Chronic Effects of DBS in Parkinson's Disease and Dystonia

Inclusion Criteria(both groups): * Ability to give informed consent for the study * Movement disorder symptoms that are sufficiently severe, in spite of best medical therapy, to warrant surgical implantation of deep brain stimulators according to standard clinical criteria Inclusion criteria (Isolated dystonia): * Age 22-75 * Isolated dystonia that is generalized or segmental, that must affect one or - Stable doses of anti-dystonia medications (such as Artane, Baclofen, or Clonopin) for at least 30 days prior to baseline assessment * For patients with craniofacial involvement, prior treatment with botulinum toxin with failure to adequately control dystonia symptoms. Inclusion criteria (PD): * Age 30-75 * Bilateral disease (Hoehn and Yahr stage 2 or greater) * Has been treated with levodopa/carbidopa, and with a dopamine agonist, at the maximal tolerated doses as determined by a movement disorders neurologist * Stable doses of antiParkinsonian medications for at least 30 days prior to their baseline assessment * Significant disability in the setting of optimal medical management by a movement disorders neurologist. Disability may be due to tremor that is unresponsive to medications, or to motor fluctuations * UPDRS-III score off medication between 20 and 60 * Improvement of at least 30% in the baseline UPDRS-III on medication score, compared to the baseline off-medication score. Exclusion Criteria (both groups): * Pregnancy or breast feeding * MRI showing cortical atrophy out of proportion to age * MRI showing focal brain lesions that could indicate a non-idiopathic movement disorder, * Major comorbidity increasing the risk of surgery (prior stroke, severe hypertension, severe diabetes, or need for chronic anticoagulation other than aspirin) * Inability to comply with study follow-up visits * Any prior intracranial surgery * Mood depression with a Beck depression inventory score of \> 17 on baseline screening * Significant cognitive impairment (MoCA\<25). * History of seizures * Immunocompromised * Has an active infection * Requires diathermy, electroconvulsive therapy (ECT) or transcranial magnetic - Has an implanted electronic device such as a neurostimulator, cardiac pacemaker or medication pump.