The Motor Network in Essential Tremor: Mechanisms of Therapy
The Motor Network in Essential Tremor: Mechanisms of Therapy
Essential tremor (ET) is among the most common movement disorders, and is the most prevalent
 tremor disorder. It is a progressive, degenerative brain disorder that results in
 increasingly debilitating tremor, and afflicts an estimated 7 million people in the US (2.2%
 of the population) and estimates from population studies worldwide range from 0.4% to 6.3%.
 ET is directly linked to progressive functional impairment, social embarrassment, and even
 depression. Intention (kinetic) tremor of the arms occurs in approximately half of ET
 patients, and is typically a slow tremor (~5-10Hz) that occurs at the end of a purposeful
 movement, and is insidiously progressive over many years. Based on direct and indirect
 neurophysiological studies, it has been suggested that a pathological synchronous oscillation
 in a neuronal network involving the ventral intermediate nucleus (Vim) of the thalamus, the
 premotor (PM), primary motor (M1) cortices, and the cerebellum, may result in the production
 of ET. In spite of the numerous therapeutic modalities available, 65% of those suffering from
 upper limb tremor report serious difficulties during their daily lives. Deep brain
 stimulation (DBS) has emerged as an effective treatment option for those suffering from
 medically refractory ET. The accepted target for ET DBS therapy is the Vim thalamus. Vim
 projects to PM, M1, and supplementary motor areas (SMA) and receives afferents from the
 ipsilateral cerebellum. Moreover, electrophysiological recordings from Vim during
 stereotactic surgery have identified "tremor cells" that synchronously discharge with
 oscillatory muscle activity during tremor. Clinical and computational findings indicate that
 DBS suppresses tremor by masking these "burst driver" inputs to the thalamus. The overall
 goal is to investigate the neural signatures of tremor generation in the thalamocortical
 network by recording data during DBS implantation surgery. Investigators will record data
 from the macroelectrode implanted in the Vim for DBS therapy, and through an additional
 6-contact subdural cortical strip that will be placed on the hand motor cortical area
 temporarily through the same burr hole opened for the implantation of the DBS electrode.
The research study goal is to advance the understanding of the mechanisms for essential
 tremor through brain recordings. The investigators will collect brain signals in persons with
 essential tremor undergoing neurosurgical treatment (deep brain stimulation implantation). By
 recording from the implanted electrodes for deep brain stimulation along with two other
 non-invasive intraoperative monitoring electrodes, the origins of tremor will be studied in
 the human motor network. Moreover, by performing recordings during deep brain stimulation
 delivery, the mechanisms in which deep brain stimulation modulates this network to suppress
 tremor will be investigated.

 During the standard of care DBS procedure neural recordings are performed as the participant
 is in a reclined position on the operating table. In addition to neural recordings it is
 standard to ask the patient to move their arms and legs during the procedure. An additional
 intraoperative monitoring subdural electrode strip, used in epilepsy and tumor surgeries to
 perform functional mapping, will be placed by the neurosurgeon after the DBS electrode is
 placed per the clinical need of the patient. In addition, the Ad-Tech Medical Instrumentation
 Corp. device will be used to test responses with wireless sensors placed on the participant's
 arms, which can record EMG activity. Brain signals will be recorded using the clinical FHC
 Guideline 4000+ system or Medtronic RC+S, which are devices capable of recording during
 stimulation. This additional testing will add approximately 30-45 minutes to the surgical
 time. The Medtronic RC+S stimulator will not be implanted in these subjects, and will not
 used as a therapy. No interventions are compared against any controls for this study.
Inclusion Criteria:

 -  Neurosurgical patient populations with essential tremor (main cohort) and Parkinson's
 disease (control cohort)

 Exclusion Criteria:

 -  Non surgical candidates