Neurotransplantation in Parkinson's disease: from open microsurgery to bilateral stereotactic approach: first clinical trial using microelectrode recording technique

Role and contributions of women in revolutionizing neurosurgery

We owe it to the women neurosurgeons for paving the way to a more gender-inclusive world of medicine. Their dedication and sacrifices have led them and their followers to scale unimaginable heights in terms of administrative positions, leadership, and academics. In today's scenario, it is safe to say that society has progressed considerably. Past years have seen an uprise in the number of females enrolling in a medical degree programme however, this proportion is highly distorted when it comes to specialties such as Neurosurgery. This disparity seems to be evolving and leveling out in all specialties, as more and more women are stepping out of their comfort zone and challenging the established standards of the society. It is with the collective efforts of all stakeholders and women that we see more women not only choosing such specialties which were previously uncharted terrain, but also leading organizations globally and excelling on the administrative and academic fronts. Veteran female surgeons have revolutionized neurosurgery and its subspecialties in unimaginable ways and the present as well as the future generation neurosurgeons continue to take inspiration from them and follow their footsteps. This paper has put together the contributions of female neurosurgeons in various subspecialties of neurosurgery as well as giving an account of the leadership and administrative positions served by women. We also shed light on the role of women as an academician and a researcher.

Women in Neuromodulation: Innovative Contributions to Stereotactic and Functional Neurosurgery

Stereotactic neurosurgery emerged in the mid-20th century following the development of a stereotactic frame by Spiegel and Wycis. Historically women were underrepresented in clinical and academic neurosurgery. There is still a significant deficit of female scientists in this field. This article aims to demonstrate the career and scientific work of some of the most important women who contributed to the development of stereotactic and functional neurosurgery. Exceptional women from all over the world, represented in this review, assisted the evolution of modern stereotactic and functional neurosurgery as neurosurgeons, neuropathologists, neurologists, neurophysiologists and occupational therapists. Fortunately, we could conclude that in the last two decades the number of female researchers has increased significantly.

L-DOPA for Parkinson's disease-a bittersweet pill

3,4-dihydroxy-L-phenylalanine (L-DOPA) is the gold standard treatment for Parkinson's disease. It has earned that title through its highly effective treatment of some of the motor symptoms in the early stages of the disease but it is a far from perfect drug. The inevitable long-term treatment that comes with this chronic neurodegenerative condition raises the risk significantly of the development of motor fluctuations including disabling L-DOPA-induced dyskinesia. Being unsurpassed as a therapy means that understanding the mechanisms of dyskinesia priming and induction is vital to the search for therapies to treat these side effects and allow optimal use of L-DOPA. However, L-DOPA use may also have consequences (positive or negative) for the development of other interventions, such as cell transplantation, which are designed to treat or repair the ailing brain. This review looks at the issues around the use of L-DOPA with a focus on its potential impact on advanced reparative interventions.

Influence of cell preparation and target location on the behavioral recovery after striatal transplantation of fetal dopaminergic neurons in a primate model of Parkinson's disease

Surgeries involving transplantation of fetal dopamine (DA) neurons into the caudate-putamen of patients with Parkinson's disease (PD) have been performed in various clinical trials to examine a potential restoration of motor function. The absence of studies in non-human primates to define the best transplantation protocols have lead to the use of a broad variety of techniques that potentially could have a major impact on the clinical outcome. The effects of using different cell and tissue preparation, and surgical targets, remain unknown. For this purpose, 20 St. Kitts African Green Monkeys (AFG) rendered parkinsonian by i.m. injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were balanced into 4 groups and unilaterally grafted in the (a) caudate or (b) putamen with fetal ventral mesencephalic (VM) tissue as (c) solid pieces or as a (d) cell suspension. By 9 months post-transplantation all animals showed significant and similar behavioral improvement as determined by a UPDRS based PD scale. Postmortem analyses showed that VM transplants survived in all animals. They were located in both surgical target sites, producing a broad DA reinnervation of the targeted nuclei that could also extend to the non-grafted nucleus on the ipsilateral side. Although no differences between groups were found in survival of DA neurons or degree of DA reinnervation, there was a significant correlation between striatal reinnervation and behavioral recovery only in animals transplanted in the putamen surgical target. Additionally, there was in general a stronger glial reaction to solid grafts than to cell suspensions. These studies provide data for the optimal time course, cell preparation and surgical targets for systematic examinations of both potential benefits and side effects of dopamine neuron cell transplantation in primate models of PD.

Stem cells for neurodegenerative disorders: where can we go from here?

The use of stem cells in cell replacement therapy for neurodegenerative diseases has received a great deal of scientific and public interest in recent years. This is due to the remarkable pace at which paradigm-changing discoveries have been made regarding the neurogenic potential of embryonic, fetal, and adult cells. Over the last decade, clinical fetal tissue transplants have demonstrated that dopaminergic neurons can survive long term and provide functional clinical benefits for patients with Parkinson's disease. Pluripotent embryonic stem cells and multipotent neural stem cells may provide renewable sources that could replace these primary fetal grafts. Considerable advancement has been made in generating cultures with high numbers of neurons in general and of dopaminergic neurons using a varied array of techniques. However, much of this encouraging progress still remains to be tested on long-term expanded human cultures. Further problems include the low survival rate of these cells following transplantation and the tumorigenic tendencies of embryo-derived cells. However, pre-differentiation or genetic modification of stem cell cultures prior to transplantation may help lead to the generation of high numbers of cells of the desired phenotype following grafting. Boosting particular factors or substrates in the culture media may also protect grafted neurons from oxidative and metabolic stress, and provide epigenetic trophic support. Possible endogenous sources of cells for brain repair include the transdifferentiation of various types of adult cells into neurons. Despite the excitement generated by examples of this phenomenon, further work is needed in order to identify the precise instructive cues that generate neural cells from many other tissue types, and whether or not the new cells are functionally normal. Furthermore, issues such as cell homogeneity and fusion need to be addressed further before the true potential of transdifferentiation can be known. Endogenous stem cells also reside in the neurogenic zones of the adult brain (ventricle lining and hippocampus). Further elucidation of the mechanisms that stimulate cell division and migration are required in order to learn how to amplify the small amount of new cells generated by the adult brain and to direct these cells to areas of injury or degeneration. Finally, a more fundamental understanding of brain injury and disease is required in order to circumvent local brain environmental restrictions on endogenous cell differentiation and survival.

Cellular replacement therapy for Parkinson's disease--where we are today?

The concept of replacing lost dopamine neurons in Parkinson's disease using mesencephalic brain cells from fetal cadavers has been supported by over 20 years of research in animals and over a decade of clinical studies. The ambitious goal of these studies was no less than a molecular and cellular "cure" for Parkinson's disease, other neurodegenerative diseases, and spinal cord injury. Much research has been done in rodents, and a few studies have been done in nonhuman primate models. Early uncontrolled clinical reports were enthusiastic, but the outcome of the first randomized, double blind, controlled study challenged the idea that dopamine replacement cells can cure Parkinson's disease, although there were some significant positive findings. Were the earlier animal studies and clinical reports wrong? Should we give up on the goal? Some aspects of the trial design and implantation methods may have led to lack of effects and to some side effects such as dyskinesias. But a detailed review of clinical neural transplants published to date still suggests that neural transplantation variably reverses some aspects of Parkinson's disease, although differing methods make exact comparisons difficult. While the randomized clinical studies have been in progress, new methods have shown promise for increasing transplant survival and distribution, reconstructing the circuits to provide dopamine to the appropriate targets and with normal regulation. Selected promising new strategies are reviewed that block apoptosis induced by tissue dissection, promote vascularization of grafts, reduce oxidant stress, provide key growth factors, and counteract adverse effects of increased age. New sources of replacement cells and stem cells may provide additional advantages for the future. Full recovery from parkinsonism appears not only to be possible, but a reliable cell replacement treatment may finally be near.

An overview of central nervous system transplantation in human disease

Although its roots date back over a century, the field of neurotransplantation has been shaped mostly by advances over the past 30 years. Animal models of nigrostriatal disconnection in the 1970s allowed investigators to explore the feasibility of neural grafting. By the end of that decade, functional and behavioral effects had been demonstrated using fetal tissue grafts. In the 1980s, animal experimentation continued, as did clinical trials involving patients with idiopathic Parkinson's disease. Both autologous adrenal medullary tissue and fetal allografts were tested in the clinical setting, with the latter proving to yield superior results. Animal models of striatal cell loss provided the impetus for limited clinical trials in patients with Huntington's disease by the early 1990s, and work with both diseases continues today. Although much has been learned, neural grafting remains experimental. Broader applications are being explored even now, though, as transplant techniques are applied to animal models of dementia, spinal cord injury, cortical injury, and pain. Some very limited human trials have already begun in some of these areas. In this review some of the advances in the field are highlighted.

Computer analysis of the tonic, phasic, and kinesthetic activity of pallidal discharges in Parkinson patients

OBJECTIVE

Intraoperative analysis of microrecording data during pallidotomy often depends on subjective interpretation of the oscilloscope signal, especially during the analysis of phasic activity. The goals of this project were: 1) to develop an inexpensive system that allowed on-line, objective characterization of single-unit pallidal discharges, and 2) to have objective criteria to differentiate the internal part (GPi) from the external part (GPe) of the globus pallidus.

METHODS

A computer program was developed that allowed the analysis of firing rates (mean, median, and quartiles), spike count per unit time, and interspike interval (ISI) histograms with Chi-square statistical evaluation. Indices were developed that measured phasic activity, including burst index (BI) for the measurement of bursts, pause index (PI) for the measurement of pauses, and pause ratio (PR) for analysis of time spent in pauses. Single-unit activity of 152 GPe and 203 GPi cells in 47 Parkinson patients were digitized using the computer soundcard during pallidotomy and analyzed using this software.

RESULTS

GPe discharges had a mean firing rate = 42 Hz, BI = 0.81, PI = 0.21, and PR = 1.41. GPi had a mean firing rate = 81, BI = 1.61, PI = 0.04, and PR = 0.21. The PR was the best index that differentiated GPe from GPi, followed by PI, BI, and firing rates, in that order. Kinesthetic cells were recorded equally in GPe from GPi, and their responses to generalized movements were not significantly different.

CONCLUSION

(1) Signal analysis using the digitization process of a computer sound card and dedicated software is satisfactory for the objective "on-line" and "off-line" analysis of microrecordings (including phasic activity); (2) PI and PR are most helpful in differentiating neurons of GPi from those of GPe; (3) no single parameter can differentiate GPe from GPi activity in all cases; and (4) unlike the findings in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys, GPe and GPi of Parkinson patients have similar prevalence of kinesthetic cells and similar responses to generalized somatotopic effects.