Algorithms for Programming DBS Systems for ET

Primary Endpoint/Event/Outcome: Endpoint: Identify the neural pathways within the brain that are involved in the reduction of action and postural tremor using directional DBS leads and advanced computational optimization algorithms. Event: Using anatomical segmentation of high-field 7-Tesla MRI and diffusion tensor imaging from 25 human ET subjects, the investigators will build prospective subject-specific, multi-compartment neuron models of the afferent and efferent projections from and to the sensorimotor thalamus. Using these models, the investigators will then apply a semi-automated algorithm that can efficiently identify stimulation settings that most selectively target one pathway over other adjacent pathways. Note that these stimulation settings will not exceed the FDA-approved safety limits that are already programmed into the implanted pulse generator. The optimization algorithm defined stimulation settings will then be tested in human ET subjects to compare the therapeutic efficacy and efficiency of DBS targeting the: interposed-receiving area of motor thalamus, dentate-receiving area of motor. Rendering of a 4-channel DBS lead implant in the VIM nucleus (ventralis intermedius nucleus) of thalamus for treating Essential Tremor. thalamus, pre-lemniscal radiations (raprl) with medial and lateral divisions, and zona incerta, all of which have been implicated in the therapeutic mechanisms of DBS. This clinical evaluation will occur during routine clinical follow-up sessions in which the Essential Tremor Rating Assessment Scale (TETRAS) will serve as the primary form of qualification scoring of each setting tested. Outcome: The investigators hypothesize that targeting the interposed-receiving region of motor thalamus and in particular the ascending cerebello-thalamic fibers to this region will result in the strongest and most energy-efficient suppression of action and postural tremor.