Despite the recent success of DBS and the benefit it provides in treating advanced PD, DBS has a number of adverse effects. These range from psychiatric effects of mania or depression to effects of vocal hypophonia, weight gain, eyelid apraxia, increased libido, sialorrhea, decreased memory, dyskinesia, and dystonia. A review of reported series noted the occurrence of adverse effects in 19% of patients receiving DBS of the subthalamic nucleus (STN) (1-5). Another issue is the apparently high suicide rate among patients having undergone DBS surgery; one study noted a rate of 4.3% in a cohort of 140 patients (6). Secondly, there are many elements that reflect the progression of the disease that are not effectively addressed by DBS. These include the prominent gait and balance issues that are inherent to PD and the gradual cognitive and emotional decline that is known to occur from extranigral neuronal attrition (7).
There remains a need to investigate and refine the effect of DBS for PD. Several areas of research deal with refining the technique of neural stimulation. The exploration of novel targets may also lead to stimulatory therapies that address some of the current shortcomings. It is hoped that some of these targets will yield similar or greater benefits while producing more limited side effects. Beyond improvements in stimulatory therapies lie restorative treatments that offer the hope of reversing the pathology of PD.
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