Deep Brain Stimulation (DBS) is an effective treatment option for individuals with debilitating tremors that do not respond to medical therapy. However, severe tremors, particularly those that develop after central nervous system insult or from multiple sclerosis, can be comprised of several underlying components that represent dysfunction within distinct brain circuits. Some of these dysfunctional brain circuits can be successfully treated with DBS while others respond poorly DBS therapy. For severe tremors, it can be very difficult to discriminate between the underlying components of a patient movement disorder and is exclusively dependent upon clinical expertise. Even with extensive clinical experience, it is difficult to reliably predict the results of DBS therapy for patients suffering from severe, debilitating tremor. In an attempt to gain more knowledge, an electromagnetic tracking system will be used which can precisely measure the position of a patient's upper extremity in space during routine neurologic examination. The goal is to use this tool to quantitatively identify various components of severe tremor, which can be discriminated based on oscillatory frequency and regularity of tremor amplitude. The purpose of this research study is to better understand the nature of complex, severe tremors by carefully measuring movement of the upper extremities with sensors during simple tasks. The goal is to break down complicated tremors into their components and then determine which components will respond to deep brain stimulation.

As a participant in the research study small sensors that are connected to wires will be affixed to points on your hand, wrist, elbow and/or shoulder. These sensors are painless and otherwise noninvasive. They will be used to measure the precise location of the hand and arm in space during the neurologic examination. This exam will test the tremors during short, simple tasks using the hand and arm. This information will be stored along with your name and medical record number for analysis after your testing is complete.

The sensors that are used to measure movements are connected to thin, flexible wires that will be attached with adhesive tape. The motion sensors use a magnet that produces a weak electromagnetic field. This electromagnetic field poses no direct harm, but could potentially interfere with medical devices such as cardiac pacemakers or deep brain stimulators if placed very close to the electromagnetic emitter.

Inclusion Criteria:

• Adults
• Individuals who have undergone or are scheduled to undergo Deep Brain Stimulation (DBS) placement

Exclusion Criteria:

• Individuals who have not had or are not scheduled for Deep Brain Stimulation (DBS) placement

Patients between 18 and 80 years old who have undergone deep brain stimulator implantation or are being considered for deep brain stimulation for severe, intractable tremor.