Novel Stimulation Patterns for the Treatment of Dystonia

Overview

Deep brain stimulation (DBS) is an effective surgical therapy for select Dystonia patients who are refractory to medications or who have generalized symptoms (e.g. patients with Early-Onset Primary Dystonia(DYT1) mutations and other dystonia subtypes). DBS patients typically experience significant improvement in disabling symptoms; however, detailed programming is always required, and stimulation-induced side effects commonly emerge. Clinicians may empirically vary voltage, pulse width, frequency and also the active contacts on the DBS lead to achieve observed optimal benefits. The majority of DBS patients undergo repeat surgeries to replace the implantable pulse generator (IPG) every 2.5 to 5 years. It has been demonstrated that, in dystonia patients, that higher settings are required for adequate symptomatic control, and that neurostimulators have a considerably shorter life when compared to neurostimulators from patients with essential tremor or Parkinson's disease. Additionally, several smaller studies have suggested that alternative pulse stimulation properties and pulse shape modifications can lower IPG battery consumption. Newer patterns of stimulation (regularity of pulses and shapes of pulses) have not been widely tested in clinical practice, and are not part of the current FDA device labeling. Novel patterns of stimulation do however, have the potential to improve symptoms, reduce side effects, and to preserve the neurostimulator life. The current research proposal will prospectively study biphasic pulse stimulation paradigms and its effects on dystonic symptoms. The investigators aim to demonstrate that we can tailor DBS settings to address dystonia symptoms, improve the safety profile, characterize distinct clinical advantages, and carefully document the safety and neurostimulator battery consumption profile for biphasic stimulation.

In this research study, different stimulation patterns on the DBS device will be tried for effectiveness against current symptoms. There will be two different stimulation patterns that will be performed and can occur at different clinic dates. Each of the stimulation patterns will have times varying between 2-3 hours per stage. One part of the study will deliver stimulation in a continuous manner, while the other part of the study will deliver stimulation based upon responses obtained from changes in brain wave patterns. These procedures can be performed while in the clinic for regular programming visits or at different visits. The current DBS setting will be recorded and at the end of the session the setting will be reset to back to the previous settings. The participant will have the option of participating in both or just one part. During the visit, the participant will be analyzed for tremor and slowness by using the Trigno wireless Electromyography (EMG) and the Kinesia system. The system includes a unit composed of two modules: a wrist module, which is the size of an I-Pod and will be attached to the wrist over a comfortable wristband, and a sensor module, which will be placed over the index finger. The entire visit will be videotaped and UDRS (Unified Dystonia Disease Rating Scale) and BFMDRS (Burke-Fahn-Marsden Dystonia Rating Scale) scores will be evaluated by two scorers. Pre-DBS "off" and "on" scores will also be taken.