• Ventral Intermediate Nucleus (Vim): A nucleus medially located within the ventral nuclei of the thalamus. It is the specific stimulation target for Tremor Control Therapy.
• Electrodes: The metal rings on a lead that transfer electricity to the tissue.
• Lead: A thin wire with electrodes that deliver electrical stimulation to the brain.
• Extension: A thin cable that conducts electrical pulses from the Implantable Pulse Generator to the lead.
• Implantable Pulse Generator (IPG): An implantable battery source and electrical pulse generator.
  

• The system consists of three implantable components:
  • DBS lead. A thin, insulated wire lead with four electrodes at the distal tip. Using standard clinical imaging techniques and stereotactic equipment, the electrode is positioned in the brain's thalamus, and the lead is anchored to the skull.
  • Itrel II implantable pulse generator (IPG). This device, which contains a battery and microelectronic circuitry, is surgically implanted under the skin near the collarbone. The pulse generator is 2 1/4 in x 2 1/4in. x 3/8 in. and weighs 1.72 oz.
  • Extension. An insulated wire that is surgically passed under the skin of the head, neck and shoulder to connect the lead to the implanted pulse generator. External components of the therapy include a console programmer and the patient's hand-held magnet.
• The Itrel II device generates mild electrical pulses that are delivered by the extension and lead to the targeted cells of the thalamus. These pulses can be non-invasively adjusted by neurologist, Dr. Beric from a console programmer and transmitted painlessly via radio telemetry to the implanted Itrel II device.
• Patients use the magnet to switch the stimulator between high, low and off settings. For example, they can turn their stimulation level to high when their tremor increases due to stress, or they can turn the pulse generator off when they go to sleep (tremor ceases with sleep).

Physician researchers have found that the electrical pulses block faulty brain signals that cause tremor. Certain nerve cells become overactive to the point of causing uncontrollable muscle excitation in tremor patients and electrical stimulation interferes with this abnormal activity. This has been characterized as "a jamming of the neural network" to interrupt the tremor.

Drs. Kelly uses a stereotactic headframe and imaging techniques to map the brain and localize the target.

• magnetic resonance imaging (MRI),
• computed tomography (CT) scan
• ventriculogram (contrast media - radio-opaque dye- is injected into the lateral ventricle in order to localize various thalamic nuclei, via their relative locations to the ventricle system)

The lead is inserted through a small opening in the bone and implanted in the thalamus, deep within the brain. Before the lead implant procedure, the patient's scalp is anesthetized, but the patient remains awake and alert, so that Dr. Kelly, Dr. Beric & Dr. Sterio can test the stimulation to maximize tremor suppression and minimize side effects. To ensure proper placement of the lead, the patient must be alert during this part of the procedure for the following reasons:

• the patient must demonstrate how well tremor is suppressed, for example, by drawing a circle or by holding a cup,
• the patient needs to report any side effects, and
• anesthesia may temporarily suppress tremor independently of the Tremor Control System's mechanism of action.

If the patient's tremor is suppressed during this test stimulation, the Tremor Control System is implanted. The patient is given a general anesthetic before the pulse generator and extension wire are implanted. A small incision is made near the collarbone and the pulse generator is implanted under the skin. The extension is passed under the skin of the scalp, neck and shoulder to connect the lead to the implanted pulse generator.

What is the typical length of hospitalization for pre-operative tests and recovery?

Pre-Operative tests take approximately two days. The patient is hospitalized for approximately three days.

What can the patients expect after the implant procedure?

Immediately following surgery, the patient may experience a "thalamotomy" effect, which is a reduction in tremor. When swelling subsides the tremor returns. One week after surgery, the patient returns to Dr. Kelly for suture removal. Three weeks following the surgery, the patient returns to Dr. Beric for programming the stimulation parameters to tremor control and to minimize any side effects. Dr. Beric will schedule follow up appointments and the patient's medication regime will be monitored by his/her neurologist.

How do patients benefit from Tremor Control Therapy?

In clinical research, tremor was usually suppressed entirely or significantly reduced as soon as the pulse generator is turned on in the operating room. Patients in clinical studies have resumed daily life activities that were previously difficult or impossible, such as writing, pouring liquids and dressing themselves. Tremor medications have often been markedly reduced or discontinued in these patients, especially for Essential Tremor patients, although patients with Parkinsonian tremor may still need medications for other Parkinson's disease symptoms. Because brain tissue is not destroyed after the lead is implanted, patients have preserved their future options as new therapies develop. (Benabid AL, Pollak P, Gao D, et. al. Chronic electrical stimulation of the ventralis intermedius nucleas of the thalamus as a treatment of movement disorders. Journal of Neurosurgery 1996; (84):203-214.)

What are the potential side effects of this therapy?

Clinical research suggests that the potential side effects of stimulation are generally mild, reversible, and well tolerated by patients. (Benabid AL, Pollak P, Gao D, et. al. Chronic electrical stimulation of the ventralis intermedius nucleas of the thalamus as a treatment of movement disorders. Journal of Neurosurgery 1996; (84):203-214.) The most common potential side effects include temporary tingling in the limbs (paresthesia), slight paralysis (paresis), slurred speech (dysarthia), and loss of balance (disequilibrium). These sides effects are reduced or disappear when stimulation is decreased or stopped. Risk typically associated with the surgery includes loss of effect and intracranial hemorrhage.

How long does the pulse generator battery last?

Battery longevity varies, depending upon the parameter settings and number of hours the pulse generator is turned on each day. Estimated longevity is about five years at typical settings, 16 hours of use per day. When the pulse generator battery needs to be repalced, the old pulse generator is replaced by an entirely new pulse generator; the extension and lead are not replaced. The replacement procedure can by done under local anesthesia.

Is Tremor Control Therapy new? What is its history?

This therapy is an entirely new treatment for suppression of tremor. However, electrical stimulation has been used by neurologists and neurosurgeons for more than 35 years as a way to locate and distinguish specific sites in the brain. In doing this, they discovered that by stimulating a portion of the the thalamus, severe tremor could be rapidly and dramatically suppressed. The system is based upon advanced cardiac pacemaker technology adapted to neurostimulation of the brain for the suppression of tremor.