Neurosurgical interventions in the treatment of idiopathic Parkinson disease: neurostimulation and neural implantation

With the exception of thalamotomy for drug-refractory tremor, surgical ther apy for Parkinson's disease has been almost abondoned as treatment for Park insonian symptoms between 1965 and 1985. Reasons for this development relat e to inconsistent postoperative results, complications associated with ster eotactic surgical techniques and, most importantly, the advent: of levodopa , which is still considered to be the gold standard in pharmacotherapy for Parkinson's disease. However, both, the long-term experience with L-DOPA th erapy on the one hand and the progress of advanced stereotactic techniques and fetal graft research on the other hand have lead to reconsideration of surgical therapy in Parkinson's disease for patients, who can not be treate d satisfactorily with medication. Both lesions (via thermocoagulation) and for neurostimulation (via chronic intracerebral implantation of electrodes) in thalamic nuclei (nucleus ventralis oralis pasterior/intermedialis thala mi; VOP/VIM) may alleviate rest tremor in PD patients. In principle neurost imulation has the significant advantage of reversibility with regard to sid e effects in comparison to lesion surgery. Furthermore ventro-posterior pal lidotomy or chronic stimulation in this structures may ameliorate bradykine sia and levodopa-induced dyskinesias. Additionally, "switching-off" the sub thalamic nucleus by neurostimulation has been reported to reduce rigidity, bradykinesia and levodopa-induced ON-OFF-fluctuations. On the othe hand, ne uronal transplantation of fetal nigral dopamine precursor cells aims at res toring the striatal dopamine deficit. Both animal and clinical experiments have shown that fetal grafts survive intrastriatal transplantation and may ensue moderate to satisfactory improvements, especially in regard to bradyk inesia and ON-OFF-fluctuations. Further progress in the field of neuronal t ransplantation will largely depend on the development of alternative cell r esources.