa complications. To this end, there is ample evidence that the early use of dopamine agonists is beneficial in younger Parkinsonian patients but monotherapy with dopamine agonists is for only a select few. Nonergot dopamine agonists offer the potential for fewer side effects. Lower dose levodopa therapy delays the onset and reduces severity of dyskinesia and end of dose failure. However levodopa remains the treatment of choice in Parkinson's disease and should not be restricted unnecessarily in patients with disability. There is no evidence that levodopa is toxic to dopaminergic neurons in people with Parkinson's disease. As yet, no drugs are of proven neuroprotective value. Dopamine agonists, catechol-o-methyltransferase inhibitors, amantadine and apomorphine have differing but beneficial roles in the management of levodopa side effects. Ablative surgery and deep brain stimulation of thalamus, globus pallidus and subthalamic nucleus are increasingly available but choice of procedure depends not just on patient symptomatology, but also on local experience and results. Ideally, deep brain stimulation is the treatment of choice as it offers less morbidity than bilateral ablative surgery, the possibility of postoperative adjustments and the potential for reversibility if better treatments become available.

Age Factors↗

Surgical treatments for Parkinson's disease.

OBJECTIVE: This article reviews surgical treatments for Parkinson's disease, emphasizing aspects pertinent to family physicians: rationale for and description of surgeries, patient selection issues, and outcome expectations. QUALITY OF EVIDENCE: No published series describes long-term follow up of a randomized controlled study of any surgery for Parkinson's disease. Some reports, however, describe thorough but brief follow up of functioning in small numbers of patients following surgery. MEDLINE articles were identified using Parkinson's disease, surgery, pallidotomy, thalamotomy, stimulation, grafting, and transplantation as search words. Articles chosen for this paper described patients with systematic follow up using accepted validated rating scales. MAIN MESSAGE: Reported series show impressive improvements to patients undergoing lesioning, stimulation, and grafting surgery for Parkinson's disease. These patients are typically severely disabled but highly selected, and follow up is brief. Stereotactic lesioning (pallidotomy and thalamotomy), deep brain stimulation (thalamic, and elsewhere) and grafting (striatal) can be performed safely, but results vary greatly among centres. CONCLUSIONS: Certain Parkinson's disease patients might benefit from surgery. Ideal candidates for pallidotomy experience motor fluctuations with disabling levodopa-induced dyskinesias. Tremors resistant to antiparkinsonian medications sometimes respond to thalamotomy or thalamic stimulation. Other parkinsonian syndromes, dementias, and difficulties with gait and balance respond poorly to unilateral pallidotomy. Bilateral deep brain stimulation procedures could benefit "midline" dysfunction.

Brain Tissue Transplantation↗