Pallidal stimulation: an alternative to pallidotomy?

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.

Long-term potentiation promotes proliferation/survival and neuronal differentiation of neural stem/progenitor cells

Neural stem cell (NSC) replacement therapy is considered a promising cell replacement therapy for various neurodegenerative diseases. However, the low rate of NSC survival and neurogenesis currently limits its clinical potential. Here, we examined if hippocampal long-term potentiation (LTP), one of the most well characterized forms of synaptic plasticity, promotes neurogenesis by facilitating proliferation/survival and neuronal differentiation of NSCs. We found that the induction of hippocampal LTP significantly facilitates proliferation/survival and neuronal differentiation of both endogenous neural progenitor cells (NPCs) and exogenously transplanted NSCs in the hippocampus in rats. These effects were eliminated by preventing LTP induction by pharmacological blockade of the N-methyl-D-aspartate glutamate receptor (NMDAR) via systemic application of the receptor antagonist, 3-[(R)-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (CPP). Moreover, using a NPC-neuron co-culture system, we were able to demonstrate that the LTP-promoted NPC neurogenesis is at least in part mediated by a LTP-increased neuronal release of brain-derived neurotrophic factor (BDNF) and its consequent activation of tropomysosin receptor kinase B (TrkB) receptors on NSCs. Our results indicate that LTP promotes the neurogenesis of both endogenous and exogenously transplanted NSCs in the brain. The study suggests that pre-conditioning of the host brain receiving area with a LTP-inducing deep brain stimulation protocol prior to NSC transplantation may increase the likelihood of success of using NSC transplantation as an effective cell therapy for various neurodegenerative diseases.

Selective GABA release as a mechanistic basis of high-frequency stimulation used for the treatment of neuropsychiatric diseases

Electrical high-frequency stimulation (HFS) is applied in many brain areas to treat various clinical syndromes. The nearly identical constellation of stimulation parameters raises the question of a unique mechanism of action of this therapeutic option. The identification of a single HFS mechanism may help to optimize the HFS technology by targeting this single mechanism. Experimentally, only axonal membranes are targets of HFS, but not other membranes of neurons or glial cells. Within all HFS target regions, axons of excitatory glutamatergic and inhibitory GABAergic neurons are present and play roles in all clinical syndromes treated successfully with HFS. Therefore, glutamatergic or GABAergic fibres are likely candidates as mediators of a unique HFS mode of action. The selective involvement of another neuronal fibre type (e.g. monoaminergic, cholinergic, etc.) in the HFS mode of action is highly unlikely since the regional and syndromal dissimilarity of the clinical HFS applications precludes the assumption of such a fibre type as primary HFS site of action. Our recent experimental finding that HFS of human neocortical slices induces the action potential-mediated release of GABA, but not of glutamate, simplifies the possibilities to explain the HFS mode of action, as the explanation now may concentrate on GABAergic axons only. Thus, we are analysing, on the basis of the pathophysiological grounds of the various syndromes treated with deep brain stimulation, whether a selective GABA release is a collective explanation of the mode of action of HFS. We suggest that selective GABA release indeed may needfully and sufficiently explain efficacy and side effects of HFS.

Deep brain stimulation for Parkinson's disease: prevalence of adverse events and need for standardized reporting

Deep brain stimulation (DBS) has assumed a prominent role in the treatment of Parkinson's disease (PD). In this manuscript, we attempt to estimate the prevalence and categorize adverse events (AEs) of DBS in PD, based on efficacy studies published over the last decade. We conclude that reliable categorization and quantification of AEs based on available data poses many challenges and argue that a standardized scheme for reporting AEs should be created. This would provide a foundation for a meaningful risk/benefit analysis, for comparison of results between centers and, ultimately, for a well informed decision by physicians and patients as to whether surgery should be pursued.

Complications in subthalamic nucleus stimulation surgery for treatment of Parkinson's disease. Review of 272 procedures

BACKGROUND

Deep brain stimulation (DBS) is a surgical technique used to alleviate symptoms in patients with advanced Parkinson's disease (PD). It is a reversible procedure and its effect is based on electrical modulation of the nervous system and has considerable advantages in morbidity-mortality when compared to lesion techniques such as thalamotomy and/or pallidotomy. The objective was to evaluate the adverse events during the surgical placement of leads in the subthalamic nucleus for the treatment of Parkinson's disease.

METHODS

A retrospective data collection was made in a total of 130 patients in whom we performed 272 procedures for the implant of leads in the subthalamic nucleus between May 1998 and December 2005. All the patients were operated by the same surgeon, in the same institution and with the same surgical methodology. The complications under evaluation were: aborted procedure, misplaced leads, intracranial haemorrhage, seizures, hardware complications and other complications.

RESULTS

130 patients were treated (62 women, 68 men; average age 62 (36-74) years). The average duration of disease from the time of diagnosis to operation was 15.3 years (4-28 years) and the mean follow-up was of 37 months (3-93 months). One hundred and twenty four patients were implanted bilaterally and 6 unilaterally. 62% did not present any complications, 30% had one complication, and 8% more than one complication. Aborted procedures amounted to 5.14% of all procedures, misplaced leads 2.2%, intracranial haemorrhage 3.3%, seizures 4.7%, hardware complications 1.8% and other complications 5.1%.

CONCLUSION

Deep brain stimulation surgery is an effective and safe method to treat Parkinson's disease with a low incidence of permanent adverse events.

Deep brain stimulation for Parkinson's disease

Indications for the treatment of Parkinson's disease (PD) with deep brain stimulation (DBS) are severe, therapy refractory tremor and complications of long-term levodopa uptake. Since its first application DBS has become a standard therapy for these patients. Theoretically, the ventrolateral part of the internal pallidum (GPI) or the subthalamic nucleus (STN) are suitable targets in order to treat all cardinal symptoms of patients in an advanced stage of PD stereotactically. Although clinical efficacy of both GPI or STN stimulation is obviously comparable, it has become widely accepted to prefer STN over GPI DBS. If PD-associated, medically intractable tremor is the most disabling symptom, stimulation of the ventrolateral motor thalamus can be an alternative. Anatomical targets for DBS are small and located in critical brain areas. Furthermore, this type of surgery is highly elective. As a consequence, high resolution multiplanar imaging and adequate treatment planning software are indispensable prerequisites for DBS surgery. Currently, commercially available impulse generators deliver a permanent high frequency periodic pulse train stimulation that interacts rather unspecifically with the firing pattern of both normal and pathological neurons. Prospectively, the development of more specific stimulation paradigms may help to improve the efficacy of this treatment modality.

Comparative Evaluation of the Effects of Unilateral Lesion versus Electrical Stimulation of the Globus Pallidus Internus in Advanced Parkinson’s Disease

OBJECTIVE

To perform a prospective analysis on the effects of unilateral lesion versus unilateral electrical stimulation (ES) of the globus pallidus internus (Gpi) in the treatment of bilateral Parkinson's disease (PD).

MATERIALS AND METHODS

We studied 18 patients with stages III-V on the Hoehn and Yahr (H-Y) scale having prominent rigidity, bradykinesia and gait disturbances. Nine patients were treated with lesions and 9 patients with ES. Both groups were evaluated using the New York Parkinson's Disease Scale, the Unified Parkinson's Disease Rating Scale part III, and the H-Y scale and with specific items of tremor, rigidity and bradykinesia independently on each side. Both lesions and electrodes for ES were placed stereotactically in the Gpi as confirmed by postoperative magnetic resonance images. Significance of changes was evaluated with the Wilcoxon test after 3 and 6 months. Significance of intergroup differences was evaluated using the Mann-Whitney U test.

RESULTS

Lesions and ES significantly decreased rigidity (p < 0.01) and bradykinesia (p < 0.005) in the contralateral extremities. ES significantly decreased tremor in the contralateral extremities (p < 0.01) and rigidity and bradykinesia ipsilaterally (p < 0.01) at 3 months. There were no significant intergroup differences. The H-Y scale score showed improvement in self-sufficiency. L-DOPA dose was decreased by 31%.

CONCLUSIONS

ES was a safer procedure and more efficient in controlling PD symptoms. Unilateral lesions and ES may improve bilateral symptoms to the point of making patients self-sufficient.

Deep brain stimulation: Preoperative issues

Numerous factors need to be taken into account in deciding whether a patient with Parkinson's disease (PD) is a candidate for deep brain stimulation. Patient-related personal factors including age and the presence of other comorbid disorders need to be considered. Neuropsychological and neuropsychiatric concerns relate both to the presurgical status of the patient and to the potential for surgery to result in new problems postoperatively. A number of factors related to the underlying PD need to be considered, including the specific parkinsonian motor indications (e.g., tremor, bradykinesia, gait dysfunction), previous medical therapies, including benefit from current therapy and adverse effects, and past surgical treatments. Definable causes of Parkinsonism, particularly atypical Parkinsonisms, should be considered. Finally, methods of evaluating outcomes should be defined and formalized. This is a report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society (MDS). The report has been endorsed by the Scientific Issues Committee of the MDS and the American Society of Stereotactic and Functional Neurosurgery. It outlines answers to a series of questions developed to address all aspects of deep brain stimulation preoperative decision-making.

Arvanil, a hybrid endocannabinoid and vanilloid compound, behaves as an antihyperkinetic agent in a rat model of Huntington's disease

The present study was designed to examine whether arvanil (N-arachidonoyl-vanillyl-amide), an endocannabinoid/vanilloid structural "hybrid", might provide symptom relief in the rat model of Huntington's disease (HD) generated by bilateral intrastriatal application of 3-nitropropionic acid (3-NP), where previous evidence suggests that hybrid cannabinoid/vanilloid compounds might be effective. As expected, arvanil did reduce ambulation, stereotypic activity, and number of hole entries, and increased the inactivity, in control rats. It was also active in 3-NP-lesioned rats, where, despite its lowering effects on stereotypic activity and number of hole entries, arvanil reduced the hyperkinesia (increased ambulation) typical of these rats, and also increased the inactivity, these two effects being more moderate than those found in control rats. Arvanil caused its antihyperkinetic effects in 3-NP-lesioned rats presumably by enhancing excitatory transmission at the globus pallidus, since it increased glutamate content in this region. This contrasts with its effects in control rats where arvanil enhanced GABA transmission at the globus pallidus. In summary, arvanil does alleviate hyperkinesia typical of HD, although it also affects locomotion in normal rats. Nevertheless, considering the lack of efficacious pharmacological treatments in this basal ganglia disorder, our findings might provide the basis for the development of more specific drugs against HD.

Incidence of hemorrhage associated with electrophysiological studies performed using macroelectrodes and microelectrodes in functional neurosurgery

Object. The goal of this study was to analyze the incidence of intracranial bleeding in patients who underwent procedures guided by microelectrode recording (MER) rather than by macroelectrode stimulation alone.

Methods. Between March 1994 and July 2001, 178 patients underwent 248 functional neurosurgical procedures performed by the same team at the University of California at Los Angeles. The procedures included pallidotomy (122 patients), thalamotomy (19 patients), and implantation of deep brain stimulation electrodes in the subthalamic nucleus (36 patients), globus pallidus internus (17 patients), and ventralis intermedius nucleus (54 patients). One hundred forty-four procedures involved macroelectrode stimulation and 104 involved MER. Groups were analyzed according to the presence of arterial hypertension, MER or macroelectrode stimulation use, and occurrence of hemorrhage. Nineteen patients with arterial hypertension underwent 28 surgical procedures.

Five cases of hemorrhage (2.02%) occurred. One patient presented with hemiparesis and dysphasia but no surgery was required. The incidence of hemorrhage in patients in whom MER was performed was 2.9%, whereas the incidence in patients in whom MER was not used was 1.4% (p = 0.6529). Bleeding occurred in 10.71% of patients with hypertension and 0.91% of those who were nonhypertensive (p = 0.0111). Among the 104 patients in whom MER was performed, 12 had hypertension. Bleeding occurred in two (16.67%) of these 12 patients. An increased incidence of bleeding in hypertensive patients who underwent MER (p = 0.034) was noticed when compared with nonhypertensive patients who underwent MER. A higher number of electrode passes through the parenchyma was observed when MER was used (p = 0.0001). A positive trend between the occurrence of hemorrhage and multiple passes was noticed.

Conclusions. Based on the data the authors suggest that a higher incidence of hemorrhage occurs in hypertensive patients, and a higher incidence as well in hypertensive patients who underwent MER rather than macroeletrode stimulation. Special attention should be given to MER use in hypertensive patients and particular attention should be made to multiple passes.

[Kinematic evaluation of dystonic syndromes in patients treated with deep brain stimulation]

INTRODUCTION

Quantification of motor functions of patients with dystonic syndromes treated by chronic high frequency stimulation of the internal globulus pallidus is a challenge.

OBJECTIVE

Through a series of clinical examples this paper shows that kinematic analysis of movements in dystonic syndromes treated by deep brain stimulation (DBS) is a complement to clinical evaluation. In addition, it provides valuable information for early detection of improvement or impairment of movements associated with modifications of stimulation parameters.

METHOD

Thirteen dystonic patients and eleven reference subjects completed three tests (i.e., rest: lying supine; posture: standing with arms held in front (at shoulder height); and alternative movements: bimanual finger-to-nose test). These tests were recorded with an electromagnetic system quantifying movement kinematics (position) in three-dimensional space.

RESULTS

From the recorded data, several indices were developed and provided a quantitative evaluation of movements during each test. In addition, a clinical evaluation (BMFDRS) was also completed. No correlation between clinical and kinematic evaluations was found.

CONCLUSION

It is shown that kinematic analysis is a useful complement of clinical evaluation and can assist clinicians in monitoring the evolution of movements in dystonic patients treated by DBS in a simple, reliable and valid fashion.

Role of surgery in the treatment of motor complications

When medications no longer provide patients with Parkinson's disease a reasonable quality of life due to the presence of levodopa-associated motor fluctuations and dyskinesias, surgical treatment is often pursued. Numerous studies have examined the antiparkinsonian efficacy of procedures currently available, but surprisingly few studies have evaluated their effect on motor response complications in a systematic, controlled manner, using appropriate instruments. Nonetheless, the combined evidence from uncontrolled case series and more recent randomized controlled trials reviewed here indicates that unilateral pallidotomy, bilateral pallidal deep brain stimulation, and bilateral subthalamic deep brain stimulation all substantially alleviate levodopa-induced dyskinesias and, to a lesser extent, motor fluctuations. Incorporation of standardized, validated instruments for the quantification of motor response complications in future surgical study protocols will not only allow more accurate comparison of different interventions but also will help physicians select the most appropriate procedure for their patients.

Deep brain stimulation in myoclonus-dystonia syndrome

Myoclonus-dystonia syndrome (MDS) is an autosomal dominant disorder characterized by bilateral myoclonic jerks. An 8-year-old boy presenting with early onset, medically intractable, MDS due to a mutation in the epsilon-sarcoglycan gene (SGCE) underwent chronic bilateral stimulation of the globus pallidus internus, which eliminates both myoclonus and dystonia. We conclude that deep brain stimulation can be an effective and safe treatment for MDS.

Electrical stimulation of the globus pallidus internus in patients with primary generalized dystonia: long-term results

Object. Primary generalized dystonia (PGD) is a medically refractory disease of the brain causing twisting or spasmodic movements and abnormal postures. In more than 30% of cases it is associated with the autosomal DYT1 mutation. Continuous electrical stimulation of the globus pallidus internus (GPi) has been used successfully in the treatment of PGD. The aim of this study was to examine the long-term efficacy and safety of deep brain stimulation (DBS) in the treatment of PGD in children and adults with and without the DYT1 mutation.

Methods. Thirty-one patients with PGD were selected for surgery. Electrodes were bilaterally implanted under stereotactic guidance and connected to neurostimulators that were inserted subcutaneously. Efficacy was evaluated by comparing scores on the clinical and functional Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) before and after implantation.

The efficacy of stimulation improved with time. After 2 years, compared with preoperative values, the mean (± standard deviation) clinical and functional BFMDRS scores had improved by 79 ± 19% and 65 ± 33%, respectively. At the 2-year follow-up examination the improvement was comparable in patients with and without the DYT1 mutation in both the functional (p = 0.12) and clinical (p = 0.33) scores. Children displayed greater improvements in the clinical score than adult patients (p = 0.04) at 2 years of follow up. In contrast, there was no significant difference in functional scores between children and adults (p = 0.95).

Conclusions. Electrical stimulation of the GPi is an effective, reversible, and adaptable treatment for PGD and should be considered for conditions refractory to pharmaceutical therapies.

The mechanism and effect of chronic electrical stimulation of the globus pallidus for treatment of Parkinson disease

Object. Although chronic electrical stimulation of the globus pallidus (GP) has been shown to ameliorate motor disabilities in Parkinson disease (PD), the underlying mechanism remains to be clarified. In this study the authors explored the mechanism for the effects of deep brain stimulation of the GP by investigating the changes in neurotransmitter levels in the cerebrospinal fluid (CSF) during the stimulation.

Methods. Thirty patients received chronic electrical stimulation of the GP internus (GPi). Clinical effects were assessed using the Unified PD Rating Scale (UPDRS) and the Hoehn and Yahr Staging Scale at 1 week before surgery and at 6 and 12 months after surgery. One day after surgery, CSF samples were collected through a ventricular tube before and 1 hour after GPi stimulation. The concentration of neurotransmitters such as γ-aminobutyric acid (GABA), noradrenaline, dopamine, and homovanillic acid (HVA) in the CSF was measured using high-performance liquid chromatography.

The treatment was effective for tremors, rigidity, and drug-induced dyskinesia. The concentration of GABA in the CSF increased significantly during stimulation, although there were no significant changes in the level of noradrenaline, dopamine, and HVA. A comparison between an increased rate of GABA concentration and a lower UPDRS score 6 months postimplantation revealed that the increase in the GABA level correlated with the stimulation-induced clinical effects.

Conclusions. Stimulation of the GPi substantially benefits patients with PD. The underlying mechanism of the treatment may involve activation of GABAergic afferents in the GP.

La stimulation cérébrale profonde dans la maladie de Parkinson

The present renewal of the surgical treatment of Parkinson's disease, almost abandoned for twenty Years, arises from two main reasons. The first is the better understanding of the functional organization of the basal ganglia. It was demonstrated in animal models of Parkinson's disease that the loss of dopaminergic neurons within the substantia nigra, at the origin of the striatal dopaminergic defect, induces an overactivity of the excitatory glutamatergic subthalamo-internal pallidum pathway. The decrease in this hyperactivity might lead to an improvement in the pakinsonian symptoms. The second reason is the improvement in stereotactic neurosurgery in relation with the progress in neuroimaging techniques and with intraoperative electrophysiological microrecordings and stimulations, which help determine the location of the deep brain targets. In the 1970s chronic deep brain stimulation in humans was applied to the sensory nucleus of the thalamus for the treatment of intractable pain. In 1987, Benabid and colleagues suggested high frequency stimulation of the ventral intermediate nucleus of the thalamus in order to treat drug-resistant tremors and to avoid the adverse effects of thalamotomies. How deep brain stimulation works is not well known but it has been hypothetized that it could change the neuronal activities and thus avoid disease-related abnormal neuronal discharges. Potential candidates for deep brain stimulation are selected according to exclusion and inclusion criteria. Surgery can be applied to patients in good general and mental health, neither depressive nor demented and who are severely disabled despite all available drug therapies but still responsive to levodopa. The first session of surgery consists in the location of the target by ventriculography and/or brain MRI. The electrodes are implanted during the second session. The last session consists in the implantation of the neurostimulator. The ventral intermediate nucleus of the thalamus was the first target in which chronic deep brain stimulation electrodes were implanted in order to alleviate tremor. This technique can be applied bilaterally without the adverse effects of bilateral thalamotomies. Like pallidotomy, internal globus pallidum stimulation has a dramatic beneficial effect on levodopa-induced dyskinesia but its effects on the parkinsonian triad are less constant and opposite motor effects are sometimes observed in relation with the stimulated contact. The inconstant results, perhaps related to the complexity of the structure led to the development of subthalamic nucleus stimulation. The alleviation of motor fluctuations and the improvement in all motor symptoms allows a significant decrease in levodopa daily dose and in levodopa-induced dyskinesia. Presently, deep brain stimulation is a fashionable neurosurgical technique to treat Parkinson's disease. Subthalamic nucleus stimulation seems to be the most suitable target to control the parkinsonian triad and the motor fluctuations. Because of the possible adverse effects it must be reserved for disabled parkinsonian patients. No large randomized study comparing different targets and different neurosurgical techniques has been performed yet. Such studies, including cost benefit studies would be useful to assess the respective value of these different techniques.

Deep brain stimulation for Parkinson’s disease

Deep brain stimulation at high frequency was first used in 1997 to replace thalamotomy in treating the characteristic tremor of Parkinson's disease, and has subsequently been applied to the pallidum and the subthalamic nucleus. The subthalamic nucleus is a key node in the functional control of motor activity in the basal ganglia. Its inhibition suppresses symptoms in animal models of Parkinson's disease, and high frequency chronic stimulation does the same in human patients. Acute and long-term results after deep brain stimulation show a dramatic and stable improvement of a patient's clinical condition, which mimics the effects of levodopa treatment. The mechanism of action may involve a functional disruption of the abnormal neural messages associated with the disease. Long-term changes, neural plasticity and neural protection might be induced in the network. Similar effects of stimulation and lesioning have led to the extension of this technique for other targets and diseases.

Deep brain stimulation for movement disorders: morbidity and mortality in 109 patients

OBJECT

Deep brain stimulation (DBS) has been advocated as a more highly effective and less morbidity-producing alternative to ablative stereotactic surgery in the treatment of medically intractable movement disorders. Nevertheless, the exact incidence of morbidity and mortality associated with the procedure is not well known. In this study the authors reviewed the surgical morbidity and mortality rates in a large series of DBS operations.

METHODS

The authors retrospectively analyzed surgical complications in their consecutive series of 179 DBS implantations in 109 patients performed by a single surgical team at one center between July 1998 and April 2002. The mean follow-up period was 20 months. There were 16 serious adverse events related to surgery in 14 patients (12.8%). There were two perioperative deaths (1.8%), one caused by pulmonary embolism and the second due to aspiration pneumonia. The other adverse events were two pulmonary embolisms, two subcortical hemorrhages, two chronic subdural hematomas, one venous infarction, one seizure, four infections, one cerebrospinal fluid leak, and one skin erosion. The incidence of permanent sequelae was 4.6% (five of 109 patients). The incidence of device-related complications, such as infection or skin erosion, was also 4.6% (five of 109 patients).

CONCLUSIONS

There is a significant incidence of adverse events associated with the DBS procedure. Nevertheless, DBS is clinically effective in well-selected patients and should be seriously considered as a treatment option for patients with medically refractory movement disorders.

Treatment results: Parkinson's disease

Deep brain stimulation (DBS) is a neurosurgical treatment of Parkinson's disease that is applied to three targets: the ventral intermediate nucleus of the thalamus (Vim), the globus pallidus internas (GPi) and the subthalamic nucleus (STN). Vim DBS mainly improves contralateral tremor and, therefore, is being supplanted by DBS of the two other targets, even in patients with tremor dominant disease. STN and GPi DBS improve off-motor phases and dyskinesias. There is little comparative data between these procedures. The magnitude of the motor improvement seems more constant with STN than GPi DBS. STN DBS allows a decrease in antiparkinsonian drug doses and consumes moderate current. These advantages of STN over GPi DBS are offset by the need for more intensive postoperative management. The DBS procedure has the unique advantage of reversibility and adjustability over time. Patients with young-onset Parkinson's disease suffering from levodopa-induced motor complications but still responding well to levodopa and who exhibit no behavioral, mood, or cognitive impairment benefit the most from STN DBS. Adverse effects more specific of the DBS procedure are infection, cutaneous erosion, and lead breaking or disconnection. Intracranial electrode implantation can induce a hematoma or contusion. Most authors agree that the benefit to risk ratio of DBS is favorable.

Long-term pallidal deep brain stimulation in patients with advanced Parkinson disease: 1-year follow-up study

OBJECT

The goal of this study was to investigate the efficacy of long-term deep brain stimulation (DBS) of the posteroventral lateral globus pallidus internus (GPi) accomplished using a single-contact monopolar electrode in patients with advanced Parkinson disease (PD).

METHODS

Sixteen patients suffering from severe PD and levodopa-induced side effects such as dyskinesias and on-off fluctuations were enrolled in a prospective study protocol. There were six women and 10 men and their mean age at surgery was 65 years. All patients underwent implantation of a monopolar electrode in the posteroventral lateral GPi. Initially, nine patients received unilateral stimulation. Three of these patients underwent contralateral surgery at a later time. Ten patients received bilateral stimulation (contemporaneous bilateral surgery was performed in seven patients and staged bilateral surgery in the three patients who had received unilateral stimulation initially). Formal assessments were performed during both off-medication and on-medication (levodopa) periods preoperatively, and at 3 and 12 months postoperatively. There were no serious complications related to surgery or to DBS. Two transient adverse events occurred: in one patient a small pallidal hematoma developed, resulting in a prolonged micropallidotomy effect, and in another patient a subcutaneous hemorrhage occurred at the site of the pacemaker. In patients who received unilateral DBS, the Unified Parkinson's Disease Rating Scale activities of daily living (ADL) score during the off-levodopa period decreased from 30.8 at baseline to 20.4 at 3 months (34% improvement) and 20.6 at 12 months (33% improvement) postoperatively. The motor score during the off period improved from 57.2 at baseline to 35.2 at 3 months (38% improvement) and 35.3 at 12 months (38% improvement) postoperatively. Bilateral DBS resulted in a reduction in the ADL score during the off period from 34.9 at baseline to 22.3 at 3 months (36% improvement) and 22.9 at 12 months (34% improvement). The motor score for the off period changed from 63.4 at baseline to 40.3 at 3 months (36% improvement) and 37.5 at 12 months (41% improvement). In addition, there were significant improvements in patients' symptoms during the on period and in on-off motor fluctuations.

CONCLUSIONS

Pallidal DBS accomplished using a monopolar electrode is a safe and effective procedure for treatment of advanced PD. Compared with pallidotomy, the advantages of pallidal DBS lie in its reversibility and the option to perform bilateral surgery in one session. Comparative studies in which DBS is applied to other targets are needed.

An analysis of the respective risks of hematoma formation in 361 consecutive morphological and functional stereotactic procedures

OBJECTIVE

The risk of hematoma formation in stereotactic procedures is generally considered to range between 1 and 4%, and it has been speculated that morphological procedures may have a higher risk of bleeding than functional procedures.

METHODS

Between 1989 and 1999, all patients who underwent a stereotactic procedure performed by the same surgeon were enrolled sequentially onto the study. All patients had normal preoperative prothrombin time, partial thromboplastin time, and platelet count. High-resolution computed tomography or magnetic resonance imaging with a 1.5-T machine were used for the target definition. None of the patients had an angiogram before surgery.

RESULTS

A total of 361 procedures was performed comprising 175 morphological procedures (139 biopsies, 18 lesion evacuations [cysts, abscesses, and hematomas], and 18 drain implantations) and 186 functional procedures (137 lesions [thalamotomy or pallidotomy], 47 deep brain electrode implantations, and two physiological explorations without lesions or implantations). There were no infections or seizures in either group. Three hematomas (1.7%) occurred in the morphological group, two of them in inflammatory lesions in immunocompromised patients (one death) and one in a pineal tumor. Three hematomas (1.6%) occurred in the functional group (no mortality). There was no statistically significant difference (P > 0.05; Fisher's exact test) in the risk of hematoma formation between morphological and functional stereotactic procedures. The morbidity and mortality related to bleeding also were not statistically different (P > 0.05; Fisher's exact test) between these two groups.

CONCLUSION

In this series, the risk of bleeding was not higher for morphological procedures than for functional procedures. This suggests that the risk of bleeding for stereotactic procedures is related more to the patient than to the type of procedure performed. Our study confirms an overall risk of bleeding of 1.7% for any type of stereotactic procedure, resulting in a mortality of 0.3% and a morbidity of 1.4%.

Bilateral GPi DBS is useful to reduce abnormal involuntary movements in advanced Parkinson's disease patients, but its action is related to modality and site of stimulation

In Parkinson's disease (PD) patients, internal globus pallidus (GPi) stimulation has been reported to produce good effects on abnormal involuntary movements (AIM); less improvement has been observed in extrapyramidal symptoms. We assessed the effect of monopolar dorsal (uppermost), ventral (lowest) and bipolar (uppermost vs. lowest) bilateral globus pallidus stimulation by quadripolar electrode on extrapyramidal symptoms and AIM induced by a dose of apomorphine. Six PD patients were studied in OFF therapy condition after surgery without stimulation (STIM OFF) and during stimulation (STIM ON) with the three different modalities. All patients were evaluated by the unified Parkinson's disease rating scale, section III (UPDRS) and by the AIM. Our results show that all three bilateral GPi stimulation modalities reduce the UPDRS score (between 49.7 and 31.5%), although the bipolar and lowest stimulation are the most effective. Similarly, bipolar and lowest stimulation were also the most effective in reducing the occurrence and intensity of the apomorphine-induced AIM. On the contrary, uppermost stimulation (UP ON) produced an AIM occurrence similar to that observed in the OFF stimulus condition. We suggest that bilateral GPi stimulation is an useful procedure to ameliorate extrapyramidal signs of advanced PD patients; however, it produces an antidyskinetic effect only if the ventral or the entire GPi is stimulated. On the contrary, the UP ON, most probably located in the external globus pallidus (GPe), does not modify the AIM occurrence.

Functional brain networks in Parkinson's disease

With the advent of new methods of network analysis, we have utilized metabolic data acquired through positron emission tomography (PET) to identify disease-related patterns of functional pathology in the movement disorders. In Parkinson's disease (PD), we have used [(18)F]-fluorodeoxyglucose (FDG)/PET to identify a disease-related regional metabolic covariance pattern characterized by lentiform and thalamic hypermetabolism associated with regional metabolic decrements in the lateral premotor cortex, the supplementary motor area, the dorsolateral prefrontal cortex, and the parieto-occipital association regions. The expression of this network is modulated in a predictable fashion by levodopa therapy and by stereotaxic interventions for PD.We have extended this network analytical approach from studies of glucose metabolism in the resting state to dynamic studies of brain activation during motor performance. These PET studies utilized [(15)O]-water (H(2) (15)O) to measure cerebral blood flow activation responses during the execution of simple and complex motor tasks. In addition to the modulation of abnormal resting metabolic networks, effective PD therapy can enhance brain activation responses during motor execution, with specific regional associations with improvements in timing and spatial accuracy.This approach is also useful in identifying specific brain networks mediating the learning of sequential information. We have found that the normal relationship between brain networks and learning performance are altered in the earliest stages of PD with a functional shift from striatal to cortical processing. Brain activation PET studies during therapeutic interventions for PD demonstrate how normal brain-behavior relationships can be restored with successful therapy. Thus, functional brain imaging with network analysis can provide insights into the mechanistic basis of basal ganglia disorders and their treatment.

Deep brain stimulation in neuropsychiatric disorders

Deep brain stimulation (DBS) of the ventral intermediate nucleus of the thalamus, subthalamic nucleus, and internal globus pallidus has been put forth as an alternative to surgical ablation for the treatment of movement disorders. In this paper, the authors discuss the history and putative physiologic mechanisms underlying DBS of these target regions. The authors then review empirical findings pertaining to the effects of DBS on neurological symptoms, cognitive functioning, and psychiatric symptoms in Parkinson's disease and essential tremor, the disorders for which the procedure has been most extensively applied. Finally, emerging and potential novel areas of application of DBS for the treatment of neuropsychiatric disorders and symptoms are discussed.

Electrical stimulation of the prelemniscal radiation in the treatment of Parkinson's disease: an old target revised with new techniques

OBJECTIVE

In the treatment of tremor and rigidity in patients with Parkinson's disease (PD), the prelemniscal radiation (RAPRL), a subthalamic bundle of fibers, is an exquisite target that can be visualized easily on ventriculograms. We sought to evaluate the effect of electrical stimulation of the RAPRL on symptoms and signs of PD in a long-term trial and to determine the localization of the stimulated area by means of stereotactic magnetic resonance imaging studies.

METHODS

Ten patients with PD predominantly on one side had tetrapolar electrodes stereotactically oriented through a frontal parasagittal approach to the RAPRL contralateral to the most prominent symptoms. Preoperative and postoperative evaluations at 3, 6, 9, and 12 months after surgery were performed using conventional PD scales and quantitative evaluations of tremor amplitude and reaction time. Stereotactic high-resolution magnetic resonance imaging studies with the electrodes in place were used for anatomic localization.

RESULTS

In all patients, temporary suppression of tremor occurred when the electrodes reached the target. The most effective stimulation was obtained when the pair of contacts was placed in the RAPRL. Long-term stimulation at 130 Hz, 0.09 to 0.450 milliseconds, and 1.5 to 3.0 V produced significant improvement in tremor and rigidity and mild improvement in bradykinesia.

CONCLUSION

The RAPRL is an effective target for the alleviation of tremor and rigidity in patients with PD by either lesioning or neuromodulation; however, neuromodulation has the advantage of not inducing an increase in bradykinesia. The stimulated area seems to be independent of the subthalamic nucleus.

Functional mapping of the human globus pallidus: contrasting effect of stimulation in the internal and external pallidum in Parkinson's disease

Our objective was to elaborate a functional map of the globus pallidus by correlating the intrapallidal localization of quadripolar electrodes implanted in parkinsonian patients with the clinical effect of the stimulation of each contact. Five patients with L-DOPA-responsive Parkinson's disease presenting severe motor fluctuations and L-DOPA-induced dyskinesias were treated by continuous bilateral high-frequency stimulation of the globus pallidus. The effects of stimulation on parkinsonian disability were tested through each of the four stimulating contacts of each electrode. The anatomical localization of each of the stimulating contacts was determined by confronting the pre- and post-operative magnetic resonance imaging with the anatomical atlas of Schaltenbrand and Wharen.(34) The registration procedure comprised digitization of the atlas, the use of deformation tools to fit atlas sections with magnetic resonance imaging sections, and three-dimensional reconstruction of both the atlas and the magnetic resonance imaging sections. Analysis of the 32 stimulating contacts tested did not reveal a somatotopic organization in the pallidal region investigated but demonstrated that high-frequency stimulation had contrasting effects depending on whether it was applied to the external or the internal pallidum. Akinesia was improved by stimulation of the external pallidum but worsened by stimulation of the internal pallidum. In contrast, parkinsonian rigidity was improved by stimulation of either part of the pallidum. The areas in the internal pallidum where stimulation worsened akinesia were those in which stimulation reduced or suppressed L-DOPA-induced dyskinesias. Conversely, stimulation applied to the external pallidum induced dyskinesias. The fact that rigidity was improved by stimulation of the internal and external pallidum suggests that the neuronal bases of parkinsonian rigidity are different from those of akinesia and dyskinesias. The effect on akinesia and dyskinesias is in agreement with the current model of basal ganglia circuitry(10) if high-frequency stimulation activates rather than inhibits pallidal neurons, a possibility which is very likely since there are marked anatomical, biochemical and electrophysiological differences between the globus pallidus and the subthalamic nucleus. This study demonstrates that high-frequency stimulation of the globus pallidus in parkinsonian patients has contrasting effects depending on whether it is applied to the external or the internal part of this nucleus. The effect on akinesia and dyskinesias suggests that stimulation activates pallidal neurons, a result which challenges the generally accepted concept that high-frequency stimulation inactivates neurons in the region stimulated.

99Tc(m)-ECD SPET perfusion changes by internal pallidum stimulation in Parkinson's disease

High-frequency stimulation of the internal pallidum is an effective surgical approach for patients with advanced Parkinson's disease suffering from motor fluctuations and L-dopa induced dyskinesia. To study the acute effects of internal pallidum stimulation, changes in cerebral blood flow were measured by means of a single-day split-dose protocol using 99Tc(m)-ECD SPET. Nine patients with advanced Parkinson's disease and with a clinical picture predominated by tremor and drug-induced dyskinesia, were imaged before and immediately after electrostimulation. Brain perfusion data were mirrored to the same electrode side (five left and four right implants), co-registered and analysed statistically on a voxel-by-voxel basis (Statistical Parametric Mapping) and by an automated volume-of-interest approach. Acute stimulation of the internal pallidum induced a significantly decreased perfusion in the ipsilateral thalamus and striatum, as well as in the right parietal cortex. For the subgroup of seven patients with effective motor score improvements, a significant correlation between thalamic and striatal perfusion changes and UPDRS III motor score was present (P = 0.04). These results suggest that effective stimulation of the internal globus pallidus may produce symptom relief through decreased activity in pallido-thalamo-cortical circuits.

Double blinded evaluation of the effects of pallidal and subthalamic nucleus stimulation on daytime activity in advanced Parkinson's disease

The results of a double blinded evaluation of the effects of globus pallidus (GPi; n=7) and subthalamic nucleus (STN; n=11) stimulation in patients with advanced Parkinson's disease are summarized. The patients were evaluated at 6-8months after surgery. In order to determine the benefits afforded by the stimulation to the actual daily activities, the patients were maintained on-medication with optimal doses and schedules. The stimulation was turned off overnight for at least 12h. It was turned on in the morning (or maintained turned off), and the best and worst scores during daytime activity were recorded, as on-period and off-period scores, respectively. A reduction in total motor score on the Unified Parkinson's Disease Rating Scale was clearly elicited by GPi and STN stimulation at both the off-period (-57 and -29%, respectively) and the on-period (-36 and -25%, respectively). The difference in effects between GPi and STN stimulation appeared to be due largely to an unintended difference in the patients' preoperative symptoms. The benefits provided by stimulation to the actual daily activities appears to be limited in patients who have become unresponsive to a large dose of levodopa. Two advantages of GPi and STN stimulation were identified. Firstly, the stimulation can supplement a reduced action of levodopa during the off-period. It thus improves the patient's daily activities through attenuation of the motor fluctuations. Secondly, the stimulation can replace part of the action of levodopa during the on-period. It thus attenuates dopa-induced dyskinesia through a reduced dose of medication. More importantly, the stimulation improves the daily activities in dopa-intolerant patients who are being administered a small dose of levodopa because of unbearable side effects. In addition, GPi stimulation has its own inhibitory effect on dopa-induced dyskinesia. Clinically important improvement was observed in severe gait freezing in 2 patients following unilateral anterodorsal GPi stimulation on the right side alone.

Deep brain stimulation for advanced Parkinson's disease

Deep brain stimulation (DBS) is a new and promising technique for the treatment of movement disorders. Medically intractable Parkinson's disease (PD) is one of the most common indications for DBS. There are three possible subcortical targets for PD, depending on the symptomatology (i.e., the motor subdivision of the thalamus, the globus pallidus internus, the subthalamic nucleus [STN]). Thalamic stimulation has been well established as a safe and effective treatment for essential tremor and the tremor associated with PD. Globus pallidus internus and STN DBS are being investigated for the treatment of all the cardinal signs of PD. This article describes the pathophysiology of PD, the surgical treatment history of PD, surgical techniques used for DBS implants, and the role the perioperative nurse has in the care of the patients undergoing these procedures.

Life-threatening dystonia-dyskinesias in a child: successful treatment with bilateral pallidal stimulation

We report a 13-year-old boy who developed severe, refractory dystonia-dyskinesias as an abrupt worsening of a previously nonprogressive movement disorder. The movements became continuous, requiring artificial respiration and continuous sedation in the intensive-care unit. Various drugs and drug combinations failed to achieve control. The child was then treated successfully with bilateral pallidal (GPi) stimulation as shown in the videotape. Four months later and without medication, the boy regained autonomous gait and audible speech; his neurologic condition continues to improve.

The surgical treatment of Parkinson's disease

Surgical treatment of Parkinson's disease (PD) can provide gratifying symptomatic improvements for many individuals who suffer from persistent disabling symptoms despite the best available medical management. Current surgical therapies include ablative techniques (thalamotomy and pallidotomy), augmentative techniques (nondestructive) (deep brain stimulation), and restorative techniques (tissue transplantation and gene therapy). Ablative procedures can provide substantial clinical benefit, but the current trend is toward deep brain stimulation, which can provide similar symptomatic improvement in a nondestructive manner. Restorative techniques, such as tissue transplantation and gene therapy, are exciting but have significant obstacles to overcome before their promise can be realized. Until the underlying pathological defect of PD can be identified and treated, surgical intervention is likely to remain important in the symptomatic treatment of this disabling disease.

Acute effects of thalamotomy and pallidotomy on regional cerebral metabolism, evaluated by PET

The subacute effect of thalamotomy and pallidotomy on regional cerebral metabolism was studied by means of Positron Emission Tomography (PET). In this way we aimed to identify the pattern of functional deafferentiation following a specific lesion in the basal ganglia. The cerebral distribution of 2-[18F]fluoro 2-deoxy-D-glucose (FDG) uptake at 1-2 weeks after operation was compared with the uptake before operation. Analysis of the changes was done by statistical parametric mapping (SPM). Thalamotomy resulted in a reduction of FDG uptake in predominantly the lateral prefrontal- and the parietal cortex, whereas pallidotomy affected only uptake in the (pre)frontal cortex. The absence of change in the primary sensory-motor cortex after either surgical procedure may suggest that, in man, the motor portions of the thalamus exert a predominantly indirect influence on the human motor cortex.

Subthalamic stimulation for Parkinson's disease

Deep brain stimulation by high frequency (HFS) has been developed starting in the thalamic target (Vim) from pragmatic observations and subsequently followed by other targets, such as the subthalamic nucleus (STN) and pallidum as an application of current knowledge from basic preclinical research in neuroscience. The mechanism involved by this neurosurgical approach is not completely solved. For Vim we have formed the hypothesis that HFS induces a jamming of sensory-motor loops but for the STN, from our experimental research in rats we have shown that HFS induces functional inhibition of cell activity in the target nuclei. In our patients the implantation of the stimulation electrodes was carried out stereotactically, under local anesthesia, using ventriculography, MRI, microrecordings and clinical evaluation of the effects of stimulation on rigidity. When the stimulation is turned ON in the STN area a significant decrease in rigidity was determined by the neurologists. Stimulation or even penetration of the electrode may be responsible for transient dyskinesias. The average location of the clinically efficient contact of the chronic stimulating electrodes is statistically located at 5.02 +/- 0.71 1/12 degrees of AC-PC in the AP direction, at -1.5 +/- 0.66 1/8 degrees of the height of the thalamus in the ventricle direction, with laterality at 11.98 +/- 1.12 mm in the lateral direction. The beneficial effects of STN stimulation are significant providing that the electrodes are correctly placed into the target. There is strong improvement of the symptoms of the triad in which akinesia, rigidity, and tremor are reduced on average to 41. 6, 48.6, and 27%, respectively, when compared with the previous preoperative level. From our experience, HFS of the STN could be considered the surgical therapy of choice at advanced stages of Parkinson's disease.

Bilateral subthalamic stimulation for Parkinson's disease by using three-dimensional stereotactic magnetic resonance imaging and electrophysiological guidance

OBJECT

Several methods are used for stereotactically guided implantation of electrodes into the subthalamic nucleus (STN) for continuous high-frequency stimulation in the treatment of Parkinson's disease (PD). The authors present a stereotactic magnetic resonance (MR) method relying on three-dimensional (3D) T1-weighted images for surgical planning and multiplanar T2-weighted images for direct visualization of the STN, coupled with electrophysiological recording and stimulation guidance.

METHODS

Twelve patients with advanced PD were enrolled in this study of bilateral STN implantation. Both STNs were visible as 3D ovoid biconvex hypointense structures located in the upper mesencephalon. The coordinates of the centers of the STNs were determined with reference to the patient's anterior commissure-posterior commissure line by using a new landmark, the anterior border of the red nucleus. Electrophysiological monitoring through five parallel tracks was performed simultaneously to define the functional target accurately. Microelectrode recording identified high-frequency, spontaneous, movement-related activity and tremor-related cells within the STNs. Acute STN macrostimulation improved contralateral rigidity and akinesia, suppressed tremor when present, and could induce dyskinesias. The central track, which was directed at the predetermined target by using MR imaging, was selected for implantation of 19 of 24 electrodes. No surgical complications were noted.

CONCLUSIONS

At evaluation 6 months after surgery, continuous STN stimulation was shown to have improved parkinsonian motor disability by 64% and 78% in the "off' and "on" medication states, respectively. Antiparkinsonian drug treatment was reduced by 70% in 10 patients and withdrawn in two patients. The severity of levodopa-induced dyskinesias was reduced by 83% and motor fluctuations by 88%. Continuous high-frequency stimulation of the STN applied through electrodes implanted with the aid of 3D MR imaging and electrophysiological guidance is a safe and effective therapy for patients suffering from severe, advanced levodopa-responsive PD.

Pallidal stimulation for generalized dystonia. Report of three cases

Pallidal stereotactic surgery is a well-accepted treatment alternative for Parkinson's disease. Another indication for this procedure is medically refractory dystonia, especially generalized dystonia with abnormal axial and extremity movements and postures. Improvement of dystonia after pallidotomy has been reported in several recent papers. In this report the authors describe three patients with generalized dystonia (two primary, one secondary) and their improvement after bilateral pallidal stimulation at follow-up times of between 6 and 18 months.

Effects of speech therapy and pharmacologic and surgical treatments on voice and speech in Parkinson's disease: a review of the literature

The purpose of this review was to examine the different treatment approaches for persons with Parkinson's Disease (PD) and to examine the effects of these treatments on speech. Treatment methods reviewed include speech therapy, pharmacological, and surgical. Research from the 1950s through the 1970s had not demonstrated significant improvements following speech therapy. Recent research has shown that speech therapy (when persons with PD are optimally medicated) has proven to be the most efficacious therapeutic method for improving voice and speech function. Pharmacological methods of treatment in isolation do not appear to significantly improve voice and speech function in PD across research studies. Surgical treatment methods including pallidotomy and deep brain stimulation may be significant treatment options which improve voice and speech function in some persons with PD. Possible explanations for the differential responses to treatment are discussed. Future studies should investigate the effects of combined treatment approaches. Perhaps the combination of pharmacological, surgical and speech treatment will prove superior to treatments combining pharmacological and surgical or pharmacological and speech therapy in improving the communication abilities of persons with PD.

Thalamic, subthalamic nucleus and internal pallidum stimulation in Parkinson's disease

The limits of drug therapy in severe forms of Parkinson's disease have lead to a renewal of functional neurosurgery of the basal ganglia and the thalamus. Deep brain stimulation (DBS) of these structures was developed with the aims of reducing the morbidity of surgery and of offering an adaptative treatment. DBS was first applied to the thalamus in patients with severe tremor. Tremor of the hemibody is greatly reduced by stimulation of the contralateral electrode in 85% of the cases. There is little change in other symptoms. However, motor fluctuations and dyskinesias are a more frequent problem than severe tremor; in attempt to treat these symptoms, DBS has recently been applied to the subthalamic nucleus (STN) and the internal pallidum (GPi). STN stimulation greatly decreases off motor symptoms and motor fluctuations, which allows a reduction of drug dosage and consequently of dyskinesias. GPi stimulation decreases dyskinesias in most patients, but the effect on off motor symptoms is more variable from one series to another, from very good to nil. The severe morbidity of DBS applied to these 3 targets is low. Comparative studies of the cost and the efficacy of DBS and lesions applied to these different targets are now required.

Posteroventral medial pallidotomy in Parkinson's disease

There has been a resurgence in the use of functional neurosurgery for Parkinson's disease. An important factor that has played a role in this development is the recent understanding of the functional anatomy of the basal ganglia including a knowledge of the changes in the activities of neurons in the internal segment of the globus pallidus (Gpi) and the subthalamic nucleus (STN) in Parkinson's disease as well as the knowledge of the presence of segregated functional loops within the basal ganglia which include a sensory-motor loop that involves the posteromedial globus pallidus rather than the anterior GPi where earlier pallidotomy lesions had been made. Laitinen reintroduced the modern posteroventral medial pallidotomy (PVMP) in 1992. Since then it has become clear that this treatment has major effects on levodopa-induced dyskinesias and, unlike Vim thalamotomy, improves bradykinesia and rigidity as well as tremor. In this report, we review a number of topics related to PVMP including the clinical results of pallidotomy available in the literature as well as an update of our own 2 year follow-up data, studies evaluating factors that might predict the subsequent response to pallidotomy, the neuropsychological effects of the procedure, results of imaging studies including the correlation of clinical effects with lesion location, the question of bilateral pallidotomy and pallidotomy combined with deep brain stimulation and finally whether PVMP is effective in other parkinsonian disorders.

New developments in the surgery for Parkinson's disease

Despite optimization of medical therapy, a large number of patients with Parkinson's disease continue to be disabled. For this group, alternate treatment strategies such as neurosurgical intervention can be considered. Recent advances in neurosurgical techniques and in understanding the pathophysiology of motor disturbances in PD have made surgery safer and more effective. Functional neurosurgical procedures to lesion or electrically modulate dysfunctional basal ganglia circuits or to protect or restore dopaminergic transmission are being increasingly used. These procedures are having a profound impact on the motor disturbances of PD and are producing important improvements in quality of life of patients.

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.

Surgical options in Parkinson's disease

Surgical treatments for Parkinson's disease (PD) have again become important adjuncts of care in these patients. We have learned much from the thousands of lesions performed historically, and are now advancing the entire field of movement disorder surgery to new levels of sophistication and understanding. The last 5 years have seen more precise and reliable lesioning and the arrival of multiple sites of intervention afforded by recent developments in deep brain stimulators. Because patients typically derive significant benefit in their quality of life from these procedures, while undergoing little risk, the surgical options should be carefully considered for selected PD patients.

Magnetic resonance imaging-based stereotactic localization of the globus pallidus and subthalamic nucleus

OBJECTIVE

To optimize the accuracy of initial stereotactic targeting for movement disorders surgery, we performed stereotactic localization of the internal segment of the globus pallidus (GPi) and subthalamic nucleus (STN) using magnetic resonance imaging protocols in which the borders of these nuclei were directly visualized.

METHODS

Fifty-one consecutive cases using the pallidal target and six using the subthalamic target were studied. Localization of these nuclei was performed using the Leksell stereotactic head frame and inversion recovery sequences (GPi) or T2-weighted spin echo sequences (STN). Targeting accuracy and individual variation in the spatial coordinates of these structures were independently measured by identification of nuclear boundaries during multiple microelectrode penetrations.

RESULTS

The lateral and vertical coordinates of an atlas-defined point in the GPi, with respect to the line between the anterior and posterior commissures, was highly variable. Initial targeting the GPi based on direct visualization of the target boundaries (external medullary lamina and optic tract) resulted in greater precision than would be expected using fixed anterior and posterior commissure-based coordinates. Initial targeting the STN using magnetic resonance imaging was sufficiently precise to place the initial microelectrode penetration within STN in all six cases.

CONCLUSION

Magnetic resonance imaging-based initial stereotactic targeting of the GPi, based on direct visualization of the target boundaries, is useful to improve target accuracy over that of purely indirect anterior and posterior commissure-based targeting methods. Initial targeting of the STN was reliably accomplished by direct visualization. However, there remains sufficient variability that the final target location in both GPi and STN required electrophysiological mapping in all cases.

Bilateral high-frequency stimulation of the internal globus pallidus in advanced Parkinson's disease

We report here the results of an open prospective study in 9 patients suffering from severe Parkinson's disease with on/off fluctuations and restricted off-period mobility, who underwent bilateral implantation of stimulating electrodes in the internal pallidum. At 3-month follow-up, the total Unified Parkinson's Disease Rating Scale (UPDRS) motor score in the medication-off state was reduced from 54.1+/-14.8 to 23.9+/-11.7 (44.2%) when stimulation was turned on. Comparison of UPDRS subscores revealed significant improvements for tremor, rigidity, bradykinesia, gait and posture, and dyskinesias. The results of the clinical scoring could be confirmed by significant changes in the quantitative assessment of hand function and walking. Bilateral pallidal stimulation reduced the amount and severity of on/off fluctuations. Additional follow-up at 6 months (n=6), 9 months (n=6), and 12 months (n=4) did not show a decline in effectiveness of stimulation. There was no permanent morbidity associated with the procedure. A subtle reduction of verbal fluency, which was not evident to the patients, was the only cognitive side effect of the procedure in neuropsychological testing. Chronic bilateral high-frequency stimulation of the internal pallidum seems to be a neurologically safe and highly effective treatment for "off" symptoms, dyskinesias, and motor fluctuations in advanced stages of Parkinson's disease.