Visual fields in patients with posterior GPi pallidotomy

Healthy and pathological pallidal regulation of thalamic burst versus tonic mode firing: a computational simulation

The mechanisms by which the basal ganglia influence the pallidal-receiving thalamus remain to be adequately defined. Our prior in vivo recordings in fully alert normal and dystonic rats revealed that normally fast tonic discharging entopeduncular [EP, rodent equivalent of the globus pallidus internus (GPi)] neurons are pathologically slow, highly irregular, and bursty under dystonic conditions. This, in turn, induces pallidal-receiving thalamic movement-related neurons to change from a healthy burst predominant to a pathological tonic-predominant resting firing mode. This study aims to understand the pallidal influence on thalamic firing modes using computational simulations. We inputted various combinations of healthy and pathological (dystonic) in vivo neuronal recordings to the Rubin and Terman's computational model of low threshold spiking pallidothalamic neurons. The input sets consist of representative tonic, burst, irregular tonic and irregular burst inputs collected from EP/GPi in our animal lab. Initial test combinations of EP/ GPi input to the model were identical to the neuronal population distributions observed in vivo. The thalamic neuron model outputted similar firing rate and mode as observed in corresponding in-vivo thalamus. Further influence of each individual patterns was also delineated. By simulating the firing properties of encountered neurons, the basal ganglia output is suggested to critically act as firing mode selector for thalamic motor relay neurons. By selecting and determining the timing and extent of opening of thalamic T-type calcium channels via GABAergic hyperpolarizing input, GPi neurons are in position to precisely orchestrate thalamocortical burst motor signaling.

Trial of Globus Pallidus Focused Ultrasound Ablation in Parkinson's Disease

BACKGROUND

Unilateral focused ultrasound ablation of the internal segment of globus pallidus has reduced motor symptoms of Parkinson's disease in open-label studies.

METHODS

We randomly assigned, in a 3:1 ratio, patients with Parkinson's disease and dyskinesias or motor fluctuations and motor impairment in the off-medication state to undergo either focused ultrasound ablation opposite the most symptomatic side of the body or a sham procedure. The primary outcome was a response at 3 months, defined as a decrease of at least 3 points from baseline either in the score on the Movement Disorders Society-Unified Parkinson's Disease Rating Scale, part III (MDS-UPDRS III), for the treated side in the off-medication state or in the score on the Unified Dyskinesia Rating Scale (UDysRS) in the on-medication state. Secondary outcomes included changes from baseline to month 3 in the scores on various parts of the MDS-UPDRS. After the 3-month blinded phase, an open-label phase lasted until 12 months.

RESULTS

Of 94 patients, 69 were assigned to undergo ultrasound ablation (active treatment) and 25 to undergo the sham procedure (control); 65 patients and 22 patients, respectively, completed the primary-outcome assessment. In the active-treatment group, 45 patients (69%) had a response, as compared with 7 (32%) in the control group (difference, 37 percentage points; 95% confidence interval, 15 to 60; P = 0.003). Of the patients in the active-treatment group who had a response, 19 met the MDS-UPDRS III criterion only, 8 met the UDysRS criterion only, and 18 met both criteria. Results for secondary outcomes were generally in the same direction as those for the primary outcome. Of the 39 patients in the active-treatment group who had had a response at 3 months and who were assessed at 12 months, 30 continued to have a response. Pallidotomy-related adverse events in the active-treatment group included dysarthria, gait disturbance, loss of taste, visual disturbance, and facial weakness.

CONCLUSIONS

Unilateral pallidal ultrasound ablation resulted in a higher percentage of patients who had improved motor function or reduced dyskinesia than a sham procedure over a period of 3 months but was associated with adverse events. Longer and larger trials are required to determine the effect and safety of this technique in persons with Parkinson's disease. (Funded by Insightec; ClinicalTrials.gov number, NCT03319485.).

Bilateral pallidotomy for acquired or heredodegenerative generalized dystonia in children

OBJECTIVE

Dystonias are relatively rare disorders characterized by sustained or intermittent muscle contractions causing abnormal movements or postures. Generalized dystonia is a therapeutic challenge because medications are unable to control dystonia adequately in most patients. These patients may be candidates for surgical therapy. The commonly used surgical procedures in these patients are pallidotomy and deep brain stimulation. Limited studies are available on the role of pallidotomy in children with acquired/heredodegenerative generalized dystonia. The objective of this study was to describe the authors’ experience with bilateral pallidotomy in this group of patients.

METHODS

The authors retrospectively reviewed all pediatric patients (less than 18 years of age) with acquired/heredodegenerative generalized dystonia who underwent bilateral simultaneous pallidotomy at their center between January 2014 and January 2021. Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) scores before and after surgery were recorded. Complications arising after the procedure were recorded as well.

RESULTS

Ten patients (8 male and 2 female) with a mean (range) age of 11.1 (5–17) years were included in this study. The mean duration between disease onset and surgical intervention was 3.9 years. Two patients presented in status dystonicus. The mean ± SD (range) preoperative BFMDRS score of the patients without status dystonicus (n = 8) was 80 ± 18.9 (59.5–108). The mean ± SD BFMDRS score at the time of discharge from the hospital after surgery was 58.8 ± 37.9. Three patients had more than 20% change in BFMDRS score at the time of discharge from the hospital. The mean improvement was 25.5% at the end of 1 year. Of 5 surviving patients in the non–status dystonicus group, 3 patients had more than 40% change in BFMDRS score while the other 2 patients developed recurrence at the last follow-up (4.5 years). Status dystonicus abated after bilateral pallidotomy in both patients. Permanent bulbar complications were seen in 2 patients.

CONCLUSIONS

Bilateral pallidotomy may result in clinically significant improvement in children with acquired/heredodegenerative generalized dystonia, although the benefits should be closely weighed against the risk of irreversible bulbar dysfunction. It is a viable option for children in resource-limited settings.

MR-guided focused ultrasound pallidotomy for Parkinson's disease: safety and feasibility

OBJECTIVE

Stereotactic radiofrequency pallidotomy has demonstrated improvement in motor fluctuations in patients with Parkinson's disease (PD), particularly levodopa (L-dopa)-induced dyskinesias. The authors aimed to determine whether or not unilateral pallidotomy with MR-guided focused ultrasound (MRgFUS) could safely improve Unified Dyskinesia Rating Scale (UDysRS; the primary outcome measure) scores over baseline scores in patients with PD.

METHODS

Twenty patients with PD and L-dopa responsiveness, asymmetrical motor signs, and motor fluctuations, including dyskinesias, participated in a 1-year multicenter open-label trial of unilateral MRgFUS ablation of the globus pallidus internus.

RESULTS

The sonication procedure was successfully completed in all 20 enrolled patients. MRgFUS-related adverse neurological events were generally mild and transient, including visual field deficit (n = 1), dysarthria (n = 4, 2 mild and 2 moderate), cognitive disturbance (n = 1), fine motor deficit (n = 2), and facial weakness (n = 1). Although 3 adverse events (AEs) were rated as severe (transient sonication-related pain in 2, nausea/vomiting in 1), no AE fulfilled US FDA criteria for a Serious Adverse Effect. Total UDysRS, the primary outcome measure, improved 59% after treatment (baseline mean score 36.1, 95% CI 4.88; at 3 months 14.2, 95% CI 5.72, p < 0.0001), which was sustained throughout the study (at 12 months 20.5, 95% CI 7.39, 43% improvement, p < 0.0001). The severity of motor signs on the treated side (Movement Disorder Society version of the United Parkinson's Disease Rating Scale [MDS-UPDRS] part III) in the "off" medication state also significantly improved (baseline mean score 20.0, 95% CI 2.4; at 3 months 10.6, 95% CI 1.86, 44.5% improvement, p < 0.0001; at 12 months 10.4, 95% CI 2.11, 45.2% improvement, p > 0.0001). The vast majority of patients showed a clinically meaningful level of improvement on the impairment component of the UDysRS or the motor component of the UPDRS, while 1 patient showed clinically meaningful worsening on the UPDRS at month 3.

CONCLUSIONS

This study supports the feasibility and preliminary efficacy of MRgFUS pallidotomy in the treatment of patients with PD and motor fluctuations, including dyskinesias. These preliminary data support continued investigation, and a placebo-controlled, blinded trial is in progress. Clinical trial registration no.: NCT02263885 (clinicaltrials.gov).

The role of high-intensity focused ultrasound as a symptomatic treatment for Parkinson's disease

MR-guided focused ultrasound is a novel, minimally invasive surgical procedure for symptomatic treatment of PD. With this technology, the ventral intermediate nucleus, STN, and internal globus pallidus have been targeted for therapeutic cerebral ablation, while also minimizing the risk of hemorrhage and infection from more invasive neurosurgical procedures. In a double-blinded, prospective, sham-controlled randomized controlled trial of MR-guided focused ultrasound thalamotomy for treatment of tremor-dominant PD, 62% of treated patients demonstrated improvement in tremor scores from baseline to 3 months postoperatively, as compared to 22% in the sham group. There has been only one open-label trial of MR-guided focused ultrasound subthalamotomy for patients with PD, demonstrating improvements of 71% for rigidity, 36% for akinesia, and 77% for tremor 6 months after treatment. Among the two open-label trials of MR-guided focused ultrasound pallidotomy for patients with PD, dyskinesia and overall motor scores improved up to 52% and 45% at 6 months postoperatively. Although MR-guided focused ultrasound thalamotomy is now approved by the U.S. Food and Drug Administration for treatment of parkinsonian tremor, additional high-quality randomized controlled trials are warranted and are underway to determine the safety and efficacy of MR-guided focused ultrasound subthalamotomy and pallidotomy for treatment of the cardinal features of PD. These studies will be paramount to aid clinicians to determine the ideal ablative target for individual patients. Additional work will be required to assess the durability of MR-guided focused ultrasound lesions, ideal timing of MR-guided focused ultrasound ablation in the course of PD, and the safety of performing bilateral lesions. © 2019 International Parkinson and Movement Disorder Society.

Visual Dysfunction in Parkinson's Disease

This chapter describes the visual problems likely to be encountered in Parkinson's disease (PD) and whether such signs are useful in differentiating the parkinsonian syndromes. Visual dysfunction in PD may involve visual acuity, contrast sensitivity, color discrimination, pupil reactivity, saccadic and pursuit eye movements, motion perception, visual fields, and visual processing speeds. In addition, disturbance of visuospatial orientation, facial recognition problems, rapid eye movement (REM) sleep behavior disorder, and chronic visual hallucinations may be present. Problems affecting pupil reactivity, stereopsis, pursuit eye movement, and visuomotor adaptation, when accompanied by REM sleep behavior disorder, could be early features of PD. Dementia associated with PD is associated with enhanced eye movement problems, visuospatial deficits, and visual hallucinations. Visual dysfunction may be a useful diagnostic feature in differentiating PD from other parkinsonian symptoms, visual hallucinations, visuospatial dysfunction, and variation in saccadic eye movement problems being particularly useful discriminating features.

Ocular and visual disorders in Parkinson's disease: Common but frequently overlooked

Patients with Parkinson's disease (PD) often compensate for their motor deficits by guiding their movements visually. A wide range of ocular and visual disorders threatens the patients' ability to benefit optimally from visual feedback. These disorders are common in patients with PD, yet they have received little attention in both research and clinical practice, leading to unnecessary - but possibly treatable - disability. Based on a literature search covering 50 years, we review the range of ocular and visual disorders in patients with PD, and classify these according to anatomical structures of the visual pathway. We discuss six common disorders in more detail: dry eyes; diplopia; glaucoma and glaucoma-like visual problems; impaired contrast and colour vision; visuospatial and visuoperceptual impairments; and visual hallucinations. In addition, we review the effects of PD-related pharmacological and surgical treatments on visual function, and we offer practical recommendations for clinical management. Greater awareness and early recognition of ocular and visual problems in PD might enable timely instalment of tailored treatments, leading to improved patient safety, greater independence, and better quality of life.

Oculo-Visual Dysfunction in Parkinson's Disease

This review describes the oculo-visual problems likely to be encountered in Parkinson's disease (PD) with special reference to three questions: (1) are there visual symptoms characteristic of the prodromal phase of PD, (2) is PD dementia associated with specific visual changes, and (3) can visual symptoms help in the differential diagnosis of the parkinsonian syndromes, viz. PD, progressive supranuclear palsy (PSP), dementia with Lewy bodies (DLB), multiple system atrophy (MSA), and corticobasal degeneration (CBD)? Oculo-visual dysfunction in PD can involve visual acuity, dynamic contrast sensitivity, colour discrimination, pupil reactivity, eye movement, motion perception, and visual processing speeds. In addition, disturbance of visuo-spatial orientation, facial recognition problems, and chronic visual hallucinations may be present. Prodromal features of PD may include autonomic system dysfunction potentially affecting pupil reactivity, abnormal colour vision, abnormal stereopsis associated with postural instability, defects in smooth pursuit eye movements, and deficits in visuo-motor adaptation, especially when accompanied by idiopathic rapid eye movement (REM) sleep behaviour disorder. PD dementia is associated with the exacerbation of many oculo-visual problems but those involving eye movements, visuo-spatial function, and visual hallucinations are most characteristic. Useful diagnostic features in differentiating the parkinsonian symptoms are the presence of visual hallucinations, visuo-spatial problems, and variation in saccadic eye movement dysfunction.

Pallidotomy for medically refractory status dystonicus in childhood

AIM

Status dystonicus is a rare and potentially fatal condition of continuous and generalized muscle contraction that can complicate dystonia. As status dystonicus is usually refractory to traditional pharmacological therapy, alternative and invasive strategies have been developed, but so far there are no guidelines on status dystonicus management. Pallidotomy has shown good results in status dystonicus treatment.

METHOD

We report indications, surgical strategy, and outcome of bilateral pallidotomy in four pediatric patients (four males; mean age at surgery 11y 5mo) with secondary dystonia, who developed refractory status dystonicus. Pallidotomy was performed in the area corresponding to the mid portion of the globus pallidus internus.

RESULTS

This procedure allowed patients to recover the pre-status dystonicus condition, controlling dystonic postures and movements of trunk and limbs. Moreover oromandibular dystonia, which is resistant to conservative approaches and deep brain stimulation, was significantly reduced. No postoperative complications were registered.

INTERPRETATION

Our study suggests pallidotomy as a feasible treatment in patients with secondary dystonia complicated by status dystonicus.

Visual symptoms in Parkinson's disease

Parkinson's disease (PD) is a common disorder of middle-aged and elderly people in which degeneration of the extrapyramidal motor system causes significant movement problems. In some patients, however, there are additional disturbances in sensory systems including loss of the sense of smell and auditory and/or visual problems. This paper is a general overview of the visual problems likely to be encountered in PD. Changes in vision in PD may result from alterations in visual acuity, contrast sensitivity, colour discrimination, pupil reactivity, eye movements, motion perception, visual field sensitivity, and visual processing speeds. Slower visual processing speeds can also lead to a decline in visual perception especially for rapidly changing visual stimuli. In addition, there may be disturbances of visuospatial orientation, facial recognition problems, and chronic visual hallucinations. Some of the treatments used in PD may also have adverse ocular reactions. The pattern electroretinogram (PERG) is useful in evaluating retinal dopamine mechanisms and in monitoring dopamine therapies in PD. If visual problems are present, they can have an important effect on the quality of life of the patient, which can be improved by accurate diagnosis and where possible, correction of such defects.

Disorders of the optic tract, radiation, and occipital lobe

Disorders of the optic tract, lateral geniculate nucleus, optic radiation, and occipital lobe - collectively called the retrochiasmal visual pathways - are commonly encountered in neurological practice, and may result from a number of causes. The major visual morbidity of retrochiasmal disease is the homonymous visual field defect, which is found in approximately 8% of stroke patients. A homonymous visual field defect may have profound legal, occupational, and financial consequences for patients, with many patients unable to read, drive, or return to work after sustaining retrochiasmal damage. Some homonymous hemianopias may improve, usually within days of a cerebral infarction, but remain stable after 3 months. Although treatment options are limited to those of the underlying cause, appropriate counseling and low-vision rehabilitation may be helpful.

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.

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.

Surgical management of Parkinson's disease: update and review

SUMMARY

Although medical therapy is still the mainstay of treatment for Parkinson's disease, the development of surgical precision and decreased morbidity have made stereotatic lesioning and deep brain stimulation more popular. Neurosurgical ablations include pallidotomy, thalamotomy, and, more recently, subthalamotomy. Because of concern over the high risk of side-effects resulting from bilateral ablative procedure, alternative approaches have been explored.With improved deep brain stimulation (DBS) technology, DBS has been successfully applied in the internal globus pallidus, ventral intermediate nucleus and subthalamic nucleus for Parkinson's disease. In addition, recent surgical approaches including biological neurorestorative technologies - surgical therapies with transplantation, gene therapy, and growth factor are all being discussed in this review. Although a great deal of work remains to be done for researchers, advances in surgical therapies for the treatment of Parkinson's disease are moving forward at an unprecedented pace, and, not surprisingly, would give PD patients more choices and hope.

Congruency in homonymous hemianopia

PURPOSE

To evaluate the value of congruency in the localization of brain lesions in patients with homonymous hemianopia (HH).

DESIGN

Retrospective observational study.

METHODS

Charts of all patients with HH seen over 15 years were reviewed. Only patients with incomplete HH documented on formal visual field testing and neuroimaging were included. HH was said to be congruent when the fields of both eyes were identical in shape, depth, and size. Patients were divided into two groups based on congruency of HH; demographic, clinical, and radiological characteristics were compared.

RESULTS

Five hundred and thirty patients with 548 incomplete HH were included (373 congruent HH and 175 incongruent HH). Demographic variables were similar in both groups. Stroke caused 75% of congruent HH and 55.8% of incongruent HH; trauma and tumors caused 20.5% of congruent HH and 34.5% of incongruent HH (P < .001). The lesion locations in congruent HH vs incongruent HH included occipital lobe in 47.9% vs 21.3%, occipital lobe and optic radiations in 8.3% vs 5.6%, optic radiations in 32.4% vs 50.6%, optic tract in 7.2% vs 16.3%, and other locations in 4.2% vs 6.3% (P < .0001). Although there was a trend toward more congruent HH for lesions of the posterior visual pathways (P < .001), 50% of optic tract lesions and 59% of optic radiation lesions produced congruent HH.

CONCLUSION

Although lesions involving the occipital lobe characteristically produce congruent HH, at least 50% of lesions in other locations also produce congruent HH, especially if these lesions are stroke-related. The rule of congruency should be used cautiously and may not apply to optic tract lesions.

Homonymous Hemianopia in Stroke

BACKGROUND

Previous reports have suggested that most cases of homonymous hemianopia (HH) are caused by occipital stroke. However, these reports have not always been supported by brain imaging.

METHODS

We reviewed the medical records of all patients seen in our unit between 1989 and 2004 who had HH documented by formal perimetry or confrontation visual fields and had undergone brain imaging. HHs were divided into those caused by stroke and by non-stroke conditions. The clinical and visual field characteristics were compared in the two groups.

RESULTS

Among 850 patients with 902 HHs, 629 (69.7%) resulted from stroke, of which 531 (84.4%) were from infarction and 98 (15.6%) from primary intraparenchymal hemorrhage. Non-stroke causes included head trauma (123), brain tumor (102), neurosurgical procedures (22), multiple sclerosis (13), and miscellaneous conditions (13). Occipital lesions most commonly resulted from stroke. The configuration of the HH did not predict where in the retrochiasmal visual pathway the responsible lesion lay.

CONCLUSIONS

Ischemic stroke causes most HHs from lesions in the occipital lobe that generally do not produce other neurologic manifestations. The configuration of the HH does not predict the location of the lesion within the retrochiasmal visual pathway.

Deep brain stimulation: Postoperative issues

Numerous factors need to be taken into account when managing a patient with Parkinson's disease (PD) after deep brain stimulation (DBS). Questions such as when to begin programming, how to conduct a programming screen, how to assess the effects of programming, and how to titrate stimulation and medication for each of the targeted sites need to be addressed. Follow-up care should be determined, including patient adjustments of stimulation, timing of follow-up visits and telephone contact with the patient, and stimulation and medication conditions during the follow-up assessments. A management plan for problems that can arise after DBS such as weight gain, dyskinesia, axial symptoms, speech dysfunction, muscle contractions, paresthesia, eyelid, ocular and visual disturbances, and behavioral and cognitive problems should be developed. Long-term complications such as infection or erosion, loss of effect, intermittent stimulation, tolerance, and pain or discomfort can develop and need to be managed. Other factors that need consideration are social and job-related factors, development of dementia, general medical issues, and lifestyle changes. This report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society, outlines answers to a series of questions developed to address all aspects of DBS postoperative management and decision-making with a systematic overview of the literature (until mid-2004) and by the expert opinion of the authors. The report has been endorsed by the Scientific Issues Committee of the Movement Disorder Society and the American Society of Stereotactic and Functional Neurosurgery.

Surgical treatment for Parkinson's disease

Since the early 1930s, physicians have developed and refined various surgical therapies for the treatment of Parkinson's disease. In this review we examine some of the problems associated with early surgical therapies, the development of new techniques and targets, and the results of clinical trials examining the safety and efficacy of these techniques. Ablative techniques include pallidotomy, thalamotomy, and, more recently, subthalamotomy. Because of concern over the high incidence of side-effects associated with bilateral ablative procedures, alternative approaches were explored. Deep brain stimulation (DBS) was subsequently developed and successfully applied in the internal globus pallidus, subthalamic nucleus, and thalamus for the treatment of Parkinson's disease. Recent approaches include biological neurorestorative techniques--surgical therapies with transplantation, gene therapy, and growth factors are all being studied. Although a great deal of work remains to be done, advances in surgical therapies for the treatment of Parkinson's disease are moving forward at an unprecedented pace.

A metaanalysis comparing the results of pallidotomy performed using microelectrode recording or macroelectrode stimulation

OBJECT

There is an active debate regarding whether pallidotomy should be performed using macroelectrode stimulation or the more sophisticated and expensive method of microelectrode recording. No prospective, randomized trial results have answered this question, although personnel at many centers claim one method is superior. In their metaanalysis the authors reviewed published reports of both methods to determine if there is a significant difference in clinical outcomes or complication rates associated with these methods.

METHODS

A metaanalysis was performed with data from reports on the use of unilateral pallidotomy in patients with Parkinson disease (PD) that were published between 1992 and 2000. A Medline search was conducted for the key word "pallidotomy" and additional studies were added following a review of the references. Only those studies dealing with unilateral procedures performed in patients with PD were included. Papers were excluded if they described a cohort smaller than 10 patients or a follow-up period shorter than 3 months or included cases that previously had been reported. The primary end points for outcome were the percentages of improvement in dyskinesias and in motor scores determined by the Unified PD Rating Scale (UPDRS). Complications were categorized as mortality, intracranial hemorrhage, visual deficit, speech deficit, cognitive decline, weakness, and other. There were no significant differences between the two methods with respect to improvements in dyskinesias (p = 0.66) or UPDRS motor scores (p = 0.62). Microelectrode recording was associated with a significantly higher (p = 0.012) intracranial hemorrhage rate (1.3 +/- 0.4%), compared with macroelectrode stimulation (0.25 +/- 0.2%).

CONCLUSIONS

In reports of patients with PD who underwent unilateral pallidotomy, operations that included microelectrode recording were associated with a small, but significantly higher rate of symptomatic intracranial hemorrhage; however, there was no difference in postoperative reduction of dyskinesia or bradykinesia compared with operations that included macroelectrode stimulation.

Microelectrode recordings in the pallidum

The internal segment of the globus pallidus (GPi) is being targeted in neurosurgical procedures to treat Parkinson's disease and dystonia. Precise targeting of the pallidal complex is important in determining the efficacy of the surgical intervention and for the avoidance of adverse effects. Intraoperative microelectrode recording can be used to characterize the patterns of activity and receptive field properties of single pallidal neurons and to identify important bordering structures, including the optic tract and internal capsule. Because the clinical features of movement disorders can be differentially affected as a function of location within the pallidal complex, further refinements in intraoperative targeting may become important.

Bilateral pallidotomy for generalized dystonia

OBJECTIVE

To evaluate the efficacy and safety of bilateral pallidotomies in five patients with generalized dystonia.

BACKGROUND

Generalized dystonias are frequently a therapeutic challenge, with poor responses to pharmacological treatment. GPi (globus pallidus internus) pallidotomies for Parkinson's disease ameliorate all kinds of dyskinesias/dystonia, and recent studies reported a marked improvement of refractory dystonias with this procedure.

METHODS

Five patients with generalized dystonias refractory to medical treatment were selected; one posttraumatic and four idiopathic. The decision to perform bilateral procedures was based on the predominant axial involvement in these patients. Dystonia severity was assessed with the Burke-Fahn-Marsden Dystonia Scale (BFM). Simultaneous procedures were performed in all but one patient, who had a staged procedure. They were reevaluated with the same scale (BFM) by an unblinded rater at 1, 2, 3, 30, 60, 90, 120 and 180 days post-operatively.

RESULTS

The four patients with idiopathic dystonia showed a progressive improvement up to three months; the patient with posttraumatic dystonia relapsed at three months. One patient had a marked improvement, being able to discontinue all the medications. A mean decrease in the BFM scores of 52,58% was noted. One patient had a trans-operative motor seizure followed by a transient hemiparesis secondary to rack hemorrhage; other was lethargic up to three days after the procedure.

CONCLUSIONS

Our results show that bilateral GPi pallidotomies may be a safe and effective approach to medically refractory generalized dystonias; it can also be speculated that the posttraumatic subgroup may not benefit with this procedure.

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.

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.

Systemic hyperosmolality improves beta-glucuronidase distribution and pathology in murine MPS VII brain following intraventricular gene transfer

Mucopolysaccharidosis VII, a classical lysosomal storage disease, is caused by deficiency of the enzyme beta-glucuronidase. Central nervous system (CNS) manifestations are severe with accumulations of storage vacuoles in all cell types. Intraventricular gene transfer can lead to transduction of the ependyma, with production and secretion of beta-glucuronidase into the cerebral spinal fluid and underlying cortex resulting in reversal of disease pathology restricted to the periventricular areas. We tested if systemic hyperosmolality would increase the distribution of beta-glucuronidase in brain parenchyma after intraventricular virus injection. Mice were administered mannitol, intraperitoneally, 20 days after gene transfer and 1 day prior to sacrifice. Mannitol-induced systemic hyperosmolality caused a marked penetration of beta-glucuronidase into the brain parenchyma. If mannitol was administered at the time of the intraventricular injection of virus, there was penetration of vector across the ependymal cell layer, with infection of cells in the subependymal region. This also resulted in increased beta-glucuronidase activity throughout the brain. Sections of brains from beta-glucuronidase-deficient mice showed correction of cellular pathology in the subependymal region plus cortical structures away from the ventricular wall. These data indicate that virus-mediated gene transfer to the brain via the ventricles, coupled with systemic mannitol administration, can lead to extensive CNS distribution of beta-glucuronidase with concomitant correction of the storage defect. Our findings have positive therapeutic implications for the treatment of CNS disorders with gene transfer vectors and recombinant proteins.

Convection-enhanced selective excitotoxic ablation of the neurons of the globus pallidus internus for treatment of parkinsonism in nonhuman primates

OBJECT

Selective treatment of central nervous system (CNS) structures holds therapeutic promise for many neurological disorders, including Parkinson's disease (PD). The ability to inhibit or augment specific neuronal populations within the CNS reliably by using present therapeutic techniques is limited. To overcome this problem, the authors modeled and developed a method in which convection was used to deliver compounds to deep brain nuclei in a reproducible, homogeneous, and targeted manner. To determine the feasibility and clinical efficacy of convective drug delivery for treatment of a neurological disorder, the investigators selectively ablated globus pallidus internus (GPi) neurons with quinolinic acid (QA), an excitotoxin, in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced model of primate parkinsonism.

METHODS

After the parameters of convective distribution to the GPi were confirmed by infusion of biotinylated albumin into the GPi of a primate (Macaca mulatta), seven adult monkeys of this species were rendered either fully parkinsonian by intravenous injections of MPTP (five animals) or hemiparkinsonian by a right-sided intracarotid injection of this agent (two monkeys). Using convection-enhanced delivery to the GPi, animals were infused with either QA (three fully parkinsonian, two hemiparkinsonian) or saline (two fully parkinsonian). The three fully parkinsonian animals that underwent GPi lesioning with QA had substantial improvement of PD symptoms, manifested by a marked increase in activity (34 +/- 2.5%; mean +/- standard deviation) and dramatic improvement of parkinsonian clinical scores. In contrast, the control animals did not improve (activity monitor change = -1.5 +/- 0.5%). The two hemiparkinsonian animals that underwent QA lesioning of the GPi had dramatic recovery of extremity use. Histological examination revealed selective neural ablation of GPi neurons (mean loss 87%) with sparing of surrounding gray and white matter structures. No animal developed worsening signs of PD or neurological deficits after infusion.

CONCLUSIONS

Convection-enhanced delivery of QA permits selective, region-specific (GPi), and safe lesioning of neuronal subpopulations, resulting in dramatic improvement in parkinsonian symptomatology. The properties of convection-enhanced delivery indicate that this method could be used for chemical neurosurgery for medically refractory PD and that it may be ideal for cell-specific therapeutic ablation or trophic treatment of other targeted structures associated with CNS disorders.

New developments in the surgery for Parkinson's disease

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

Surgical treatment of Parkinson's disease

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

Bilateral contemporaneous posteroventral pallidotomy for the treatment of Parkinson's disease: neuropsychological and neurological side effects. Report of four cases and review of the literature

The authors report the underestimated cognitive, mood, and behavioral complications in patients who have undergone bilateral contemporaneous pallidotomy, as seen in their early experience with functional neurosurgery for Parkinson's disease (PD) that is accompanied by severe motor fluctuations before pallidal stimulation. Four patients, not suffering from dementia, with advanced (Hoehn and Yahr Stages III-IV), medically untreatable PD featuring severe "on-off" fluctuations underwent bilateral contemporaneous posteroventral pallidotomy (PVP). All patients were evaluated according to the Core Assessment Program for Intracerebral Transplantations (CAPIT) protocol without positron emission tomography scans but with additional neuropsychological cognitive, mood, and behavior testing. For the first 3 to 6 months postoperatively, all patients showed a mean improvement of motor scores on the Unified Parkinson's Disease Rating Scale (UPDRS), in the best "on" (21%) and worst "off" (40%) UPDRS III motor subscale, a mean 30% improvement in the UPDRS II activities of daily living (ADL) subscore, and 60% on the UPDRS IV complications of treatment subscale. Dyskinesia disappeared almost completely, and the mean daily duration of the off time was reduced by an average of 60%. Despite these good results in the CAPIT scores, one patient experienced a partially regressive corticobulbar syndrome with dysphagia, dysarthria, and increased drooling. No emotional lability was found in this patient, but he did demonstrate severe bilateral postoperative pretarsal blepharospasm (apraxia of eyelid opening), which interfered with walking and which required treatment with high-dose subcutaneous injections of botulinum toxin. No patient showed visual field defects or hemiparesis, but postoperative depression, changes in personality, behavior, and executive functions were seen in two individuals. Postoperative abulia was reported by the family of one patient, who lost his preoperative aggressiveness and drive in terms of ADL, speech, business, family life, and hobbies, and became more sleepy and fatigued. One patient reported postoperative mental automatisms, such as compulsive mental counting, and circular thoughts and reasoning during off phases; postoperative depression was found in two patients. However, none of the patients demonstrated these symptoms during intraoperative microelectrode stimulation. These findings are compatible with previous reports on bilateral pallidal lesions. A progressive lowering of UPDRS subscores was seen after 12 months, consistent with the progression of the disease. Bilateral simultaneous pallidotomy may be followed by emotional, behavioral, and cognitive deficits such as depression, obsessive-compulsive disorders, and loss of psychic autoactivation-abulia, as well as disabling corticobulbar dysfunction and apraxia of eyelid opening, in addition to previously described motor and visual field deficits, which make this surgery undesirable even though significant improvement in motor deficits can be achieved.

Reassessment of unilateral pallidotomy in Parkinson's disease. A 2-year follow-up study

Unilateral pallidotomy has gained popularity in treating the motor symptoms of Parkinson's disease. We present the results of a 2-year post-pallidotomy follow-up study. Using the Unified Parkinson's Disease Rating Scale (UPDRS), the Goetz dyskinesia scale and the Purdue Pegboard Test (PPBT), we evaluated 20 patients at regular intervals both off and on medications for 2 years post-pallidotomy. There were no significant changes in the dosages of antiparkinsonian medications from 3 months pre-pallidotomy to 2 years post-pallidotomy. On the side contralateral to the operation, the improvements were preserved in 'on'-state dyskinesia (83% reduction from pre-pallidotomy to 2 years post-pallidotomy, P < 0.001) and 'off'-state tremor (90% reduction from pre-pallidotomy to 2 years post-pallidotomy, P = 0.005). There were no statistically significant differences between pre-pallidotomy scores and those at 2 years post-pallidotomy in ipsilateral dyskinesia, axial dyskinesia, 'off'- or 'on'-state PPBT, 'off'-state Activities of Daily Living (ADL) and 'off'-state gait and postural stability. After 2 years, the 'on'-state ADL scores worsened by 75%, compared with pre-pallidotomy (P = 0.005). We conclude that 2 years after pallidotomy, the improvements in dyskinesia and tremor on the side contralateral to pallidotomy are preserved, while the initial improvements in most other deficits disappear, either because of progression of pathology or loss of the early efficacy achieved by surgery.

Ablative surgery and deep brain stimulation for Parkinson's disease

Surgical options for Parkinson's disease (PD) are rapidly expanding and include ablative procedures, deep brain stimulation, and cell transplantation. The target nuclei for ablative surgery and deep brain stimulation are the motor thalamus, the globus pallidus, and the subthalamic nucleus. Multiple factors have led to the resurgence of interest in the surgical treatment of PD: 1) recognition that long-term medical therapy for PD is often unsatisfactory, with patients eventually suffering from drug-induced dyskinesias, motor fluctuations, and variable responses to medication; 2) greater understanding of the pathophysiology of PD, providing a better scientific rationale for some previously developed procedures and suggesting new targets; and 3) use of improved techniques, such as computed tomography- and magnetic resonance imaging-guided stereotaxy and single-unit microelectrode recording, making surgical intervention in the basal ganglia more precise. We review the present status of ablative surgery and deep brain stimulation for PD, including theoretical aspects, surgical techniques, and clinical results.

Efficiency and safety of bilateral contemporaneous pallidal stimulation (deep brain stimulation) in levodopa-responsive patients with Parkinson's disease with severe motor fluctuations: a 2-year follow-up review

OBJECT

The aim of this study was to evaluate the long-term safety and efficacy of bilateral contemporaneous deep brain stimulation (DBS) in patients who have levodopa-responsive parkinsonism with untreatable motor fluctuations. Bilateral pallidotomy carries a high risk of corticobulbar and cognitive dysfunction. Deep brain stimulation offers new alternatives with major advantages such as reversibility of effects, minimal permanent lesions, and adaptability to individual needs, changes in medication, side effects, and evolution of the disease.

METHODS

Patients in whom levodopa-responsive parkinsonism with untreatable severe motor fluctuations has been clinically diagnosed underwent bilateral pallidal magnetic resonance image-guided electrode implantation while receiving a local anesthetic. Pre- and postoperative evaluations at 3-month intervals included Unified Parkinson's Disease Rating Scale (UPDRS) scoring, Hoehn and Yahr staging, 24-hour self-assessments, and neuropsychological examinations. Six patients with a mean age of 55 years (mean 42-67 years), a mean duration of disease of 15.5 years (range 12-21 years), a mean "on/off' Hoehn and Yahr stage score of 3/4.2 (range 3-5), and a mean "off' time of 40% (range 20-50%) underwent bilateral contemporaneous pallidal DBS, with a minimum follow-up period lasting 24 months (range 24-30 months). The mean dose of levodopa in these patients could not be changed significantly after the procedure and pergolide was added after 12 months in five patients because of recurring fluctuations despite adjustments in stimulation parameters. All but two patients had no fluctuations until 9 months. Two of the patients reported barely perceptible fluctuations at 12 months and two at 15 months; however, two patients remain without fluctuations at 2 years. The mean improvements in the UPDRS motor score in the off time and the activities of daily living (ADL) score were more than 50%; the mean off time decreased from 40 to 10%, and the mean dyskinesia and complication of treatment scores were reduced to one-third until pergolide was introduced at 12 months. No significant improvement in "on" scores was observed. A slight worsening after 1 year was observed and three patients developed levodopa- and stimulation-resistant gait ignition failure and minimal fluctuations at 1 year. Side effects, which were controlled by modulation of stimulation, included dysarthria, dystonia, and confusion.

CONCLUSIONS

Bilateral pallidal DBS is safe and efficient in patients who have levodopa-responsive parkinsonism with severe fluctuations. Major improvements in motor score, ADL score, and off time persisted beyond 2 years after the operation, but signs of decreased efficacy started to be seen after 12 months.