Deep Brain Stimulation of the Internal Segment of the Globus Pallidus in Delayed Runaway Dyskinesia

A video-atlas of levodopa-induced dyskinesia in Parkinson's disease: terminology matters

Dyskinesia is a common complication of long-term levodopa therapy in patients with Parkinson's disease (PD), which often worsens the quality of life. It is usually dose-dependent and emerges possibly due to pulsatile stimulation of dopamine receptors. Delineating the pattern of dyskinesia is crucial for determining the most effective therapeutic approach, a task that often presents challenges for numerous neurologists. This article comprehensively describes various patterns of dyskinesia in PD patients and features video demonstration of some of the common forms of dyskinesia. We have used a real case scenario as an example to lead the discussion on the phenomenology, distinguishing features, and management of various types of dyskinesia. A comprehensive literature search was conducted in PubMed using "dyskinesia" as a keyword. The prototype case with videos highlights the differentiating features of dyskinesia along with the treatment strategies. A wide range of descriptive rubrics have been used for certain dyskinesia which are described in detail in this article. The newer types of dyskinesia associated with continuous dopaminergic stimulation in patients with advanced PD and their implications have been described. As there are distinct ways of managing various types of dyskinesia, understanding the phenomenology and chronology of dyskinesia is vital for the optimal management of dyskinetic PD patients. We suggest that dyskinesia should be classified broadly into peak-dose dyskinesia (PDD), biphasic dyskinesia (BD), and OFF-period dystonia. The occurrence of low-dose dyskinesia and complex dyskinesia of continuous dopaminergic treatments should be known to specialists and will require additional studies.

Peripheral nerve grafts implanted into the substantia nigra in patients with Parkinson's disease during deep brain stimulation surgery: 1-year follow-up study of safety, feasibility, and clinical outcome

OBJECTIVECurrently, there is no treatment that slows or halts the progression of Parkinson's disease. Delivery of various neurotrophic factors to restore dopaminergic function has become a focus of study in an effort to fill this unmet need for patients with Parkinson's disease. Schwann cells provide a readily available source of such factors. This study presents a 12-month evaluation of safety and feasibility, as well as the clinical response, of implanting autologous peripheral nerve grafts into the substantia nigra of patients with Parkinson's disease at the time of deep brain stimulation (DBS) surgery.METHODSStandard DBS surgery targeting the subthalamic nucleus was performed in 8 study participants. After DBS lead implantation, a section of the sural nerve containing Schwann cells was harvested and unilaterally grafted to the substantia nigra. Adverse events were continually monitored. Baseline clinical data were obtained during standard preoperative evaluations. Clinical outcome data were obtained with postoperative clinical evaluations, neuropsychological testing, and MRI at 1 year after surgery.RESULTSAll 8 participants were implanted with DBS systems and grafts. Adverse event profiles were comparable to those of standard DBS surgery with the exception of 1 superficial infection at the sural nerve harvest site. Three participants also reported numbness in the distribution of the sural nerve distal to the harvest site. Motor scores on Unified Parkinson's Disease Rating Scale (UPDRS) part III while the participant was off therapy at 12 months improved from baseline (mean ± SD 25.1 ± 15.9 points at 12 months vs 32.5 ± 9.7 points at baseline). An analysis of the lateralized UPDRS scores also showed a greater overall reduction in scores on the side contralateral to the graft.CONCLUSIONSPeripheral nerve graft delivery to the substantia nigra at the time of DBS surgery is feasible and safe based on the results of this initial pilot study. Clinical outcome data from this phase I trial suggests that grafting may have some clinical benefit and certainly warrants further study to determine if this is an efficacious and neurorestorative therapy.Clinical trial registration no.: NCT01833364 (clinicaltrials.gov).

Treatment of Parkinson's disease using cell transplantation

The clinical trials with intrastriatal transplantation of human fetal mesencephalic tissue, rich in dopaminergic neurons, in Parkinson's disease (PD) patients show that cell replacement can work and in some cases induce major, long-lasting improvement. However, owing to poor tissue availability, this approach can only be applied in very few patients, and standardization is difficult, leading to wide variation in functional outcome. Stem cells and reprogrammed cells could potentially be used to produce dopaminergic neurons for transplantation. Importantly, dopaminergic neurons of the correct substantia nigra phenotype can now be generated from human embryonic stem cells in large numbers and standardized preparations, and will soon be ready for application in patients. Also, human induced pluripotent stem cell-derived dopaminergic neurons are being considered for clinical translation. Available data justify moving forward in a responsible way with these dopaminergic neurons, which should be tested, using optimal patient selection, cell preparation and transplantation procedures, in controlled clinical studies.

Clinical translation of stem cell transplantation in Parkinson's disease

In Parkinson's disease (PD), the main pathology underlying the motor symptoms is a loss of nigrostriatal dopaminergic neurons. Clinical trials of intrastriatal transplantation of human foetal mesencephalic tissue have shown that the grafted dopaminergic neurons re-innervate the striatum, restore striatal dopamine release and, in some cases, induce major, long-lasting improvement of motor function. However, nonmotor symptoms originating from degeneration outside the striatum or in nondopaminergic systems are not alleviated by intrastriatal implantation of dopaminergic neurons. Stem cells and reprogrammed cells could potentially be used to produce dopaminergic neurons for transplantation in patients with PD. Recent studies demonstrate that standardized preparations of dopaminergic neurons of the correct substantia nigra phenotype can be generated from human embryonic stem cells in large numbers, and they will soon be available for patient application. In addition, dopaminergic neurons derived from human induced pluripotent stem cells are being considered for clinical translation. Important challenges include the demonstration of potency (growth capacity and functional efficacy) and safety of the generated dopaminergic neurons in preclinical animal models. The dopaminergic neurons should subsequently be tested, using optimal patient selection and cell preparation and transplantation procedures, in controlled clinical studies.

Cell-based therapies for Parkinson disease—past insights and future potential

Parkinson disease (PD) is characterized by loss of the A9 nigral neurons that provide dopaminergic innervation to the striatum. This discovery led to the successful instigation of dopaminergic drug treatments in the 1960s, although these drugs were soon recognized to lose some of their efficacy and generate their own adverse effects over time. Despite the fact that PD is now known to have extensive non-nigral pathology with a wide range of clinical features, dopaminergic drug therapies are still the mainstay of therapy, and work well for many years. Given the success of pharmacological dopamine replacement, pursuit of cell-based dopamine replacement strategies seemed to be the next logical step, and studies were initiated over 30 years ago to explore the possibility of dopaminergic cell transplantation. In this Review, we outline the history of this therapeutic approach to PD and highlight the lessons that we have learned en route. We discuss how the best clinical outcomes have been obtained with fetal ventral mesencephalic allografts, while acknowledging inconsistencies in the results owing to problems in trial design, patient selection, tissue preparation, and immunotherapy used post-grafting. We conclude by discussing the challenges of bringing the new generation of stem cell-derived dopamine cells to the clinic.

Long-term clinical outcome of fetal cell transplantation for Parkinson disease: two case reports

IMPORTANCE

Recent advances in stem cell technologies have rekindled an interest in the use of cell replacement strategies for patients with Parkinson disease. This study reports the very long-term clinical outcomes of fetal cell transplantation in 2 patients with Parkinson disease. Such long-term follow-up data can usefully inform on the potential efficacy of this approach, as well as the design of trials for its further evaluation.

OBSERVATIONS

Two patients received intrastriatal grafts of human fetal ventral mesencephalic tissue, rich in dopaminergic neuroblasts, as restorative treatment for their Parkinson disease. To evaluate the very long-term efficacy of the grafts, clinical assessments were performed 18 and 15 years posttransplantation. Motor improvements gained gradually over the first postoperative years were sustained up to 18 years posttransplantation, while both patients have discontinued, and remained free of any, pharmacological dopaminergic therapy.

CONCLUSIONS AND RELEVANCE

The results from these 2 cases indicate that dopaminergic cell transplantation can offer very long-term symptomatic relief in patients with Parkinson disease and provide proof-of-concept support for future clinical trials using fetal or stem cell therapies.

L-DOPA and graft-induced dyskinesia: different treatment, same story?

One of the well-recognized problems of long-term L-3,4-dihydroxyphenylalanine (L-DOPA) therapy in the treatment of Parkinson's disease is the development of L-DOPA induced dyskinesia. These abnormal movements cause significant disability and narrow the therapeutic window of L-DOPA. Cell transplantation is one of the most promising upcoming therapies for the treatment of Parkinson's disease, and may help alleviate or avoid L-DOPA-induced dyskinesia. However, the more recently acknowledged phenomenon of graft-induced dyskinesia is posing a major obstacle to the success of this treatment. This motor side-effect closely resembles abnormal movements induced by chronic L-DOPA treatment, yet they remain after withdrawal of the medication indicating their origins lie in the transplant. In this review, we compare these two therapy-induced adverse effects, from the way they manifest in patients to the possible mechanisms underlying their development.

The Movement Disorder Society Evidence-Based Medicine Review Update: Treatments for the motor symptoms of Parkinson's disease

The objective was to update previous evidence-based medicine reviews of treatments for motor symptoms of Parkinson's disease published between 2002 and 2005. Level I (randomized, controlled trial) reports of pharmacological, surgical, and nonpharmacological interventions for the motor symptoms of Parkinson's disease between January 2004 (2001 for nonpharmacological) and December 2010 were reviewed. Criteria for inclusion, clinical indications, ranking, efficacy conclusions, safety, and implications for clinical practice followed the original program outline and adhered to evidence-based medicine methodology. Sixty-eight new studies qualified for review. Piribedil, pramipexole, pramipexole extended release, ropinirole, rotigotine, cabergoline, and pergolide were all efficacious as symptomatic monotherapy; ropinirole prolonged release was likely efficacious. All were efficacious as a symptomatic adjunct except pramipexole extended release, for which there is insufficient evidence. For prevention/delay of motor fluctuations, pramipexole and cabergoline were efficacious, and for prevention/delay of dyskinesia, pramipexole, ropinirole, ropinirole prolonged release, and cabergoline were all efficacious, whereas pergolide was likely efficacious. Duodenal infusion of levodopa was likely efficacious in the treatment of motor complications, but the practice implication is investigational. Entacapone was nonefficacious as a symptomatic adjunct to levodopa in nonfluctuating patients and nonefficacious in the prevention/delay of motor complications. Rasagiline conclusions were revised to efficacious as a symptomatic adjunct, and as treatment for motor fluctuations. Clozapine was efficacious in dyskinesia, but because of safety issues, the practice implication is possibly useful. Bilateral subthalamic nucleus deep brain stimulation, bilateral globus pallidus stimulation, and unilateral pallidotomy were updated to efficacious for motor complications. Physical therapy was revised to likely efficacious as symptomatic adjunct therapy. This evidence-based medicine review updates the field and highlights gaps for research.

Cell-based therapies for Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide, classically characterized by a triad of motor features: bradykinesia, rigidity and resting tremor. Neurodegeneration in PD critically involves the dopaminergic neurons of the substantia nigra pars compacta, which results in a severe reduction in dopamine levels in the dorsal striatum. However, the disease also exhibits extensive non-nigral pathology and as many non-motor as motor features. Nevertheless, owing to the relatively circumscribed nature of the nigrostriatal lesion in PD, dopaminergic cell transplantation has emerged as a potentially reparative therapy for the disease. Sources for such cells are varied and include the developing ventral mesencephalon, several autologous somatic cell types, embryonic stem cells and induced pluripotent stem cells. In this article, we review the origins of dopaminergic transplantation for PD and the emergent hunt for a suitable long-term source of transplantable dopaminergic neurons.

Cell therapeutics in Parkinson's disease

The main pathology underlying motor symptoms in Parkinson's disease (PD) is a rather selective degeneration of nigrostriatal dopamine (DA) neurons. Intrastriatal transplantation of immature DA neurons, which replace those neurons that have died, leads to functional restoration in animal models of PD. Here we describe how far the clinical translation of the DA neuron replacement strategy has advanced. We briefly summarize the lessons learned from the early clinical trials with grafts of human fetal mesencephalic tissue, and discuss recent findings suggesting susceptibility of these grafts to the disease process long-term after implantation. Mechanisms underlying graft-induced dyskinesias, which constitute the only significant adverse event observed after neural transplantation, and how they should be prevented and treated are described. We summarize the attempts to generate DA neurons from stem cells of various sources and patient-specific DA neurons from fully differentiated somatic cells, with particular emphasis on the requirements of these cells to be useful in the clinical setting. The rationale for the new clinical trial with transplantation of fetal mesencephalic tissue is described. Finally, we discuss the scientific and clinical advancements that will be necessary to develop a competitive cell therapy for PD patients.

Graft-induced dyskinesias in Parkinson's disease: High striatal serotonin/dopamine transporter ratio

Graft-induced dyskinesias are a serious complication after neural transplantation in Parkinson's disease. One patient with Parkinson's disease, treated with fetal grafts 14 years ago and deep brain stimulation 6 years ago, showed marked improvement of motor symptoms but continued to suffer from OFF-medication graft-induced dyskinesias. The patient received a series of clinical and imaging assessments. Positron emission tomography and single-photon emission computed tomography 14 years posttransplantation revealed an elevated serotonin/dopamine transporter ratio in the grafted striatum compatible with serotonergic hyperinnervation. Inhibition of serotonin neuron activity by systemic administration of a 5-HT(1A) agonist suppressed graft-induced dyskinesias. Our data provide further evidence that serotonergic neurons mediate graft-induced dyskinesias in Parkinson's disease. Achieving a normal striatal serotonin/dopamine transporter ratio following transplantation of fetal tissue or stem cells should be necessary to avoid the development of graft-induced dyskinesias.

Neural grafting in Parkinson's disease unraveling the mechanisms underlying graft-induced dyskinesia

The development of neural transplantation as a treatment for Parkinson's disease has been compromised by a lack of functional efficacy and the appearance of transplant-induced motor side-effects in some patients. Since the first reports of these graft-induced dyskinesias (GID), and the realization of their impact on the progress of the field, a great deal of experimental work has been performed to determine the underlying cause(s) of this problematic side-effect. In this review we describe the clinical phenomenon of GID, explore the different representations of GID in rodent models, and examine the various hypotheses that have been postulated to be the cause. Based on the available clinical and preclinical data we outline strategies to avoid GID in future clinical trials using fetal cell transplants or cell preparations derived from stem cells.

Prospects of stem cell therapy for replacing dopamine neurons in Parkinson's disease

In Parkinson's disease (PD), the main pathology is a loss of nigrostriatal dopamine (DA) neurons. Clinical trials with intrastriatal transplantation of human embryonic mesencephalic tissue have shown that grafted DA neurons reinnervate the striatum, restore striatal DA release and, in some patients, induce major clinical benefit. Stem cells could provide an unlimited source of DA neurons for transplantation. Recent studies demonstrate that cells with properties of mesencephalic DA neurons can be produced from stem cells of different sources including reprogrammed somatic cells. However, as we discuss here, it remains to be shown that these cells can provide efficient functional reinnervation and behavioral recovery in animal PD models. Moreover, a clinically competitive cell therapy for PD will require better criteria for patient selection, improved functional efficacy of grafts by a tailor-made transplantation procedure providing optimum repair of the patient's DA system and strategies to prevent dyskinesias and tumor formation.