Microelectrode-guided posteroventral pallidotomy for treatment of Parkinson's disease: postoperative magnetic resonance imaging analysis

Outcomes of Unilateral Pallidotomy in Focal and Hemidystonia Cases: A Single-Blind Cohort Study

BACKGROUND

The role of deep brain stimulation in the treatment of dystonia has been widely documented. However, there is limited literature on the outcome of lesioning surgery in unilateral dystonia.

OBJECTIVE

We restrospectively reviewed our cases of focal and hemidystonia undergoing unilateral Pallidotomy at our institute to evaluate the short-term and long-term outcome.

METHODS

Patients who underwent radiofrequency lesioning of GPi for unilateral dystonia between 1999 and 2019 were retrospectively reviewed. All patients were evaluated using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) and Dystonia Disability Scale (DDS) preoperatively at the short term follow-up (<1 year) and at long-term follow-up (2-7.5 years). Video recordings performed at these time points were independently reviewed by a blinded movement disorders specialist.

RESULTS

Eleven patients were included for analysis. The preoperative, short-term, and long-term follow-up motor BFMDRS and DDS scores were 15.5 (IQR [interquartile range]: 10.5, 23.75) and 10.5 (IQR: 6.0, 14.5); 3.0 (IQR: 1.0, 6.0, P = 0.02) and 3.0 (IQR: 3.0, 8.0, P = 0.016); and 14.25 (IQR: 4.0, 20.0, P = 0.20) and 10.5 (IQR: 2.0, 15.0, P = 0.71) respectively. For observers B, the BFMDRS scores at the same time points were 19 (IQR: 12.5, 27.0), 7.5 (IQR: 6.0, 15.0, P = 0.002), and 21 (IQR: 7.0, 22.0, P = 0.65) respectively. The improvement was statistically significant for all observations at short-term follow-up but not at long-term follow-up.

CONCLUSION

Pallidotomy is effective for hemidystonia or focal dystonia in the short term. Continued benefit was seen in the longer term in some patients, whereas others worsened. Larger studies may be able to explain this in future.

A Single-Neuron: Current Trends and Future Prospects

The brain is an intricate network with complex organizational principles facilitating a concerted communication between single-neurons, distinct neuron populations, and remote brain areas. The communication, technically referred to as connectivity, between single-neurons, is the center of many investigations aimed at elucidating pathophysiology, anatomical differences, and structural and functional features. In comparison with bulk analysis, single-neuron analysis can provide precise information about neurons or even sub-neuron level electrophysiology, anatomical differences, pathophysiology, structural and functional features, in addition to their communications with other neurons, and can promote essential information to understand the brain and its activity. This review highlights various single-neuron models and their behaviors, followed by different analysis methods. Again, to elucidate cellular dynamics in terms of electrophysiology at the single-neuron level, we emphasize in detail the role of single-neuron mapping and electrophysiological recording. We also elaborate on the recent development of single-neuron isolation, manipulation, and therapeutic progress using advanced micro/nanofluidic devices, as well as microinjection, electroporation, microelectrode array, optical transfection, optogenetic techniques. Further, the development in the field of artificial intelligence in relation to single-neurons is highlighted. The review concludes with between limitations and future prospects of single-neuron analyses.

Functional lesional neurosurgery for tremor: back to the future?

For nearly a century, functional neurosurgery has been applied in the treatment of tremor. While deep brain stimulation has been in the focus of academic interest in recent years, the establishment of incisionless technology, such as MRI-guided high-intensity focused ultrasound, has again stirred interest in lesional approaches.In this article, we will discuss the historical development of surgical technique and targets, as well as the technological state-of-the-art of conventional and incisionless interventions for tremor due to Parkinson's disease, essential and dystonic tremor and tremor related to multiple sclerosis (MS) and midbrain lesions. We will also summarise technique-inherent advantages of each technology and compare their lesion characteristics. From this, we identify gaps in the current literature and derive future directions for functional lesional neurosurgery, in particularly potential trial designs, alternative targets and the unsolved problem of bilateral lesional treatment. The results of a systematic review and meta-analysis of the consistency, efficacy and side effect rate of lesional treatments for tremor are presented separately alongside this article.

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.

Factors predicting incremental administration of antihypertensive boluses during deep brain stimulator placement for Parkinson's disease

Hypertension is common in deep brain stimulator (DBS) placement predisposing to intracranial hemorrhage. This retrospective review evaluates factors predicting incremental antihypertensive use intraoperatively. Medical records of Parkinson's disease (PD) patients undergoing DBS procedure between 2008-2011 were reviewed after Institutional Review Board approval. Anesthesia medication, preoperative levodopa dose, age, preoperative use of antihypertensive medications, diabetes mellitus, anxiety, motor part of the Unified Parkinson's Disease Rating Scale score and PD duration were collected. Univariate and multivariate analysis was done between each patient characteristic and the number of antihypertensive boluses. From the 136 patients included 60 were hypertensive, of whom 32 were on angiotensin converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB), told to hold on the morning of surgery. Antihypertensive medications were given to 130 patients intraoperatively. Age (relative risk [RR] 1.01; 95% confidence interval [CI] 1.00-1.02; p=0.005), high Joint National Committee (JNC) class (p<0.0001), diabetes mellitus (RR 1.4; 95%CI 1.2-17; p<0.0001) and duration of PD >10 years (RR 1.2; 95%CI 1.1-1.3; p=0.001) were independent predictors for antihypertensive use. No difference was noted in the mean dose of levodopa (p=0.1) and levodopa equivalent dose (p=0.4) between the low (I/II) and high severity (III/IV) JNC groups. Addition of dexmedetomidine to propofol did not influence antihypertensive boluses required (p=0.38). Intraoperative hypertension during DBS surgery is associated with higher age group, hypertensive, diabetic patients and longer duration of PD. Withholding ACEI or ARB is an independent predictor of hypertension requiring more aggressive therapy. Levodopa withdrawal and choice of anesthetic agent is not associated with higher intraoperative antihypertensive medications.

Relationship between neuropsychological outcome and DBS surgical trajectory and electrode location

BACKGROUND

The outcome literature of subthalamic nuclei (STN) deep brain stimulation (DBS) suggests that cognitive declines are commonly reported following surgery. We hypothesized that differences in electrode position and surgical trajectory may lead to a differential neuropsychological outcome.

METHODS

We conducted a standardized evaluation of the location of the DBS electrode tip and the active electrodes, the surgical trajectory through which they were placed, and their relation to neuropsychological change scores (mental status, verbal memory, verbal fluency, and psychological measures) in 17 bilateral STN DBS patients using 6 months post-surgical magnetic resonance imaging data.

RESULTS

Declines in mental status scores were related to electrodes that were more posterior-laterally placed within the frontal quadrant in either hemisphere or those located superiorally in the left hemisphere. Electrodes that were closer to the approximated STN and more superiorally located in the left hemisphere were associated with verbal learning declines at 6 months following surgery. In the right hemisphere, the electrodes that were located more in the lateral direction were related to verbal short-term memory declines; while for verbal long-term memory declines were found for electrodes located more posterior-laterally in the left hemisphere. Declines in verbal fluency scores were more variable with associations found between change scores and electrodes in the lateral and superior directions in the left hemisphere and those electrodes closer to the approximated STN and more superiorally and posteriorally located in the right hemisphere. In contrast, semantic fluency declines were only related to right hemisphere electrodes located more superiorally. Declines in mood were related to those electrodes located further away from the approximated STN, particularly those located more inferiorally and laterally in the left hemisphere. Anxiety change scores were not associated with the location of the electrodes.

CONCLUSIONS

The results provide preliminary evidence that 6 months following bilateral STN DBS cognitive and emotional changes may be related to the surgical trajectory and electrode placement.

Functional surgery for Parkinson's disease treatment: a structured analysis of a decade of published literature

The aim of this study was to analyse and compare published data during the last decade on the different approaches to Parkinson's disease surgery. Eighty-eight papers published between 1990 and 2001 fulfilled the inclusion criteria. Full-text and prospective papers on lesion and stimulation of GPi or STN were assessed. Descriptive analysis of surgery procedure and population under study was performed, as well as a meta-analysis of the most consistently reported variables. A total of 1702 patients underwent surgery with a mean age of 58.75 years (range 46.5 - 72.5), mean duration of illness 13.6 years (8.1 - 18.1) and a male:female ratio 1.5:1. Mean postoperative follow-up was 9 months (1 - 52). Single blind assessment was performed in two papers, while double blind evaluation was used in 6. In the GPi group, no difference was found between the pre- and postoperative levodopa equivalent daily dose (960.39 v. 943.13; p > 0.05), while the STN group showed a marked reduction (1104.8 v. 483.04; p < 0.05) of this dosage. Meta-analysis of the most consistently reported variables (UPDRS total score, UPDRS motor score, UPDRS ADL score and Schwab & England score showed that Nucleus, Bilaterality of Approach and Surgical Procedure were the best moderators for defining outcome. Bilateral DBS STN procedures proved to be associated with better outcome. Microelectrode recording was not found to be a moderator that influenced outcome. Although there was a significant improvement of dyskinesias among the different approaches described in the papers, the heterogeneity of data makes it impossible to perform a structured analysis on this item.

Treatment of levodopa-induced motor complications

Chronic levodopa treatment for Parkinson's disease patients is frequently associated with the development of motor complications such as end-of-dose wearing-off and dyskinesias. In this review, we provide an overview of the strategies available for dealing with these problems. Medical management includes manipulation of levodopa dosing to establish the optimum treatment schedule, improving levodopa absorption, catechol-O-methyl transferase-inhibition (COMT), Monoamine oxidase-B (MAO-B) inhibition, dopaminergic agonists, amantadine, and continuous dopaminergic infusions. Surgical procedures and particularly deep brain stimulation are also reviewed. It should be noted that none of these treatments has been shown to provide anti-parkinsonian efficacy that is greater than what can be achieved with levodopa. We highlight the importance of initiating therapy with a treatment strategy that reduces the risk that a Parkinson's disease patient will develop motor complications in the first place. Key Words: Advanced PD, dyskinesias, motor fluctuations, levodopa, dopamine agonists, COMT inhibitors, MAO-B inhibitors.

Correlation of outcome to neurosurgical lesions: confirmation of a new method using data after microelectrode-guided pallidotomy

The purpose of this study was the development of a new method to correlate functional surgery with outcome measures. Lesions following microelectrode guided globus pallidus internus (GPi) pallidotomy for Parkinson's disease are presented to demonstrate this new method in regard to clinical outcome. A clinical series of 26 patients with extensive neurological and neuropsychological data were studied. Three-month postoperative MRI lesion borders at the AC-PC plane were scaled to a standard size, and the lesions were stored in a virtual array with a cell size of one voxel. The average outcome measure for each voxel is presented graphically. Unified Parkinson's disease rating scale (UPDRS) motor scores improved more with posterolateral and centrally located GPi lesions than with anteromedial lesions. A correlation of lesion location to outcome was also visible for subscales of the UPDRS. The distributions were similar for the left and right sides, as well as for ipsi- and contralateral measurements. In general, verbal fluency decreased after lesioning the dominant hemisphere, and posterolateral lesions caused less impairment. This method enables associative analyses between brain area and outcome down to the size of a few voxels. This may be particularly helpful for planning and validating neurosurgical targets for various disorders.

Five-year follow-up of unilateral posteroventral pallidotomy in Parkinson's disease

BACKGROUND

Neurocognitive outcome research of individuals with Parkinson's disease after unilateral pallidotomy is inconsistent. Although some studies reported few cognitive changes, other investigations have more consistently shown both transient and long-term cognitive decline postoperatively.

METHODS

We report the long-term motor and neurocognitive outcome 5 years post surgery for 18 patients with Parkinson's disease (12 men and 6 woman; all right-handed) who underwent right or left unilateral posteroventral pallidotomy.

RESULTS

Pallidotomy patients revealed long-term motor benefits from the surgery in their "off" state and control of dopa-induced dyskinesias in their "on" state, which is consistent with previous research. We found mild declines in oral and visuomotor information processing speed, verbal recognition memory, and mental status 5 years after surgery, which differs from previous literature regarding the long-term neurocognitive outcome after pallidotomy. Differences between the right and left pallidotomy patients for both motor and cognitive skills were not found.

CONCLUSION

Although deep brain stimulation is presently the treatment of choice, pallidotomy continues to be performed around the world. Consequently, although unilateral pallidotomy should be considered a treatment option for patients with Parkinson's disease who suffer from severe unilateral disabling motor symptoms or dyskinesias, the long-term neurocognitive outcome should also be considered in treatment decisions.

Subthalamic deep brain stimulation in patients with a previous pallidotomy

The safety and efficacy of subthalamic nucleus (STN) deep brain stimulation (DBS) in patients who have had a previous unilateral pallidotomy is not clear. We identified 10 patients (9 male) at the Baylor College of Medicine Parkinson's Disease Center who underwent STN DBS after prior unilateral pallidotomy. Demographics, efficacy as determined by off Unified Parkinson's Disease Rating Scale (UPDRS) part III scores, and levodopa equivalent dosing were analyzed. We then compared these to an age- and sex-matched group of 25 DBS patients who had no prior pallidotomy. After their initial pallidotomy (mean age, 51.8 +/- 10.8 years), the mean UPDRS motor off medicine scores improved from 51.3 +/- 14.3 to 34.9 +/- 12.8, and the UPDRS dyskinesia score improved from 1.8 +/- 1.0 to 0.8 +/- 0.7. Their STN DBS off UPDRS motor scores (mean age, 56.0 +/- 10.2 years) improved by 16.0% from 53.1 +/- 9.7 (range, 42-68) to 44.6 +/- 11.1 (range, 25-67). In contrast, the UPDRS off motor scores in a control group of 25 DBS patients improved by 49.9%, from 49.7 +/- 11.1 to 25.7 +/- 18.9, (16.0% vs. 49.9%; P < 0.001). Changes in UPDRS dyskinesia scores were similar in both groups. AE thought to be related to the STN DBS following pallidotomy included worse dysarthria (three) and worse balance (two). STN DBS patients with prior pallidotomy had less improvement in UPDRS off motor score compared to other STN DBS patients, despite relatively good outcomes immediately after their pallidotomy. This may be partially due to a selection bias, but it may also indicate that prior pallidotomy is a negative predictor of outcome of STN DBS and should be considered in patient selection.

Operative indications and neuroendoscopic management of symptomatic cysts of the septum pellucidum

OBJECTIVE

Since there is no current consensus on the diagnostic standards or surgical indications for symptomatic cysts of the septum pellucidum (CSP), we presented our experience treating such cases with neuroendoscopic surgery in order to possibly make a contribution to the attainment of such a consensus.

METHODS

In the last 5 years, we effectively treated 5 patients (4 males and 1 female) with CSP by neuroendoscopic surgery. The 3 congenital cases were young: 9, 14, and 29 years old. The 2 secondary cases were adults aged 51 and 65 years old. We were able to fenestrate, and biopsy for pathological analysis, the cyst walls of symptomatic CSP using a minimally invasive neuroendoscopic technique, with postoperative improvement in compression of adjacent structures, as well as clinical signs.

CONCLUSIONS

It is necessary to consider the overall picture including clinical signs, progress of the condition, intracranial pressure, and cerebral circulation, in deciding whether surgery is indicated. Neuroendoscopic surgery is an effective, optimal, and convenient therapeutic modality for symptomatic CSP.

Radio frequency electrode system for optical lesion size estimation in functional neurosurgery

Radiofrequency (RF) lesioning in the human brain is one possible surgical therapy for severe pain as well as movement disorders. One obstacle for a safer lesioning procedure is the lack of size monitoring. The aim of this study was to investigate if changes in laser Doppler or intensity signals could be used as markers for size estimation during experimental RF lesioning. A 2 mm in diameter monopolar RF electrode was equipped with optical fibers and connected to a digital laser Doppler system. The optical RF electrode's performance was equal to a standard RF electrode with the same dimensions. An albumin solution with scatterers was used to evaluate the intensity and laser Doppler signal changes during lesioning at 70, 80, and 90 degrees C. Significant signal changes were found for these three different clot sizes, represented by the temperatures (p<0.05, n=10). The volume, width, and length of the created coagulations were correlated to the intensity signal changes (r=0.88, n=30, p<0.0001) and to the perfusion signal changes (r=0.81, n=30, p<0.0001). Both static and Doppler-shifted light can be used to follow the lesioning procedure as well as being used for lesion size estimation during experimental RF lesioning.

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.

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

During the last decade deep brain stimulation (DBS) has become a routine method for the treatment of advanced Parkinson's disease (PD), leading to striking improvements in motor function and quality of life of PD patients. It is associated with minimal morbidity. The rationale of targeting specific structures within basal ganglia such as the subthalamic nucleus (STN) or the internal segment of the globus pallidus (GPi) is strongly supported by the current knowledge of the basal ganglia pathophysiology, which is derived from extensive experimental work and which provides the theoretical basis for surgical therapy in PD. In particular, the STN has advanced to the worldwide most used target for DBS in the treatment of PD, due to the marked improvement of all cardinal symptoms of the disease. Moreover on-period dyskinesias are reduced in parallel with a marked reduction of the equivalent daily levodopa dose following STN-DBS. The success of the therapy largely depends on the selection of the appropriate candidate patients and on the precise implantation of the stimulation electrode, which necessitates careful imaging-based pre-targeting and extensive electrophysiological exploration of the target area. Despite the clinical success of the therapy, the fundamental mechanisms of high-frequency stimulation are still not fully elucidated. There is a large amount of evidence from experimental and clinical data that stimulation frequency represents a key factor with respect to clinical effect of DBS. Interestingly, high-frequency stimulation mimics the functional effects of ablation in various brain structures. The main hypotheses for the mechanism of high-frequency stimulation are: (1) depolarization blocking of neuronal transmission through inactivation of voltage dependent ion-channels, (2) jamming of information by imposing an efferent stimulation-driven high-frequency pattern, (3) synaptic inhibition by stimulation of inhibitory afferents to the target nucleus, (4) synaptic failure by stimulation-induced neurotransmitter depletion. As the hyperactivity of the STN is considered a functional hallmark of PD and as there is experimental evidence for STN-mediated glutamatergic excitotoxicity on neurons of the substantia nigra pars compacta (SNc), STN-DBS might reduce glutamatergic drive, leading to neuroprotection. Further studies will be needed to elucidate if STN-DBS indeed provides a slow-down of disease progression.

Lesion therapy for Parkinson's disease and other movement disorders: Update and controversies

An analysis of the international literature on lesioning for movement disorders was undertaken to review lesion therapy for Parkinson's disease (PD) and other movement disorders and to highlight important controversies surrounding this surgical technique. Lesions have been placed throughout the neuraxis with varying approaches and success. Our understanding of the pathophysiological basis underlying the development of PD and other movement disorders has led to a better understanding of why lesioning certain portions of the nervous system should improve motor function. Advances in imaging technology and electrophysiological techniques used for localization of brain structures, such as microelectrode mapping, have improved the ability to accurately identify and lesion target structures deep in the brain. This improvement has led to an increase in the degree and consistency of clinical benefit. The major controversies in lesion therapy include: (1) which target for which disorder; (2) determination of the optimal lesion site and whether the external globus pallidus (GPe) should be included in the pallidotomy lesion for PD; (3) determination of the size of the lesion; (4) whether bilateral lesions can be placed without the high incidence of side effects reported by some investigators; (5) whether microelectrodes aid in the ability to improve clinical outcomes or increase the risk of side effects by making multiple microelectrode penetrations; (6) whether the subthalamic nucleus (STN) should be explored further as a lesioning target; and (7) whether lesioning should be abandoned entirely in favor of deep brain stimulation (DBS). Many important questions and controversies regarding lesion therapy remain unanswered. It is unlikely given the pro-DBS environment that these questions will be answered in the near future. We should, however, be careful not to abandon an effective therapy before fully exploring through randomized trials the relative effect of different surgical approaches for the treatment of patients with movement disorders.

Basal ganglia neuronal discharge in primary and secondary dystonia in patients undergoing pallidotomy

OBJECTIVE

Basal ganglia neuronal activity in patients undergoing posteroventral pallidotomy (PVP) for the treatment of primary genetic, secondary, or idiopathic dystonia (DYS) was studied to gain a better understanding of the pathophysiology of DYS.

METHODS

Intraoperative neurophysiological data recorded from 15 DYS patients were compared with those from 78 patients with Parkinson's disease (PD) who underwent PVP.

RESULTS

Putamen neurons in both DYS and PD patients had low discharge rates. Globus pallidus externa (GPe) and globus pallidus interna (GPi) neurons in DYS patients had significantly lower discharge rates and more irregular discharge patterns than in PD patients. GPe and GPi neurons displayed similar discharge rates and patterns in DYS, whereas in PD, the discharge rate of GPe neurons was lower than that of the GPi neurons. The discharge rate and pattern of GPe and GPi neurons in patients whose DYS was ameliorated by PVP were similar to those in DYS patients who did not benefit from PVP. No significant differences in the rate or pattern of neuronal discharge in patients with DYS of different causes were discernible. PVP was most beneficial in patients with primary genetic DYS. Anesthesia with desflurane depressed the discharge rate of the GPe and GPi neurons, particularly in patients with PD.

CONCLUSION

Significant differences in the rates and patterns of discharge of GPe and GPi neurons exist in DYS and PD. The findings are discussed with reference to the current model of the functional connections of the basal ganglia.

Hemorrhagic complication of stereotactic surgery in patients with movement disorders

OBJECT

Small, asymptomatic hemorrhages are easier to detect during stereotactic surgery when magnetic resonance (MR) imaging is used for targeting rather than when traditional approaches, such as ventriculography, are performed with contrast material. In the present study the authors examined the actual incidence of intraoperative hemorrhages in patients with movement disorders who had undergone MR imaging-targeted surgery, microelectrode recording (MER)-guided implantation of deep brain stimulation (DBS) electrodes, or radiofrequency-induced coagulation surgery performed.

METHODS

Ninety-six consecutive patients underwent a total of 116 stereotactic operations for movement disorders (57 operations for radiofrequency-induced coagulation and 59 for DBS electrode implantation) between January 1998 and November 2002. The authors investigated the correlation between hemorrhages and other factors including the location of the hemorrhage and the type of surgery performed. Postoperative computerized tomography scans demonstrated the occurrence of intraoperative hemorrhages at 12 locations during 11 procedures (9.5% of all procedures). Nine hemorrhages occurred during 57 coagulation operations (15.8%). Within this group, the frequency of hemorrhages was highest during thalamotomy (five [21.7%] of 23 procedures) and lower during pallidotomy (four [11.8%] of 34 procedures). In contrast, only two intraventricular hemorrhages developed during 59 operations in which DBS electrodes were implanted (3.4%). In no case was hemorrhage detected in the main DBS target, that is, the subthalamic nucleus.

CONCLUSIONS

When small, asymptomatic hemorrhages were included in the estimation, the actual rate of hemorrhage was higher than that previously reported. Judging from the incidence of hemorrhage during coagulation and DBS surgeries, the authors suggest that the heat induced by coagulation may play a larger role than microelectrode penetration in the development of hemorrhage.

Randomized trial of pallidotomy versus medical therapy for Parkinson's disease

Thirty-six patients with Parkinson's disease (PD) were randomized to either medical therapy (N = 18) or unilateral GPi pallidotomy (N = 18). The primary outcome variable was the change in total Unified Parkinson's Disease Rating Scale (UPDRS) score at 6 months. Secondary outcome variables included subscores and individual parkinsonian symptoms as determined from the UPDRS. At the six month follow-up, patients receiving pallidotomy had a statistically significant reduction (32% decrease) in the total UPDRS score compared to those randomized to medical therapy (5% increase). Following surgery, patients' showed improvement in all the cardinal motor signs of PD including tremor, rigidity, bradykinesia, gait and balance. Drug-induced dyskinesias were also markedly improved. Although the greatest improvement occurred on the side contralateral to the lesion, significant ipsilateral improvement was also observed for bradykinesia, rigidity and drug-induced dyskinesias. A total of twenty patients have been followed for 2 years to assess the effect of time on clinical outcome. These patients have shown sustained improvement in the total UPDRS (p < 0.0001), "off" motor (p < 0.0001) and complications of therapy subscores (p < 0.0001). Sustained improvement was also seen for tremor, rigidity, bradykinesia, percent on time and drug-induced dyskinesias.

Anatomic and neurophysiological methods for the targeting and lesioning of the subthalamic nucleus: Cuban experience and review

OBJECTIVE

To develop a method to place a lesion precisely in the subthalamic nucleus (STN) and evaluate its effectiveness.

METHODS

A retrospective study of targeting data collected during stereotactic planning to lesion the STN in 31 patients with Parkinson's disease and of results in more than 50 procedures was performed. The targeting method was based on computed tomographic imaging together with semimicroelectrode recording digital processing and electrical stimulation. Two statistical methods were used to correlate initial with final target coordinates and assess the efficacy of the targeting procedure.

RESULTS

The anatomic target based on computed tomographic imaging data showed electrical activity in the subthalamus in the first pass in 82% of the procedures. In the remaining 18%, the STN was an average of 1.93 mm away from the nearest trajectory that recorded the STN (range, 1.41-2.24 mm). The average number of trajectories per procedure was 7.2; the location of the first trajectory relative to the center of the nucleus determined by electrical and physiological means (P < 0.01, analysis of variance, Student's t test) was as follows: in the lateral direction, 1.25 +/- 1.15 mm; in the anteroposterior direction, 1.53 +/- 1.31 mm; and in the vertical direction, 0.67 +/- 0.51 mm. The average number of tracts necessary to lesion the STN was two.

CONCLUSION

The combination of computed tomographic imaging, semimicroelectrode recording, and microstimulation provides an effective method to identify the STN lesion in parkinsonian patients. The method used for anatomic localization and electrophysiological mapping of the subthalamus was found to be effective in reaching the sensorimotor region of the nucleus. We carried out an accurate determination of the subthalamus location and its volume in the lesioning.

Unilateral subthalamic nucleus lesioning: a safe and effective treatment for Parkinson's disease

The present study, the largest in the literature, was performed to assess the effectiveness and safety of unilateral subthalamic nucleus (STN) lesioning for Parkinson's disease (PD). From August 1999 to September 2000, 21 consecutive patients evaluated pre- and postoperatively by a single examiner were operated. Levodopa intake and dyskinesia, Hoehn & Yahr, Schwab & England and UPDRS motor scores were recorded. Stereotactic CT and MRI and the effects of macrostimulation were used to determine STN coordinates. A single radiofrequency lesion was made (60-75 degrees C/60"). Concomitant ipsilateral Vim/VOp lesions were made in 8 patients. Using a new technique, we were able to determine the territory of STN involved by the surgical lesion. The Wilcoxon and Mann-Whitney statistical tests were applied to evaluate the surgical results. All recorded parameters showed stable improvement after a mean follow up of 13.5 months. Recurrence occurred in two patients. Contralateral tremor arrest and decrease of rigidity and bradykinesia should be regarded as STN hallmarks to stimulation. Hyperintense lesions in the early-phase MRI seem to be a poor prognostic factor. Lateral territory lesioning correlates with better results. There was no significant difference between the cohorts with and without a Vim/VOp lesion. Dyskinesias happened in two patients (promptly abolished by a Vim/VOp lesion). Other complications were transient and/or rare. In conclusion, STN lesioning is a safe and very effective procedure to treat PD and probably an underutilized operation for those who can not afford the costs of DBS.

Effect of chronic pallidal deep brain stimulation on off period dystonia and sensory symptoms in advanced Parkinson's disease

OBJECTIVE

To investigate the efficacy of chronic pallidal deep brain stimulation (DBS) on off period dystonia, cramps, and sensory symptoms in advanced Parkinson's disease (PD).

METHODS

16 patients (6 women, 10 men; mean age at surgery 65 years) suffering from advanced PD were followed up prospectively for one year after implantation of a monopolar electrode in the posteroventral lateral globus pallidus internus. Unilateral DBS was performed in 9 patients. 10 patients had bilateral procedures (contemporaneous bilateral surgery in 7 and staged bilateral surgery in 3 instances). The decision whether to perform unilateral or bilateral surgery depended on the clinical presentation of the patient. Patients were formally assessed preoperatively, at 3-5 days, 3 months, and 12 months after surgery.

RESULTS

In patients who underwent unilateral surgery, pain was present in 7 (78%), off dystonia in 5 (56%), cramps in 6 (67%), and dysaesthesia in 4 (44%). In patients who underwent bilateral surgery, pain was present in 7 (70%), off dystonia in 6 (60%), cramps in 7 (70%), and dysaesthesia in 4 (40%). With unilateral DBS, contralateral off period dystonia was improved by 100% at 1 year postoperatively, pain by 74%, cramps by 88%, and dysaesthesia by 100%. There was less pronounced amelioration of ipsilateral off period dystonia and sensory symptoms. With bilateral DBS, total scores for dystonia were improved by 86%, for pain by 90%, for cramps by 90%, and for dysaesthesia by 88%. The benefit appeared early at the first evaluation 3-5 days after surgery and was stable throughout the follow up period.

CONCLUSIONS

Pallidal DBS yields major improvement of off period dystonia, cramps, and sensory symptoms in patients with advanced PD.

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.

Effects of transient focal inactivation of the basal ganglia in parkinsonian primates

Ablative and chronic stimulation procedures targeting the internal pallidum (GPi) and the subthalamic nucleus (STN) have led to major advancements in the treatment of Parkinson's disease and other movement disorders. Although these procedures have evolved to primarily target the posterior ventrolateral sensorimotor portion of GPi and to less selectively target STN, centrally, the ideal targets within these structures remain to be fully established. In this study, we sought to identify the optimal targeting sites in GPi and STN for reversal of parkinsonian signs through a series of reversible injections of the GABA(A) agonist muscimol in these nuclei in parkinsonian primates. Akinesia and bradykinesia were strongly ameliorated by discrete inactivation within the centromedial extent of the sensorimotor territory in GPi and the lateral portion of the sensorimotor territory in STN. This suggests that akinesia and bradykinesia might, in fact, originate from abnormalities in the same, or at least overlapping, motor circuits in the parkinsonian state. Inactivation of areas outside of the motor territories did not improve parkinsonism but induced circling and behavioral abnormalities. The segregation of basal ganglia-thalamocortical circuits appears to be therefore maintained, at least to a large extent, in the parkinsonian state. These results underscore that inactivation of discrete regions in the central territory of GPi and the lateral portion of STN are sufficient to ameliorate parkinsonian motor signs and that extension of lesions into nonmotor territories may be deleterious. Surgical outcomes might therefore be optimized by placing more discrete lesions and by restricting the extent of chronic stimulation.

Neurochemical organization of the human basal ganglia: anatomofunctional territories defined by the distributions of calcium-binding proteins and SMI-32

The distribution of the calcium-binding proteins calbindin-D28K (CB), parvalbumin (PV) and calretinin (CR), and of the nonphosphorylated neurofilament protein (with SMI-32) was investigated in the human basal ganglia to identify anatomofunctional territories. In the striatum, gradients of neuropil immunostaining define four major territories: The first (T1) includes all but the rostroventral half of the putamen and is characterized by enhanced matriceal PV and SMI-32 immunoreactivity (-ir). The second territory (T2) encompasses most part of the caudate nucleus (Cd) and rostral putamen (PuT), which show enhanced matriceal CB-ir. The third and fourth territories (T3 and T4) comprise rostroventral parts of Cd and PuT characterized by complementary patch/matrix distributions of CB- and CR-ir, and the accumbens nucleus (Acb), respectively. The latter is separated into lateral (prominently enhanced in CB-ir) and medial (prominently enhanced in CR-ir) subdivisions. In the pallidum, parallel gradients also delimit four territories, T1 in the caudal half of external (GPe) and internal (GPi) divisions, characterized by enhanced PV- and SMI-32-ir; T2 in their rostral half, characterized by enhanced CB-ir; and T3 and T4 in their rostroventral pole and in the subpallidal area, respectively, both expressing CB- and CR-ir but with different intensities. The subthalamic nucleus (STh) shows contrasting patterns of dense PV-ir (sparing only the most medial part) and low CB-ir. Expression of CR-ir is relatively low, except in the medial, low PV-ir, part of the nucleus, whereas SMI-32-ir is moderate across the whole nucleus. The substantia nigra is characterized by complementary patterns of high neuropil CB- and SMI-32-ir in pars reticulata (SNr) and high CR-ir in pars compacta (SNc) and in the ventral tegmental area (VTA). The compartmentalization of calcium-binding proteins and SMI-32 in the human basal ganglia, in particular in the striatum and pallidum, delimits anatomofunctional territories that are of significance for functional imaging studies and target selection in stereotactic neurosurgery.

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%.

Outcome of unilateral pallidotomy in advanced Parkinson's disease: cohort study of 32 patients

OBJECTIVES

In a randomised trial to study the efficacy of unilateral pallidotomy in patients with advanced Parkinson's disease, patients having pallidotomy within 1 month after randomisation were compared with patients having pallidotomy 6 months after the primary outcome assessment. Of the 37 patients enrolled 32 had a unilateral pallidotomy. The follow up study of these patients is presented to report (1) clinical outcome; (2) adverse effects; (3) cognitive and behavioural effects; (4) relation between lesion location and outcome; and (5) preoperative patient characteristics predictive for good outcome.

METHODS

Outcome measures were the motor section of the unified Parkinson's disease rating scale (UPDRS), levodopa induced dyskinesias, disability, quality of life, and a comprehensive neuropsychological assessment. Multivariate logistic regression was used to identify preoperative patient characteristics independently associated with good outcome.

RESULTS

Off phase assessment showed a reduction in parkinsonism from 49 to 36.5 points on the UPDRS 6 months after surgery. Improvements were also demonstrated for activities of daily living and quality of life. In the on phase dyskinesias were reduced. All effects lasted up to 12 months after surgery. Three patients had major permanent adverse effects. Besides worsening of verbal fluency after left sided surgery, systematic cognitive deterioration was not detected. Patients taking less than 1000 levodopa equivalent units (LEU)/day were more likely to improve.

CONCLUSIONS

The positive effects of unilateral pallidotomy are stable up to 1 year after surgery. Patients taking less than 1000 LEU per day were most likely to improve.

Staged bilateral pallidotomy for treatment of Parkinson disease

OBJECT

Several investigators have described the motor benefits derived from performing unilateral stereotactic pallidotomy for the treatment of Parkinson disease (PD), but little is known about the efficacy and complication rates of bilateral procedures. The goal of this study was to assess both these factors in 12 patients.

METHODS

Eleven patients with medically intractable PD underwent staged bilateral pallidotomy and one patient underwent a simultaneous bilateral procedure. Unilateral pallidotomy resulted in an improvement in the patients' Unified Parkinson Disease Rating Scale (UPDRS) total scores and motor subscores, Hoehn and Yahr stages, and Schwab and England Activities of Daily Living scores. There were no complications. The second procedures were performed 5 to 25 months after the first, and nearly complete 3-month follow-up data are available for eight of these patients. Staged bilateral pallidotomy did result in further improvements in some symptoms, but the patients proved to be less responsive to levodopa. In contrast to outcomes of the initial unilateral pallidotomy, there were significant complications. One patient suffered an acute stroke, two patients suffered delayed infarctions of the internal capsule, four patients had mild-to-moderate worsening of speech and increased drooling, and one patient complained of worsening memory.

CONCLUSIONS

Bilateral pallidotomy results in modest benefits but is associated with an increased risk of complications.

Pallidotomy for parkinson disease: a review of contemporary literature

OBJECT

The authors conducted an evidence-based review of contemporary published articles on pallidotomy to obtain an appraisal of this procedure in the treatment of Parkinson disease (PD).

METHODS

A search of the Pubmed database performed using the key word "pallidotomy" yielded 263 articles cited between January 1, 1992, and July 1, 1999. Articles that included original, nonduplicated descriptions of patients with PD treated with radiofrequency pallidotomy were selected. In 85 articles identified for critical review, 1959 patients with PD underwent pallidotomies at 40 centers in 12 countries. There were 1735 unilateral (88.6%) and 224 bilateral procedures (11.4%). The mean age of the patients was 61.4+/-3.6 years and the mean duration of PD symptoms in these patients was 12.3+/-1.9 years. Microelectrode recordings were used in 46.2% of cases. Outcomes were objectively documented using the Unified Parkinson Disease Rating Scale (UPDRS) in 501 (25.6%) of the cases at 6 months and in 218 (11.1%) of the cases at 1 year. There was a consensus on the benefits of pallidotomy for off period motor function and on period, drug-induced dyskinesias, with variations in the extent of symptomatic benefit across studies. At the 1-year assessment, the mean improvement in the UPDRS motor score during off periods was 45.3% and the mean improvement in contralateral dyskinesias during on periods was 86.4%. The overall mortality rate was 0.4% and the rate of persistent adverse effects was estimated at 14%. Major adverse events, including intracerebral hemorrhages, contralateral weakness, and visual field defects, occurred in 5.3% of patients reported.

CONCLUSIONS

Unilateral pallidotomy is effective and relatively safe in the treatment of PD; however, limited data are available on the long-term outcome of this procedure.

Internal globus pallidotomy in dystonia secondary to Huntington's disease

INTRODUCTION AND METHOD

The prototypic motor feature of Huntington's disease (HD) is chorea, but parkinsonism and involuntary movements such as dystonia and myoclonus can also be present. Pallidotomy has been shown to be an effective treatment for medically refractory Parkinson's disease (PD). We performed bilateral microelectrode guided-stereotactic pallidotomies targeted at globus pallidum internus (GPi) to treat a 13-year-old patient diagnosed with Westphal variant of HD with intractable generalized dystonia and parkinsonism.

RESULTS

Intraoperative microelectrode recordings of GPi cells showed a relatively low firing rate, 29 +/- 14 Hz, with most neurons showing pauses. Acutely, after surgery, limb dystonia mildly improved but trunk dystonia persisted. Postoperative follow up 3 months later showed minimal clinical improvement in dystonic features with marked worsening of spasticity.

CONCLUSION

In our case, bilateral pallidotomy produced modest palliative functional improvement in dystonic features. Cellular firing patterns were markedly different than in PD and were similar to those found in dystonia.

Predictors of neuropsychological outcome in patients following microelectrode-guided pallidotomy for Parkinson's disease

OBJECT

The authors studied neuropsychological performance following microelectrode-guided posteroventral pallidotomy in patients with Parkinson's disease (PD) and evaluated correlations with presurgical and surgical factors.

METHODS

Neuropsychological changes 3 months (43 patients) and 12 months (27 patients) after microelectrode-guided pallidotomy for PD are reported in a series of 44 consecutive patients with the disease, who improved neurologically, as measured by the Unified Parkinson's Disease Rating Scale (UPDRS) in both the "off' (p<0.001) and best "on" (p<0.001) states. Findings of the vocabulary subtest of the Wechsler Adult Intelligence Scale-Revised (p<0.01), Letter Fluency (p<0.001), Verbal Fluency for semantic categories (p<0.001), and the Wisconsin Card Sorting Test (p<0.01) showed a significant decline in neuropsychological performance in patients 3 months after undergoing left-sided pallidotomy. Impairment in the language domain (semantic fluency) persisted at the 12-month follow-up examination (p<0.01). Visual memory improved after right-sided pallidotomies (p<0.01 after 3 months), with a nonsignificant trend toward persistent improvement 1 year postsurgery (p<0.02 after 12 months). Preoperative semantic fluency was influenced by patient age (p<0.001) and by the width of the third ventricle (p<0.05), as measured by magnetic resonance imaging. A regression model revealed that semantic fluency 3 months postoperatively was significantly affected by the baseline score (p<0.001), side of surgery (p<0.001), handedness (p<0.01), and patient age (p<0.05). However, postoperative lesion volume, lesion location, number of tracks, number of lesions, distance from anatomical landmarks, or UPDRS score did not significantly contribute to neuropsychological outcome.

CONCLUSIONS

Neuropsychological changes in a cohort of patients with PD who underwent pallidotomy and experienced excellent clinical benefits and minimum postoperative complications, emphasize the importance of neuropsychological examinations and further investigation of predictive factors.

Neuropsychological outcome after unilateral pallidotomy for the treatment of Parkinson's disease

OBJECTIVE

To assess the long term cognitive outcome of unilateral posteroventral pallidotomy (PVP) and the overall efficacy of the surgery.

METHODS

Forty two (29 left and 13 right PVP) patients with Parkinson's disease underwent neurological and neuropsychological testing before PVP and at 3 and 12 months after PVP. The neuropsychological testing battery emphasised measures of verbal learning and memory, visuospatial abilities, speed of information processing, executive functioning, and affective functioning.

RESULTS

All patients demonstrated motor improvements after surgery during their off state, and 86% of patients also showed improvements in motor functioning in their on state. Repeated measures ANOVA showed significant improvements in confrontational naming, visuospatial organisation, and affective functioning 3 months and 12 months after surgery, with inconsistent improvements in executive functioning 12 months post-PVP. Patients demonstrated a transient impairment in verbal memory, with verbal learning performance returning to baseline 12 months post-PVP after a significant decline 3 months after PVP. When three patients with lesions extending outside of the PVP were excluded from the analysis, a decline in verbal fluency performance after PVP was not found to be significant. Differences due to side of lesion placement were not found on any of the cognitive measures.

CONCLUSIONS

In the largest long term follow up study reported to date, the cognitive changes found up to a year after PVP are minimal compared with the robust improvements in motor function. The findings highlight the need to investigate the relation between the specific fibre tracts affected by the lesions and cognitive outcome.

Comparison of anatomic and neurophysiological methods for subthalamic nucleus targeting

OBJECTIVE

The subthalamic nucleus (STN) has recently become the surgical target of choice for the treatment of medically refractory idiopathic Parkinson's disease. A number of anatomic and physiological targeting methods have been used to localize the STN. We retrospectively reviewed the various anatomic targeting methods and compared them with the final physiological target in 15 patients who underwent simultaneous bilateral STN implantation of deep brain stimulators.

METHODS

The x, y, and z coordinates of our localizing techniques were analyzed for 30 STN targets. Our final targets, as determined by single-cell microelectrode recording, were compared with the following: 1) targets selected on coronal magnetic resonance inversion recovery and T2-weighted imaging sequences, 2) the center of the STN on a digitized scaled Schaltenbrand-Wahren stereotactic atlas, 3) targeting based on a point 13 mm lateral, 4 mm posterior, and 5 mm inferior to the midcommissural point, and 4) a composite target based on the above methods.

RESULTS

All anatomic methods yielded targets that were statistically significantly different (P < 0.001) from the final physiological targets. The average distance error between the final physiological targets and the magnetic resonance imaging-derived targets was 2.6 +/- 1.3 mm (mean +/- standard deviation), 1.7 +/- 1.1 mm for the atlas-based method, 1.5 +/- 0.8 mm for the indirect midcommissural method, and 1.3 +/- 1.1 mm for the composite method. Once the final microelectrode-refined target was determined on the first side, the final target for the contralateral side was 1.3 +/- 1.2 mm away from its mirror image.

CONCLUSION

Although all anatomic targeting methods provide accurate STN localization, a combination of the three methods offers the best correlation with the final physiological target. In our experience, direct magnetic resonance targeting was the least accurate method.

Treatment of advanced Parkinson's disease by unilateral posterior GPi pallidotomy: 4-year results of a pilot study

To assess the long-term outcome following unilateral pallidotomy for advanced Parkinson's disease, we performed nonblinded Core Assessment Program for Intracerebral Transplantations protocol assessments in 10 of the original 15 patients in our pilot study for 4 years following surgery. Although Unified Parkinson's Disease Rating Scale motor examination scores returned to baseline levels at 3 and 4 years, most patients continued to show sustained improvements in contralateral tremor, akinesia, and drug-induced dyskinesias. Contralateral tremor was absent at 4 years in all seven patients with preoperative tremor. Contralateral "off" arm movement times (averaged for three tasks) decreased by 37% at 1 year and by 30% at 4 years. Contralateral dyskinesia scores improved by 82% at 1 year and by 64% at 4 years. In contrast, after reaching speeds equal to the contralateral side at 1 year, ipsilateral "off" movement times increased by 13% over baseline levels at 4 years. Although most gait and postural stability measures showed modest initial improvement followed by a return to baseline values, "on" stand-walk-sit task performance declined significantly at 4 years. Despite the restriction of our surgeries to one side and the expected natural progression of Parkinson's disease, the results of patient self-assessments suggest that 4 years after unilateral pallidotomy, most patients continue to experience a quality of life above preoperative levels.

Stereotactic pallidotomy performed without using microelectrode guidance in patients with Parkinson's disease: surgical technique and 2-year results

OBJECT

Pallidotomy for the treatment of medically refractory Parkinson's disease (PD) has enjoyed renewed popularity. However, the optimal surgical technique, lesion location, and long-term effectiveness of pallidotomy remain subjects of debate. In this article the authors describe their surgical technique for performing pallidotomy without using microelectrode guidance, and the clinical and radiological results of this procedure.

METHODS

Patients were evaluated preoperatively by using a battery of validated clinical rating scales and magnetic resonance (MR) imaging of the brain. Individuals with severe treatment-refractory idiopathic PD who were believed to be good candidates for surgery underwent computerized tomography scanning- and MR imaging-guided stereotactic pallidotomy. Intraoperative macrostimulation was used to optimize lesion placement and to avoid injury to nearby structures. Lesion location and size were calculated from MR imaging sequences of the brain obtained within the first 24 hours after surgery and again 3 months later. Clinical examinations were conducted at 1.5, 3, 6, 12, and 24 months after surgery. Seventy-five patients (mean age 61 years, range 38-79 years) underwent unilateral pallidotomy. Significant improvements were observed in the "off' period scores for the activities of daily living portion of the Unified Parkinson's Disease Rating Scale (UPDRS), the UPDRS motor scores, total "on" time, levodopa-induced dyskinesias, and contralateral tremor. These improvements were maintained 24 months postoperatively. The mean lesion volume measured on the immediate postoperative MR image was 73 +/- 5.4 mm3. Radiological analysis suggests that initial lesion volume does not predict outcome. The only permanent major complication was a single visual field defect.

CONCLUSIONS

Pallidotomy performed without using microelectrode guidance is a safe and effective treatment for selected patients with medically refractory PD.

Long-term follow-up study of chronic globus pallidus internus stimulation for posttraumatic hemidystonia

The authors report the first case of chronic globus pallidus internus (GPi) stimulation for treatment of medically intractable hemidystonia for which long-term follow-up data are available. The patient had developed left-sided low-frequency tremor and hemidystonia after a severe head trauma sustained at 15 years of age. He experienced relief of the tremor but not of the hemidystonia after a thalamotomy was performed in the right hemisphere 3 years postinjury. When the patient was 24 years old, the authors performed a magnetic resonance-guided stereotactic implantation of a monopolar electrode in the right-sided posteroventral GPi. Chronic deep brain stimulation resulted in remarkable improvement of dystonia-associated pain, phasic dystonic movements, and dystonic posture, which was accompanied by functional gain. Postoperative improvement was sustained after 4 years of follow up. Chronic GPi stimulation appears to be a valuable treatment option for posttraumatic dystonia.

Unilateral pallidotomy in advanced Parkinson's disease: a retrospective study of 26 patients

OBJECTIVE

To evaluate the effects of unilateral pallidotomy in patients with Parkinson's disease (PD).

PATIENTS AND METHODS

Twenty-six patients with PD and disabling dyskinesias, painful and/or disabling dystonia, and/or pain as part of PD despite optimal pharmacotherapy underwent unilateral pallidotomy. For assessment, the Unified Parkinson's Disease Rating Scale (UPDRS; part II and III), Hoehn and Yahr staging, the Schwab and England scale, a Dyskinesia Rating Scale, and timed tests were used. Assessment was performed in defined "off' and "on," and on average 2 months before and 7.5 months after the unilateral pallidotomy. Adverse effects were classified as transient or permanent and as major or minor.

RESULTS

In the "off' phase, the median UPDRS II score improved from 26.5 to 20.5 (23%) and the median UPDRS III score improved from 47.5 to 33.0 (31%). In the "on" phase, dyskinesias contralateral to the side of the procedure improved with 88% ipsilateral dyskinesias improved only temporarily, and the total UPDRS II and III scores remained unchanged. Thirteen patients had transient adverse effects, three patients had permanent, and two patients had a combination of transient and permanent adverse effects. The transient adverse effects in two patients were classified as major.

CONCLUSION

Stereotactic unilateral pallidotomy can improve symptoms and disability in the "off' phase. In the "on" phase, dyskinesias disappeared at the side contralateral to the procedure. Permanent minor complications of pallidotomy occurred in 19% of the patients.

Electrophysiological versus image-based targeting in the posteroventral pallidotomy

OBJECTIVE

To study the functional accuracy of stereotactic targeting for the posteroventral pallidotomy (PVP), comparing targets chosen on magnetic resonance images (MRI), and fused MRI to computed tomographic (CT) images, with electrophysiologically refined anatomical targets. METHDOS AND MATERIALS: For each of the 10 pallidotomies three sets of targets were collected, beginning with the MRI targets. The second target set was measured on images generated by nonlinear volumetric fusion of MRI images with CT using Image Fusion (Radionics, Inc.). The anatomical target site was then determined electrophysiologically with intraoperative microelectrode recording and macroelectrode stimulation guidance.

RESULTS

Magnetic resonance imaging or MRI-CT fused images alone would not have been sufficiently accurate to preclude visual or motor complications in the posteroventral pallidotomy, based on our target located within 1 mm of the optic tract and within 2 mm of the internal capsule. In 2 of the 10 cases of either MRI or fused images, the targets were dangerously close to the optic tract. Two of 10 of the fused targets were within the internal capsule. The fusion of MRI with CT did not functionally improve the targeting accuracy of MRI, since the means of the MRI targets and the fused targets were statistically the same. Individually, however, the MRI target was different from the fused target in each case by an average radial distance of 3.5 +/- 2.3 mm, but such corrections were not statistically or surgically significant.

CONCLUSIONS

Image-based targeting including MRI or fused MRI-CT data may not be sufficiently accurate to prevent capsular or visual deficits in the posteroventral pallidotomy, necessitating electrophysiological refinement. In this report, the functional accuracy of MRI was not improved by fusion with CT.

Cognitive outcome following staged bilateral pallidal stimulation for the treatment of Parkinson's disease

As neurosurgical treatment of parkinsonian symptoms has become increasingly popular, concern about the cognitive morbidity which may result from such interventions has risen proportionately. Previous reports of cognitive difficulties associated with pallidotomy and thalamotomy, especially in bilateral cases, have provided the impetus for research into chronic electrical deep brain stimulation procedures which are believed to be safer than ablation. Given the lack of neurobehavioral research following bilateral deep brain stimulation procedures, this preliminary study of six Parkinson's disease patients undergoing staged bilateral pallidal stimulation was undertaken. A battery of tests assessing attention, executive function, visuomotor coordination, language, visuoperceptual function, learning memory and mood revealed no significant change in overall level of cognitive functioning after either unilateral or bilateral pallidal deep brain stimulation. No significant declines were observed about three months following bilateral stimulation, and in fact, significant gains in delayed recall and relief of anxiety symptoms were noted. It was concluded from this preliminary data that bilateral pallidal stimulation for the treatment of Parkinson's disease, at least in the absence of operative complications, offers a cognitively safe alternative to ablation.

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.

Levodopa-induced dyskinesias treated by pallidotomy

Pallidotomy has been reported to improve parkinsonian symptoms, but its effects on levodopa-induced dyskinesia (LID) have not been thoroughly examined. We describe here the results of stereotactic, unilateral, posteroventral pallidotomy on LID in 42 patients (22 women), who were followed for up to 9 months. Their mean age was 60. 6+/-9.3 (range: 40-74), age at onset was 46.1+/-9.1 (range: 24-46), and duration of symptoms was 14.5+/-5.3 (range: 4-25) years. Three months following pallidotomy, the percent time with dyskinesia decreased from 37.0 to 17.3 (P<0.0001) and the percent time the patients were 'on' with dyskinesias decreased even more, from 71.0 to 22.9 (P<0.0001). Furthermore, the number of patients with troublesome (moderate to violent) dyskinesia had decreased from 36 (86%) prior to surgery to only 5 (12%) after surgery. The mean unified Parkinson disease rating scale (UPDRS) scores for LID-related disability and pain decreased from 1.95 to 0.74 (P<0. 0001) and from 1.02 to 0.17 (P<0.0001), respectively. Since the pre- and post-pallidotomy daily levodopa dosage remained essentially the same, the improvement in LID could not be attributed to a reduction in levodopa. Surgery-related complications occurred in eight (19%) patients, but none of them had persistent disability as a result of these complications. We conclude that pallidotomy is an effective and safe procedure in the treatment of medically intractable LID.

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.