Safety Study of Deep Brain Stimulation to Manage Thalamic Pain Syndrome

This is a pilot clinical study of the therapeutic benefits of ventral capsular/ventral striatal deep brain stimulation (DBS) as a treatment for 10 patients with medically refractory thalamic pain syndrome. Patients to be enrolled under this protocol will have experienced severe pain for more than six months and will be considered medically refractory. Study subjects may have undergone and failed other surgical procedures or interventional procedures. Study subjects will have chronic, medically refractory pain of disabling severity, refractory to treatment attempts with conventional medications. Patients that are enrolled in the study will have bilateral DBS surgery, with implantation of one Medtronic 3391 DBS lead on either side of the brain. These leads will then be connected at first to a single Medtronic PC pulse generator to be implanted in the infraclavicular region on one side. Once the PC pulse generator is depleted, and the patient has completed the blinded phase of the study, the PC pulse generator will be replaced for an RC pulse generator. The RC pulse generator has a battery life of 9 years and is a good option for the open label phase and for continued stimulation after the study is completed. However, the RC is not ideal for the blinded phase because patients may be able to tell if they are receiving active or sham stimulation. For this reason, patients enrolled in this study will receive, initially, the implant with the PC generator. Patients will have at least 6 months of stable chronic pain associated with TPS.

Inclusion criteria

• Clinical diagnosis of thalamic pain syndrome
• with allodynia or dysesthesia
• with pinprick anesthesia or hypoesthesia on the affected hemibody (anesthesia dolorosa).
• Six months or more of medically refractory severe pain (see below).
• Pain disability reported by the pain index >30 points at the time of enrollment.
• Average daily pain for the past 30 days reported as >5 on a 0-10 scale
• Failure to respond adequately to at least one antidepressant, one anti-seizure medication and one oral narcotic.
• MRI done within one year of the first visit showing a lesion that involves the posterior thalamic region or a lesion in the dorsal or ventral vicinity of the thalamus (i.e. semi oval white matter or brain stem). The lesion will be contralateral to the hemibody affected by chronic pain or will involve cortical-subcortical areas in topography consistent with sensory thalamocortical connections. This will include patients with infarcts in the territory of the middle cerebral artery. A more recent MRI may be required if the patient's condition changed within the previous year.
• Capable of understanding and providing informed consent
• Age ≥ 21 years
• Women of childbearing age must be on regular use of an accepted contraceptive method(s).
• Previous surgical procedures: Patients with severe and refractory thalamic pain syndrome may have undergone other interventional or surgical procedures, as an attempt to alleviate the thalamic pain syndrome. Surgical procedure may include blocks, spinal cord stimulation, thalamic DBS, posterior limb of the internal capsule DBS or periaqueductal gray / periventricular gray DBS, cortical stimulation, peripheral ablative procedures or cerebral ablative procedures. In this study, patients with previously implanted cortical stimulation systems, or spinal and peripheral nervous system stimulation systems may be included. However, patients with previous motor cortex stimulation must have had the cortical stimulation system before being considered a candidate for this protocol. Removal of the cortical stimulation system will not be covered under this protocol. Patients with spinal or peripheral neuromodulation system may be included in the research provided that the implanted systems are compatible with the all research protocols (including fMRI) to be performed during the research. Patients with pervious DBS implants will not be considered candidates.

Exclusion criteria

• Not capable of understanding or providing informed consent.
• Aphasia severe enough to limit the consent process or communication between the investigators and the patient. Patients with mild or recovering aphasia may be considered candidates at the discretion of the PI.
• Coagulopathy. Patients will be excluded unless assessed and cleared by hematology
• Inability to stop Coumadin or platelet anti-aggregation therapy for surgery and after surgery. Patients taking these medications will need to discuss the need/risk of continuing these medications with their physicians and the PI or study personnel may contact the treating physician(s) as well to discuss the risks of anticoagulation / antiaggregation therapy discontinuation.
• Uncontrolled hypertension.
• Malignancy with < 5 years life expectancy.
• Major medical co-morbidities: end stage renal failure, heart failure, severe congestive heart disease, severe respiratory problems, liver failure or other significant medical co morbidities.
• Major neurological disorder other than the one that led to the TPS.
• MRI (done within one year of the first visit) with abnormalities other than those associated with the neurological disorder causing TPS.
• Age < 21 years.
• Pregnancy or lack of regular use of contraceptives. Patients who become pregnant after enrollment may be excluded from the study. Patients who become pregnant prior to the surgical implantation of the DBS systems will be excluded from the study.
• Previous ablative intracranial surgery for the management of the TPS.
• Previously implanted with deep brain stimulation system.
• Concurrent enrolment in any other trial / study for TPS.
• Implantable hardware not compatible with MRI or with the study.
• Patients may be excluded from enrollment due to a condition that, in the judgment of the PI, significantly increases risk or reduces significantly the likelihood of benefit from VC/VS DBS.
• Untreated / uncontrolled (severe at the time of enrolment) depression or other psychiatric disorder.
• Bipolar disorder, current PTSD, severe personality disorder, active psychosis, Severe OCD.
• Psychological co-morbidities that indicates higher risk to the patient and / or higher risk of failure.
• Suicide attempt </= 12 months
• Communication of a plan for suicide, prior to implant, should the study treatment fail
• Imminent suicide risk