Dual Lead Thalamic Deep Brain Recording (DBR)-DBS Interface for Closed Loop Control of Severe Essential Tremor

Inclusion criteria

• Patient gives an informed consent.
• Patient is over 21 years of age.
• Patient is diagnosed with a postural-intention (essential) tremor for at least 3 years, meets diagnostic criteria for ET, has been evaluated and examined by a movement disorders fellowship trained neurologist, and is being treated with traditional VIM DBS therapy.
• Patient has no evidence of non-ET central nervous system disease or injury and has had a significantly disabling, upper extremity tremor despite ongoing VIM DBS therapy for at least three (3) months prior to DBS revision surgery.
• Patient has a postural or kinetic tremor severity score of at least 2 out of 4 in the extremity intended for treatment on the Fahn-Tolosa-Marin Clinical Rating Scale for Tremor (TRS) despite ongoing VIM DBS therapy.
• Patient has a TRS score of 2 or above in any one of the items 16-23 from the Disability subsection of the TRS: speaking, feeding other than liquids, bringing liquids to mouth, hygiene, dressing, writing, working and social activities despite ongoing VIM DBS therapy.
• Patient's tremor is refractory to adequate trials of at least two medications, one of which should be either propranolol or primidone. Proof of this is not required for patients with a current device that is being removed and replaced with a new device. An adequate medication trial is defined as a therapeutic dose of each medication or the development of side effects as the medication dose is titrated.
• Patient is available for appropriate follow-up times for the length of the study.

Exclusion criteria

• Any previous neurosurgical intervention other than VIM DBS, including ablative brain lesions for tremor suppression.
• Medication related movement disorders.
• Any suspicion of Parkinson's disease, including presence of Parkinsonian features such as bradykinesia, rigidity, or postural instability.
• Any behaviors consistent with alcohol or substance abuse as defined by the criteria outlined in Diagnostic and Statistical Manual of Mental Disorders (DSM-V).
• Severe medical co-morbidity including cardiovascular disorder, lung disorder, kidney disease, continuous neurological disease, hematological disease, or frailty that impact tolerability of the surgery as judged by the screening physicians.
• Abnormal brain MRI including hydrocephalus, stroke, structural lesions, demyelinating lesions, or infectious lesions. Also excluded will be subjects with severe brain atrophy.
• Any uncontrolled symptoms or signs of increased intracranial pressure (e.g., headache, nausea, vomiting, lethargy, papilledema).
• A history of seizures within the past year.
• A dementia rating scale score (DRS) \<130 signifying significant cognitive dysfunction and a potential for inability to cooperate with tasks involved in the study.
• Any attempt or intent of suicide during the previous six months.
• Presence or history of psychosis.
• Any person known to have abnormal coagulation or any medications which interfere with coagulation
• Significant untreated or unstable mood disorders including depression. This will be determined by the Neuropsychological team during FastTrack and by the Neurologist
• In addition, patients who are pregnant or plan to become pregnant will be excluded from this study.