MRI Guided Focused Ultrasound for Tremor in Multiple Sclerosis

This study is designed as a prospective, single site, single arm, nonrandomized study. Assessments will be made before and after MRgFUS for clinical symptom relief, quality of life (QoL) improvements, and safety of MRgFUS in the treatment of multiple sclerosis patients with severe medication refractory tremor. This study will be performed on the 3T MR scanners. The ExAblate system is a medical device that involves a focused ultrasound system and an MRI scanner. During MRgFUS a pulse of focused ultrasound energy, or sonication,are delivered to the targeted tissue. In this particular study the targeted tissue is a unilateral thermal lesion created in the ventralis intermedius nucleus of the thalamus. The treatment begins with a series of standard diagnostic MR images to identify the location and shape of tumor to be treated. The computer uses the physician's designation of the target volume to plan the best way to cover the target volume with small spots called "sonications". These treatment spots are cylinder shaped. Their size depends on sonication power and duration. During the treatment, a specific MR scan, which can be processed to identify changes in tissue temperature, provides a thermal map of the treatment volume to confirm the therapeutic effect. The thermal map is used to monitor the treatment in progress, and confirm that the ablation is proceeding according to plan, thus closing the therapy loop. MRgFUS uses a transcranial operated helmet-shaped transducer positioned above the subject head. The transcranial system includes means to immobilize the subject head, cool the interface water, and software for CT analysis and phase correction computation. MRgFUS transcranial system to relieve tremor in multiple sclerosis patients is being investigated in this study.