Subthalamotomy for advanced Parkinson disease

Prognostic factors of unilateral prelemniscal radiations radiofrequency lesions: A surgical technique for the treatment of Parkinson's disease motor symptoms

OBJECTIVE

A group of patients with Parkinson's disease (PD) were managed with unilateral prelemniscal radiation radiofrequency lesions (U-Raprl). The current study aims to evaluate prognostic factors that could influence clinical response.

METHODS

Patients previously diagnosed with PD managed with U-Raprl were included in the study, classifying them into two groups according to their percentage of clinical response (</≥ 50%) at 5 years of follow-up in relation to the part III of the Unified Parkinson's Disease Rating Scale (UPDRS-III), analyzing the possible factors associated with their response (age, evolution of PD, Hoehn and Yahr scale (HYS), and levodopa dose). To show differences between groups before and after the intervention, a T-test was performed, and a Mann-Whitney U test was carried out to determine differences between the response groups, added to an effect size calculation using a Cohen's d (α = 0.05, and β = 0.20).

RESULTS

Thirty-four patients were included, where the most prevalent symptoms were tremor and rigidity, with 52.9% percentage of males, 59.3 ± 6.4 mean age, and 7.4 ± 2.1 of mean evolution of PD. Analysis shows differences between groups (p < 0.05) according to the HYS, UPDRS, and levodopa intake, after the intervention. The analysis of the groups according to their response showed differences between the HYS (p < 0.01, ∆ > 1.5), Age (p < 0.0001, ∆ = 2.38), Evolution (p < 0.0001, ∆ = 2.38), and post-operative UPDRS (p < 0.01, ∆ = 1.38). The qualitative analysis of the distribution regarding the responder group shows that those patients with an age under 58 years, an evolution fewer than 7 years, and a preoperative HYS score smaller than 2, showed a response ≥ 50% according to the UPDRS-III in all cases.

CONCLUSION

U-Raprl is a highly effective procedure with a 5-year persistence of improvement. The most relevant prognostic factors to consider for a clinical response according to UPDRS-III greater than 50% are age under 58 years, less than 7 years of PD evolution, and HYS less or equal to 3.

Changing views of the pathophysiology of Parkinsonism

Studies of the pathophysiology of parkinsonism (specifically akinesia and bradykinesia) have a long history and primarily model the consequences of dopamine loss in the basal ganglia on the function of the basal ganglia/thalamocortical circuit(s). Changes of firing rates of individual nodes within these circuits were originally considered central to parkinsonism. However, this view has now given way to the belief that changes in firing patterns within the basal ganglia and related nuclei are more important, including the emergence of burst discharges, greater synchrony of firing between neighboring neurons, oscillatory activity patterns, and the excessive coupling of oscillatory activities at different frequencies. Primarily focusing on studies obtained in nonhuman primates and human patients with Parkinson's disease, this review summarizes the current state of this field and highlights several emerging areas of research, including studies of the impact of the heterogeneity of external pallidal neurons on parkinsonism, the importance of extrastriatal dopamine loss, parkinsonism-associated synaptic and morphologic plasticity, and the potential role(s) of the cerebellum and brainstem in the motor dysfunction of Parkinson's disease. © 2019 International Parkinson and Movement Disorder Society.

Functional lesional neurosurgery for tremor: a systematic review and meta-analysis

BACKGROUND

This work evaluates the consistency, effect size and incidence of persistent side effects of lesional neurosurgical interventions in the treatment of tremor due to Parkinson's disease (PD), essential tremor (ET), multiple sclerosis (MS) and midbrain lesions.

METHODS

Systematic review and meta-analysis according to PRISMA-P guidelines. Random effects meta-analysis of standardised mean difference based on a peer-reviewed protocol (PROSPERO no. CRD42016048049).

RESULTS

From 1249 abstracts screened, 86 peer-reviewed studies reporting 102 cohorts homogeneous for tremor aetiology, surgical target and technique were included.Effect on PD tremor was better when targeted at the ventral intermediate nucleus (V.im.) by radiofrequency ablation (RF) (Hedge's g: -4.15;) over V.im. by Gamma Knife (GK) (-2.2), subthalamic nucleus (STN) by RF (-1.12) and globus pallidus internus (GPi) by RF (-0.89). For ET MRI-guided focused ultrasound (MRIgFUS) ablation of the cerebellothalamic tract (CTT) (-2.35) and V.im. (-2.08) showed similar mean tremor reductions to V.im. ablation by RF (-2.42) or GK (-2.13). In MS V.im. ablation by GK (-1.96) and RF (-1.63) were similarly effective.Mean rates of persistent side effects after unilateral lesions in PD were 12.8% (RF V.im.), 13.6% (RF STN), 9.2% (RF GPi), 0.7% (GK V.im.) and 7.0% (MRIgFUS V.im.). For ET, rates were 9.3% (RF V.im.), 1.8% (GK V.im.), 18.7% (MRIgFUS V.im.) and 0.0% (MRIgFUS CTT), for MS 37.7% (RF V.im.) and for rubral tremor 30.3% (RF V.im.).

CONCLUSION

This meta-analysis quantifies safety, consistency and efficacy of lesional neurosurgical interventions for tremor by target, technique and aetiology.

Sub-synaptic localization of Cav3.1 T-type calcium channels in the thalamus of normal and parkinsonian monkeys

T-type calcium channels (Ca_v3) are key mediators of thalamic bursting activity, but also regulate single cells excitability, dendritic integration, synaptic strength and transmitter release. These functions are strongly influenced by the subcellular and subsynaptic localization of Ca_v3 channels along the somatodendritic domain of thalamic cells. In Parkinson's disease, T-type calcium channels dysfunction in the basal ganglia-receiving thalamic nuclei likely contributes to pathological thalamic bursting activity. In this study, we analyzed the cellular, subcellular, and subsynaptic localization of the Ca_v3.1 channel in the ventral anterior (VA) and centromedian/parafascicular (CM/Pf) thalamic nuclei, the main thalamic targets of basal ganglia output, in normal and parkinsonian monkeys. All thalamic nuclei displayed strong Ca_v3.1 neuropil immunoreactivity, although the intensity of immunolabeling in CM/Pf was significantly lower than in VA. Ultrastructurally, 70-80 % of the Ca_v3.1-immunoreactive structures were dendritic shafts. Using immunogold labeling, Ca_v3.1 was commonly found perisynaptic to asymmetric and symmetric axo-dendritic synapses, suggesting a role of Ca_v3.1 in regulating excitatory and inhibitory neurotransmission. Significant labeling was also found at non-synaptic sites along the plasma membrane of thalamic neurons. There was no difference in the overall pattern and intensity of immunostaining between normal and parkinsonian monkeys, suggesting that the increased rebound bursting in the parkinsonian state is not driven by changes in Ca_v3.1 expression. Thus, T-type calcium channels are located to subserve neuronal bursting, but also regulate glutamatergic and non-glutamatergic transmission along the whole somatodendritic domain of basal ganglia-receiving neurons of the primate thalamus.

The T-type calcium channel as a new therapeutic target for Parkinson's disease

Parkinson's disease (PD) is one of the most prevalent movement disorder caused by degeneration of the dopaminergic neurons in substantia nigra pars compacta. Deep brain stimulation (DBS) at the subthalamic nucleus (STN) has been a new and effective treatment of PD. It is interesting how a neurological disorder caused by the deficiency of a specific chemical substance (i.e., dopamine) from one site could be so successfully treated by a pure physical maneuver (i.e., DBS) at another site. STN neurons could discharge in the single-spike or the burst modes. A significant increase in STN burst discharges has been unequivocally observed in dopamine-deprived conditions such as PD, and was recently shown to have a direct causal relation with parkinsonian symptoms. The occurrence of burst discharges in STN requires enough available T-type Ca(2+) currents, which could bring the relatively negative membrane potential to the threshold of firing Na(+) spikes. DBS, by injection of negative currents into the extracellular space, most likely would depolarize the STN neuron and then inactivate the T-type Ca(2+) channel. Burst discharges are thus decreased and parkinsonian locomotor deficits ameliorated. Conversely, injection of positive currents into STN itself could induce parkinsonian locomotor deficits in animals without dopaminergic lesions. Local application of T-type Ca(2+) channel blockers into STN would also dramatically decrease the burst discharges and improve parkinsonian locomotor symptoms. Notably, zonisamide, which could inhibit T-type Ca(2+) currents in STN, has been shown to benefit PD patients in a clinical trial. From the pathophysiological perspectives, PD can be viewed as a prototypical disorder of "brain arrhythmias". Modulation of relevant ion channels by physical or chemical maneuvers may be important therapeutic considerations for PD and other diseases related to deranged neural rhythms.

Subthalamotomy in the treatment of Parkinson's disease: clinical aspects and mechanisms of action

Parkinson's disease (PD) is a neurodegenerative condition that can be pharmacologically treated with levodopa. However, important motor and nonmotor symptoms appear with its long-term use. The subthalamic nucleus (STN) is known to be involved in the pathophysiology of PD and to contribute to levodopa-induced complications. Surgery is considered in patients who have advanced PD that is refractory to pharmacotherapy and who display disabling dyskinesia. Deep brain stimulation of the STN is currently the main surgical procedure for PD, but lesioning is still performed. This review covers the clinical aspects and complications of subthalamotomy as one of the lesion-based options for PD patients with levodopa-induced dyskinesias. Moreover, the authors discuss the possible effects of subthalamic lesioning.

Drug-induced dyskinesia in Parkinson's disease. Should success in clinical management be a function of improvement of motor repertoire rather than amplitude of dyskinesia?

BACKGROUND

Dyskinesia, a major complication in the treatment of Parkinson's disease (PD), can require prolonged monitoring and complex medical management.

DISCUSSION

The current paper proposes a new way to view the management of dyskinesia in an integrated fashion. We suggest that dyskinesia be considered as a factor in a signal-to-noise ratio (SNR) equation where the signal is the voluntary movement and the noise is PD symptomatology, including dyskinesia. The goal of clinicians should be to ensure a high SNR in order to maintain or enhance the motor repertoire of patients. To understand why such an approach would be beneficial, we first review mechanisms of dyskinesia, as well as their impact on the quality of life of patients and on the health-care system. Theoretical and practical bases for the SNR approach are then discussed.

SUMMARY

Clinicians should not only consider the level of motor symptomatology when assessing the efficacy of their treatment strategy, but also breadth of the motor repertoire available to patients.

The subthalamic microlesion story in Parkinson's disease: electrode insertion-related motor improvement with relative cortico-subcortical hypoactivation in fMRI

Electrode implantation into the subthalamic nucleus for deep brain stimulation in Parkinson's disease (PD) is associated with a temporary motor improvement occurring prior to neurostimulation. We studied this phenomenon by functional magnetic resonance imaging (fMRI) when considering the Unified Parkinson's Disease Rating Scale (UPDRS-III) and collateral oedema. Twelve patients with PD (age 55.9± (SD)6.8 years, PD duration 9-15 years) underwent bilateral electrode implantation into the subthalamic nucleus. The fMRI was carried out after an overnight withdrawal of levodopa (OFF condition): (i) before and (ii) within three days after surgery in absence of neurostimulation. The motor task involved visually triggered finger tapping. The OFF/UPDRS-III score dropped from 33.8±8.7 before to 23.3±4.8 after the surgery (p<0.001), correlating with the postoperative oedema score (p<0.05). During the motor task, bilateral activation of the thalamus and basal ganglia, motor cortex and insula were preoperatively higher than after surgery (p<0.001). The results became more enhanced after compensation for the oedema and UPDRS-III scores. In addition, the rigidity and axial symptoms score correlated inversely with activation of the putamen and globus pallidus (p<0.0001). One month later, the OFF/UPDRS-III score had returned to the preoperative level (35.8±7.0, p = 0.4).In conclusion, motor improvement induced by insertion of an inactive electrode into the subthalamic nucleus caused an acute microlesion which was at least partially related to the collateral oedema and associated with extensive impact on the motor network. This was postoperatively manifested as lowered movement-related activation at the cortical and subcortical levels and differed from the known effects of neurostimulation or levodopa. The motor system finally adapted to the microlesion within one month as suggested by loss of motor improvement and good efficacy of deep brain stimulation.

Computed three-dimensional atlas of subthalamic nucleus and its adjacent structures for deep brain stimulation in Parkinson's disease

Background. Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is one of the standard surgical treatments for advanced Parkinson's disease. However, it has been difficult to accurately localize the stimulated contact area of the electrode in the subthalamic nucleus and its adjacent structures using a two-dimensional atlas. The goal of this study is to verify the real and detailed localization of stimulated contact of the DBS electrode therapeutically inserted into the STN and its adjacent structures using a novel computed three-dimensional atlas built by a personal computer. Method. A three-dimensional atlas of the STN and its adjacent structures (3D-Subthalamus atlas) was elaborated on the basis of sagittal slices from the Schaltenbrand and Wahren stereotactic atlas on a personal computer utilizing a commercial software. The electrode inserted into the STN and its adjacent structures was superimposed on our 3D-Subthalamus atlas based on intraoperative third ventriculography in 11 cases. Findings. Accurate localization of the DBS electrode was identified using the 3D-Subthalamus atlas, and its clinical efficacy of the electrode stimulation was investigated in all 11 cases. Conclusion. This study demonstrates that the 3D-Subthalamus atlas is a useful tool for understanding the morphology of deep brain structures and for the precise anatomical position findings of the stimulated contact of a DBS electrode. The clinical analysis using the 3D atlas supports the contention that the stimulation of structures adjacent to the STN, particularly the zona incerta or the field of Forel H, is as effective as the stimulation of the STN itself for the treatment of advanced Parkinson's disease.

Parkinson's disease therapeutics: new developments and challenges since the introduction of levodopa

The demonstration that dopamine loss is the key pathological feature of Parkinson's disease (PD), and the subsequent introduction of levodopa have revolutionalized the field of PD therapeutics. This review will discuss the significant progress that has been made in the development of new pharmacological and surgical tools to treat PD motor symptoms since this major breakthrough in the 1960s. However, we will also highlight some of the challenges the field of PD therapeutics has been struggling with during the past decades. The lack of neuroprotective therapies and the limited treatment strategies for the nonmotor symptoms of the disease (ie, cognitive impairments, autonomic dysfunctions, psychiatric disorders, etc.) are among the most pressing issues to be addressed in the years to come. It appears that the combination of early PD nonmotor symptoms with imaging of the nigrostriatal dopaminergic system offers a promising path toward the identification of PD biomarkers, which, once characterized, will set the stage for efficient use of neuroprotective agents that could slow down and alter the course of the disease.

Relative contributions of local cell and passing fiber activation and silencing to changes in thalamic fidelity during deep brain stimulation and lesioning: a computational modeling study

Deep brain stimulation (DBS) and lesioning are two surgical techniques used in the treatment of advanced Parkinson's disease (PD) in patients whose symptoms are not well controlled by drugs, or who experience dyskinesias as a side effect of medications. Although these treatments have been widely practiced, the mechanisms behind DBS and lesioning are still not well understood. The subthalamic nucleus (STN) and globus pallidus pars interna (GPi) are two common targets for both DBS and lesioning. Previous studies have indicated that DBS not only affects local cells within the target, but also passing axons within neighboring regions. Using a computational model of the basal ganglia-thalamic network, we studied the relative contributions of activation and silencing of local cells (LCs) and fibers of passage (FOPs) to changes in the accuracy of information transmission through the thalamus (thalamic fidelity), which is correlated with the effectiveness of DBS. Activation of both LCs and FOPs during STN and GPi-DBS were beneficial to the outcome of stimulation. During STN and GPi lesioning, effects of silencing LCs and FOPs were different between the two types of lesioning. For STN lesioning, silencing GPi FOPs mainly contributed to its effectiveness, while silencing only STN LCs did not improve thalamic fidelity. In contrast, silencing both GPi LCs and GPe FOPs during GPi lesioning contributed to improvements in thalamic fidelity. Thus, two distinct mechanisms produced comparable improvements in thalamic function: driving the output of the basal ganglia to produce tonic inhibition and silencing the output of the basal ganglia to produce tonic disinhibition. These results show the importance of considering effects of activating or silencing fibers passing close to the nucleus when deciding upon a target location for DBS or lesioning.

Deep-Brain Stimulation for Basal Ganglia Disorders

The realization that medications used to treat movement disorders and psychiatric conditions of basal ganglia origin have significant shortcomings, as well as advances in the understanding of the functional organization of the brain, has led to a renaissance in functional neurosurgery, and particularly the use of deep brain stimulation (DBS). Movement disorders are now routinely being treated with DBS of 'motor' portions of the basal ganglia output nuclei, specifically the subthalamic nucleus and the internal pallidal segment. These procedures are highly effective and generally safe. Use of DBS is also being explored in the treatment of neuropsychiatric disorders, with targeting of the 'limbic' basal ganglia-thalamocortical circuitry. The results of these procedures are also encouraging, but many unanswered questions remain in this emerging field. This review summarizes the scientific rationale and practical aspects of using DBS for neurologic and neuropsychiatric disorders.

Surgical approach to l-dopa-induced dyskinesias

Many patients treated chronically with l-dopa for Parkinson disease (PD) become functionally disabled by l-dopa-induced dyskinesias (LID). Evolved from early empirical procedures, modern stereotactic surgical lesioning techniques and deep brain stimulation (DBS) can effectively treat LID while simultaneously improving the cardinal motor symptoms of PD. Here we review the common surgical targets used to treat LID, and compare their relative efficacy. We explain the anti-dyskinetic action of surgery at each of these targets based on evolving models of basal ganglia function. Finally, we discuss the appropriate selection of patients with LID for surgery and address relevant technical and management issues in these patients.

THE POSTERIOR SUBTHALAMIC AREA IN THE TREATMENT OF MOVEMENT DISORDERS

THE INTRODUCTION OF thalamotomy in 1954 led naturally to exploration of the underlying subthalamic area, with the development of such procedures as campotomy and subthalamotomy in the posterior subthalamic area. The most popular of these procedures was the subthalamotomy, which was performed in thousands of patients for various movement disorders. Today, in the deep brain stimulation (DBS) era, subthalamic nucleus DBS is the treatment of choice for Parkinson's disease, whereas thalamic and pallidal DBS are mainly used for nonparkinsonian tremor and dystonia, respectively. The interest in DBS in the posterior subthalamic area has been quite limited, however, with a total of 95 patients presented in 14 articles. During recent years, interest has increased, and promising results have been published concerning both Parkinson's disease and nonparkinsonian tremor. We reviewed the literature to investigate the development of surgery in the posterior subthalamic area from the lesional era to the present.

Clinical cases where lesion therapy was chosen over deep brain stimulation

Deep brain stimulation (DBS) surgery has become the gold standard for treatment of select refractory cases of Parkinson disease and essential tremor. Despite the usefulness of DBS surgery in many cases, there remain situations where lesion therapy (subthalamotomy, pallidotomy or thalamotomy) may provide a reasonable alternative to DBS. We reviewed the University of Florida Institutional Review Board-approved database for movement disorders surgery and identified 286 DBS leads placed in 189 patients as well as 4 additional patients who had lesion therapy. In these 4 cases we reviewed the clinical presentations that resulted in a multidisciplinary team opting for lesion therapy over DBS. Lesion therapy represents a viable alternative and has several important advantages, including a decreased need for access to specialists and clinical follow-up, improved affordability, and a lower infection risk.

L-DOPA-INDUCED DYSKINESIA AND STEREOTACTIC SURGERY FOR PARKINSON'S DISEASE

OBJECTIVE

To assess the impact of different surgical targets and techniques, such as ablation and deep brain stimulation, to treat patients with L-dopa-induced dyskinesia (LID), a major therapeutic complication of Parkinson's disease.

METHODS

This review analyzes the effects of early surgical procedures to treat hyperkinesia and the current methods and targets used to combat LID in Parkinson's disease, which are mainly thalamotomy, pallidotomy, and deep brain stimulation of the globus pallidus internus and the subthalamic nucleus.

RESULTS

Available information indicates that surgery of the globus pallidus internus and thalamus (the pallidal receiving area) and of the subthalamic nucleus has a pronounced antidyskinetic effect. This effect is associated with a concomitant improvement in the parkinsonian (“off”-medication) state. Although it is more profound with pallidal and subthalamic surgery, such an effect can also be observed to some extent with thalamic surgery. The latter is attributable to the fact that surgery of the ventralis intermedius is primarily effective for treating tremor. An integral pallidothalamic pathway is needed for dyskinesia to be expressed. Thus, LID is less frequent after subthalamotomy or deep brain stimulation of the subthalamic nucleus through a functional effect mediated by the physiological normalization of the motor system and by an indirect effect associated with a reduction in the daily dose of L-dopa.

CONCLUSION

Surgery is the only treatment available for Parkinson's disease that can predictably improve both the parkinsonian motor syndrome and LID. The exact mechanisms involved in these effects are not well understood. Pallidal and thalamic surgery affecting pallidal relays reduce LID frequency by disrupting the pallidothalamic circuit, probably eliminating the neuronal activity associated with dyskinesia. Alternatively, the antidyskinetic effect of subthalamic nucleus surgery may in part be attributable to a reduction in the L-dopa dose as well as to the stabilization of the basal ganglia circuits after the surgical procedure.

The history and future of deep brain stimulation

The advancement of electrical stimulation of the central nervous system has been a story of fits and bursts with numerous setbacks. In many ways, this history has paralleled the history of medicine and physics. We have moved from anecdotal observation to double-blinded, prospective randomized trials. We have moved from faradic stimulation to systems that lie completely under the skin and can deliver complex electrical currents to discrete areas of the brain while controlled through a device that is not much bigger than a PDA. This review will discuss how deep brain stimulation has developed into its current form, where we see the field going and the potential pitfalls along the way.

Network modulation by the subthalamic nucleus in the treatment of Parkinson's disease

Deep brain stimulation of the subthalamic nucleus (STN DBS) has become an accepted tool for the treatment of Parkinson's disease (PD). Although the precise mechanism of action of this intervention is unknown, its effectiveness has been attributed to the modulation of pathological network activity. We examined this notion using positron emission tomography (PET) to quantify stimulation-induced changes in the expression of a PD-related covariance pattern (PDRP) of regional metabolism. These metabolic changes were also compared with those observed in a similar cohort of patients undergoing STN lesioning. We found that PDRP activity declined significantly (P < 0.02) with STN stimulation. The degree of network modulation with DBS did not differ from that measured following lesioning (P = 0.58). Statistical parametric mapping (SPM) revealed that metabolic reductions in the internal globus pallidus (GPi) and caudal midbrain were common to both STN interventions (P < 0.01), although declines in GPi were more pronounced with lesion. By contrast, elevations in posterior parietal metabolism were common to the two procedures, albeit more pronounced with stimulation. These findings indicate that suppression of abnormal network activity is a feature of both STN stimulation and lesioning. Nonetheless, these two interventions may differ metabolically at a regional level.

Atlas-based identification of targets for functional radiosurgery

Functional disorders of the brain, such as Parkinson's disease, dystonia, epilepsy, and neuropathic pain, may exhibit poor response to medical therapy. In such cases, surgical intervention may become necessary. Modern surgical approaches to such disorders include radio-frequency lesioning and deep brain stimulation (DBS). The subthalamic nucleus (STN) is one of the most useful stereotactic targets available: STN DBS is known to induce substantial improvement in patients with end-stage Parkinson's disease. Other targets include the Globus Pallidus pars interna (GPi) for dystonia and Parkinson's disease, and the centromedian nucleus of the thalamus (CMN) for neuropathic pain. Radiosurgery is an attractive noninvasive alternative to treat some functional brain disorders. The main technical limitation to radiosurgery is that the target can be selected only on the basis of magnetic resonance anatomy without electrophysiological confirmation. The aim of this work is to provide a method for the correct atlas-based identification of the target to be used in functional neurosurgery treatment planning. The coordinates of STN, CMN, and GPi were identified in the Talairach and Tournoux atlas and transformed to the corresponding regions of the Montreal Neurological Institute (MNI) electronic atlas. Binary masks describing the target nuclei were created. The MNI electronic atlas was deformed onto the patient magnetic resonance imaging-T1 scan by applying an affine transformation followed by a local nonrigid registration. The first transformation was based on normalized cross correlation and the second on optimization of a two-part objective function consisting of similarity criteria and weighted regularization. The obtained deformation field was then applied to the target masks. The minimum distance between the surface of an implanted electrode and the surface of the deformed mask was calculated. The validation of the method consisted of comparing the electrode-mask distance to the clinical outcome of the treatments in ten cases of bilateral DBS implants. Electrode placement may have an effect within a radius of stimulation equal to 2 mm, therefore the registration process is considered successful if error is less than 2 mm. The registrations of the MNI atlas onto the patient space succeeded in all cases. The comparison of the distance to the clinical outcome revealed good agreement: where the distance was high (at least in one implant), the clinical outcome was poor; where there was a close correlation between the structures, clinical outcome revealed an improvement of the pathological condition. In conclusion, the proposed method seems to provide a useful tool for the identification of the target nuclei for functional radiosurgery. Also, the method is applicable to other types of functional treatment.

Operative techniques and morbidity with subthalamic nucleus deep brain stimulation in 100 consecutive patients with advanced Parkinson's disease

OBJECTIVE

Subthalamic nucleus (STN) stimulation for patients with medically refractory Parkinson disease (PD) is expanding. Reported experience has provided some indication of techniques, efficacy, and morbidity, but few centres have reported more than 50 patients. To expand this knowledge, we reviewed our experience with a large series of consecutive patients.

METHODS

From March 1999 to September 2003, 191 subthalamic stimulator devices (19 unilateral) were implanted in 100 patients with PD at New York Presbyterian Hospital/Columbia University Medical Center. Sixteen patients had undergone a prior surgery for PD (pallidotomy, thalamotomy, or fetal transplant). Microelectrode guided implantations were performed using techniques similar to those described previously. Electrode implantation occurred 1-2 weeks before outpatient pulse generator implantation.

RESULTS

Reductions of dyskinesias and off severity/duration were similar to prior published reports. Morbidity included: 7 device infections (3.7%), 1 cerebral infarct, 1 intracerebral haematoma, 1 subdural haematoma, 1 air embolism, 2 wound haematomas requiring drainage (1.0%), 2 skin erosions over implanted hardware (1.0%), 3 periprocedural seizures (1.6%), 6 brain electrode revisions (3.1%), postoperative confusion in 13 patients (6.8%), and 16 battery failures (8.4%). Of the 100 patients, there were no surgical deaths or permanent new neurological deficits. The average hospital stay for all 100 patients was 3.1 days.

CONCLUSION

Subthalamic stimulator implantation in a large consecutive series of patients with PD produced significant clinical improvement without mortality or major neurological morbidity. Morbidity primarily involved device infections and hardware/wound revisions.

Unilateral stimulation of the subthalamic nucleus in Parkinson disease: a double-blind 12-month evaluation study

OBJECT

Bilateral deep brain stimulation (DBS) of the subthalamic nucleus (STN) has been established as an effective treatment for Parkinson disease (PD). Nevertheless, bilateral surgical procedures can be associated with frequent and severe complications. The aim in the present study was to assess the safety and efficacy of unilateral STN stimulation, and the need for a second procedure.

METHODS

Twelve patients with PD underwent unilateral DBS of the STN and were followed up for 12 months. Patients were assessed at baseline and at each visit in a double-blind fashion by analyzing the Unified PD Rating Scale (UPDRS), ambulation speed, and home diaries. Levodopa-off/stimulation-on UPDRS motor scores were improved by 26 +/- 8% (p < 0.05, mean +/- standard deviation [SD]) compared with the baseline levodopa-off score; there was a 50% improvement in contralateral features, a 17% improvement ipsilaterally, and a 36% improvement in axial features. The mean ambulation speed increased by 83 +/- 44% (p < 0.01, mean +/- SD). The medication-on time with dyskinesias was significantly reduced (p < 0.01) and the daily levodopa dose was reduced by 19 +/- 6% (p < 0.05, mean +/- SD). There were no clinically significant side effects.

CONCLUSIONS

Unilateral DBS of the STN is safe and well tolerated, and may provide sufficient benefit so that additional surgery is not required.

Evolving metabolic changes during the first postoperative year after subthalamotomy

OBJECT

Short-term benefit from unilateral subthalamotomy for advanced Parkinson disease (PD) is associated with metabolic alterations in key targets of subthalamic nucleus (STN) and globus pallidus (GP) output. In this study positron emission tomography (PET) scanning was used to assess these changes and their relation to long-term benefits of subthalamotomy.

METHODS

To determine whether the early postoperative changes persisted at longer-term follow up, the authors assessed six patients with advanced PD by using [18F]fluorodeoxyglucose-PET at 3 and 12 months postsurgery. The authors compared each of the postoperative images with baseline studies, and assessed interval changes between the short- and long-term follow-up scans. Clinical improvement at 3 and 12 months was associated with sustained metabolic decreases in the midbrain GP internus (GPi), thalamus, and pons of the lesioned side (p < 0.01). The activity of a PD-related multiregional brain network, which correlated with bradykinesia and rigidity, was reduced at both postoperative time points (p < 0.05). Comparisons of 3- and 12-month images revealed a relative metabolic increase in the GP externus (GPe) (p < 0.001), which was associated with worsening gait, postural stability, and tremor at long-term follow up.

CONCLUSIONS

These findings indicate that subthalamotomy may have differential effects on each of the functional pathways that mediate parkinsonian symptomatology. Sustained relief of akinesia and rigidity is associated with suppression of a pathological network involving the GPi and its output. In contrast, the recurrence of tremor may relate to changes in the function of an STN-GPe oscillatory network.

Hemiballism: revisiting a classic disorder

Hemiballism is a rare movement disorder that presents with unilateral flinging movements of the limbs. In traditional teaching, it has been characterised as almost pathognomonic of a lesion in the subthalamic nucleus (STN). The prognosis was described as grave, with severe disability and death in many cases. However, review of more recent reports shows that the STN is directly involved in only a minority of cases. The prognosis is benign in most cases, with almost all patients responding well to treatment and many having spontaneous remission, although long-term prognosis of cerebrovascular disease may not be so good. There have also been recent insights into the pathophysiology of hemiballism, which have emphasised the importance of altered firing patterns in basal-ganglia structures. Recent studies have pointed to previously unrecognised causes, particularly non-ketotic hyperosmolar hyperglycaemia and complications of HIV infection, that may account for a substantial proportion of cases of hemiballism.

Future and current surgical therapies in Parkinson's disease

PURPOSE OF REVIEW

The mainstay of treatment for Parkinson's disease remains medical therapy. With improved surgical precision and decreased morbidity, stereotactic lesioning and deep brain stimulation have become more popular. New therapies currently in clinical trials include gene therapy and direct drug delivery to the brain. The present review discusses surgical therapies for the treatment of Parkinson's disease and the status of experimental strategies currently in preclinical and clinical testing.

RECENT FINDINGS

Both stereotactic ablation and deep brain stimulation of the thalamus, globus pallidus interna, and subthalamic nucleus are discussed and compared in the current literature. New therapies such as drug infusions into the brain, gene therapy, and neural transplantation are in clinical trials and have been tested extensively in animals. Safety and efficacy of such therapies are discussed in recent literature.

SUMMARY

Although medication remains the first and main line of treatment and the mainstay for Parkinson's disease, advances in techniques and safety of operations have made surgical interventions more popular. Thalamic surgery remains helpful only in a limited subset of patients with predominent tremor that is unresponsive to medication. Bilateral subthalamic nucleus DBS holds the most promising results for patients with tremor, severe motor fluctuations and dyskinesias from L-dopa, with the best improvements seen in daily activities and quality of life. Newer therapies currently in clinical trial include gene therapy to replace lost gamma-aminobutyric acid inputs to the subthalamic nucleus and globus pallidus interna/substantia nigra pars reticulata, and infusion of recombinant glial derived neurotrophic factor to support at-risk nigrostriatal neurons. Further developments in these areas, along with evolution in stem cell science that hopefully will permit replacement of lost neurons, may alter the nature of surgical practice in Parkinson's disease patients in the not too distant future.