Relief From Side Effects: Clinical Use of Electrodes With Direction (RESCUED)

Relief From Side Effects: Clinical Use of Electrodes With Direction: a Prospective, Open Label, Clinical Trial for Thalamic Deep Brain Stimulation

Deep Brain Stimulation (DBS) uses electrical pulses sent through a lead (insulated wire) to help stop unwanted symptoms in a variety of brain diseases, including the tremor seen in patients with Essential Tremor (ET). The current standard lead allows this stimulation to spread out uniformly in all directions. As these diseases progress, however, the amount of electrical stimulation required to stop the symptom usually increases. This may become problematic because the increased electrical stimulation required for advanced symptoms may spread outside the desired targeted area, and effect other parts of the brain and causing unwanted side effects. A new type of DBS lead has been developed which can steer, or focus, the electrical stimulation in a given direction toward the desired target area and away from areas that would cause side effects. We would like to quantify the benefit seen in patients who have been switched from the traditional lead to this new directional lead.

Patients implanted with a DBS may experience unwanted side effects such as motor contractures, paresthesia, or dysarthria. This occurs when the electrical field of the stimulation spreads out beyond the targeted area. This is especially common in patients whose disease has progressed, and must use increasingly higher currents in order to regain control of their tremor. Unfortunately, because the electrical field affects neurons in a symmetrical sphere around the DBS, it is often impossible to reach the additional desired neuronal elements without simultaneously affecting equidistant brain regions responsible for side effects. For many of our advanced patients, this means choosing between a debilitating tremor or disabling side effects.The directional lead is a FDA and Health Canada approved DBS lead which features radially segmented electrodes which can selectively steer the electrical field in a predefined direction, orthogonal to the lead trajectory. This will allow DBS clinicians to steer current towards desired structural areas, while avoiding locations, which produce negative side effects.

Patients who were previously implanted with a traditional DBS lead and have subsequently developed stimulation induced side effects will gain significantly more tremor control without side effects when re-implanted with a directional DBS lead. We expect these patients' quality of life will improve. These patients typically will have had significant tremor relief (greater than 75% reduction from preoperative tremor rating scale) without side effects at their one year post operative follow-up. With the expected disease progression they will have had to increase their DBS stimulation to the degree that their DBS now causes side effects in order to block their tremor

Individuals in this arm will have their stimulator settings programmed to the point in which they have maximum tremor control with no side effects.

Maximum percentage change in tremor (as measured by the Tremor Rating Scale) without side-effects (comparing DBS "on" versus "off") in each patient using the standard lead compared to the directional lead.

Quality of life will be based on each participant's subjective opinion using the Short Form 36 (SF36) (a patient-reported survey focusing on health and quality of life) assessment form.

Assessed during study visits - The initial assessment will occur during a pre-operative study visit which will be compared post operatively 3 months after outcome 1 has been measured

Quality of life will be based on each participant's subjective opinion using the Quality of Life in Essential Tremor Questionare.

Assessed during study visits - The initial assessment will occur during a pre-operative study visit which will be compared post operatively 3 months after outcome 1 has been measured

Quality of life will be based on each participant's subjective opinion using the Vocal handicap Index scale.

Assessed during study visits - The initial assessment will occur during a pre-operative study visit which will be compared post operatively 3 months after outcome 1 has been measured

Inclusion Criteria: Participants must have been implanted with the DBS Participants must have been diagnosed with Essential Tremor Participants must experience negative side effects from their DBS which limit control over their tremor Participants must be able to receive benefit from their stimulator, but at the cost of negative side effects Exclusion Criteria: All individuals who meet criteria outlined in "inclusion criteria" may be eligible for this study

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Reinacher PC, Kruger MT, Coenen VA, Shah M, Roelz R, Jenkner C, Egger K. Determining the Orientation of Directional Deep Brain Stimulation Electrodes Using 3D Rotational Fluoroscopy. AJNR Am J Neuroradiol. 2017 Jun;38(6):1111-1116. doi: 10.3174/ajnr.A5153. Epub 2017 Apr 6.