Deep Brain Stimulation Surgery for Focal Hand Dystonia

Objectives

To confirm the safety and possible trends toward efficacy of thalamic deep brain stimulation (DBS) targeting the ventralis oralis anterior/ventralis oralis posterior (VOA/VOP) nuclear complex in the treatment of subjects with focal hand dystonia (FHD); and to study the electrophysiologic properties of neurons in the VOA/VOP complex. DBS is FDA approved for Parkinson's disease, Essential tremor, Dystonia (humanitarian exemption), Obsessive- Compulsive disorder (humanitarian exemption) but not for focal hand dystonia.

Study population

Five adults with focal hand dystonia will be studied.

Design

This is a pilot study of 5 subjects with severe intractable FHD whose activities of daily living and quality of life are severely impaired. They will be recruited from our clinic and from referring practices. The subjects will undergo unilateral VOA/VOP DBS implantation, followed by programming to optimal parameters. The subjects will be followed at monthly intervals for 3 months, then every 3 months for 2 years, and then every 6 months until 5 years from the start. The safety of the procedure will be the primary outcome of the study. Trends toward efficacy will be assessed in several secondary outcomes, the most important ones being the change in dystonia severity and a quality of life scores. The electrophysiologic features of the motor ventral thalamic neurons will be recorded intraoperatively.

Outcome measures

Primary

-Number and severity of adverse events in the 5-year follow-up period.

Secondary

• Upper extremity sub-score of the Burke-Fahn-Marsden (BFM) scale and Arm Dystonia Disability Scale (ADDS) at baseline and every follow up visit
• For subjects with FHD type musician's dystonia: Tubiana and Chamagne scale at every follow up visit
• For subjects with FHD type Writer's cramp: Writer's Cramp Impairment Scale
• Improvement on patient reported outcomes evaluated by the SF-12 Health Status Survey at baseline and at every follow up visit
• Neuropsychological evaluation at baseline, 3 and 12 months post DBS surgery
• Dose of botulinum toxin injection required at baseline, 1 and 5 years.

Exploratory

• Intraoperatory electrophysiologic characteristics of the motor ventral thalamic neurons
• Local field potentials and their response to stimulation (in participants with implanted pulse generator capable of sensing capabilities)

• INCLUSION CRITERIA:
• FHD diagnosed by a neurologist
• BFM upper extremity subscore of 3 or more (score range 0 to 4) or ADDS difficulty of performing score equal to or more than 3.
• Patients must score 3 or below on the Tubiana and Chamagne scale or inability to perform at the concert level or patients must score a rating of "severe" on at least one item, impacting the patient s employment or essential activities on the Writer s Cramp Impairment scale.
• Symptoms causing significant impairment in quality of life and work or daily activities by patient self-assessment and SF12 scale, as reported by subjects. The subjects should be severely impaired in at least one of the following domains: handwriting, typing or playing an instrument. The impairment needs to have affected employment, manifested by substantive change in, or loss of, employment or career of choice.
• All patients must have failed or achieved inadequate benefit (continuing functional impairment) with at least two trials of botulinum toxin treatments.
• Women of childbearing age will have to agree to use contraception methods for the first 3 post operative months.

Exclusion criteria

• Subjects younger than 22 years old.
• MRI findings that would make participation and surgery unsafe (such as tumor or other space occupying lesion, stroke, hemorrhage or hematoma, edema, hydrocephalus, abscess) and MRI findings that would confound study outcomes (such as iron deposits in the basal ganglia, demyelinating disease, traumatic brain injury, structural or developmental abnormality, moderate or severe white matter hyperintensities).
• Subjects with prior brain surgery
• Pregnant or nursing women as safety of DBS has not been established in this group.
• Presence of a more widespread neurologic syndrome with the dystonia being part of it, and/or dystonia caused by an ongoing etiology, such as tardive dystonia associated with ongoing psychotropic treatment or an inherited neurodegenerative syndrome associated with intractable dystonia
• Intellectual disability as measured by the estimated General Ability Index (GAI) of the Wechsler Adult Intelligence Scale 4th Edition (WAIS-IV), which would render the participant not able to provide informed consent or to comply with the study procedures (estimated GAI less than 70)
• Dementia as evidenced by formal neuropsychological evaluation and Mattis Dementia Rating Scale-2 (DRS-2) score below 128.
• Depressed subjects as determined by the neuropsychology or psychiatry screen, including Beck Depression Inventory (BDI) and psychiatric evaluation. Subjects scoring above 20 on the BDI or exhibiting moderate or severe active depression will be excluded
• Subjects with uncontrolled co-existing medical conditions: uncontrolled systemic hypertension with values above 170/100; active heart disease needing immediate intervention; active respiratory disease needing immediate intervention; uncorrected coagulation abnormalities; any condition that would render the patient unable to safely cooperate with the surgery and study tests as judged by the screening physician
• Presence of a contraindication to undergo a brain MRI

• Metal in the body which would make having an MRI scan unsafe, such as pacemakers, medication pumps, aneurysm clips, metallic prostheses (including metal pins and rods, heart valves or cochlear implants), shrapnel fragments, permanent eye liner or small metal fragments in the eye that welders and other metal workers may have;
• Uncomfortable in small closed spaces (have claustrophobia) such that the participant will be uncomfortable in the MRI machine;
• Unable to lay comfortably flat on their back for up to one hour in the MRI scanner;
• Subjects who require diathermy
• Subjects who require post-op MRIs with full body coil

-- Subjects with an active systematic infection

• Subjects who are immune-compromised
• Subjects who are on anticoagulation therapy that would preclude their ability to undergo the implant procedure
• Subjects who are allergic or have shown hypersensitivity to any materials of the neurostimulation system which may come in contact with the body
• Subjects that cannot appoint a Durable power of attorney (DPA)